Phylogeography of the canyon treefrog, Hyla arenicolor (Cope) based on mitochondrial DNA sequence data

Patterns of phylogeography and gene flow were examined in the canyon treefrog, Hyla arenicolor. A total of 973 bp of mitochondrial cytochrome b sequence data were obtained for 65 individuals from 53 populations, yielding 50 unique haplotypes. Interpopulation sequence variation ranged from 0 to 13.7%. Phylogenetic analysis revealed three deeply divergent mtDNA lineages. These three Clades were mapped onto geography and found to represent completely concordant, nonoverlapping, geographical regions. Levels of sequence divergence between the three Clades were equal to or greater than published levels of divergence found in other vertebrate species and genera. Furthermore, one Clade of H. arenicolor was found to be more closely related to the outgroup H. eximia than to other H. arenicolor, suggesting that the taxonomy of this species may require revision.

Viable amphibian hybrids produced by circumventing a block to cross-fertilization(Rana clamitans female x Rana catesbeiana male)

Eggs of Rana clamitans in their own jelly coat are not fertilized by sperm of other species. When the eggs were surrounded by jelly from another species, they were fertilized by R. catesbeiana and R. septentrionalis sperm. The hybrid nature of the resulting embryos was confirmed by detection of paternal enzyme forms. The R. clamitans female times R. septentrionalis male embryos arrested by the tailbud stage. The R. clamitans female times R. catesbeiana male embryos developed into viable tadpoles and subsequently metamorphosed. The hybridization results coupled with the similarity of enzyme patterns indicate that R. clamitans and R. catesbeiana are genetically closely related. R. clamitans is probably not as closely related to R. septentrionalis based on the enzyme patterns. Since cross-fertilization or early developmental failures of hybrids could be explained by a small number of genes, such failures must be considered with caution in determining species relationships.