Papers by Fernando Valladares
Lichenologist, 1992
The ultrastructure of the symbionts within the algal layer of Lasallia hispamca and Umbilicaria s... more The ultrastructure of the symbionts within the algal layer of Lasallia hispamca and Umbilicaria spodochroa has been investigated by applying stereological techniques to quantify cellular organelles and structures. The stereological par- ameters calculated were volume density (Vv) and surface density (Sv). To obtain these parameters for each cellular structure, a systematic sampling of photographic fields of the algal layer for each sample was utilized. Significant differences between the two lichen species with respect to both symbionts were observed. The cellular structures of the photobiont that differed the most between the two lichen species were the chloroplast, which differed by 15",, in the Vv values and 25",, in the Sv values, the pyrenoid (as a whole and in the diameter of pyrenoglobuli) and the mitochondria. With respect to the mycobiont, the vacuolar apparatus was of great importance in characterizing the two species, as was to a lesser extent the protoplast vol...
La informacion cuantitativa sobre la radiacion disponible en el sotobosque es crucial para la com... more La informacion cuantitativa sobre la radiacion disponible en el sotobosque es crucial para la comprension de multitud de aspectos relacionados con la ecologia y dinamica del bosque. Dado que la gestion del bosque es en buena medida la gestion de la luz, la combinacion de estudios sobre ecofisiologia, heterogeneidad luminica, dinamica forestal y cambio global representa un punto de encuentro entre la ecologia y la gestion forestal, algo muy necesario en ecosistemas mediterraneos donde las incertidumbres son grandes y las predicciones poco optimistas. En este trabajo se presentan resultados sobre la heterogeneidad temporal y espacial de la luz en el sotobosque de diversas formaciones forestales ibericas (encinares, alcornocales, pinares, abedulares y hayedos). En general se observa que las formaciones mediterraneas tiene una mayor estructura espacial y una mayor heterogeneidad luminica que los bosques no mediterraneos, que la radiacion disponible bajo un dosel es inversamente proporci...
Annals of Forest Science
& Key message In our study of colonisation of abandoned farmland by Juniperus thurifera L., envir... more & Key message In our study of colonisation of abandoned farmland by Juniperus thurifera L., environmental and geographic distances were stronger drivers of functional differentiation among trees than genetic distance and tree intrinsic features. However, these effects varied both along the colonisation gradient and across predictors' values, highlighting the complexity of the conditions under which functional diversity of forests is maximised. & Context Forest expansion after land abandonment is changing Mediterranean landscapes, but the underlying ecological and evolutionary processes remain poorly understood. & Aims We evaluated whether forest expansion reduces within-stand tree functional distances and whether its environmental, geographical and genetic drivers vary along the expansion gradient. & Methods We sampled Juniperus thurifera in mature, transition and expanding stands along a colonisation gradient in Spain. We measured functional traits, genetic relatedness, surrounding vegetation cover and intrinsic features (size, phytosanitary status) Jesus Villellas and Irene Martín-Forés are the co-first authors Handling Editor: Raquel Alfaro-Sánchez Contributions of the co-authors: AH, IMF and FV conceived the study. IMF and BAM carried out sampling. SM, MM and EG performed genetic analyses. JV performed the statistical analyses and wrote the original draft with the help from IMF, AH, FV and BAM. All authors revised and approved the final manuscript. This article is part of the topical collection on Establishment of secondgrowth forests in human landscapes: ecological mechanisms and genetic consequences * Jesus Villellas
Forests
Research Highlights: Water use efficiency (WUE) varied along a gradient of Juniperus thurifera (L... more Research Highlights: Water use efficiency (WUE) varied along a gradient of Juniperus thurifera (L.) forest expansion, being higher in recently colonised areas. Background and Objectives: WUE is a classic physiological process of plants that reflects the compromise between carbon assimilation and water loss and has a profound influence on their performance in water-limited environments. Forest expansion in Mediterranean regions associated with land abandonment can influence the WUE of plants due to the existence of two opposing gradients: one of favourable–unfavourable environmental conditions and another one of increased–decreased intraspecific competition, the former increasing and the latter decreasing towards the expanding front. The main objective of this study was to elucidate how the WUE of Juniperus thurifera varied along the stages of forest expansion and to provide insight on how this variation is influenced by intraspecific competition and abiotic factors. Materials and Me...
PLOS ONE
Intraspecific trait variation has been singled out as an important mechanism by which individuals... more Intraspecific trait variation has been singled out as an important mechanism by which individuals can cope with environmental variations and avoid local extinctions. Here we evaluate variation in metamer traits (i.e., traits associated with internodes, petioles and their corresponding leaves) and parameters of chlorophyll fluorescence within and among populations of a neotropical tree, Copaifera langsdorffii. We also evaluated phenotypic plasticity in natural settings comparing traits between shade and sun-exposed metamers. We selected six populations along a climatic gradient ranging from semi-arid to humid and representing three different biomes (Caatinga, Cerrado, and Atlantic Forest). Local climatic conditions significantly affected the morphological and physiological traits of populations. Trait variation among populations was explained mainly by aridity index and evapotranspiration. Individuals from drier regions had lower specific leaf area (SLA), lower investment in leaf area per total dry mass of metamer (LARm), lower specific petiole length (SPL) and lower potential quantum yield (Fv/Fm, only for sun-exposed metamers). Populations from locations with greater environmental heterogeneity (interannual variation) had greater plasticity in response to light for Fv/Fm and electron transport rate (ETR) and morphological traits related to the hydraulic and biomechanical aspects of the leaves (petiole length, internode length and SPL). High intraspecific variation in metamer traits in C. langsdorffii coupled with its ability to modify these traits in response to different climate conditions can explain the success of the species over a range of different habitats and represent important factors for the persistence of this species in the face of climate change.
Tree physiology, Jan 21, 2017
Pine (Pinus) species exhibit extensive variation in needle shape and size between juvenile (prima... more Pine (Pinus) species exhibit extensive variation in needle shape and size between juvenile (primary) and adult (secondary) needles (heteroblasty), but few studies have quantified the changes in needle morphological, anatomical and chemical traits upon juvenile-to-adult transition. Mediterranean pines keep juvenile needles longer than most other pines, implying that juvenile needles play a particularly significant role in seedling and sapling establishment in this environment. We studied needle anatomical, morphological and chemical characteristics in juvenile and different-aged adult needles in Mediterranean pines Pinus halepensis Mill., Pinus pinea L. and Pinus nigra J. F. Arnold subsp. salzmannii (Dunal) Franco hypothesizing that needle anatomical modifications upon juvenile-to-adult transition lead to a trade-off between investments in support and photosynthetic tissues, and that analogous changes occur with needle aging albeit to a lower degree. Compared with adult needles, juve...
Proceedings of the National Academy of Sciences of the United States of America, Dec 1, 2017
Our ability to understand and predict the response of ecosystems to a changing environment depend... more Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration-specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen ([Formula: see text]) and phosphorus ([Formula: see text]), we characterize how traits vary within and among over 50,000 [Formula: see text]-km cells across the entire ...
Ecology Letters
The importance of biodiversity in supporting ecosystem functioning is generally well accepted. Ho... more The importance of biodiversity in supporting ecosystem functioning is generally well accepted. However, most evidence comes from small-scale studies, and scaling-up patterns of biodiversityecosystem functioning (B-EF) remains challenging, in part because the importance of environmental factors in shaping B-EF relations is poorly understood. Using a forest research platform in which 26 ecosystem functions were measured along gradients of tree species richness in six regions across Europe, we investigated the extent and the potential drivers of context dependency of B-EF relations. Despite considerable variation in species richness effects across the continent, we found a tendency for stronger B-EF relations in drier climates as well as in areas with longer growing seasons and more functionally diverse tree species. The importance of water availability in driving context dependency suggests that as water limitation increases under climate change, biodiversity may become even more important to support high levels of functioning in European forests.
Ecology and Evolution
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Nature ecology & evolution, Jan 17, 2017
Climate change, land-use change, pollution and exploitation are among the main drivers of species... more Climate change, land-use change, pollution and exploitation are among the main drivers of species' population trends; however, their relative importance is much debated. We used a unique collection of over 1,000 local population time series in 22 communities across terrestrial, freshwater and marine realms within central Europe to compare the impacts of long-term temperature change and other environmental drivers from 1980 onwards. To disentangle different drivers, we related species' population trends to species- and driver-specific attributes, such as temperature and habitat preference or pollution tolerance. We found a consistent impact of temperature change on the local abundances of terrestrial species. Populations of warm-dwelling species increased more than those of cold-dwelling species. In contrast, impacts of temperature change on aquatic species' abundances were variable. Effects of temperature preference were more consistent in terrestrial communities than ef...
Scientific reports, Jan 24, 2017
The Antarctic Peninsula has had a globally large increase in mean annual temperature from the 195... more The Antarctic Peninsula has had a globally large increase in mean annual temperature from the 1951 to 1998 followed by a decline that still continues. The challenge is now to unveil whether these recent, complex and somewhat unexpected climatic changes are biologically relevant. We were able to do this by determining the growth of six lichen species on recently deglaciated surfaces over the last 24 years. Between 1991 and 2002, when mean summer temperature (MST) rose by 0.42 °C, five of the six species responded with increased growth. MST declined by 0.58 °C between 2002 and 2015 with most species showing a fall in growth rate and two of which showed a collapse with the loss of large individuals due to a combination of increased snow fall and longer snow cover duration. Increased precipitation can, counter-intuitively, have major negative effects when it falls as snow at cooler temperatures. The recent Antarctic cooling is having easily detectable and deleterious impacts on slow gro...
Quercus, Mar 1, 2012
Información del artículo Florivoría frente a polinización.
Forest Ecology and Management, 2016
Highlights Forest fragmentation reduces tree-to-tree competition for water resources. Reduced... more Highlights Forest fragmentation reduces tree-to-tree competition for water resources. Reduced competition entails enhanced acorn production at small forest fragments. Local conditions, like fragmentation, may override climatic effects on acorn crops. Positive effects of fragmentation need to be scaled up temporally and spatially.
Botanical Journal of the Linnean Society, 2014
Flower size and number usually evolve under pollinator-mediated selection. However, hot, dry envi... more Flower size and number usually evolve under pollinator-mediated selection. However, hot, dry environments can also modulate display, counteracting pollinator attraction. Increased pollen deposition on larger flower displays may not involve higher female fitness. Consequently, stressful conditions may constrain flower size, favouring smaller-sized flowers. The large-flowered, self-incompatible Mediterranean shrub Cistus ladanifer was used to test that: (1) this species suffers pollen limitation; (2) pollinators are spatially-temporally variable and differentially visit plants with more/larger flowers; (3) increased visits enhance reproduction under pollen limitation; (4) stressful conditions reduce female fitness of larger displays; and (5) phenotypic selection on floral display is not just pollinator-mediated. We evaluated pollen limitation, related floral display to pollinator visits and fruit and seed production and estimated phenotypic selection. Flower size was 7.2-10.5 cm and varied spatially-temporally. Visitation rates (total visits/50 min) ranged from 0.26 to 0.43 and increased with flower size. Fruit set averaged 80% and seed number averaged 855, but only fruit set varied between populations and years. Selection towards larger flowers was detected under conditions of pollen limitation. Otherwise, we detected stabilizing selection on flower size and negative selection on flower number. Our results suggest that selection on floral display is not only pollinator-dependent through female fitness in C. ladanifer.
En este capítulo mostraremos que, tanto el clima mediterráneo como la estructura y funcionamiento... more En este capítulo mostraremos que, tanto el clima mediterráneo como la estructura y funcionamiento de los ecosistemas mediterráneos, han estado en constante cambio durante los últimos millones de años. Veremos la importancia de incluir la intervención humana para comprender los procesos que han dado lugar a los ecosistemas que ahora tenemos. Repasaremos las principales amenazas actuales que se ciernen sobre los ecosistemas mediterráneos, analizando la importancia relativa de los cinco principales motores de cambio ambiental, con especial incidencia en el cambio climático y los cambios de uso del terreno. Finalmente, resumiremos algunos aspectos que deben tenerse en cuenta en la gestión de los ecosistemas mediterráneos, notables por su elevada diversidad biológica.
Frontiers in Plant Science, 2015
The consequences of global change for the maintenance of species diversity will depend on the sum... more The consequences of global change for the maintenance of species diversity will depend on the sum of each species responses to the environment and on the interactions among them. A wide ecological literature supports that these species-specific responses can arise from factors related to life strategies, evolutionary history and intraspecific variation, and also from environmental variation in space and time. In the light of recent advances from coexistence theory combined with mechanistic explanations of diversity maintenance, we discuss how global change drivers can influence species coexistence. We revise the importance of both competition and facilitation for understanding coexistence in different ecosystems, address the influence of phylogenetic relatedness, functional traits, phenotypic plasticity and intraspecific variability, and discuss lessons learnt from invasion ecology. While most previous studies have focused their efforts on disentangling the mechanisms that maintain the biological diversity in species-rich ecosystems such as tropical forests, grasslands and coral reefs, we argue that much can be learnt from pauci-specific communities where functional variability within each species, together with demographic and stochastic processes becomes key to understand species interactions and eventually community responses to global change.
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Papers by Fernando Valladares