Studies of animal communication offer insight into the evolutionary processes of selection and speciation. Signals and displays serve to attract mates and convey information about species and condition of the signaler to the receiver. Because signals are usually a crucial element of mate choice, selective responses by the receiver to species-specific signals represent an important reproductive barrier. Thus geographic variation in signals among populations may be an important factor in speciation.
Advertisement signals and mate recognition are thought to covary with genetic divergence. Interestingly, some populations of the canyon treefrog, Hyla arenicolor, show the expected pattern, but other populations do not. I am interested in understanding why some of these populations do not follow this pattern.
Three genetically distinct (mtDNA) clades occur in the US southwest, and populations range as far as southern Mexico. Genetic divergence among the US clades is similar in magnitude to that found among species in other taxa (Barber, 1999). By contrast, little variation in call traits exists among US clades. Thus, character evolution in call structure does not appear to reflect molecular mtDNA evolution in the US clades. Differences in both fine temporal (pulse rate) and gross temporal (call duration/ rate) properties do, however, exist both between Mexican populations and between US and Mexican populations. The mtDNA data suggests that H. arenicolor may be made up of several species, whereas the call analysis only indicates a possible divergence among the Mexican populations.
My research addresses three main questions:(1) Why are US populations not as divergent in call phenotype as might be expected based on differences in mitochondrial DNA? (2) Are the Mexican populations with different call properties also genetically divergent and hence may represent different or incipient species? (3) Are the differences in calls between Mexican and US populations sufficient to promote selective phonotaxis by females and hence serve as potential reproductive barriers? To address these objectives, I use both molecular phylogenetic methods and behavioral assays.
Recently, we found evidence of mitochondrial introgression between US populations of H. arenicolor with its sister species H. wrightorum. An analysis of calls and genetic divergence among US populations of H. arenicolor found that call divergence better reflects the nuclear phylogeny than that of the mitochondrial phylogeny.
Klymus et al. 2010
Currently, I am using AFLPs to hopefully attain better phylogenetic resolution at a population level.