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Rodrigo Medel

Universidad de Chile, Departamento de Ciencias Ecológicas, Faculty Member

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I am interested in understanding the way natural selection has shaped the structure of plant-animal interactions in Chilean ecosystems. I am also interested in History and Philosophy of Science, with emphasis in the philosophy of discovery, abduction, and Quinean reorganization of conceptual networks after discovery.
Phone: +56994407351
Address: Departamento de Ciencias Ecológicas, Facultad de Ciencias, Casilla 653, Santiago, Chile.

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Kristen J Gremillion

Ohio State University

Masaryk University

Kansas State University

Francisco E. Fonturbel

Pontificia Universidad Catolica de Valparaiso

University of East London

Armando Marques-Guedes

UNL - New University of Lisbon

Massachusetts Institute of Technology (MIT)

Universidade Federal do Rio Grande do Sul

Swansea University

Michaela Valente

Università degli Studi "La Sapienza" di Roma

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Books by Rodrigo Medel

Mas alla de la Perdida de Especies: Interacciones Ecológicas en el Antropoceno

by Rodrigo Medel, Anna Traveset, and Luis Navarro

Mas allá de la Perdida de Especies: Interacciones Ecológicas en el Antropoceno, 2024

El presente libro es un volumen multiautoreado que resulta de la colaboración entre ecólogos de I... more El presente libro es un volumen multiautoreado que resulta de la colaboración entre ecólogos de Iberoamérica que estudiamos interacciones planta-animal. Hace algunos años, al alero de CYTED (Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo), nos propusimos publicar un libro que resumiera nuestras diversas perspectivas sobre la importancia de las interacciones ecológicas para el mantenimiento de la biodiversidad en un contexto de pérdida biológica acelerada en el Antropoceno.

Ecología y evolución de interacciones planta animal

by Rodrigo Medel and Regino Zamora

Editorial Universitaria, 2009

Andres Bello Cientifico. Escritos publicados (1823-1843)

Editorial Universitaria, 2018

Papers by Rodrigo Medel

La abducción interrogativa de Hintikka en el razonamiento de Darwin

Ludus Vitalis, 2024

Una de las propuestas más innovadoras al concepto original de abducción de Peirce es la efectuada... more Una de las propuestas más innovadoras al concepto original de abducción de Peirce es la efectuada por Hintikka. A diferencia de la concepción Peirceana construida a partir de una estructura silogística de bajo poder lógico, Hintikka libera la abducción de las restricciones impuestas por el aparato deductivo, ubicando el concepto en un esquema interrogativo más flexible en que el investigador orienta sus pasos de manera estratégica y organizada hacia el descubrimiento final. Paavola ejemplifica la nueva definición de abducción usando el descubrimiento de la teoría de evolución de Darwin como eviden- cia histórica. En este trabajo sostengo que el ejemplo usado por Paavola es equivocado, principalmente por una interpretación incorrecta de los descubrimientos de Darwin. Una inspección detallada de las libretas de Darwin, sin embargo, revela que el razo- namiento de Darwin en la búsqueda del Principio de Divergencia, la última hipótesis antes de publicar el Origen de las Especies, es consistente con la propuesta de Hintikka, aunque en un segmento histórico distinto del señalado por Paavola.

Nectar-feeding behaviour of passerine birds in Puya chilensis (Bromeliaceae): the functional role of sterile branch apices

The functional role of plant morphological structures in the behavior of non-specialized nectarfe... more The functional role of plant morphological structures in the behavior of non-specialized nectarfeeding passerines has received few attention in the literature on plant-pollinator interactions. The bromeliad Puya chilensis is characterized by having sterile branch apices that project outward from the inflorescence. Although casual observations suggest a role for these structures as perches for various bird species, their relevance for the pollination process has not been analyzed. In this study, we evaluated the functional role of sterile apices as secondary perches that facilitate the foraging behavior of birds that need perching to reach flowers. To this end, we recorded bird visitation and flower probings in the presence and absence of the sterile branches. The results revealed that the removal of these structures reduces the overall number of bird visits and flower probings, indicating that sterile branches play an important role on the nectar-feeding behaviour of passerine birds and probably on plant reproduction.

The most effective pollinator principle applies to new invasive pollinators.

Biology Letters, 2018

G.L. Stebbins’ most effective pollinator principle states that when pollinators are not limiting,... more G.L. Stebbins’ most effective pollinator principle states that when pollinators are not limiting, plants are expected to specialize and adapt to the more abundant and effective pollinator species available. In this study, we quantify the effectiveness of bees, hummingbirds and hawkmoths in a Chilean population of Erythranthe lutea (Phrymaceae), and examine whether flower traits are subject to pollinator-mediated selection by the most effective pollinator species during two consecutive years. Unlike most species in the pollinator community, the visitation rate of the recently arrived Bombus terrestris did not change substantially between years, which together with its high and stable pollen delivery to flower stigmas made this species the most important in the pollinator assemblage followed by the solitary bee Centris nigerrima. Flower traits were under significant selection in the direction expected for short-tongue bees, suggesting that E. lutea is in the initial steps of adaptation to the highly effective exotic bumblebee. Our results illustrate the applicability of Stebbins' principle for new invasive pollinators, and stress their importance in driving flower adaptation of native plant species, a critical issue in the face of biotic exchange and homogenization.

The Mass Exponent In Population Energy Use: the Fallacy of Averages Reconsidered

American Naturalist, Jan 1, 1995

Pollinator-mediated selection on the nectar guide phenotype in the Andean monkey flower, Mimulus luteus

Ecology, Jan 1, 2003

Mimulus luteus (Scrophulariaceae) is a perennial herb occurring in the South American Andes that ... more Mimulus luteus (Scrophulariaceae) is a perennial herb occurring in the South American Andes that shows a wide variation in the size and shape of a red spot on the lower lobe of the yellow flower. We describe the preference of four insects (three bees and one butterfly) and one hummingbird species for floral characters, and estimated the strength, direction, and form of pollinator-mediated selection through female fitness. We applied geometric morphometrics to describe the preference of pollinator species for different guide shapes. Our results revealed striking differences in the floral phenotypes preferred by insects and hummingbirds. Insects visited flowers with corollas 1.25-fold larger and guides 1.72-fold larger than the hummingbird species did. While insects preferred flowers with nectar guides pointing toward the corolla tube, the hummingbird preferred flowers with heartshaped nectar guides. Most of the floral preferences shown by pollinators translated into significant linear and nonlinear selection coefficients. When selection was analyzed on a per-flower basis and for female fitness, corolla size was under positive directional selection, and nectar guide size and shape were under disruptive selection. Because the insect and hummingbird pollinators showed a strong segregation in their daily activity time, we suggest that current disruptive selection on the nectar guide phenotype can result from the differential availability of the rewarding floral variants over a day. Our findings suggest that pollinator-mediated selection favoring extreme phenotypes in M. luteus may not only contribute to high nectar guide variation found in this species, but also can promote divergence of corolla and nectar guide traits.

Convergence and historical effects in harvester ant assemblages of Australia, North America, and South America

Biological Journal of the Linnean Society, Jan 1, 1995

In this paper I examine the extent to which contemporary ecological patterns in 42 ant assemblage... more In this paper I examine the extent to which contemporary ecological patterns in 42 ant assemblages of three continents can be explained as a result of present-day environments or from differences in the history of each ant biota. The contribution of each factor to the overall variation of six community characters was evaluated through Schluter`s ANOVA procedure.

Effects of sampling completeness on the structure of plant-pollinator networks

Ecology, 2012

Plant-animal interaction networks provide important information on community organization. One of... more Plant-animal interaction networks provide important information on community organization. One of the most critical assumptions of network analysis is that the observed interaction patterns constitute an adequate sample of the set of interactions present in plant-animal communities. In spite of its importance, few studies have evaluated this assumption and in consequence there is no consensus on the sensitivity of network metrics to sampling methodological shortcomings. In this study we examine how variation in sampling completeness influences the estimation of six network metrics frequently used in the literature (connectance, nestedness, modularity, robustness to species loss, path length, and centralization). We analyze data of 186 flowering plants and 336 pollinator species in ten networks from a forest fragmented system in central Chile. Using species-based accumulation curves we estimated the deviation of network metrics in undersampled communities with respect to exhaustively sampled communities and the effect of network size and sampling evenness on network metrics. Our results indicate that: 1) most metrics were affected by sampling completeness, but they differ in their sensitivity to sampling effort, 2) nestedness, modularity, and robustness to species loss were less influenced by insufficient sampling than connectance, path length, and centralization, 3) robustness was mildly influenced by sampling evenness. These results caution studies that summarize information from databases with high, or unknown, heterogeneity in sampling effort per species, and stimulate researchers to report sampling intensity to standardize its effects in the search for broad patterns in plant-pollinator networks.

Assessment of parasite-mediated selection in a host-parasite system in plants

Ecology, Jan 1, 2000

A two-year field study was conducted to evaluate the potential of two cactus species, Echinopsis ... more A two-year field study was conducted to evaluate the potential of two cactus species, Echinopsis chilensis and Eulychnia acida, to evolve defensive traits against the parasitic mistletoe Tristerix aphyllus (Loranthaceae). The adaptive value of host traits against parasitism was inferred through: (1) identification of the relevant characters of cacti to prevent infection, (2) evaluation of the fitness impact of parasitism on cacti, and (3) estimation of the linear and nonlinear selection coefficients on the relevant characters. Different lines of experimental and correlative evidence indicated that spine length was
important in preventing individuals of the two cactus species from becoming parasitized. However, the impact of the mistletoe on cactus fecundity was contingent on the species
involved. Even though parasitism decreased fruit production, seed number per fruit, and the total seed output in E. chilensis, low and nonsignificant linear and nonlinear gradients
of selection were prevalent in this species, indicating absence of directional and stabilizing/disruptive selection for spine length. Additional analysis based on logistic regression, however, revealed that long-spined E. chilensis had a higher probability of reproduction than did short-spined individuals. Unlike its effect on E. chilensis, the mistletoe had no fitness impact on E. acida, and the maintenance and evolution of spines in this species could not be attributed to parasite-mediated selection. Even though spines act as a first line of defense against parasitism in the two cactus species, selection was detected only on E. chilensis. These results indicate that inferences on the adaptive value of host traits based only upon their role in preventing infection run the risk of overestimating parasite-mediated selection, and thus the potential for host–parasite coevolution.

Seed dispersers as disease vectors: bird transmission of mistletoes seeds to plant hosts

Ecology

The relationship between mistletoes and birds has been studied from the perspectives of mutualism... more The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We describe the patterns of transmission of the seeds of Tristerix aphyllus, an endophytic Chilean mistletoe, on two of its columnar cacti hosts (Eulychnia acida and Echinopsis skottsbergii) by the Chilean Mockingbird Mimus thenca. In north-central Chile, these cacti grow in relatively discrete subpopulations on north-facing slopes. We measured variation in seed transmission within 10 subpopulations varying in species composition, host density, parasite density, parasite prevalence (defined as the percentage of hosts infested in a given population), and disperser abundance. Seed transmission was independent of species, but was strongly de- pendent on prior parasitism. Parasitized individuals received seeds much more frequently than expected from their relative abundance. We found no correlation between the density of hosts and seed transmission. We found strong positive correlations, however, between parasite prevalence and seed transmission to both parasitized and nonparasitized hosts. Seed transmission of T. aphyllus seeds by M. thenca appeared to be frequency- rather than density- dependent. Seed transmission was also tightly and positively correlated with the abundance of seed-dispersing birds at each site. Because bird abundance and parasite prevalence were correlated, we conducted path analysis to disentangle their relative effect on seed trans- mission. A model including only the direct effect of bird abundance and the indirect effect of parasite prevalence through bird abundance explained roughly the same variance as a full model including both the direct and indirect effects of bird abundance and prevalence on seed transmission. Apparently, variation in bird abundance was the main determinant of variation in transmission. We suggest that mistletoes, host plants, and the birds that disperse mistletoe seeds are systems well suited for studies of the ecological and evolu- tionary dynamics of disease transmission.

Global agricultural productivity is threatened by increasing pollinator dependence without a parallel increase in crop diversification

by Rodrigo Medel and Carolina Laura Morales

Global Change Biology, 2019

The global increase in the proportion of land cultivated with pollinator-dependent crops implies ... more The global increase in the proportion of land cultivated with pollinator-dependent crops implies increased reliance on pollination services. Yet agricultural practices themselves can profoundly affect pollinator supply and pollination. Extensive mon-ocultures are associated with a limited pollinator supply and reduced pollination, whereas agricultural diversification can enhance both. Therefore, areas where agricultural diversity has increased, or at least been maintained, may better sustain high and more stable productivity of pollinator-dependent crops. Given that >80% of all crops depend, to varying extents, on insect pollination, a global increase in agricultural pollinator dependence over recent decades might have led to a concomitant increase in agricultural diversification. We evaluated whether an increase in the area

Arms Race Coevolution: The Local and Geographical Structure of a Host-Parasite Interaction

Evolution: Education and Outreach, Jan 1, 2010

Consideration of complex geographic patterns of mreciprocal adaptation has provided insight into ... more Consideration of complex geographic patterns of mreciprocal adaptation has provided insight into new features of the coevolutionary process. In this paper, we provide mecological, historical, and geographical evidence for coevolution under complex temporal and spatial scenarios that include intermittent selection, species turnover across localities, and a range of trait match/mismatch across populations. Our study focuses on a plant host–parasitic plant interaction endemic to arid and semiarid regions of Chile. The long spines of Chilean cacti have been suggested to evolve under parasite-mediated selection as a first line of defense against the mistletoe Tristerix aphyllus. The mistletoe, in turn, has evolved an extremely long morphological structure that emerges from the seed endosperm (radicle) to reach the host cuticle. When spine length was traced along cactus phylogenies, a significant association between spine length and parasitism was detected, indicating that defensive traits evolved in high correspondence with the presence or absence of parasitism in two cactus lineages. Assessment of spine-radicle matching across populations revealed a potential for coevolution in 50% of interaction pairs. Interestingly, hot spots for coevolution did not distribute at random across sites. On the contrary, interaction pairs showing high matching values occur mostly in the northern distribution of the interaction, suggesting a geographical structure for coevolution in this system. Only three sampled interaction pairs were so mismatched that reciprocal selection could not occur given current trait distributions. Overall, different lines of evidence indicate that arms-race coevolution is an ongoing phenomenon that occurs in the global system of interconnected populations.

Seed dispersers as disease vectors: bird transmission of mistletoe seeds to plant hosts

The relationship between mistletoes and birds has been studied from the perspectives of mutualism... more The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We describe the patterns of transmission of the seeds of Tristerix aphyllus, an endophytic Chilean mistletoe, on two of its columnar cacti hosts (Eulychnia acida and Echinopsis skottsbergii) by the Chilean Mockingbird Mimus thenca. In north-central Chile, these cacti grow in relatively discrete subpopulations on north-facing slopes. We measured variation in seed transmission within 10 subpopulations varying in species composition, host density, parasite density, parasite prevalence (defined as the percentage of hosts infested in a given population), and disperser abundance. Seed transmission was independent of species, but was strongly dependent on prior parasitism. Parasitized individuals received seeds much more frequently than expected from their relative abundance. We found no correlation between the density of hosts and seed transmission. We found strong positive correlations, however, between parasite prevalence and seed transmission to both parasitized and nonparasitized hosts. Seed transmission of T. aphyllus seeds by M. thenca appeared to be frequency-rather than densitydependent. Seed transmission was also tightly and positively correlated with the abundance of seed-dispersing birds at each site. Because bird abundance and parasite prevalence were correlated, we conducted path analysis to disentangle their relative effect on seed transmission. A model including only the direct effect of bird abundance and the indirect effect of parasite prevalence through bird abundance explained roughly the same variance as a full model including both the direct and indirect effects of bird abundance and prevalence on seed transmission. Apparently, variation in bird abundance was the main determinant of variation in transmission. We suggest that mistletoes, host plants, and the birds that disperse mistletoe seeds are systems well suited for studies of the ecological and evolutionary dynamics of disease transmission.

Frugivore-Mediated Selection in a habitat transformation scenario

Scientific Reports, 2017

Plant-animal interactions are strong drivers of phenotypic evolution. However, the extent to whic... more Plant-animal interactions are strong drivers of phenotypic evolution. However, the extent to which anthropogenic habitat transformation creates new selective scenarios for plant-animal interactions is a little explored subject. We examined the effects of native forest replacement by exotic Eucalyptus trees on the frugivore-mediated phenotypic selection coefficients imposed by the relict marsupial Dromiciops gliroides upon traits involved in frugivore attraction and germination success of the mistletoe Tristerix corymbosus (Loranthaceae). We found significant gradients for seed weight and sugar content along the native-transformed habitat gradient. While selection for larger seed weight was more relevant in native habitats, fruits with intermediate sugar content were promoted in transformed habitats. The spatial habitat structure and microclimate features such as the degree of sunlight received influenced the natural selection processes, as they correlated with the phenotypic traits analysed. The response of this plant-frugivore interaction to human disturbance seemed to be context-dependent, in which extremely transformed habitats would offer new opportunities for natural selection on dispersal-related traits. Even in recent transformation events like this, human disturbance acts as a strong contemporary evolution driver. Plant-animal interactions are strong drivers of reciprocal phenotypic evolution 1 , leading to coevolved traits that are dynamic through time and space 2,3. However, this complex eco-evolutionary system is challenged by a world in constant change in which many anthropogenic biodiversity-loss drivers are altering natural habitats 4. Each species responds to habitat disturbance according to their life history traits 5 , which explains, at least in part, the variety of responses to human disturbance observed in nature 6,7. For example, while habitat fragmentation often modifies species abundances due to area and edge effects 8,9 , habitat transformation, involving the partial or complete replacement of the native vegetation by exotic species 10,11 , usually leads to more dramatic effects such as local extinction, arrival of new species, and changes in species composition. Even though seed dispersal is a key stage in a plant's life cycle that determines the demographic response to human-induced habitat disturbance 12,13 , studies examining phenotypic selection on seed dispersal in human-induced transformed habitats are scarce compared to those focused on pollination interactions (e.g., ref. 14). Seed dispersal shapes spatial and genetic structure of plants 15 which determines the potential of plant populations to respond to changes in selective scenarios. Recent studies showed that anthropogenic defauna-tion collapses seed dispersal and changes allelic frequencies 16,17 , but little is known about potential contemporary evolution on seed dispersal 18. Human activities are remarkably strong selection forces 19 which are able to change the eco-evolutionary scenario in which seed dispersal interactions occur. We examined the importance of frugivore-mediated phenotypic selection in a highly specialized system (a mistletoe with a single disperser species), which would allow us to examine the effects of frugivore-mediated selection without the background noise that redundant frugivore species might impose on generalist plant-frugivore system, along a habitat disturbance gradient to answer the following questions: (1) Does frugivore-mediated selection on fruit traits change along a habitat transformation gradient? (2) Do native and transformed habitats differ sufficiently in structural and microclimate conditions to create spatially variable selection scenarios for fruit traits? We hypothesize that habitat structural and microclimate features affect dispersal-related fruit traits and consequently habitat transformation would change the magnitude, direction and significance of phenotypic selection coefficients acting upon them.

Objective recognition of guilds: testing for statistically significant species clusters

Oecologia, 1990

Presently, no standard protocol for objective guild recognition is consistently used by ecologist... more Presently, no standard protocol for objective guild recognition is consistently used by ecologists. Apart from intuitive designations of guild membership, four statistically-based protocols are currently available: those of Colwell (1977); Holmes (1979); Lawlor (1980); and Adams (1985). The first is based on nearest-neighbor variance in overlap, the second on multivariate statistics, the third on clustering techniques, and the fourth on psychometric analysis. We propose a fifth approach, first developed by Strauss (1982) for purposes other than guild recognition. We advocate the use of bootstrap procedures to resample any given empirical matrix of consumers by resources, within constraints set by either of four different randomization algorithms. Subsequently, pseudovalues of similarity in resource use between the consumers are computed and their frequency distribution is displayed in a histogram. The overlap pseudovalue that exceeds percentile 95 may be considered statistically significant and chosen as the cutoff point that identifies significant species clusters (guilds) in the original (empirical) similarity matrix. We exemplify use of this approach with the food-niche matrix obtained for a predatory assemblage in California, and discuss its implications for the general analysis of guild structure.

Indirect interactions in a microcosm-assembled cladoceran community: implications for apparent competition

Oikos, Apr 1, 2002

Apparent competition occurs when species that otherwise may not directly interact still exhibit n... more Apparent competition occurs when species that otherwise may not directly interact still exhibit negative indirect effects on one another because they share a food-limited predator (enemy). Even though this type of indirect interaction has received significant theoretical and empirical attention, alternative mechanisms producing similar results have not been considered in the literature. In this paper we document the results of a series of microcosm experiments aimed to evaluate the importance of the generalist consumer Daphnia ambigua upon the relative abundance of the more specialized Moina micrura and Ceriodaphnia dubia (Cladocera). We compared the population parameters of M. micrura and C. dubia when alone, in coexistence, and in the presence and absence of D. ambigua. While M. micrura and C. dubia did not show evidence for interspecific competition, the addition of D. ambigua promoted a reduction in the maximal population density of M. micrura, causing a pattern of indirect competition with C. dubia that resembles predator-mediated apparent competition. This result suggests that non-predatory interactions need to be considered as a potential source of apparent interactions in natural communities.

Observaciones preliminares sobre uso de recursos y temperatura de actividad en ensambles de hormigas granívoras del Norte de Chile

Acta Entomologica Chilena, 1996

Acceso de usuarios registrados. Acceso de usuarios registrados Usuario Contraseña. ...

Depredacion sobre lagartijas en chile central : importancia relativa de atributos ecologicos y morfologicos

Revista Chilena De Historia Natural, 1990

RESUMEN Estimamos la intensidad de depredación experimentada por cinco especies de lagartijas del... more RESUMEN Estimamos la intensidad de depredación experimentada por cinco especies de lagartijas del género Liolaemus, en dos localidades de Chile central. La aplicación de un algoritmo de reorganización tipo bootstrap al índice de depredación de Schoener (1979) permitió realizar contrastes estadísticos interespecíficos así como entre localidades. Las lagartijas que habitan en la localidad de menor altitud (San Carlos) sufrieron globalmente una mayor depredación,la que adjudicamos a la presencia de Philodryas chamissonis y Callopistes palluma, ambos depredadores ausentes en la localidad de mayor altura (El Colorado). Al examinar la abundancia relativa de las lagartijas, se observa que ellas no son consumidas según su disponibilidad en ninguno de los sitios de estudio. En San Carlos, el tamaño corporal no se correlaciona con la intensidad de la depredación. Sin embargo, la lagartija que usa el suelo con mayor frecuencia experimenta una depredación desproporcionadamente mayor en comparación a las especies rriás saxícolas. En El Colorado la lagartija de mayor tamaño corporal es la que experimenta una mayor depredación, independientemente de su uso del microhábitat. Estos resultados sugieren que, a diferencia de la abundancia relativa, los atributos de uso del microhábitat y tamaño corporal son importantes en determinar las intensidades de depredación que experimentan las lagartijas.

Mas alla de la Perdida de Especies: Interacciones Ecológicas en el Antropoceno

by Rodrigo Medel, Anna Traveset, and Luis Navarro

Mas allá de la Perdida de Especies: Interacciones Ecológicas en el Antropoceno, 2024

El presente libro es un volumen multiautoreado que resulta de la colaboración entre ecólogos de I... more El presente libro es un volumen multiautoreado que resulta de la colaboración entre ecólogos de Iberoamérica que estudiamos interacciones planta-animal. Hace algunos años, al alero de CYTED (Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo), nos propusimos publicar un libro que resumiera nuestras diversas perspectivas sobre la importancia de las interacciones ecológicas para el mantenimiento de la biodiversidad en un contexto de pérdida biológica acelerada en el Antropoceno.

Ecología y evolución de interacciones planta animal

by Rodrigo Medel and Regino Zamora

Editorial Universitaria, 2009

Andres Bello Cientifico. Escritos publicados (1823-1843)

Editorial Universitaria, 2018

La abducción interrogativa de Hintikka en el razonamiento de Darwin

Ludus Vitalis, 2024

Una de las propuestas más innovadoras al concepto original de abducción de Peirce es la efectuada... more Una de las propuestas más innovadoras al concepto original de abducción de Peirce es la efectuada por Hintikka. A diferencia de la concepción Peirceana construida a partir de una estructura silogística de bajo poder lógico, Hintikka libera la abducción de las restricciones impuestas por el aparato deductivo, ubicando el concepto en un esquema interrogativo más flexible en que el investigador orienta sus pasos de manera estratégica y organizada hacia el descubrimiento final. Paavola ejemplifica la nueva definición de abducción usando el descubrimiento de la teoría de evolución de Darwin como eviden- cia histórica. En este trabajo sostengo que el ejemplo usado por Paavola es equivocado, principalmente por una interpretación incorrecta de los descubrimientos de Darwin. Una inspección detallada de las libretas de Darwin, sin embargo, revela que el razo- namiento de Darwin en la búsqueda del Principio de Divergencia, la última hipótesis antes de publicar el Origen de las Especies, es consistente con la propuesta de Hintikka, aunque en un segmento histórico distinto del señalado por Paavola.

Nectar-feeding behaviour of passerine birds in Puya chilensis (Bromeliaceae): the functional role of sterile branch apices

The functional role of plant morphological structures in the behavior of non-specialized nectarfe... more The functional role of plant morphological structures in the behavior of non-specialized nectarfeeding passerines has received few attention in the literature on plant-pollinator interactions. The bromeliad Puya chilensis is characterized by having sterile branch apices that project outward from the inflorescence. Although casual observations suggest a role for these structures as perches for various bird species, their relevance for the pollination process has not been analyzed. In this study, we evaluated the functional role of sterile apices as secondary perches that facilitate the foraging behavior of birds that need perching to reach flowers. To this end, we recorded bird visitation and flower probings in the presence and absence of the sterile branches. The results revealed that the removal of these structures reduces the overall number of bird visits and flower probings, indicating that sterile branches play an important role on the nectar-feeding behaviour of passerine birds and probably on plant reproduction.

The most effective pollinator principle applies to new invasive pollinators.

Biology Letters, 2018

G.L. Stebbins’ most effective pollinator principle states that when pollinators are not limiting,... more G.L. Stebbins’ most effective pollinator principle states that when pollinators are not limiting, plants are expected to specialize and adapt to the more abundant and effective pollinator species available. In this study, we quantify the effectiveness of bees, hummingbirds and hawkmoths in a Chilean population of Erythranthe lutea (Phrymaceae), and examine whether flower traits are subject to pollinator-mediated selection by the most effective pollinator species during two consecutive years. Unlike most species in the pollinator community, the visitation rate of the recently arrived Bombus terrestris did not change substantially between years, which together with its high and stable pollen delivery to flower stigmas made this species the most important in the pollinator assemblage followed by the solitary bee Centris nigerrima. Flower traits were under significant selection in the direction expected for short-tongue bees, suggesting that E. lutea is in the initial steps of adaptation to the highly effective exotic bumblebee. Our results illustrate the applicability of Stebbins' principle for new invasive pollinators, and stress their importance in driving flower adaptation of native plant species, a critical issue in the face of biotic exchange and homogenization.

The Mass Exponent In Population Energy Use: the Fallacy of Averages Reconsidered

American Naturalist, Jan 1, 1995

Pollinator-mediated selection on the nectar guide phenotype in the Andean monkey flower, Mimulus luteus

Ecology, Jan 1, 2003

Mimulus luteus (Scrophulariaceae) is a perennial herb occurring in the South American Andes that ... more Mimulus luteus (Scrophulariaceae) is a perennial herb occurring in the South American Andes that shows a wide variation in the size and shape of a red spot on the lower lobe of the yellow flower. We describe the preference of four insects (three bees and one butterfly) and one hummingbird species for floral characters, and estimated the strength, direction, and form of pollinator-mediated selection through female fitness. We applied geometric morphometrics to describe the preference of pollinator species for different guide shapes. Our results revealed striking differences in the floral phenotypes preferred by insects and hummingbirds. Insects visited flowers with corollas 1.25-fold larger and guides 1.72-fold larger than the hummingbird species did. While insects preferred flowers with nectar guides pointing toward the corolla tube, the hummingbird preferred flowers with heartshaped nectar guides. Most of the floral preferences shown by pollinators translated into significant linear and nonlinear selection coefficients. When selection was analyzed on a per-flower basis and for female fitness, corolla size was under positive directional selection, and nectar guide size and shape were under disruptive selection. Because the insect and hummingbird pollinators showed a strong segregation in their daily activity time, we suggest that current disruptive selection on the nectar guide phenotype can result from the differential availability of the rewarding floral variants over a day. Our findings suggest that pollinator-mediated selection favoring extreme phenotypes in M. luteus may not only contribute to high nectar guide variation found in this species, but also can promote divergence of corolla and nectar guide traits.

Convergence and historical effects in harvester ant assemblages of Australia, North America, and South America

Biological Journal of the Linnean Society, Jan 1, 1995

In this paper I examine the extent to which contemporary ecological patterns in 42 ant assemblage... more In this paper I examine the extent to which contemporary ecological patterns in 42 ant assemblages of three continents can be explained as a result of present-day environments or from differences in the history of each ant biota. The contribution of each factor to the overall variation of six community characters was evaluated through Schluter`s ANOVA procedure.

Effects of sampling completeness on the structure of plant-pollinator networks

Ecology, 2012

Plant-animal interaction networks provide important information on community organization. One of... more Plant-animal interaction networks provide important information on community organization. One of the most critical assumptions of network analysis is that the observed interaction patterns constitute an adequate sample of the set of interactions present in plant-animal communities. In spite of its importance, few studies have evaluated this assumption and in consequence there is no consensus on the sensitivity of network metrics to sampling methodological shortcomings. In this study we examine how variation in sampling completeness influences the estimation of six network metrics frequently used in the literature (connectance, nestedness, modularity, robustness to species loss, path length, and centralization). We analyze data of 186 flowering plants and 336 pollinator species in ten networks from a forest fragmented system in central Chile. Using species-based accumulation curves we estimated the deviation of network metrics in undersampled communities with respect to exhaustively sampled communities and the effect of network size and sampling evenness on network metrics. Our results indicate that: 1) most metrics were affected by sampling completeness, but they differ in their sensitivity to sampling effort, 2) nestedness, modularity, and robustness to species loss were less influenced by insufficient sampling than connectance, path length, and centralization, 3) robustness was mildly influenced by sampling evenness. These results caution studies that summarize information from databases with high, or unknown, heterogeneity in sampling effort per species, and stimulate researchers to report sampling intensity to standardize its effects in the search for broad patterns in plant-pollinator networks.

Assessment of parasite-mediated selection in a host-parasite system in plants

Ecology, Jan 1, 2000

A two-year field study was conducted to evaluate the potential of two cactus species, Echinopsis ... more A two-year field study was conducted to evaluate the potential of two cactus species, Echinopsis chilensis and Eulychnia acida, to evolve defensive traits against the parasitic mistletoe Tristerix aphyllus (Loranthaceae). The adaptive value of host traits against parasitism was inferred through: (1) identification of the relevant characters of cacti to prevent infection, (2) evaluation of the fitness impact of parasitism on cacti, and (3) estimation of the linear and nonlinear selection coefficients on the relevant characters. Different lines of experimental and correlative evidence indicated that spine length was
important in preventing individuals of the two cactus species from becoming parasitized. However, the impact of the mistletoe on cactus fecundity was contingent on the species
involved. Even though parasitism decreased fruit production, seed number per fruit, and the total seed output in E. chilensis, low and nonsignificant linear and nonlinear gradients
of selection were prevalent in this species, indicating absence of directional and stabilizing/disruptive selection for spine length. Additional analysis based on logistic regression, however, revealed that long-spined E. chilensis had a higher probability of reproduction than did short-spined individuals. Unlike its effect on E. chilensis, the mistletoe had no fitness impact on E. acida, and the maintenance and evolution of spines in this species could not be attributed to parasite-mediated selection. Even though spines act as a first line of defense against parasitism in the two cactus species, selection was detected only on E. chilensis. These results indicate that inferences on the adaptive value of host traits based only upon their role in preventing infection run the risk of overestimating parasite-mediated selection, and thus the potential for host–parasite coevolution.

Seed dispersers as disease vectors: bird transmission of mistletoes seeds to plant hosts

Ecology

The relationship between mistletoes and birds has been studied from the perspectives of mutualism... more The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We describe the patterns of transmission of the seeds of Tristerix aphyllus, an endophytic Chilean mistletoe, on two of its columnar cacti hosts (Eulychnia acida and Echinopsis skottsbergii) by the Chilean Mockingbird Mimus thenca. In north-central Chile, these cacti grow in relatively discrete subpopulations on north-facing slopes. We measured variation in seed transmission within 10 subpopulations varying in species composition, host density, parasite density, parasite prevalence (defined as the percentage of hosts infested in a given population), and disperser abundance. Seed transmission was independent of species, but was strongly de- pendent on prior parasitism. Parasitized individuals received seeds much more frequently than expected from their relative abundance. We found no correlation between the density of hosts and seed transmission. We found strong positive correlations, however, between parasite prevalence and seed transmission to both parasitized and nonparasitized hosts. Seed transmission of T. aphyllus seeds by M. thenca appeared to be frequency- rather than density- dependent. Seed transmission was also tightly and positively correlated with the abundance of seed-dispersing birds at each site. Because bird abundance and parasite prevalence were correlated, we conducted path analysis to disentangle their relative effect on seed trans- mission. A model including only the direct effect of bird abundance and the indirect effect of parasite prevalence through bird abundance explained roughly the same variance as a full model including both the direct and indirect effects of bird abundance and prevalence on seed transmission. Apparently, variation in bird abundance was the main determinant of variation in transmission. We suggest that mistletoes, host plants, and the birds that disperse mistletoe seeds are systems well suited for studies of the ecological and evolu- tionary dynamics of disease transmission.

Global agricultural productivity is threatened by increasing pollinator dependence without a parallel increase in crop diversification

by Rodrigo Medel and Carolina Laura Morales

Global Change Biology, 2019

The global increase in the proportion of land cultivated with pollinator-dependent crops implies ... more The global increase in the proportion of land cultivated with pollinator-dependent crops implies increased reliance on pollination services. Yet agricultural practices themselves can profoundly affect pollinator supply and pollination. Extensive mon-ocultures are associated with a limited pollinator supply and reduced pollination, whereas agricultural diversification can enhance both. Therefore, areas where agricultural diversity has increased, or at least been maintained, may better sustain high and more stable productivity of pollinator-dependent crops. Given that >80% of all crops depend, to varying extents, on insect pollination, a global increase in agricultural pollinator dependence over recent decades might have led to a concomitant increase in agricultural diversification. We evaluated whether an increase in the area

Arms Race Coevolution: The Local and Geographical Structure of a Host-Parasite Interaction

Evolution: Education and Outreach, Jan 1, 2010

Consideration of complex geographic patterns of mreciprocal adaptation has provided insight into ... more Consideration of complex geographic patterns of mreciprocal adaptation has provided insight into new features of the coevolutionary process. In this paper, we provide mecological, historical, and geographical evidence for coevolution under complex temporal and spatial scenarios that include intermittent selection, species turnover across localities, and a range of trait match/mismatch across populations. Our study focuses on a plant host–parasitic plant interaction endemic to arid and semiarid regions of Chile. The long spines of Chilean cacti have been suggested to evolve under parasite-mediated selection as a first line of defense against the mistletoe Tristerix aphyllus. The mistletoe, in turn, has evolved an extremely long morphological structure that emerges from the seed endosperm (radicle) to reach the host cuticle. When spine length was traced along cactus phylogenies, a significant association between spine length and parasitism was detected, indicating that defensive traits evolved in high correspondence with the presence or absence of parasitism in two cactus lineages. Assessment of spine-radicle matching across populations revealed a potential for coevolution in 50% of interaction pairs. Interestingly, hot spots for coevolution did not distribute at random across sites. On the contrary, interaction pairs showing high matching values occur mostly in the northern distribution of the interaction, suggesting a geographical structure for coevolution in this system. Only three sampled interaction pairs were so mismatched that reciprocal selection could not occur given current trait distributions. Overall, different lines of evidence indicate that arms-race coevolution is an ongoing phenomenon that occurs in the global system of interconnected populations.

Seed dispersers as disease vectors: bird transmission of mistletoe seeds to plant hosts

The relationship between mistletoes and birds has been studied from the perspectives of mutualism... more The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We describe the patterns of transmission of the seeds of Tristerix aphyllus, an endophytic Chilean mistletoe, on two of its columnar cacti hosts (Eulychnia acida and Echinopsis skottsbergii) by the Chilean Mockingbird Mimus thenca. In north-central Chile, these cacti grow in relatively discrete subpopulations on north-facing slopes. We measured variation in seed transmission within 10 subpopulations varying in species composition, host density, parasite density, parasite prevalence (defined as the percentage of hosts infested in a given population), and disperser abundance. Seed transmission was independent of species, but was strongly dependent on prior parasitism. Parasitized individuals received seeds much more frequently than expected from their relative abundance. We found no correlation between the density of hosts and seed transmission. We found strong positive correlations, however, between parasite prevalence and seed transmission to both parasitized and nonparasitized hosts. Seed transmission of T. aphyllus seeds by M. thenca appeared to be frequency-rather than densitydependent. Seed transmission was also tightly and positively correlated with the abundance of seed-dispersing birds at each site. Because bird abundance and parasite prevalence were correlated, we conducted path analysis to disentangle their relative effect on seed transmission. A model including only the direct effect of bird abundance and the indirect effect of parasite prevalence through bird abundance explained roughly the same variance as a full model including both the direct and indirect effects of bird abundance and prevalence on seed transmission. Apparently, variation in bird abundance was the main determinant of variation in transmission. We suggest that mistletoes, host plants, and the birds that disperse mistletoe seeds are systems well suited for studies of the ecological and evolutionary dynamics of disease transmission.

Frugivore-Mediated Selection in a habitat transformation scenario

Scientific Reports, 2017

Plant-animal interactions are strong drivers of phenotypic evolution. However, the extent to whic... more Plant-animal interactions are strong drivers of phenotypic evolution. However, the extent to which anthropogenic habitat transformation creates new selective scenarios for plant-animal interactions is a little explored subject. We examined the effects of native forest replacement by exotic Eucalyptus trees on the frugivore-mediated phenotypic selection coefficients imposed by the relict marsupial Dromiciops gliroides upon traits involved in frugivore attraction and germination success of the mistletoe Tristerix corymbosus (Loranthaceae). We found significant gradients for seed weight and sugar content along the native-transformed habitat gradient. While selection for larger seed weight was more relevant in native habitats, fruits with intermediate sugar content were promoted in transformed habitats. The spatial habitat structure and microclimate features such as the degree of sunlight received influenced the natural selection processes, as they correlated with the phenotypic traits analysed. The response of this plant-frugivore interaction to human disturbance seemed to be context-dependent, in which extremely transformed habitats would offer new opportunities for natural selection on dispersal-related traits. Even in recent transformation events like this, human disturbance acts as a strong contemporary evolution driver. Plant-animal interactions are strong drivers of reciprocal phenotypic evolution 1 , leading to coevolved traits that are dynamic through time and space 2,3. However, this complex eco-evolutionary system is challenged by a world in constant change in which many anthropogenic biodiversity-loss drivers are altering natural habitats 4. Each species responds to habitat disturbance according to their life history traits 5 , which explains, at least in part, the variety of responses to human disturbance observed in nature 6,7. For example, while habitat fragmentation often modifies species abundances due to area and edge effects 8,9 , habitat transformation, involving the partial or complete replacement of the native vegetation by exotic species 10,11 , usually leads to more dramatic effects such as local extinction, arrival of new species, and changes in species composition. Even though seed dispersal is a key stage in a plant's life cycle that determines the demographic response to human-induced habitat disturbance 12,13 , studies examining phenotypic selection on seed dispersal in human-induced transformed habitats are scarce compared to those focused on pollination interactions (e.g., ref. 14). Seed dispersal shapes spatial and genetic structure of plants 15 which determines the potential of plant populations to respond to changes in selective scenarios. Recent studies showed that anthropogenic defauna-tion collapses seed dispersal and changes allelic frequencies 16,17 , but little is known about potential contemporary evolution on seed dispersal 18. Human activities are remarkably strong selection forces 19 which are able to change the eco-evolutionary scenario in which seed dispersal interactions occur. We examined the importance of frugivore-mediated phenotypic selection in a highly specialized system (a mistletoe with a single disperser species), which would allow us to examine the effects of frugivore-mediated selection without the background noise that redundant frugivore species might impose on generalist plant-frugivore system, along a habitat disturbance gradient to answer the following questions: (1) Does frugivore-mediated selection on fruit traits change along a habitat transformation gradient? (2) Do native and transformed habitats differ sufficiently in structural and microclimate conditions to create spatially variable selection scenarios for fruit traits? We hypothesize that habitat structural and microclimate features affect dispersal-related fruit traits and consequently habitat transformation would change the magnitude, direction and significance of phenotypic selection coefficients acting upon them.

Objective recognition of guilds: testing for statistically significant species clusters

Oecologia, 1990

Presently, no standard protocol for objective guild recognition is consistently used by ecologist... more Presently, no standard protocol for objective guild recognition is consistently used by ecologists. Apart from intuitive designations of guild membership, four statistically-based protocols are currently available: those of Colwell (1977); Holmes (1979); Lawlor (1980); and Adams (1985). The first is based on nearest-neighbor variance in overlap, the second on multivariate statistics, the third on clustering techniques, and the fourth on psychometric analysis. We propose a fifth approach, first developed by Strauss (1982) for purposes other than guild recognition. We advocate the use of bootstrap procedures to resample any given empirical matrix of consumers by resources, within constraints set by either of four different randomization algorithms. Subsequently, pseudovalues of similarity in resource use between the consumers are computed and their frequency distribution is displayed in a histogram. The overlap pseudovalue that exceeds percentile 95 may be considered statistically significant and chosen as the cutoff point that identifies significant species clusters (guilds) in the original (empirical) similarity matrix. We exemplify use of this approach with the food-niche matrix obtained for a predatory assemblage in California, and discuss its implications for the general analysis of guild structure.

Indirect interactions in a microcosm-assembled cladoceran community: implications for apparent competition

Oikos, Apr 1, 2002

Apparent competition occurs when species that otherwise may not directly interact still exhibit n... more Apparent competition occurs when species that otherwise may not directly interact still exhibit negative indirect effects on one another because they share a food-limited predator (enemy). Even though this type of indirect interaction has received significant theoretical and empirical attention, alternative mechanisms producing similar results have not been considered in the literature. In this paper we document the results of a series of microcosm experiments aimed to evaluate the importance of the generalist consumer Daphnia ambigua upon the relative abundance of the more specialized Moina micrura and Ceriodaphnia dubia (Cladocera). We compared the population parameters of M. micrura and C. dubia when alone, in coexistence, and in the presence and absence of D. ambigua. While M. micrura and C. dubia did not show evidence for interspecific competition, the addition of D. ambigua promoted a reduction in the maximal population density of M. micrura, causing a pattern of indirect competition with C. dubia that resembles predator-mediated apparent competition. This result suggests that non-predatory interactions need to be considered as a potential source of apparent interactions in natural communities.

Observaciones preliminares sobre uso de recursos y temperatura de actividad en ensambles de hormigas granívoras del Norte de Chile

Acta Entomologica Chilena, 1996

Acceso de usuarios registrados. Acceso de usuarios registrados Usuario Contraseña. ...

Depredacion sobre lagartijas en chile central : importancia relativa de atributos ecologicos y morfologicos

Revista Chilena De Historia Natural, 1990

RESUMEN Estimamos la intensidad de depredación experimentada por cinco especies de lagartijas del... more RESUMEN Estimamos la intensidad de depredación experimentada por cinco especies de lagartijas del género Liolaemus, en dos localidades de Chile central. La aplicación de un algoritmo de reorganización tipo bootstrap al índice de depredación de Schoener (1979) permitió realizar contrastes estadísticos interespecíficos así como entre localidades. Las lagartijas que habitan en la localidad de menor altitud (San Carlos) sufrieron globalmente una mayor depredación,la que adjudicamos a la presencia de Philodryas chamissonis y Callopistes palluma, ambos depredadores ausentes en la localidad de mayor altura (El Colorado). Al examinar la abundancia relativa de las lagartijas, se observa que ellas no son consumidas según su disponibilidad en ninguno de los sitios de estudio. En San Carlos, el tamaño corporal no se correlaciona con la intensidad de la depredación. Sin embargo, la lagartija que usa el suelo con mayor frecuencia experimenta una depredación desproporcionadamente mayor en comparación a las especies rriás saxícolas. En El Colorado la lagartija de mayor tamaño corporal es la que experimenta una mayor depredación, independientemente de su uso del microhábitat. Estos resultados sugieren que, a diferencia de la abundancia relativa, los atributos de uso del microhábitat y tamaño corporal son importantes en determinar las intensidades de depredación que experimentan las lagartijas.

Allozyme variation and genetic relatedness in a population of Camponotus chilensis (Hymenoptera: Formicidae) in Chile Variación alozímica y parentesco genético en una población de Camponotus chilensis (Hymenoptera: Formicidae) en Chile

We presentdataon allozyme variability of7loci in l6colonies of a population of Camponotus chilens... more We presentdataon allozyme variability of7loci in l6colonies of a population of Camponotus chilensis. With thisinformation, we infer the reproductive structure of the colonies and calculate the coefficient of relatedness of workers within colonies. Colonies of C. chilensis may ha ve from one to at least four queens, based u pon both number of genotypes and degree of relatedness among workers. Our results suggest an association between the body mass of workers and their genotype for MDH-2, with more large heterozygous individuals.

Indirect interactions in a microcosm‐assembled cladoceran community: implications for apparent competition

Oikos, Jan 1, 2002

. Indirect interactions in a microcosm-assembled cladoceran community: implications for apparent ... more . Indirect interactions in a microcosm-assembled cladoceran community: implications for apparent competition. -Oikos 97: 111-115. Apparent competition occurs when species that otherwise may not directly interact still exhibit negative indirect effects on one another because they share a food-limited predator (enemy). Even though this type of indirect interaction has received significant theoretical and empirical attention, alternative mechanisms producing similar results have not been considered in the literature. In this paper we document the results of a series of microcosm experiments aimed to evaluate the importance of the generalist consumer Daphnia ambigua upon the relative abundance of the more specialized Moina micrura and Ceriodaphnia dubia (Cladocera). We compared the population parameters of M. micrura and C. dubia when alone, in coexistence, and in the presence and absence of D. ambigua. While M. micrura and C. dubia did not show evidence for interspecific competition, the addition of D. ambigua promoted a reduction in the maximal population density of M. micrura, causing a pattern of indirect competition with C. dubia that resembles predator-mediated apparent competition. This result suggests that non-predatory interactions need to be considered as a potential source of apparent interactions in natural communities.

Niche relationships between two sympatric Liolaemus lizards in a fluctuating environment: the" lean" versus" feast" scenario

Journal of Herpetology, Jan 1, 1989

Reconexión de una red planta-polinizador en un ambiente incendiado: interacciones perdidas y encontradas

by Rodrigo Medel and Milton Ortuño

Capítulo IV.I. en San Martín, J. (Ed.) 2022. Los Bosques Relictos de Ruil: Ecología, Biodiversidad, Conservación y Restauración. El Sur Impresiones Ltda.

Adaptación y selección natural (En: Introduccion a la Biologia Evolutiva)

Mediterranean type of climatic adaptation in the physiological ecology of rodent species

Ecological …, Jan 1, 1995

Capitulo 21. Efectos de la transformación del hábitat por plantaciones forestales sobre las interacciones mutualistas del muérdago Tristerix corymbosus

by Caren Vega and Rodrigo Medel

Biodiversidad y Ecología de los Bosques Costeros de Chile. (C. Smith-Ramírez y F.A. Squeo, eds) Editorial Universidad de Los Lagos (2019):, 2020

Habitat transformation due to the replacement of native forests by exotic tree plantations is a s... more Habitat transformation due to the replacement of native forests by
exotic tree plantations is a strong biodiversity loss driver. However, the
effects on ecological and evolutionary processes remain little
understood. We used a highly specialized tripartite mutualistic system,
composed of a mistletoe, its pollinator and its seed disperser, to study
the effects of habitat transformation. Mistletoes were more abundant
and densely aggregated in the transformed habitat (abandoned
Eucalyptus plantations), receiving more visits from both mutualists.
Interestingly, mistletoes inhabiting the transformed habitat had lower
levels ofgenetic diversity and were more related among each other than
those inhabiting the native forest. Our results suggest that despite the
ecological advantage of living in a transformed habitat, mistletoes pay
a significant price in terms of genetic variation and inbreeding

Selección mediada por polinizadores sobre el fenotipo floral: examinando causas y blancos de selección natural

En: Medel, R., M.A. Aizen & R. Zamora (eds.). 2009. Ecología y evolución de interacciones planta-animal. Editorial Universitaria, Chile., 2009

Una de las características más conspicuas de las angiospermas es la inmensa diversificación flora... more Una de las características más conspicuas de las angiospermas es la inmensa diversificación floral experimentada por el grupo desde su expansión evolutiva a mediados del Cretácico hasta el presente (Heywood 1985). Precisamente fue aquella variación de colores, fragancias y arquitectura de las flores lo que llamó poderosamente la atención a Darwin, quien se interesó por comprender los mecanismos florales involucrados en la reproducción de las plantas y el papel de los polinizadores en promover la diversificación floral (Darwin 1862). Actualmente es conocido que la mayor parte de las especies de angiospermas hermafroditas han adquirido a lo largo de su evolución diversos fenotipos que les permiten atraer polinizadores, exportar e importar polen de otros individuos conespecíficos, promoviendo así el entrecruzamiento por sobre la autofecundación. Esta estrategia suele ser ventajosa ya que la autofecundación usualmente conlleva depresión por endogamia en la progenie, y disminución en los componentes masculino y femenino de la adecuación biológica de la planta (Barrett 1988(Barrett , 1998. La ventaja del entrecruzamiento se ha expresado en una extraordinaria diversidad de fenotipos florales relevantes para la polinización, los cuales probablemente han experimentado una alta tasa de cambio evolutivo desde las primeras angiospermas (Pellmyr 2002). Sin embargo, solamente desde mediados de la década de 1980, con la vinculación formal de procedimientos de selección natural con elementos de la genética cuantitativa en poblaciones naturales (Lande y Arnold 1983) es que contamos con una batería de procedimientos robustos que permiten estimar la fuerza, dirección y forma de la selección mediada por los polinizadores y así conocer la manera en que los polinizadores participan en la evolución floral. Una forma de indagar de qué manera ocurre la evolución fenotípica de las plantas con flores consiste en estimar el impacto de los polinizadores en la evolución de los fenotipos a través de los componentes de la adecuación. En teoría, la selección natural debiera producir fenotipos florales que maximicen el fitness masculino y femenino a través de la exportación e importación de polen, respectivamente (Morgan 1992). El análisis de la covariación entre los fenotipos asociado a la atracción a polinizadores y el fitness (masculino, femenino, o ambos) de la planta proporciona información sobre la fuerza y naturaleza de la selección natural actuando sobre los fenotipos. Tal relación se puede expresar mediante la magnitud de la fuerza selectiva impuesta por los polinizadores sobre los fenotipos, la dirección del cambio del fenotipo promedio en la población de plantas, y la forma del impacto o cambio en la varianza de la distribución. Globalmente, todos estos descriptores pueden ser resumidos en coeficientes que permi-

ABEJAS EN CHILE: desde su biología hacia su conservación

ABEJAS EN CHILE: desde su biología hacia su conservación es un libro realizado bajo el contexto d... more

La intima relación entre ciencia y filosofía

Palabra Publica, 2024

Breve comentario de divulgación sobre la relación entre ciencia y filosofía. Específicamente se p... more

¿Qué son los algoritmos?

Revista Occidente, 2020

En la medida que las sociedades humanas se hacen crecientemente dependientes de los avances tecno... more En la medida que las sociedades humanas se hacen crecientemente dependientes de los avances tecnológicos, los algoritmos se constituyen en estructuras simbólicas cada vez más importantes de organización social. A pesar de estar presentes en la mayor parte de nuestras acciones cotidianas, normalmente no nos percatarnos de su operación ni influencia. Los algoritmos son construcciones matemáticas elaboradas que pertenecen al dominio de las ciencias de la computación, donde se han desarrollado históricamente desde formas muy simples hasta estructuras altamente sofisticadas que contribuyen a la toma de decisiones en un mundo cada vez más complejo, global, e interconectado. En esta contribución se desarrollará una breve perspectiva histórica del concepto, enfatizando algunos hitos específicos que permitirán esclarecer, al menos en parte, el significado y función de los algoritmos en el mundo contemporáneo.

Moralidad humana: ¿Culturalmente aprendida o innatamente heredada?

Iniciativa Laicista 51, 2020

Reseña de libro. Sober, E. (2024). The philosophy of evolutionary theory: concepts, inferences and probabilities. Cambridge University Press, Cambridge.

Ludus Vitalis, 2025

Reseña de libro. Sober, E. (2024). The philosophy of evolutionary theory: concepts, inferences an... more Reseña de libro. Sober, E. (2024). The philosophy of evolutionary theory: concepts, inferences and probabilities. Cambridge University Press, Cambridge. La reciente publicación en filosofía de la biología evolutiva de Elliott Sober es una obra que se inscribe en una tendencia de la filosofía de las ciencias que busca profundizar analíticamente en temas propios de las ciencias particulares, aunque ello implique, como es de esperar, sacrificar reflexiones sobre tópicos más generales. Sober, heredero intelectual de los fundadores de la filosofía de la biología como Margorie Grene, David Hull, Michael Ruse y William Wimsatt, entre otros, pertenece a la segunda generación de filósofos de la biología, siendo uno de los responsables del crecimiento y consolidación de esta disciplina, y en particular, en el desarrollo de la filosofía de la biología evolutiva.

La subvalorada interacción entre aves no especializadas y flores

Cerca del 90% de las plantas con flores del planeta requieren de polinizadores para la transferen... more Cerca del 90% de las plantas con flores del planeta requieren de polinizadores para la transferencia de polen. Esta enorme dependencia sugiere que la amplia diversidad de sistemas reproductivos en plantas se ha desplegado históricamente en estrecha asociación con animales que, al alimentarse del néctar de las flores, actúan incidentalmente en la