Avoiding extinction in a rapidly-changing environment often relies on a species’ ability to quickly adapt in the face of extreme selective pressures. Two closely-related species perched on the edge of the extinction vortex are the Panamanian golden frogs (Atelopus varius and Atelopus zeteki) (PGF). The most significant factor contributing to the decline of these two species is the fungal pathogen Batrachochytrium dendrobatidis (Bd), which swept through Panama in the early 2000’s. Once thought to be extirpated from Panama, PGF populations have recently been rediscovered in multiple sites across their historic range. Additionally, many persisting PGF individuals are Bd-positive, indicating that these populations may now be tolerant to Bd. Using tissue samples collected before and after the Bd outbreak in Panama, we used genomic sequencing to 1) describe the genetic diversity of contemporary PGF populations in the wild and in captivity 2) compare contemporary genetic diversity to pre-Bd genetic diversity in PGF populations, and 3) search for specific genes under positive selection in persisting populations. Our research aims to inform conservation and captive management of these species as well as evaluate the potential for evolutionary rescue in imperiled amphibians.
Results/Conclusions
For this study, we used an exome capture approach to sequence the coding regions of the Atelopus varius/zeteki genome. First, we sequenced, assembled, and annotated the transcriptome of three Atelopus varius (one healthy and two Bd-infected). We used these data to design a capture assay targeting 15,454 genes for a total target size of 1.9 Mb. We successfully sequenced the exome of 187 Atelopus varius/zeteki (130 pre-Bd, 39 contemporary, 18 captive individuals) and 4 outgroups. The contemporary individuals were concentrated in four localities and were exclusively A.varius. Average coverage across each sample ranged from 8x- 51x. Preliminary analyses reveal that persisting individuals are most closely related to historic populations from the same locality, indicating in-situ persistence rather than recent colonization. Further analyses, including scans for genes under selection in persisting populations and a description of the genetic diversity of wild and captive populations are currently underway. These results will reveal the current genetic diversity of this species in Panama and will contribute to our understanding of how quickly amphibian species can evolve in the face of devastating population declines, such as those caused by Bd outbreaks.