Recent and Rapid Radiation of the Highly Endangered Harlequin Frogs (Atelopus) into Central America Inferred from Mitochondrial DNA Sequences

Abstract

Populations of amphibians are experiencing severe declines worldwide. One group with the most catastrophic declines is the Neotropical genus Atelopus (Anura: Bufonidae). Many species of Atelopus have not been seen for decades and all eight Central American species are considered “Critically Endangered”, three of them very likely extinct. Nonetheless, the taxonomy, phylogeny, and biogeographic history of Central American Atelopus are still poorly known. In this study, the phylogenetic relationships among seven of the eight described species in Central America were inferred based on mitochondrial DNA sequences from 103 individuals, including decades-old museum samples and two likely extinct species, plus ten South American species. Among Central American samples, we discovered two candidate species that should be incorporated into conservation programs. Phylogenetic inference revealed a ladderized topology, placing species geographically furthest from South America more nested in the tree. Model-based ancestral area estimation supported either one or two colonization events from South America. Relaxed-clock analysis of divergence times indicated that Atelopus colonized Central America prior to 4 million years ago (Ma), supporting a slightly older than traditional date for the closure of the Isthmus. This study highlights the invaluable role of museum collections in documenting past biodiversity, and these results could guide future conservation efforts. An abstract in Spanish (Resumen) is available as supplementary material.

Whole exome sequencing identifies the potential for genetic rescue in iconic and critically endangered Panamanian harlequin frogs

“…The ESUs were delineated based on both genetic and phenotypic data (Richards & Knowles, 2007), although phenotypes for these species are highly variable across short geographic distances (Savage, 1972). Another recent study using two mitochondrial genes supports the current A. varius / zeteki split but reports little statistical support for internal nodes and overlapping ranges for these species (Ramírez et al., 2020). Therefore, our genome‐wide dataset can serve to clarify the relationships among populations of these species.…”

“…Therefore, our genome‐wide dataset can serve to clarify the relationships among populations of these species. Many of the historical samples sequenced in both mitochondrial DNA‐based studies (Ramírez et al., 2020; Richards & Knowles, 2007) were re‐sequenced for this study, giving us high power to test the original ESU/species boundary hypotheses.…”

“…This supports our finding that proximity is a good predictor of genetic divergence in Atelopus . While recent studies have made progress clarifying species relationships in this system (Ramírez et al., 2020), a broader genome‐wide molecular reanalysis of Atelopus from Central America could serve to further clarify these relationships.…”

“…This species, along with the closely related Panamanian Golden Frog ( Atelopus zeteki ), declined precipitously after Bd swept through Panamá in the early 2000’s (Crawford et al., 2010). These two species, which together form a monophyletic clade (Ramírez et al., 2020; Richards & Knowles, 2007) have garnered significant interest and funding to mitigate population losses, owing in part to their charismatic appearance, historical ubiquity, and cultural significance in Panamá (Poole, 2008). Conservation interventions have included forming robust captive colonies in Panamá and in zoos across the United States (Gagliardo et al., 2008).…”

Systematics and Conservation of Neotropical Amphibians and Reptiles

“…Biogeography is a common thread among five contributions, one on frogs and four on squamates. Ramírez et al [21] examine the radiation of the highly threatened harlequin frogs (Atelopus) into Central America. Their model-based ancestral area estimation supports one or two colonization events from South America.…”