Víctor Hugo Reynoso

Diversification in the northern neotropics: mitochondrial and nuclear DNA phylogeography of the iguana Ctenosaura pectinata and related species

While Quaternary climatic changes are considered by some to have been a major factor promoting speciation within the neotropics, others suggest that much of the neotropical species diversity originated before the Pleistocene. Using mitochondrial and nuclear sequence data, we evaluate the relative importance of Pleistocene and pre‐Pleistocene events within the evolutionary history of the Mexican iguana Ctenosaura pectinata, and related species. Results support the existence of cryptic lineages with strong mitochondrial divergence (> 4%) among them. Some of these lineages form zones of secondary contact, with one of them hybridizing with C. hemilopha. Evolutionary network analyses reveal the oldest populations of C. pectinata to be those of the northern and southern Mexican coastal regions. Inland and mid‐latitudinal coastal populations are younger in age as a consequence of a history of local extinction within these regions followed by re‐colonization. Estimated divergence times suggest that C. pectinata originated during the Pliocene, whereas geographically distinct mitochondrial DNA lineages first started to diverge during the Pliocene, with subsequent divergence continuing through the Pleistocene. Our results highlight the influence of both Pliocene and Pleistocene events in shaping the geographical distribution of genetic variation within neotropical lowland organisms. Areas of high genetic diversity in southern Mexico were detected, this finding plus the high levels of genetic diversity within C. pectinata, have implications for the conservation of this threatened species.

Erratum to: Amphibian and reptile communities of rainforest fragments: minimum patch size to support high richness and abundance

Information on animal communities inhabiting Neotropical fragmented landscapes is important for developing conservation strategies. The structure of amphibian and reptile communities in six tropical rainforest fragments (<20 ha) and two reference areas in continuous forest at Los Tuxtlas, Mexico was studied. A total of 3,481 individuals of 51 species of amphibians and reptiles were recorded across 12 bimonthly surveys during 2 years. Taxonomic composition was different between the smallest fragments and the reference areas. Six species were exclusive to large undisturbed forest and richness was significantly lower in the five smallest fragments (1.4–6.6 ha) compared with the largest patch, one or both of the reference areas. Amphibian abundance tended to be higher in large areas, while reptiles were more abundant in the five smallest fragments. Craugastor loki and Anolis uniformis were the dominant species in all sites, and particularly in the smaller fragments. Amphibian and reptile richness was positively related to larger patch sizes, deeper leaf litter, closed canopy cover, and higher relative humidity and negatively related to linear patch shape and high temperatures. Abundance of reptiles was positively associated to high temperatures, high density of woody debris, and closed canopy cover; it was negatively affected by linear patch shape, low humidity levels, and steeper slopes. While amphibian and reptile communities were strongly affected in vegetation fragments, these patches retained a considerable number of rainforest species. Fragments up to at least 17 ha have the potential for preserving communities with similar structure to those occurring in large tropical rainforests.

Species- and community-level responses to habitat spatial changes in fragmented rainforests: assessing compensatory dynamics in amphibians and reptiles

The rapid loss and degradation of tropical forests threatens the maintenance of biodiversity across different spatial scales. Nevertheless, the extirpation and population decline of some disturbance-sensitive species may be compensated for by colonization and proliferation of disturbance-adapted species, thus allowing distributions of community-level attributes (e.g., abundance and diversity) to be preserved in human-modified tropical landscapes. To test this poorly assessed hypothesis we evaluated species- and community-level responses of amphibians and reptiles to differences in forest patch (patch size, shape, and distance to water bodies) and landscape metrics (old-growth forest cover, degree of fragmentation, and matrix composition) in the fragmented Lacandona rainforest, Mexico. We found that the abundance of several amphibian and reptile species was strongly associated with forest patch and landscape attributes, being particularly higher in larger patches surrounded by a greater forest cover. Such changes at the species level generated notable changes in reptile communities. In particular, the abundance, diversity, and evenness of reptile communities were strongly related to patch size, patch shape, and matrix composition. Yet, because of compensatory dynamics in amphibians, this group showed weak responses at the community level. Despite such compensatory dynamics, our results indicate that forest loss at the patch and landscape levels represents the main threat to both amphibians and reptiles, thus indicating that to preserve herpetological communities in this biodiversity hotspot, conservation initiatives should be focused on preventing further deforestation.

Multiple colour traits signal performance and immune response in the Dickerson’s collared lizard Crotaphytus dickersonae

Conspicuous male coloration is often an honest signal of individual quality. In Dickerson’s collared lizard (Crotaphytus dickersonae), males are striking blue, have a black and white collar and have white spots on their bodies. In this study, we investigated whether this extravagant colour pattern is an indicator of male performance in variables related to resource-holding power (bite force, running speed and endurance) and immune condition (cellular response and ectoparasite load). Also, we assessed direct and indirect effects of testosterone levels and body temperature on colour traits. We found that males with bluer skin, and darker and bigger black collars performed better in variables related to resource-holding power. Also, the black colour of the collar was related to immune condition. Blue chroma was positively related to temperature, yet males with bigger and darker black collars had lower body temperatures. Testosterone had minor effects on immune response and colour traits. Our results suggest that multiple colour traits in the Dickerson’s collared lizard may honestly indicate physical and physiological performance.

Testing for hybridization and assessing genetic diversity in Morelet's crocodile (Crocodylus moreletii) populations from central Veracruz

Among the loss of genetic diversity due to population declines, population fragmentation and habitat loss, hybridization also stands as a threat to Morelet’s crocodile (Crocodylus moreletii) populations. Genetic surveys in Belize and the Yucatan Peninsula have detected evidence of hybridization with the American crocodile (C. acutus). Admixture between these two species is most likely driven by human-mediated translocations. Along the central gulf coast of Mexico, C. moreletii populations are presumed to be purebred. To test this, we use nine microsatellite loci and sequence data from the mitochondrial control region to detect if C. acutus alleles have introgressed into populations of C. moreletii from central Veracruz. In 2010, C. moreletii was transferred from Appendix I to II of CITES based on a whole species demographic analysis, which indicated that populations had recovered across its range. Our study shows that populations in central Veracruz are purebred, although they exhibit low levels of genetic diversity most likely caused by inbreeding. Our data also suggest there is fragmentation among populations of C. moreletii, which may lead to further loss of genetic variation. Due the purity and low genetic diversity of C. moreletii populations from central Veracruz, we recommend increased protection and active management practices that take genetic data into account.

Isolation and characterization of polymorphic microsatellite markers in the black spiny tailed iguana (Ctenosaura pectinata) and their cross-utility in other Ctenosaura

We isolated and characterized 10 polymorphic microsatellite loci from the Mexican black iguana (Ctenosaura pectinata) and assessed levels of polymorphism in sampling sites located in the northern areas of the species’ distribution range. Two to 19 alleles per locus and observed heterozygosity ranging from 0.15 to 0.96 were detected. These markers will be useful to describe population genetic structure, the extent of gene flow in contact zones, to study the mating system of the species and to address conservation genetics issues. Additionally, we evaluated the potential utility of these markers for studies of other species within the genus Ctenosaura (i.e. C. hemilopha, C. similis and C. oaxacana).

Predominance of single paternity in the black spiny-tailed iguana: conservation genetic concerns for female-biased hunting

Because of female-biased illegal harvesting, knowledge about the genetic mating system of the black spiny-tailed iguana Ctenosaura pectinata is of primary interest for the conservation of this threatened species. Based on the high levels of multiple paternity found in clutches of many other reptiles, particularly in lizards, it is hypothesised that multiple paternity may also be common in black iguanas. This was investigated by using microsatellite DNA to estimate the number of males siring nine litters (9 mothers, 121 offspring genotyped at ten polymorphic loci) of black iguanas. Contrary to expectations, only 11% of sampled black iguana females produced litters consistent with being sired by multiple males. These data are the first evidence for the predominance of single paternity within an iguanid lizard, and suggest that black iguana may be more susceptible to loss of genetic variation in the face of gender-biased over-hunting pressure than previously thought.

Never judge an iguana by its spines: Systematics of the Yucatan spiny tailed iguana, Ctenosaura defensor (Cope, 1866)

Spiny tailed iguanas are highly diverse clade of lizards in Mesoamerica, ranging from northern Mexico through Panama. Utilizing 2 regions of mitochondrial DNA (1948bp) and 4 nuclear loci (2232bp) we explored the relationships between these species and the phylogeographic history of the major clades. We discovered that the lineage endemic to the Yucatan Peninsula renders the genus Ctenosaura paraphyletic. To resolve this non-monophyly, we resurrect the taxon Cachryx Cope, 1866, and provide a new diagnosis for the genus. We also find that small body-size and highly spinose tails in the species previously referred to the subgenus Enyaliosaurus, have evolved independently 3 times. Cachryx were recovered as sister to the lineage of iguanines endemic to the Galapagos Islands, and we discuss biogeographic scenarios to explain this relationship as well as those among the primary clades of Ctenosaura in Mesoamerica.

Vegetation Cover and Road Density as Indicators of Habitat Suitability for the Morelet's Crocodile

Abstract Understanding the response of species to land-use change is necessary for the improvement of management and conservation policies. We assessed the impact of vegetation cover and land-use change on Morelets crocodile populations in nine wetlands located in central Veracruz, Mexico, to test the hypothesis that higher forest cover and lower anthropogenic impact increases crocodile density. We correlated the relative density of crocodiles with wetland attributes, including depth, pH, salinity, and richness and structure of bordering vegetation; and with anthropogenic disturbance factors, including the proportion of modified land surrounding the water body, road density, and road type. The relative density of crocodiles was correlated positively with vegetation cover and correlated negatively with plant density and with the presence of nonpaved roads, particularly in the zone that bordered the water bodies (core zone). Our findings suggest that as long as the water bodies are bordered with arboreal vegetation, land-use change and paved road density in inland areas had minor impacts on Morelets crocodile populations in Mexican wetlands. The vegetation cover and the number of nonpaved roads within the core zone are useful indicators of habitat suitability for the Morelets crocodile. The conservation of mangroves and forest remnants is therefore essential for the maintenance of crocodile populations. Resumen Entender la respuesta de las especies al cambio de uso del suelo es necesario para mejorar las políticas de gestión y conservación de los recursos naturales. Evaluamos el impacto de la cobertura vegetal y el cambio de uso del suelo sobre nueve poblaciones del cocodrilo de pantano localizadas en el centro de Veracruz, México. Se sometió a prueba la hipótesis de que el aumento en la cobertura forestal y la reducción del impacto antrópico incrementan la densidad de cocodrilos. Correlacionamos las densidades relativas de los cocodrilos con atributos de los humedales, tales como profundidad, pH, salinidad, riqueza y estructura de la vegetación, y con atributos de disturbio antropogénicos como la proporción de tierras modificadas que rodean el cuerpo de agua, la densidad de caminos y los tipos de carretera. La densidad relativa de los cocodrilos aumentó cuando la proporción de cobertura vegetal natural fue mayor y disminuyó con la el aumento en el número de carreteras no pavimentadas, particularmente cuando éstas se encontraban alrededor de los cuerpos de agua (zona núcleo). Nuestros hallazgos sugieren que, mientras que los cuerpos de agua estén rodeados de vegetación arbórea, el cambio de uso de suelo y la densidad de carreteras pavimentadas lejanos al cuerpo de agua tendrán un impacto mínimo sobre las poblaciones de cocodrilo de pantano en los humedales mexicanos. La cobertura de la vegetación en la zona núcleo y el número de carreteras no pavimentadas son indicadores útiles de calidad del hábitat para el cocodrilo de pantano. La preservación de los bosques remanentes y los manglares es esencial para el mantenimiento de las poblaciones de cocodrilos.