Sean M. Rovito

Coincident mass extirpation of neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis

Amphibians highlight the global biodiversity crisis because ∼40% of all amphibian species are currently in decline. Species have disappeared even in protected habitats (e.g., the enigmatic extinction of the golden toad, Bufo periglenes, from Costa Rica). The emergence of a fungal pathogen, Batrachochytrium dendrobatidis (Bd), has been implicated in a number of declines that have occurred in the last decade, but few studies have been able to test retroactively whether Bd emergence was linked to earlier declines and extinctions. We describe a noninvasive PCR sampling technique that detects Bd in formalin-preserved museum specimens. We detected Bd by PCR in 83–90% (n = 38) of samples that were identified as positive by histology. We examined specimens collected before, during, and after major amphibian decline events at established study sites in southern Mexico, Guatemala, and Costa Rica. A pattern of Bd emergence coincident with decline at these localities is revealed—the absence of Bd over multiple years at all localities followed by the concurrent emergence of Bd in various species at each locality during a period of population decline. The geographical and chronological emergence of Bd at these localities also indicates a southbound spread from southern Mexico in the early 1970s to western Guatemala in the 1980s/1990s and to Monteverde, Costa Rica by 1987. We find evidence of a historical “Bd epidemic wave” that began in Mexico and subsequently spread to Central America. We describe a technique that can be used to screen museum specimens from other amphibian decline sites around the world.

Dramatic declines in neotropical salamander populations are an important part of the global amphibian crisis

We document major declines of many species of salamanders at several sites in Central America and Mexico, with emphasis on the San Marcos region of Guatemala, one of the best studied and most diverse salamander communities in the Neotropics. Profound declines of several formerly abundant species, including 2 apparent extinctions, are revealed. Terrestrial microhabitat specialists at mid- to high elevations have declined more than microhabitat generalists. These terrestrial microhabitat specialists have largely disappeared from multiple sites in western Guatemala, including in well-protected areas, suggesting that the phenomenon cannot be explained solely by localized habitat destruction. Major declines in southern Mexican plethodontid salamanders occurred in the late 1970s to early 1980s, concurrent with or preceding many reported frog declines. The species in decline comprise several major evolutionary lineages of tropical salamanders, underscoring that significant portions of the phylogenetic diversity of Neotropical salamanders are at risk. Our results highlight the urgent need to document and understand Neotropical salamander declines as part of the larger effort to conserve global amphibian diversity.

Deep divergences and extensive phylogeographic structure in a clade of lowland tropical salamanders

BackgroundThe complex geological history of Mesoamerica provides the opportunity to study the impact of multiple biogeographic barriers on population differentiation. We examine phylogeographic patterns in a clade of lowland salamanders (Bolitoglossa subgenus Nanotriton) using two mitochondrial genes and one nuclear gene. We use several phylogeographic analyses to infer the history of this clade and test hypotheses regarding the geographic origin of species and location of genetic breaks within species. We compare our results to those for other taxa to determine if historical events impacted different species in a similar manner.ResultsDeep genetic divergence between species indicates that they are relatively old, and two of the three widespread species show strong phylogeographic structure. Comparison of mtDNA and nuclear gene trees shows no evidence of hybridization or introgression between species. Isolated populations of Bolitoglossa rufescens from Los Tuxtlas region constitute a separate lineage based on molecular data and morphology, and divergence between Los Tuxtlas and other areas appears to predate the arrival of B. rufescens in other areas west of the Isthmus of Tehuantepec. The Isthmus appears responsible for Pliocene vicariance within B. rufescens, as has been shown for other taxa. The Motagua-Polochic fault system does not appear to have caused population vicariance, unlike in other systems.ConclusionsSpecies of Nanotriton have responded to some major geological events in the same manner as other taxa, particularly in the case of the Isthmus of Tehuantepec. The deep divergence of the Los Tuxtlas populations of B. rufescens from other populations highlights the contribution of this volcanic system to patterns of regional endemism, and morphological differences observed in the Los Tuxtlas populations suggests that they may represent an undescribed species of Bolitoglossa. The absence of phylogeographic structure in B. nympha, in contrast to the other widespread species in the subgenus, may be due to historical forest contraction and more recent range expansion in the region. Phylogeographic data provide substantial insight into the evolutionary history of these morphologically similar species of salamanders, and contribute to our understanding of factors that have generated the high biodiversity of Mesoamerica.

A New Species of Cryptotriton (Caudata: Plethodontidae) from Eastern Guatemala

Abstract A new species of lungless salamander (Plethodontidae) is described from the mountains of eastern Guatemala. The new species is distinguished from all other members of its genus by its yellow ventral coloration. It is geographically closest to its sister taxon, Cryptotriton veraepacis, from which it differs in several osteological features as well as nostril size and shape. Molecular analyses with allozyme loci and mitochondrial DNA also support its distinctiveness from C. veraepacis. This miniaturized species inhabits cloud forest habitats and has been found most commonly in bromeliads.

A new species of Bolitoglossa (Amphibia, Caudata) from the Sierra de Juarez, Oaxaca, Mexico.

Abstract We describe a new species of Bolitoglossa (Nanotriton) from the Sierra de Juárez and Sierra Mixe of Oaxaca, Mexico. Bolitoglossa chinanteca sp. n. is distinguished from the three other species in the subgenus Nanotriton by its more robust body, by having substantial numbers of maxillary teeth and differences in relative head width, foot width, and limb length. The new species occurs in sympatry with Bolitoglossa (Nanotriton) rufescens at the type locality. The description of another species of salamander from the Sierra de Juárez is noteworthy, given the already high plethodontid salamander species richness of the region.

New species of salamander (Caudata: Plethodontidae: Cryptotriton) from Quebrada Cataguana, Francisco Morazán, Honduras, with comments on the taxonomic status of Cryptotriton wakei.

We describe a new species of the plethodontid salamander genus Cryptotriton from Honduras after comparing morphological, molecular, and osteological data from the holotype to that of the other nominal forms of the genus. The new species differs from all of the known species of Cryptotriton in at least one character from all three datasets. We also suggest placing C. wakei in the synonymy of C. nasalis after examining the morphological and osteological characters of the single known specimen of C. wakei.

Bromeliad Selection by Two Salamander Species in a Harsh Environment

Bromeliad phytotelmata are frequently used by several Neotropical amphibian taxa, possibly due to their high humidity, microclimatic stability, and role as a refuge from predators. Indeed, the ability of phytotelmata to buffer against adverse environmental conditions may be instrumental in allowing some amphibian species to survive during periods of environmental change or to colonize sub-optimal habitats. Association between bromeliad traits and salamanders has not been studied at a fine scale, despite the intimate association of many salamander species with bromeliads. Here, we identify microhabitat characteristics of epiphytic bromeliads used by two species of the Bolitoglossa morio group (B. morio and B. pacaya) in forest disturbed by volcanic activity in Guatemala. Specifically, we measured multiple variables for bromeliads (height and position in tree, phytotelma water temperature and pH, canopy cover, phytotelma size, leaf size, and tree diameter at breast height), as well as salamander size. We employed a DNA barcoding approach to identify salamanders. We found that B. morio and B. pacaya occurred in microsympatry in bromeliads and that phytotelmata size and temperature of bromeliad microhabitat were the most important factors associated with the presence of salamanders. Moreover, phytotelmata with higher pH contained larger salamanders, suggesting that larger salamanders or aggregated individuals might modify pH. These results show that bromeliad selection is nonrandom with respect to microhabitat characteristics, and provide insight into the relationship between salamanders and this unique arboreal environment.

A New Species of Bolitoglossa (Caudata: Plethodontidae) from the Sierra de las Minas, Guatemala

Abstract We describe a new species of the rostrata species group of Bolitoglossa (Magnadigita) from a single cloud forest site on the south slope of the Sierra de las Minas in eastern Guatemala, an area of high biodiversity for many groups of organisms. This species is distinguished from other members of the subgenus on the basis of morphology and molecular analyses, and it differs from the sympatric Bolitoglossa helmrichi in ventral coloration of the tail and in foot and body morphology.

Reply to Gamfeldt: Biodiversity and ecosystem functioning

In his letter (1), Gamfeldt asks questions concerning broader aspects of our study (2). In response, salamander biomass has been substantially reduced. In the upper cloud forest habitat at El Rincon, San Marcos, Guatemala, 3 formerly abundant salamander species and a 4th relatively rare species were not found. Although 3 other species were found as often or slightly more so than in the past, the overall salamander density at El Rincon is much lower compared to previous decades. These 7 species constitute the entire salamander community at this site, and no species were found on our recent surveys that were not present in the 1970s. The total salamander biomass at the site is only a fraction of what it once was; vastly fewer amphibians and reptiles (specifically salamander-eating snakes) were encountered than in the past. Similarly, forest habitat with formerly dense populations of Pseudoeurycea and Thorius on Cerro San Felipe, Oaxaca, Mexico, now contain no Pseudoeurycea (based on our surveys) and very few Thorius compared with previous decades, although suitable habitat remains. All salamander species have declined at this site, with no compensation from any other salamander species.

Neotropical Plethodontid Biogeography: Insights from Molecular Phylogenetics

While salamanders have a predominantly north-temperate distribution, one of the most stunning radiations of species occurred in the only group to significantly penetrate the tropics, the bolitoglossines. Biogeographic hypotheses for the group have evolved as a result of the discovery of new species and lineages, from approximately 30 species in a single genus in 1926 to nearly 300 species in 14 genera today. Molecular phylogenies provide an important tool with which to test long-standing biogeographic hypotheses. Divergence dating analyses and parametric biogeographic analyses, together with a changing understanding of the taxonomy of the bolitoglossines and new geological evidence from Mesoamerica, call into question several long-standing hypotheses related to the arrival and diversification of the bolitoglossines in Central and South America. We briefly review the geology of Mesoamerica, with an emphasis on regions of high salamander diversity, and discuss how molecular phylogenies and new species discoveries have changed our perception of the history of this salamander radiation.