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

Roberto Ibáñez,César Jaramillo,Erik Lindquist,Juan Ramírez,Andrew Crawford

doi:10.3390/d12090360

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.

Highlights

Amphibians are experiencing a global conservation crisis, with an estimated 41 to 50% of species suffering population declines [1,2,3]
Geographic variation in color pattern has been documented for A. varius and A. zeteki [63,73], and we found distinct color pattern variants among populations of A. glyphus and A. limosus along their distribution ranges
The phylogenetic analyses revealed a ladderized topology showing the Central American species as a monophyletic group, and placing the species geographically furthest from South America more nested in the tree

Summary

Introduction

Amphibians are experiencing a global conservation crisis, with an estimated 41 to 50% of species suffering population declines [1,2,3]. Harlequin frogs of the genus Atelopus (Anura: Bufonidae) have arguably suffered the most dramatic population declines and extinctions of any diverse genus of amphibians. Because of their diurnal habits, bright coloration, and previously high local abundance, species of this genus were a prominent element of many Neotropical communities until about 35 years ago [7,8,9]. Declines of Atelopus and other amphibian species have been considered to be most severe in populations at higher elevations (above 1000 m above sea level) [13], hypothetically because the lower temperatures present at higher altitudes are associated with higher levels of infectivity and fecundity in Bd [14]

Methods

Results

Discussion

Conclusion