The Tetraploid Treefrog Hyla versicolor: Evidence for a Single Origin from the Diploid H. chrysoscelis

• Published in: Herpetologica 1983-09, Vol.39 (3), p.212-225
• Main Authors: Ralin, Dennis B., Romano, Michael A., Kilpatrick, C. William
• Format: Article
• Language: English
• Subjects: Alleles; Animal genetics; Boggarts; Diploidy; Evolutionary genetics; Genetic loci; Herpetology; Hyla chrysocelis; Hyla versicolor; Population genetics; Population geography; Tetraploidy
• ISSN: 0018-0831; 1938-5099

Twelve enzyme loci are examined electrophoretically in two populations (Vermont and Illinois) of the tetraploid treefrog Hyla versicolor and in one population (Illinois) of its diploid progenitor H. chrysoscelis. Allele frequencies are compared with those found in earlier samples of northern (New York and New Jersey) and southern (Texas) H. versicolor and eastern (South Carolina, Georgia, Ohio, Mississippi) and western (south-central Texas) H. chrysoscelis. At several loci (Lda, Ldb, Sod), the Vermont tetraploids contain electromorphs that are found in Texas and Illinois populations of H. versicolor and H. chrysoscelis, but not in eastern H. chrysoscelis. A multiple origin hypothesis for H. versicolor cannot be accepted unless it is assumed that (1) a complex series of parallel independent mutations occurred between geographically distant tetraploid populations; and (2) northeastern and southern tetraploids arose simultaneously from geographically distant diploid populations, followed by a third, much later, origin from H. chrysoscelis in the central part of the range. The single origin hypothesis, that H. versicolor arose from a genetically intermediate population of H. chrysoscelis in the central part of the latter's range, and evolved allele frequencies similar to eastern and western diploid populations in the northeast and southwest, provides a better explanation of present and earlier data without requiring any biologically improbable assumptions. The observations that Illinois H. versicolor are genetically intermediate between northeastern and Texas tetraploid populations, especially at two diagnostic loci (Ldb and Sod), and that Illinois H. versicolor and H. chrysoscelis show the highest interspecific similarities in the complex, also support the single origin hypothesis. Since the Illinois population of H. chrysoscelis contains alleles at diagnostic loci that were formerly thought to occur in either eastern or western H. chrysoscelis and H. versicolor, there is no absolute biochemical distinction between the two diploid population groups. There is, therefore, no evidence to support the claim (Maxson et al., 1977) that there are two species of H. chrysoscelis. The existence of a genetically intermediate population of H. chrysoscelis in the central portion of the range, with a Nei's (1972) D of only 0.017 to a parapatric, genetically intermediate population of H. versicolor, supports earlier, erroneously interpreted information indicating that H. ver