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The composition and diversity of animal-associated microbial communities are shaped by multiple ecological and evolutionary processes acting at different spatial and temporal scales. Skin microbiomes are thought to be strongly influenced by the environment due to the direct interaction of the host’s skin with the external media. As expected, the diversity of amphibian skin microbiomes is shaped by climate and host sampling habitats, whereas phylogenetic effects appear to be weak. However, the relative strength of phylogenetic and environmental effects on salamander skin microbiomes remains poorly understood. Here, we analysed sequence data from 1164 adult salamanders of 44 species to characterise and compare the diversity and composition of skin bacteria. We assessed the relative contribution of climate, host sampling habitat, and host phylogeny to the observed patterns of bacterial diversity. We found that bacterial alpha diversity was mainly associated with host sampling habitat and climate, but that bacterial beta diversity was more strongly associated with host taxonomy and phylogeny. This phylogenetic effect predominantly occurred at intermediate levels of host divergence (0–50 Mya). Our results support the importance of environmental factors shaping the diversity of salamander skin microbiota, but also support host phylogenetic history as a major factor shaping these bacterial communities.

Parabrachycoelium longicaecum n. gen., n. sp. (Digenea: Brachycoeliidae) is described from the intestine of a plethodontid salamander Chiropterotriton sp. Hosts were collected in bromeliads at the cloud forest of Tlaquilpa, Veracruz, Mexico. Members of the Brachycoeliidae Looss, 1899 (sensu Yamaguti, 1971) are characterized by having a spined tegument; ceca usually short, not passing level of gonads, but longer in some species; gonads posterior to, or in region of, acetabulum, with ovary anterior to testes; a well developed cirrus pouch containing a bipartite seminal vesicle; and uterus occupying entire hind-body posterior to testes. However, this combination of morphological traits prevents the inclusion of the new taxon in any of the genera in that family; a new genus was, therefore, erected to accommodate the new species. The new taxon is readily distinguished from members belonging to Brachycoelium Dujardin, 1845, Mesocoelium Odhner, 1910, and Tremiorchis Mehra and Negi, 1925, by having long ceca extending into the posterior third of the body, slightly surpassing the testes, and vitellaria extending along the body. The new species morphologically resembles Caudouterina rhyacotritoniMartin, 1966, a digenean parasitizing a plethodontid salamander; however, the latter species lacks spines in the tegument and is actually placed within the Allocreadiidae. To demonstrate further the phylogenetic position of the new taxon, we sequenced the D1–D3 regions of 28S rRNA gene and conducted a phylogenetic analysis of available sequences for the order to which brachycoeliids belong (Plagiorchiida). Sequence divergence of the partial 28S rRNA gene confirms its distinction from the aforementioned brachycoeliids, and the phylogenetic position within the Plagiorchiida places the new species as closely related to a clade formed by Brachycoelium + Mesocoelium. Divergence levels and phylogenetic position within the Plagiorchiida verifies the validity of the new genus and its inclusion in Brachycoeliidae.

Salamanders of the Pseudoeurycea bellii complex are widespread in México north and west of the Isthmus of Tehuantepec. They are the largest terrestrial plethodontids and have distinctive color patterns consisting of a general black ground color with strikingly bold red-orange marks in different patterns on the dorsal surface. At present three species are recognized: P. bellii (widespread, with two subspecies), P. gigantea (restricted to a small area of eastern México), and P. naucampatepetl (known only from the vicinity of the type locality in west-central Veracruz). A phylogenetic analysis based on two mitochondrial genes (cytochrome b and 16S RNA) finds support for three main clades, one including P. gigantea and P. naucampatepetl, another including the Oaxacan samples, and a third including P. bellii. New morphological data, DNA sequences, and limited allozymic information provide evidence that the Oaxacan clade comprises two species. The name P. boneti is resurrected from synonymy and applies to northern Oaxacan populations, while a new species is described from extreme western Oaxaca at elevations lower than have been recorded elsewhere for members of the complex.

We isolated and characterized 11 polymorphic microsatellite markers for the plethodontid salamander Pseudoeurycea leprosa to obtain population genetic data necessary for the proper management of this threatened species endemic to Central México. We tested polymorphism of these loci among 50 individuals from two populations (Texcalyacac and Calpan) in the states of México and Puebla, across the Transmexican Neovolcanic Belt. The number of alleles per locus ranged from three to 33 (mean; Na = 14.5). Observed and expected heterozygosities ranged from 0.20 to 0.88 and 0.22 to 0.93, respectively. We found deviations from Hardy–Weinberg equilibrium expectations for both populations at two loci (Plt028 and Plt066) and for Calpan population at locus Plt009. Evidence of significant linkage disequilibrium between pairs of loci was found only in one population. We found no evidence of large allele dropouts or stuttering, although null alleles could be present at loci Plt028 and Plt066, which showed significant excess of homozygotes. These markers will be useful for resolving fine-scale population genetic structure, gene flow, and population genetic diversity in Pseudoeurycea leprosa .

Fossorial salamanders typically have elongate and attenuated heads and bodies, diminutive limbs, hands and feet, and extremely elongate tails. Batrachoseps from California, Lineatriton from eastern México, and Oedipina from southern México to Ecuador, all members of the family Plethodontidae, tribe Bolitoglossini, resemble one another in external morphology, which has evolved independently. Whereas Oedipina and Batrachoseps are elongate because there are more trunk vertebrae, a widespread homoplasy (parallelism) in salamanders, the genus Lineatriton is unique in having evolved convergently by an alternate \"giraffe-neck\" developmental program. Lineatriton has the same number of trunk vertebrae as related, nonelongated taxa, but individual trunk vertebrae are elongated. A robust phylogenetic hypothesis, based on sequences of three mtDNA genes, finds Lineatriton to be deeply nested within a clade characterized by generalized ecology and morphology. Lineatriton lineolus, the only currently recognized taxon in the genus, shows unanticipated genetic diversity. Surprisingly, geographically separated populations of L. lineolus are not monophyletic, but are sister taxa of different species of the morphologically generalized genus Pseudoeurycea. Lineatriton, long thought to be a unique monospecific lineage, is polyphyletic. Accordingly, the specialized morphology of Lineatriton displays homoplasy at two hierarchical levels: (i) with respect to other elongate lineages in the family (convergence), and (ii) within what is currently recognized as a single taxon (parallelism). These evolutionary events are of adaptive significance because to invade the lowland tropics salamanders must be either arboreal or fossorial; the repeated evolution of elongation and attenuation has led to multiple lowland invasions.

Amphibian populations are in decline throughout Latin America; all families of frogs have experienced declines, but the species associated with aquatic habitats in upland areas have been most affected. Declines in Latin America were most common during the 1980s, but new declines continue to be reported. The causes of declines are varied, but they have most often been associated with habitat loss, a pathogenic fungus, and climate change. Scientists are just beginning to grasp the ethical and biological implications of losses of this magnitude. In this Special Section, we provide a general summary of the phenomenon and introduce five contributed papers that provide new data and new insights into Latin American declines. /// En América Latina se ha documentado un declive generalizado en poblaciones de anfibios. Dicho declive se ha presentado en especies de todas las familias de anfibios, pero especialmente en aquellas asociadas a ambientes acuáticos en zonas montañosas. El declive en America Latina, ocurrió en la década de los 80s, pero en la actualidad todavía se siguen registrando disminuciones. Los investigadores apenas están empezando a a entender las implicaciones éticas y biológicas de pérdidadas de biodiversidad de esta magnitud. Aquí presentamos un resumen general de este fenómeno y la introducción a cinco trabajos que proveen datos nuevos para América Latina.

The loss of global amphibian biodiversity has been well documented in recent years. The greatest information from Latin America came from countries such as Costa Rica, Panama, Ecuador, and Puerto Rico. The five papers in this special section illustrate the critical status of Latin American amphibians and further demonstrate certain commonalities of amphibian population declines within the region. These studies provide a framework by which future research and management could proceed in all tropical regions. /// En los pasados años se ha documentado la perdida de biodiversidad de anfibios en muchas partes del mundo. La mayor información con respecto a América Latina proviene de trabajos realizados en Costa Rica, Panamá, Ecuador y Puerto Rico. Los cinco trabajos de esta edición especial ilustran el estado crítico de los anfibios en América Latina y demuestran que existen algunos elementos comunes en los patrones de disminuciones poblacionales de anfibios en la región. Estos estudios proveen un marco de referencia para futuras investigaciones y desarrollo de planes de manejo en regiones tropicales.

Species with highly restricted distributions are vulnerable to extinction, and modification of natural habitats within their small ranges is a primary threat to their persistence. Expansion of urban development significantly impacts natural habitats and, therefore, threatens local diversity. The Mexican axolotl, Ambystoma mexicanum, is a strictly aquatic species that persists currently in two highly threatened and isolated populations. The current habitat remaining for these species are remnants of a historically extensive lacustrine system that occupied the entire Valley of Mexico, but has been destroyed by the growth of Mexico City. Unexpectedly, a third viable population of axolotls has been found in Chapultepec Park, a public recreational area in the heart of Mexico City. Phylogenetic and haplotype network analyses of mitochondrial DNA sequences confirmed low genetic differentiation and a recurrent lack of monophyly in many of the taxa belonging to the Ambystoma tigrinum species group, including A. mexicanum, but clustered the Chapultepec samples with other A. mexicanum samples. Our data revealed higher haplotypic diversity in A. mexicanum populations than previously recorded, due to new haplotypes from Chapultepec Park. We found high incidence of parasites and deformities among individuals in this population, which could negatively impact their viability. Our results emphasize the important role that artificial or semi-natural urban habitats can play in the conservation of highly threatened species.

The genus Chiropterotriton contains only 12 described species but includes a rich variety of morphological and ecological forms ranging from diminutive to large cave-dwelling species, as well as a number of terrestrial and arboreal forms. Although morphological diversification has taken place during the evolution of this genus, morphological stasis and parallelism also characterize the evolution of this group, generating complexes of cryptic species. I obtained sequences of the 16S ribosomal mtDNA gene from most of the species. Mitochondrial DNA shows great diversification, with genetic divergence among taxa as high as 12.5%. The 531-bp mtDNA data matrix contained 121 parsimony-informative characters. Basal relationships are poorly supported by maximum parsimony analyses. There is, however, support for a clade that includes all of the samples of the C. chiropterus group. The maximum-likelihood and Bayesian topologies differ from maximum-parsimony topologies mainly in the arrangement of the basal relationships. Based on the results, the genus Chiropterotriton comprises 12 species with available names: C. arboreus, C. chiropterus, C. chondrostega, C. cracens, C. dimidiatus, C. lavae, C. magnipes, C. mosaueri, C. multidentatus, C. orculus, C. priscus, and C. terrestris, plus 7 additional undescribed species for which allozyme and mitochondrial data sets are congruent.

A generalized decline of amphibian populations is occurring worldwide. The causes for such a decline are not completely understood; however, climate change has been identified as a possible cause for amphibian extinction, among others. Ecological niche modeling has proven to be a useful tool to predict potential distribution of species in the context of climatic changes. In this paper, we used the Genetic Algorithm for Rule-set Prediction (GARP) to model the potential distributions of two species of plethodontid salamanders: Pseudoeurycea cephalica and P. leprosa. We projected their potential distributions under climatic scenarios expected in 50 yr based on a conservative scenario of global climate change and assuming a moderate dispersal ability for both species. Our analyses suggest that climate change effects may pose an additional long-term risk to both species of plethodontid salamanders, with a more dramatic scenario in the case of P. leprosa. By the year 2050, this species may lose almost 75 percent of its distributional area, and this projection is even worse when deforestation (in the way it is occurring at present) is considered within the predicted model. Our results concur with those obtained for species with limited dispersal capability because they do not track changing climates, but rather face a loss of distributional area. The survival of these species is not secure, even though their potential distributional area falls within a considerable number of natural protected areas. /// El declive de las poblaciones de anfibios a nivel mundial es un hecho bien documentado. Diversos factores se han identificado como las causas del declive, y entre ellos, el cambio climático se ha señalado como un factor importante en la extinción de poblaciones de anfibios. El modelado de nicho ecológico ha demostrado ser una herramienta útil para predecir la distribución potencial de las especies en el contexto del cambio climático global. En el presente trabajo utilizamos el algoritmo GARP (Genetic Algorithm for Rule-set Prediction) para modelar la distribución de dos especies de salamandras pletodóntidas: Pseudoerycea cephalica and P. leprosa; asimismo, proyectamos su distribución potencial bajo escenarios de cambio climático esperados que ocurran en 50 años, basándonos en un escenario de cambio global conservativo y asumiendo una capacidad de dispersión moderada para ambas especies de salamandras. Nuestros análisis sugieren que el cambio climático puede representar un riesgo adicional para ambas especies, siendo el escenario aún más dramático para el caso de P. leprosa. Para el año 2050, podríamos esperar que esta especie perdiera alrededor del 75 por ciento de su área de distribución y si consideramos la deforestación (tal como ocurre en el presente), la proyección sería aún más desoladora. Nuestros resultados concuerdan con aquellos obtenidos en especies con una capacidad de dispersión limitada dado que éstas no responden a los cambios climáticos desplazándose a zonas más favorables, sino que enfrentan una pérdida de su área de distribución. La supervivencia de estas especies de salamandra está en riesgo, sin embargo el área de distribución potencial está comprendida dentro de un número considerable de Áreas Naturales Protegidas.