Molecular systematics of the Middle American genus Hypopachus (Anura: Microhylidae)

A tale of two bellies: systematics of the oval frogs (Anura: Microhylidae: Elachistocleis Parker, 1927)

Oval frogs (Elachistocleis) have a broad geographic distribution covering nearly all of South America and parts of Central America. They also have a large inter- and intraspecific variation of the few morphological characters commonly used as diagnostic traits among species of the genus. Based on molecular data, we provide the most complete phylogeny of Elachistocleis to date, and explore its genetic diversity using distance-based and tree-based methods for putative species delimitation. Our results show that at least two of the most relevant traditional characters used in the taxonomy of this group (belly pattern and dorsal median white line) carry less phylogenetic information than previously thought. Based on our results, we propose some synonymizations and some candidate new species. This study is a first major step in disentangling the current systematics of Elachistocleis. Yet, a comprehensive review of morphological data is needed before any new species descriptions can be properly made.

Multilocus, phenotypic, behavioral, and ecological niche analyses provide evidence for two species within Euphonia affinis (Aves, Fringillidae)

The integration of genetic, morphological, behavioral, and ecological information in the analysis of species boundaries has increased, allowing integrative systematics that better reflect the evolutionary history of biological groups. In this context, the goal of this study was to recognize independent evolutionary lineages within Euphonia affinis at the genetic, morphological, and ecological levels. Three subspecies have been described: E. affinis godmani, distributed in the Pacific slope from southern Sonora to Guerrero; E. affinis affinis, from Oaxaca, Chiapas and the Yucatan Peninsula to Costa Rica; and E. affinis olmecorum from Tamaulipas and San Luis Potosi east to northern Chiapas (not recognized by some authors). A multilocus analysis was performed using mitochondrial and nuclear genes. These analyses suggest two genetic lineages: E. godmani and E. affinis, which diverged between 1.34 and 4.3 My, a period in which the ice ages and global cooling fragmented the tropical forests throughout the Neotropics. To analyze morphometric variations, six morphometric measurements were taken, and the Wilcoxon Test was applied to look for sexual dimorphism and differences between the lineages. Behavioral information was included, by performing vocalization analysis which showed significant differences in the temporal characteristics of calls. Finally, Ecological Niche Models were estimated with MaxEnt, and then compared using the method of Broennimann. These analyses showed that the lineage distributed in western Mexico (E. godmani) has a more restricted niche than the eastern lineage (E. affinis) and thus we rejected the hypotheses of niche equivalence and similarity. Based on the combined evidence from genetic, morphological, behavioral, and ecological data, it is concluded that E. affinis (with E. olmecorum as its synonym) and E. godmani represent two independent evolutionary lineages.

Introgressive hybridization in a Spiny-Tailed Iguana, Ctenosaura pectinata, and its implications for taxonomy and conservation

Introgression, the transmission of genetic material of one taxon into another through hybridization, can have various evolutionary outcomes. Previous studies have detected signs of introgression between western populations of the Mexican endemic and threatened spiny-tailed iguana, Ctenosaura pectinata. However, the extent of this phenomenon along the geographic distribution of the species is unknown. Here, we use multilocus data together with detailed geographic sampling to (1) define genotypic clusters within C. pectinata; (2) evaluate geographic concordance between maternally and biparentally inherited markers; (3) examine levels of introgression between genotypic clusters, and (4) suggest taxonomic modifications in light of this information. Applying clustering methods to genotypes of 341 individuals from 49 localities of C. pectinata and the closely related C. acanthura, we inferred the existence of five genotypic clusters. Contact zones between genotypic clusters with signatures of interbreeding were detected, showing different levels of geographic discordance with mtDNA lineages. In northern localities, mtDNA and microsatellites exhibit concordant distributions, supporting the resurrection of C. brachylopha. Similar concordance is observed along the distribution of C. acanthura, confirming its unique taxonomic identity. Genetic and geographic concordance is also observed for populations within southwestern Mexico, where the recognition of a new species awaits in depth taxonomic revision. In contrast, in western localities a striking pattern of discordance was detected where up to six mtDNA lineages co-occur with only two genotypic clusters. Given that the type specimen originated from this area, we suggest that individuals from western Mexico keep the name C. pectinata. Our results have profound implications for conservation, management, and forensics of Mexican iguanas.

Molecular phylogeny of microhylid frogs (Anura: Microhylidae) with emphasis on relationships among New World genera

BACKGROUND

Over the last ten years we have seen great efforts focused on revising amphibian systematics. Phylogenetic reconstructions derived from DNA sequence data have played a central role in these revisionary studies but have typically under-sampled the diverse frog family Microhylidae. Here, we present a detailed phylogenetic study focused on expanding previous hypotheses of relationships within this cosmopolitan family. Specifically, we placed an emphasis on assessing relationships among New World genera and those taxa with uncertain phylogenetic affinities (i.e., incertae sedis).

RESULTS

One mitochondrial and three nuclear genes (about 2.8 kb) were sequenced to assess phylogenetic relationships. We utilized an unprecedented sampling of 200 microhylid taxa representing 91% of currently recognized subfamilies and 95% of New World genera. Our analyses do not fully resolve relationships among subfamilies supporting previous studies that have suggested a rapid early diversification of this clade. We observed a close relationship between Synapturanus and Otophryne of the subfamily Otophryninae. Within the subfamily Gastrophryninae relationships between genera were well resolved.

CONCLUSION

Otophryninae is distantly related to all other New World microhylids that were recovered as a monophyletic group, Gastrophryninae. Within Gastrophryninae, five genera were recovered as non-monophyletic; we propose taxonomic re-arrangements to render all genera monophyletic. This hypothesis of relationships and updated classification for New World microhylids may serve as a guide to better understand the evolutionary history of this group that is apparently subject to convergent morphological evolution and chromosome reduction. Based on a divergence analysis calibrated with hypotheses from previous studies and fossil data, it appears that microhylid genera inhabiting the New World originated during a period of gradual cooling from the late Oligocene to mid Miocene.

Geographical patterns of genetic divergence in the widespread Mesoamerican bumble bee Bombus ephippiatus (Hymenoptera: Apidae)

Bumble bees (Bombus Latreille) are an important group of social insects, well recognized throughout northern temperate regions as important pollinators of wild and agricultural plants. Little is known about the biology of this group in southern portions of the Americas, especially in Mesoamerica, a region of geological and ecological complexity from Mexico through Central America. One ubiquitous Mesoamerican species, Bombus ephippiatus, is enigmatic. Like many other Bombus, this species is homogeneous in body structure yet exhibits striking intraspecific color pattern polymorphism across its range, leading to uncertainty about its genealogical boundaries. It has been grouped taxonomically with B. wilmattae, a species narrowly restricted to southern Mexico and northern Guatamala. Furthermore, the relationships between these two taxa and a third species, B. impatiens, found only in America north of Mexico, have been controversial. Our phylogenetic analysis of DNA sequences from mitochondrial COI and nuclear PEPCK and CAD resolves the phylogeny of these three taxa as (B. impatiens, (B. ephippiatus, B. wilmattae)). Additional data from eight nuclear microsatellite markers reveal complex patterns of genetic divergence and isolation among populations of B. ephippiatus across its extensive geographic range, providing evidence for multiple independent evolutionary lineages. These lineages correspond not only to geographic and habitat variation across their range, but also to distinct color pattern groups present in the species. Knowledge of the phylogeny and genetic divergence of the B. ephippiatus group will provide a framework for understanding evolutionary and ecological origins of color pattern polymorphism in bumble bees, as well as providing insight into geographical factors enhancing speciation in Mesoamerica.