AUTHORS: Owen M. Edwards, Oklahoma Biological Survey; Neil R. Balchan, Oklahoma State University; Kaleb M. Banks, Oklahoma State University; Michael S. Reichert, Oklahoma State University; Fabio A. Machado, Oklahoma State University; Bo Zhang, Oklahoma State University; Damien Esquerré, University of Wollongong
ABSTRACT: During the breeding season, male anurans utilize advertisement signals to attract mates. However, in many scenarios, mate signaling and subsequent reproduction can occur in shared bodies of water in which numerous different species congregate and reproduce at the same time. As a result, natural hybridization between closely related species is not uncommon, and can have major consequences on fitness and evolutionary processes. The crawfish frog (Rana areolata) is a secretive anuran that has disjunct distribution in the southern and midwestern United States. Over the last 50 years, there has been a rapid and ongoing population decline of these frogs in many states in their range, largely attributed to habitat loss and landscape changes. We conducted population monitoring using drift fences and pitfall traps in a breeding population of R. areolata in Oklahoma. During the first year of the study, we discovered individual putative R. areolata hybrids at our study pond: one breeding adult resembling R. palustris x R. areolata, and another breeding adult resembling R. sphenocephala x R. areolata. Here, we confirm the status of these hybrid individuals using 1) cranial morphology via microCT scanning and 2) genome-wide single-nucleotide polymorphism (SNP) data. Hybrid skulls represent phenotypic intermediate between parental populations, and preliminary analysis of SNP data indicate that both hybrid individuals are F1 crosses (with R. palustris a R. sphenocephala respectively). Our data confirm the ability of R. areolata to hybridize with congeners in a wild population, and offer the first documentation of hybridization occurring in R. areolata. We demonstrate that contemporary gene flow may be important for divergent ranid frogs, and suggest that associated conservation implications may be present.
