Molecular and Acoustical Verification of Hybrids of Cope’s Gray Treefrogs (Dryophytes chrysoscelis) and Pine Woods Treefrogs (Dryophytes femoralis) in Virginia and North Carolina

David R. Weisenbeck^1,*, Michael D. Martin², Benjamin J. Hall³, Christopher C. Jackson⁴, and Bryan L. Stuart⁵

¹Department of Biology, University of Kentucky, 101 T.H. Morgan Building, Lexington, KY 40508. ²Wildlife Diversity Program, North Carolina Wildlife Resources Commission, 1701 Mail Service Center, Raleigh, NC 27699-1700.³Genetics Program, North Carolina State University, Campus Box 7614, Raleigh, NC 27695. ⁴Department of Electrical and Computer Engineering, Old Dominion University, 231 Kaufman Hall, Norfolk, VA 23529. ⁵Section of Research and Collections, North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601. *Corresponding author.

Southeastern Naturalist, Volume 24, Issue 1 (2025): 83–96

First published early online: 30 March 2025

Abstract
In recent years, hybridization has come into focus as a potent force with a myriad of evolutionary outcomes. Natural hybridization has been documented across the hylid treefrog genus Dryophytes, but few studies have demonstrated the origins of putative natural hybrids. Here, we use molecular and acoustical data to test the parentage of 2 putative D. chrysoscelis x D. femoralis hybrids found in the wild in Virginia and North Carolina. Using 1 mitochondrial and 4 nuclear loci, we demonstrate that these 2 individuals are genetically intermediate between D. chrysoscelis (Cope’s Gray Treefrog) and D. femoralis (Pine Woods Treefrog), with differing maternal species. The mating calls of hybrids are consistent with those of previous studies and feature a breakdown in structure that may result from an intermediate phenotype between the unpulsed and pulsed notes of the respective parent species. While hybridization between the 2 species is apparently rare, our results combined with previous laboratory studies demonstrate the potential for introgressive hybridization, necessitating further work to identify the extent of hybridization in the system.

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