Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genu... more Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.
Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. ... more Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. Nocturnal spiders, however, face different conditions due to the type of prey found at night. A field study was conducted to observe the activity of adult females of Eriophora edax in their natural environment, and to analyze their predation efficiency and web retention properties. Most of the spiders were observed around sunset, which suggests that E. edax tends to build webs in the early evening. In order to evaluate the predation efficiency of E. edax we compared its behavior and web retention properties with the behavior of a diurnal orb-weaving spider, Verrucosa arenata. Two prey types, a diurnal Hymenoptera and a nocturnal Lepidoptera, were selected and presented to the spiders, to record approach time and prey capture time. The results showed that E. edax spent more time to capture Hymenoptera than to capture Lepidoptera. During the experiments of web prey retention time, Hymenoptera consistently showed greater tumbling than Lepidoptera, but the total retention time was the same for both prey types. Our results showed that E. edax forages strictly at night and, in terms of prey capture and web retention, was more efficient when preying on Lepidoptera.
The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal st... more The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal stages. The 1st group was exclusively offered eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), a standard diet for O. majusculus production. The 2nd group was exclusively offered 4th instars of the pea aphid, Acyrtosiphon pisum (Harris). Subsequently, adult predatory behavior in experimental arenas containing A. pisium was recorded using 2 video cameras. One camera permitted observation of the predatorÕs contact with the prey, where the 2nd camera viewed the arena from above to record the path taken by O. majusculus adults before and after contact with prey. When O. majusculus were reared on aphids, adult bugs successfully located and consumed 55% of experimental prey and continued prey search behavior after each aphid meal. O. majusculus adults that had no experience of aphid predation as nymphs, did not prey on aphids in the experimental arena. The mean walking speed of this group of predators increased from 5.9 Ϯ 1.2 mm/s to 9.8 Ϯ 0.7 mm/s after contact or detection of prey, indicating that predators rapidly moved away from unfamiliar prey. Moreover, for egg-reared O. majusculus, all contacts between aphid and predator were lateral, along the side of the prey and were effectively repelled by an aphid kicking response. In contrast, 83% of attacks by aphid-reared O. majusculus were directed at the head or posterior abdomen for which the prey could not defend themselves adequately. When egg-reared O. majusculus were exposed to novel aphid prey for 1Ð 8 d, the frequency of aphid attack increased signiÞcantly. We conclude that the standard diet used for rearing O. majusculus may adversely affect the efÞciency of this predator as an agent of biological control.
The distribution of female Leucauge venusta (Walckenaer 1841) in a coffee plantation in southern ... more The distribution of female Leucauge venusta (Walckenaer 1841) in a coffee plantation in southern Mexico was studied in order to determine the vertical distribution of this spider. Principal component analysis clearly identified the presence of three distinct groups of L. venusta webs, based on the number of spirals/web and principally on the height at which the webs were located; most L. venusta webs (63/100) were close to the ground. Spiders on high webs (153.8 ± 3.6 cm above ground, mean ± S.E.) were significantly larger and heavier than spiders on lower webs. Large spiders had significantly larger, better developed ovaries, than smaller conspecifics, presumably indicative of sexual maturity. Significantly more insects were captured by sticky traps placed at 50 cm height than in the traps placed at 150 cm height; the most numerous captures were Diptera. However, insects caught at 150 cm were signifi.cantly larger than those caught at 50 cm above ground. We concluded that as sexual development proceeds, the spider increases the height at which the web is constructed. This vertical migration is associated with changes in web construction and the type of prey captured. These results are discussed in terms of ietraspecific competition, predation risks and sexual selection.
In the Yucatan Peninsula, the ponerine ant Neoponera villosa nests almost exclusively in tank bro... more In the Yucatan Peninsula, the ponerine ant Neoponera villosa nests almost exclusively in tank bromeliads, Aechmea bracteata. In this study, we aimed to determine the factors influencing nest site selection during nest relocation which is regularly promoted by hurricanes in this area. Using ants with and without previous experience of Ae. bracteata, we tested their preference for refuges consisting of Ae. bracteata leaves over two other bromeliads, Ae. bromeliifolia and Ananas comosus. We further evaluated bromeliad-associated traits that could influence nest site selection (form and size). Workers with and without previous contact with Ae. bracteata significantly preferred this species over others, suggesting the existence of an innate attraction to this bromeliad. However, preference was not influenced by previous contact with Ae. bracteata. Workers easily discriminated between shelters of Ae. bracteata and A. comosus, but not those of the closely related Ae. bromeliifolia. In mark...
Fragmentation is the third cause of the biodiversity declination. Population genetic studies usin... more Fragmentation is the third cause of the biodiversity declination. Population genetic studies using Lepidoptera as the model species in the context of loss of habitat are scarce, particularly for tropical areas. We chose a widespread butterfly from Mexico as the model species to explore how changes of habitat characteristics (undisturbed forest, anthropogenic disturbances, and coastal areas), and climatic conditions affect genetic diversity and population structure. The Nymphalidae Eunica tatila is a common species in the Yucatan Peninsula considered to be a bio-indicator of undisturbed tropical forest, with migratory potential and a possible sex-biased dispersal. We genotyped 323 individuals collected in eight undisturbed areas, using four Inter Simple Sequence Repeats primers. Results show a high genetic diversity and no population structure. Temperature and shrub density present a positive and significant relationship with polymorphism values. Furthermore, our results show the pos...
CITES is an international agreement between governments to ensure that international trade in spe... more CITES is an international agreement between governments to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Regarding spiders, all species listed in CITES are tarantulas. They are included in Appendix II, meaning that they are species that are not necessarily now threatened with extinction but that they may become so unless trade is closely controlled. Many tarantulas are legally and illegally traded in the pet market and they are one of the most traded invertebrate groups. Originally, the CITES list published in 1995 included all the current species of the genus Brachypelma Simon, 1891 plus Aphonopelma pallidum (F. O. Pickard-Cambridge, 1897) and the so-called Aphonopelma albiceps (Pocock, 1903). After that, some taxonomic changes were done, as well as descriptions of new species in the genus Brachypelma. The objective of this paper is to assess the 21 taxonomically valid spider species listed on CITES according to the IUCN c...
A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested thoug... more A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested though some, such as the specialized Eucharitidae parasitoids, may cause direct damage to their hosts. Ants are known to discriminate between nestmates and non-nestmates, but whether they recognize the strength of a threat and their capacity to adjust their behavior accordingly have not been fully explored. We aimed to determine whether Ectatomma tuberculatum ants exhibited specific behavioral responses to potential or actual intruders posing different threats to the host colony and to contribute to an understanding of complex ant-eucharitid interactions. Behavioral responses differed significantly according to intruder type. Ants evicted intruders that represented a threat to the colony's health (dead ants) or were not suitable as prey items (filter paper, eucharitid parasitoid wasps, non myrmecophilous adult weevils), but killed potential prey (weevil larvae, termites). The timing of detection was in accordance with the nature and size of the intruder: corpses (a potential source of contamination) were detected faster than any other intruder and transported to the refuse piles within 15 min. The structure and complexity of behavioral sequences differed among those intruders that were discarded. Workers not only recognized and discriminated between several distinct intruders but also adjusted their behavior to the type of intruder encountered. Our results confirm the previously documented recognition capabilities of E. tuberculatum workers and reveal a very fine-tuned intruder discrimination response. Colony-level prophylactic and hygienic behavioral responses through effective removal of inedible intruders appears to be the most general and flexible form of defense in ants against a diverse array of intruders. However, this generalized response to both potentially lethal and harmless intruders might have driven the evolution of ant-eucharitid interactions, opening a window for parasitoid attack and allowing adult parasitoid wasps to quickly leave the natal nest unharmed.
Cupiennius salei (Ctenidae) individuals frequently live in association with tank bromeliads, incl... more Cupiennius salei (Ctenidae) individuals frequently live in association with tank bromeliads, including Aechmea bracteata, in Quintana Roo (Mexico). Whereas C. salei females without egg sacs hunt over their entire host plant, females carrying egg sacs settle above the A. bracteata reservoirs they have partially sealed with silk. There they avoid predators that use sight to detect their prey, as is known for many bird species. Furthermore, if a danger is more acute, these females dive with their egg sacs into the bromeliad reservoir. An experiment showed that this is not the case for males or females without egg sacs. In addition to the likely abundance of prey found therein, the potential of diving into the tank to protect offspring may explain the close association of this spider with bromeliads. These results show that, although arboreal, C. salei evolved a protective behavior using the water of tank bromeliads to protect offspring.
The species Eunica tatila (Herrich-Schäffer) is present in the Neotropical region and comprises t... more The species Eunica tatila (Herrich-Schäffer) is present in the Neotropical region and comprises three subspecies. In Mexico, only one subspecies is reported: E. t. tatila (Herrich-Schäffer). The Yucatan Peninsula, in southeastern Mexico, is located in a transitional geographical position, between southern Florida, the West Indies and Central America. It is part of a transitional region, important for the dispersion of insects from southern Florida via Cuba and the Yucatan Peninsula. Considering the possibility of the overlapping and delimitation of described subspecies, we sampled different populations in the Yucatan Peninsula to possibly assign a subspecies name and evaluate the magnitude of sexual dimorphism. We collected 591 individuals (♀284, ♂307) in conserved areas. The study of male genitalia led to the identification of Eunica tatila tatilista (Kaye) as a subspecies; however, hypandrium structure and wing pattern analysis suggest a mix of E. t. tatila and E. t. tatilista characteristics. The analysis of sexual dimorphism provided evidence of more complex wing morphs for females, with 12 patterns instead of four as previously described. Our results demonstrate the complexity of characterizing E. tatila and suggest that the Yucatan Peninsula is a transitional zone for subspecies of some butterflies.
As top predators, crocodilians can bioaccumulate high concentrations of persistent organochlorine... more As top predators, crocodilians can bioaccumulate high concentrations of persistent organochlorine pesticides (OCPs) that may have adverse effects on their physiology and health. Recent and illegal uses of OCPs in Mexico could affect populations of the American crocodile (Crocodylus acutus), already threatened by other factors. We analyzed 16 OCP compounds using gas chromatography with electron capture detection in seven infertile eggs and in the substratum of nine nests of American crocodiles in Banco Chinchorro, an atoll off the Mexican coast of the Yucatan peninsula. Nest type, clutch size and distance from nests to nearest lagoon were also recorded, while total length of the females attending each nest was measured directly or estimated. Although Banco Chinchorro is isolated from the mainland and from known sources of contamination, OCP residues were detected in egg and nest substratum samples collected from the atoll. OCP concentrations in eggs (range: 0.002-4.000 ppb) and nest substrata (range: 0.01-1.82 ppb) are ten to thousands times lower compared to other studies. Total OCP concentration (sum of all OCPs) in nest substrata decreased with increasing distance from the shore, suggesting that eggs deposited farther from the shore were less exposed to OCP absorption from substratum. Total OCP concentrations in eggs were positively correlated with total length of females and thus with their age. We speculate that maternal transfer from laying females is likely the major source of contaminants in eggs. Future investigations are needed to identify the origin of contaminants in Banco Chinchorro. KEYWORDS.-Banco Chinchorro Biosphere Reserve, contaminants, Crocodylus acutus, Mexico, organochlorine compounds.
As a general rule, spiders exhibit sexual dimorphism and their populations may differ in size acc... more As a general rule, spiders exhibit sexual dimorphism and their populations may differ in size according to season duration and resource availability. However, few studies have focused on dimorphism in tarantulas. Mexican redrump tarantulas, Brachypelma vagans, listed in CITES, have an exceptionally wide distribution. Surprisingly, there are no studies on the possible relationship between the abundance of tarantulas per population and the geographical areas where they are present, or on how the distribution pattern of this spider may affect individual morphological characteristics. Furthermore, there are no studies on sexual dimorphism within the genus Brachypelma. The aim of the study is to determine the existence of sexual and geographical dimorphism in populations of B. vagans. It was observed that the abundance of spiders per population may vary according to the geographical areas where they were recorded. In six localities in southern Mexico, we recorded morphological data on adult tarantulas. Sexual dimorphism was clearly observed at the site that presented numerous spiders characterized by much smaller females. Since the results of this study demonstrate differences in tarantula number of individuals per locality in southern Mexico, they make an important contribution to the conservation of this species.
Crocodilians show universal parental care, but few studies concentrate on this behavior in wild c... more Crocodilians show universal parental care, but few studies concentrate on this behavior in wild crocodiles.We studied nest and hatchling care in genetically pure wild American crocodiles (Crocodylus acutus) on two Caribbean islands of Mexico. From 2006 to 2009 we made direct observations of crocodile behavior upon discovery of nests and groups of hatchlings in Banco Chinchorro. In 2009, we installed camera traps at 4 nests from the time of their discovery to the hatching of each nest, in Banco Chinchorro and Cozumel Island. Twenty-one other species were observed to visit crocodile nests. No nest predation was observed but nine species represented some danger to nests and/or hatchlings. Females seemed to remain in the nest vicinity during incubation. There was variability in nest visit frequencies and no nest defense toward human intrusion was observed. Visit frequency by other species at nests decreased with increased crocodile visitation. Crocodiles mainly visited nests on darker n...
Después de Brasil, México es el segundo país con mayor número de especies de tarántulas. Entre el... more Después de Brasil, México es el segundo país con mayor número de especies de tarántulas. Entre ellas, las Brachypelma
Chemically mediated communication is common in spiders but has been poorly studied in burrowing t... more Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.
... In contrast, island populations on Cozumel and Banco Chinchorro have a larger number of indiv... more ... In contrast, island populations on Cozumel and Banco Chinchorro have a larger number of individuals of all ... Few studies have addressed the impact of tropical cyclones on crocodilians. ... high nest mortality and, as did Ensminger and Nichols (1957) after hurricane Audrey, report ...
Landscape fragmentation usually has a considerable effect on the genetic and demographic viabilit... more Landscape fragmentation usually has a considerable effect on the genetic and demographic viability of most species because it reduces population size and increases isolation among populations. This situation provokes loss of genetic diversity and increased inbreeding that can lead to population or species extinctions. Some studies also show that landscape fragmentation may have no effect on or even positive consequences for species genetic diversity. The protected tarantula, Brachypelma vagans, exhibits a particular situation in the Mexican Caribbean, which has experienced high lowland and coastal fragmentation because of recent increases in agricultural, urban and touristic development. This modified landscape structure creates favorable conditions for establishment of B. vagans populations in rural settlements. Populations of this tarantula have high densities of individuals, principally females and juveniles, and gene dispersion is assumed by the rare males. Within this context, we studied the influence of natural and anthropogenic fragmentation on the genetic diversity of six B. vagans populations (five continental, one insular), together with their spatial organization. Our approach used seven inter simple sequence repeat markers, which are highly polymorphic markers. The 76 loci selected revealed high genetic variability for continental populations and a low, but not critical situation, for the insular population. We detected a good level of gene exchange among continental populations, and an evident and recent isolation of the island population. This species exhibits a metapopulation structure in the lowlands with numerous local populations where mature females exhibit high birth site fidelity. We conclude that this protected species does not exhibit characteristics to warrant its current conservation status, and we propose complete revision of the ecological and genetic situation for B. vagans in particular, and for all species within the genus Brachypelma in general.
The reproductive success of sexually reproducing organisms depends on their capacity to locate po... more The reproductive success of sexually reproducing organisms depends on their capacity to locate potential partners. Research on the mating systems of webbuilding spiders, like other terrestrial invertebrates, has focused around male courtship and the signalling behaviours that facilitate copulation. In contrast, both mate searching and mate location behaviours are largely ignored and rarely quantified in field studies. We conducted a series of field removal experiments to explore the effects of male body size and female dispersion on mate locating behaviour of the golden orb-weaving spider (Nephila clavipes). The number of males that arrived on females' webs was influenced by travel distance, male body size, male body weight and female dispersal. More males returned to webs that were closer to the release point; smaller males experienced a greater weight loss; and larger numbers of males arrived at webs where males had been previously present. Female dispersion influenced the size but not the number of arriving males: males were no more likely to arrive at solitary than aggregations of webs, but males arriving at solitary webs were typically larger than those arriving at aggregations. We discuss the implications of various male traits that could act as selective pressures on male mate location and mate searching behaviours.
The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal st... more The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal stages. The 1st group was exclusively offered eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), a standard diet for O. majusculus production. The 2nd group was exclusively offered 4th instars of the pea aphid, Acyrtosiphon pisum (Harris). Subsequently, adult predatory behavior in experimental arenas containing A. pisium was recorded using 2 video cameras. One camera permitted observation of the predatorÕs contact with the prey, where the 2nd camera viewed the arena from above to record the path taken by O. majusculus adults before and after contact with prey. When O. majusculus were reared on aphids, adult bugs successfully located and consumed 55% of experimental prey and continued prey search behavior after each aphid meal. O. majusculus adults that had no experience of aphid predation as nymphs, did not prey on aphids in the experimental arena. The mean walking speed of this group of predators increased from 5.9 Ϯ 1.2 mm/s to 9.8 Ϯ 0.7 mm/s after contact or detection of prey, indicating that predators rapidly moved away from unfamiliar prey. Moreover, for egg-reared O. majusculus, all contacts between aphid and predator were lateral, along the side of the prey and were effectively repelled by an aphid kicking response. In contrast, 83% of attacks by aphid-reared O. majusculus were directed at the head or posterior abdomen for which the prey could not defend themselves adequately. When egg-reared O. majusculus were exposed to novel aphid prey for 1Ð 8 d, the frequency of aphid attack increased signiÞcantly. We conclude that the standard diet used for rearing O. majusculus may adversely affect the efÞciency of this predator as an agent of biological control.
Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genu... more Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.
Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. ... more Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. Nocturnal spiders, however, face different conditions due to the type of prey found at night. A field study was conducted to observe the activity of adult females of Eriophora edax in their natural environment, and to analyze their predation efficiency and web retention properties. Most of the spiders were observed around sunset, which suggests that E. edax tends to build webs in the early evening. In order to evaluate the predation efficiency of E. edax we compared its behavior and web retention properties with the behavior of a diurnal orb-weaving spider, Verrucosa arenata. Two prey types, a diurnal Hymenoptera and a nocturnal Lepidoptera, were selected and presented to the spiders, to record approach time and prey capture time. The results showed that E. edax spent more time to capture Hymenoptera than to capture Lepidoptera. During the experiments of web prey retention time, Hymenoptera consistently showed greater tumbling than Lepidoptera, but the total retention time was the same for both prey types. Our results showed that E. edax forages strictly at night and, in terms of prey capture and web retention, was more efficient when preying on Lepidoptera.
The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal st... more The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal stages. The 1st group was exclusively offered eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), a standard diet for O. majusculus production. The 2nd group was exclusively offered 4th instars of the pea aphid, Acyrtosiphon pisum (Harris). Subsequently, adult predatory behavior in experimental arenas containing A. pisium was recorded using 2 video cameras. One camera permitted observation of the predatorÕs contact with the prey, where the 2nd camera viewed the arena from above to record the path taken by O. majusculus adults before and after contact with prey. When O. majusculus were reared on aphids, adult bugs successfully located and consumed 55% of experimental prey and continued prey search behavior after each aphid meal. O. majusculus adults that had no experience of aphid predation as nymphs, did not prey on aphids in the experimental arena. The mean walking speed of this group of predators increased from 5.9 Ϯ 1.2 mm/s to 9.8 Ϯ 0.7 mm/s after contact or detection of prey, indicating that predators rapidly moved away from unfamiliar prey. Moreover, for egg-reared O. majusculus, all contacts between aphid and predator were lateral, along the side of the prey and were effectively repelled by an aphid kicking response. In contrast, 83% of attacks by aphid-reared O. majusculus were directed at the head or posterior abdomen for which the prey could not defend themselves adequately. When egg-reared O. majusculus were exposed to novel aphid prey for 1Ð 8 d, the frequency of aphid attack increased signiÞcantly. We conclude that the standard diet used for rearing O. majusculus may adversely affect the efÞciency of this predator as an agent of biological control.
The distribution of female Leucauge venusta (Walckenaer 1841) in a coffee plantation in southern ... more The distribution of female Leucauge venusta (Walckenaer 1841) in a coffee plantation in southern Mexico was studied in order to determine the vertical distribution of this spider. Principal component analysis clearly identified the presence of three distinct groups of L. venusta webs, based on the number of spirals/web and principally on the height at which the webs were located; most L. venusta webs (63/100) were close to the ground. Spiders on high webs (153.8 ± 3.6 cm above ground, mean ± S.E.) were significantly larger and heavier than spiders on lower webs. Large spiders had significantly larger, better developed ovaries, than smaller conspecifics, presumably indicative of sexual maturity. Significantly more insects were captured by sticky traps placed at 50 cm height than in the traps placed at 150 cm height; the most numerous captures were Diptera. However, insects caught at 150 cm were signifi.cantly larger than those caught at 50 cm above ground. We concluded that as sexual development proceeds, the spider increases the height at which the web is constructed. This vertical migration is associated with changes in web construction and the type of prey captured. These results are discussed in terms of ietraspecific competition, predation risks and sexual selection.
In the Yucatan Peninsula, the ponerine ant Neoponera villosa nests almost exclusively in tank bro... more In the Yucatan Peninsula, the ponerine ant Neoponera villosa nests almost exclusively in tank bromeliads, Aechmea bracteata. In this study, we aimed to determine the factors influencing nest site selection during nest relocation which is regularly promoted by hurricanes in this area. Using ants with and without previous experience of Ae. bracteata, we tested their preference for refuges consisting of Ae. bracteata leaves over two other bromeliads, Ae. bromeliifolia and Ananas comosus. We further evaluated bromeliad-associated traits that could influence nest site selection (form and size). Workers with and without previous contact with Ae. bracteata significantly preferred this species over others, suggesting the existence of an innate attraction to this bromeliad. However, preference was not influenced by previous contact with Ae. bracteata. Workers easily discriminated between shelters of Ae. bracteata and A. comosus, but not those of the closely related Ae. bromeliifolia. In mark...
Fragmentation is the third cause of the biodiversity declination. Population genetic studies usin... more Fragmentation is the third cause of the biodiversity declination. Population genetic studies using Lepidoptera as the model species in the context of loss of habitat are scarce, particularly for tropical areas. We chose a widespread butterfly from Mexico as the model species to explore how changes of habitat characteristics (undisturbed forest, anthropogenic disturbances, and coastal areas), and climatic conditions affect genetic diversity and population structure. The Nymphalidae Eunica tatila is a common species in the Yucatan Peninsula considered to be a bio-indicator of undisturbed tropical forest, with migratory potential and a possible sex-biased dispersal. We genotyped 323 individuals collected in eight undisturbed areas, using four Inter Simple Sequence Repeats primers. Results show a high genetic diversity and no population structure. Temperature and shrub density present a positive and significant relationship with polymorphism values. Furthermore, our results show the pos...
CITES is an international agreement between governments to ensure that international trade in spe... more CITES is an international agreement between governments to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Regarding spiders, all species listed in CITES are tarantulas. They are included in Appendix II, meaning that they are species that are not necessarily now threatened with extinction but that they may become so unless trade is closely controlled. Many tarantulas are legally and illegally traded in the pet market and they are one of the most traded invertebrate groups. Originally, the CITES list published in 1995 included all the current species of the genus Brachypelma Simon, 1891 plus Aphonopelma pallidum (F. O. Pickard-Cambridge, 1897) and the so-called Aphonopelma albiceps (Pocock, 1903). After that, some taxonomic changes were done, as well as descriptions of new species in the genus Brachypelma. The objective of this paper is to assess the 21 taxonomically valid spider species listed on CITES according to the IUCN c...
A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested thoug... more A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested though some, such as the specialized Eucharitidae parasitoids, may cause direct damage to their hosts. Ants are known to discriminate between nestmates and non-nestmates, but whether they recognize the strength of a threat and their capacity to adjust their behavior accordingly have not been fully explored. We aimed to determine whether Ectatomma tuberculatum ants exhibited specific behavioral responses to potential or actual intruders posing different threats to the host colony and to contribute to an understanding of complex ant-eucharitid interactions. Behavioral responses differed significantly according to intruder type. Ants evicted intruders that represented a threat to the colony's health (dead ants) or were not suitable as prey items (filter paper, eucharitid parasitoid wasps, non myrmecophilous adult weevils), but killed potential prey (weevil larvae, termites). The timing of detection was in accordance with the nature and size of the intruder: corpses (a potential source of contamination) were detected faster than any other intruder and transported to the refuse piles within 15 min. The structure and complexity of behavioral sequences differed among those intruders that were discarded. Workers not only recognized and discriminated between several distinct intruders but also adjusted their behavior to the type of intruder encountered. Our results confirm the previously documented recognition capabilities of E. tuberculatum workers and reveal a very fine-tuned intruder discrimination response. Colony-level prophylactic and hygienic behavioral responses through effective removal of inedible intruders appears to be the most general and flexible form of defense in ants against a diverse array of intruders. However, this generalized response to both potentially lethal and harmless intruders might have driven the evolution of ant-eucharitid interactions, opening a window for parasitoid attack and allowing adult parasitoid wasps to quickly leave the natal nest unharmed.
Cupiennius salei (Ctenidae) individuals frequently live in association with tank bromeliads, incl... more Cupiennius salei (Ctenidae) individuals frequently live in association with tank bromeliads, including Aechmea bracteata, in Quintana Roo (Mexico). Whereas C. salei females without egg sacs hunt over their entire host plant, females carrying egg sacs settle above the A. bracteata reservoirs they have partially sealed with silk. There they avoid predators that use sight to detect their prey, as is known for many bird species. Furthermore, if a danger is more acute, these females dive with their egg sacs into the bromeliad reservoir. An experiment showed that this is not the case for males or females without egg sacs. In addition to the likely abundance of prey found therein, the potential of diving into the tank to protect offspring may explain the close association of this spider with bromeliads. These results show that, although arboreal, C. salei evolved a protective behavior using the water of tank bromeliads to protect offspring.
The species Eunica tatila (Herrich-Schäffer) is present in the Neotropical region and comprises t... more The species Eunica tatila (Herrich-Schäffer) is present in the Neotropical region and comprises three subspecies. In Mexico, only one subspecies is reported: E. t. tatila (Herrich-Schäffer). The Yucatan Peninsula, in southeastern Mexico, is located in a transitional geographical position, between southern Florida, the West Indies and Central America. It is part of a transitional region, important for the dispersion of insects from southern Florida via Cuba and the Yucatan Peninsula. Considering the possibility of the overlapping and delimitation of described subspecies, we sampled different populations in the Yucatan Peninsula to possibly assign a subspecies name and evaluate the magnitude of sexual dimorphism. We collected 591 individuals (♀284, ♂307) in conserved areas. The study of male genitalia led to the identification of Eunica tatila tatilista (Kaye) as a subspecies; however, hypandrium structure and wing pattern analysis suggest a mix of E. t. tatila and E. t. tatilista characteristics. The analysis of sexual dimorphism provided evidence of more complex wing morphs for females, with 12 patterns instead of four as previously described. Our results demonstrate the complexity of characterizing E. tatila and suggest that the Yucatan Peninsula is a transitional zone for subspecies of some butterflies.
As top predators, crocodilians can bioaccumulate high concentrations of persistent organochlorine... more As top predators, crocodilians can bioaccumulate high concentrations of persistent organochlorine pesticides (OCPs) that may have adverse effects on their physiology and health. Recent and illegal uses of OCPs in Mexico could affect populations of the American crocodile (Crocodylus acutus), already threatened by other factors. We analyzed 16 OCP compounds using gas chromatography with electron capture detection in seven infertile eggs and in the substratum of nine nests of American crocodiles in Banco Chinchorro, an atoll off the Mexican coast of the Yucatan peninsula. Nest type, clutch size and distance from nests to nearest lagoon were also recorded, while total length of the females attending each nest was measured directly or estimated. Although Banco Chinchorro is isolated from the mainland and from known sources of contamination, OCP residues were detected in egg and nest substratum samples collected from the atoll. OCP concentrations in eggs (range: 0.002-4.000 ppb) and nest substrata (range: 0.01-1.82 ppb) are ten to thousands times lower compared to other studies. Total OCP concentration (sum of all OCPs) in nest substrata decreased with increasing distance from the shore, suggesting that eggs deposited farther from the shore were less exposed to OCP absorption from substratum. Total OCP concentrations in eggs were positively correlated with total length of females and thus with their age. We speculate that maternal transfer from laying females is likely the major source of contaminants in eggs. Future investigations are needed to identify the origin of contaminants in Banco Chinchorro. KEYWORDS.-Banco Chinchorro Biosphere Reserve, contaminants, Crocodylus acutus, Mexico, organochlorine compounds.
As a general rule, spiders exhibit sexual dimorphism and their populations may differ in size acc... more As a general rule, spiders exhibit sexual dimorphism and their populations may differ in size according to season duration and resource availability. However, few studies have focused on dimorphism in tarantulas. Mexican redrump tarantulas, Brachypelma vagans, listed in CITES, have an exceptionally wide distribution. Surprisingly, there are no studies on the possible relationship between the abundance of tarantulas per population and the geographical areas where they are present, or on how the distribution pattern of this spider may affect individual morphological characteristics. Furthermore, there are no studies on sexual dimorphism within the genus Brachypelma. The aim of the study is to determine the existence of sexual and geographical dimorphism in populations of B. vagans. It was observed that the abundance of spiders per population may vary according to the geographical areas where they were recorded. In six localities in southern Mexico, we recorded morphological data on adult tarantulas. Sexual dimorphism was clearly observed at the site that presented numerous spiders characterized by much smaller females. Since the results of this study demonstrate differences in tarantula number of individuals per locality in southern Mexico, they make an important contribution to the conservation of this species.
Crocodilians show universal parental care, but few studies concentrate on this behavior in wild c... more Crocodilians show universal parental care, but few studies concentrate on this behavior in wild crocodiles.We studied nest and hatchling care in genetically pure wild American crocodiles (Crocodylus acutus) on two Caribbean islands of Mexico. From 2006 to 2009 we made direct observations of crocodile behavior upon discovery of nests and groups of hatchlings in Banco Chinchorro. In 2009, we installed camera traps at 4 nests from the time of their discovery to the hatching of each nest, in Banco Chinchorro and Cozumel Island. Twenty-one other species were observed to visit crocodile nests. No nest predation was observed but nine species represented some danger to nests and/or hatchlings. Females seemed to remain in the nest vicinity during incubation. There was variability in nest visit frequencies and no nest defense toward human intrusion was observed. Visit frequency by other species at nests decreased with increased crocodile visitation. Crocodiles mainly visited nests on darker n...
Después de Brasil, México es el segundo país con mayor número de especies de tarántulas. Entre el... more Después de Brasil, México es el segundo país con mayor número de especies de tarántulas. Entre ellas, las Brachypelma
Chemically mediated communication is common in spiders but has been poorly studied in burrowing t... more Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.
... In contrast, island populations on Cozumel and Banco Chinchorro have a larger number of indiv... more ... In contrast, island populations on Cozumel and Banco Chinchorro have a larger number of individuals of all ... Few studies have addressed the impact of tropical cyclones on crocodilians. ... high nest mortality and, as did Ensminger and Nichols (1957) after hurricane Audrey, report ...
Landscape fragmentation usually has a considerable effect on the genetic and demographic viabilit... more Landscape fragmentation usually has a considerable effect on the genetic and demographic viability of most species because it reduces population size and increases isolation among populations. This situation provokes loss of genetic diversity and increased inbreeding that can lead to population or species extinctions. Some studies also show that landscape fragmentation may have no effect on or even positive consequences for species genetic diversity. The protected tarantula, Brachypelma vagans, exhibits a particular situation in the Mexican Caribbean, which has experienced high lowland and coastal fragmentation because of recent increases in agricultural, urban and touristic development. This modified landscape structure creates favorable conditions for establishment of B. vagans populations in rural settlements. Populations of this tarantula have high densities of individuals, principally females and juveniles, and gene dispersion is assumed by the rare males. Within this context, we studied the influence of natural and anthropogenic fragmentation on the genetic diversity of six B. vagans populations (five continental, one insular), together with their spatial organization. Our approach used seven inter simple sequence repeat markers, which are highly polymorphic markers. The 76 loci selected revealed high genetic variability for continental populations and a low, but not critical situation, for the insular population. We detected a good level of gene exchange among continental populations, and an evident and recent isolation of the island population. This species exhibits a metapopulation structure in the lowlands with numerous local populations where mature females exhibit high birth site fidelity. We conclude that this protected species does not exhibit characteristics to warrant its current conservation status, and we propose complete revision of the ecological and genetic situation for B. vagans in particular, and for all species within the genus Brachypelma in general.
The reproductive success of sexually reproducing organisms depends on their capacity to locate po... more The reproductive success of sexually reproducing organisms depends on their capacity to locate potential partners. Research on the mating systems of webbuilding spiders, like other terrestrial invertebrates, has focused around male courtship and the signalling behaviours that facilitate copulation. In contrast, both mate searching and mate location behaviours are largely ignored and rarely quantified in field studies. We conducted a series of field removal experiments to explore the effects of male body size and female dispersion on mate locating behaviour of the golden orb-weaving spider (Nephila clavipes). The number of males that arrived on females' webs was influenced by travel distance, male body size, male body weight and female dispersal. More males returned to webs that were closer to the release point; smaller males experienced a greater weight loss; and larger numbers of males arrived at webs where males had been previously present. Female dispersion influenced the size but not the number of arriving males: males were no more likely to arrive at solitary than aggregations of webs, but males arriving at solitary webs were typically larger than those arriving at aggregations. We discuss the implications of various male traits that could act as selective pressures on male mate location and mate searching behaviours.
The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal st... more The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal stages. The 1st group was exclusively offered eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), a standard diet for O. majusculus production. The 2nd group was exclusively offered 4th instars of the pea aphid, Acyrtosiphon pisum (Harris). Subsequently, adult predatory behavior in experimental arenas containing A. pisium was recorded using 2 video cameras. One camera permitted observation of the predatorÕs contact with the prey, where the 2nd camera viewed the arena from above to record the path taken by O. majusculus adults before and after contact with prey. When O. majusculus were reared on aphids, adult bugs successfully located and consumed 55% of experimental prey and continued prey search behavior after each aphid meal. O. majusculus adults that had no experience of aphid predation as nymphs, did not prey on aphids in the experimental arena. The mean walking speed of this group of predators increased from 5.9 Ϯ 1.2 mm/s to 9.8 Ϯ 0.7 mm/s after contact or detection of prey, indicating that predators rapidly moved away from unfamiliar prey. Moreover, for egg-reared O. majusculus, all contacts between aphid and predator were lateral, along the side of the prey and were effectively repelled by an aphid kicking response. In contrast, 83% of attacks by aphid-reared O. majusculus were directed at the head or posterior abdomen for which the prey could not defend themselves adequately. When egg-reared O. majusculus were exposed to novel aphid prey for 1Ð 8 d, the frequency of aphid attack increased signiÞcantly. We conclude that the standard diet used for rearing O. majusculus may adversely affect the efÞciency of this predator as an agent of biological control.
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Papers by Yann Henaut