Mating Signal Evolution and Sexual Selection in Western Toads
A Department of Ecology and Evolutionary Biology Seminar presented by Greg Pauly, Los Angeles Museum of Natural History
Wednesday, October 03, 2012
12:00 PM - 1:00 PM
Understanding the evolution of mate-recognition systems is of major interest to evolutionary biologists because changes in mating signal production and/or reception can lead to reproductive isolation and speciation. I will describe a unique situation in the western toad, Bufo boreas, in which there is apparent among-population variation in the occurrence of the major mating signal, the male advertisement call. Call surveys and a morphological study of over 1200 specimens for the occurrence of vocal sacs, which are necessary for producing the long calls of most toads, reveal that only populations at the northeastern limit of the species’ range in Alberta and northern Montana can call. I also determine the presence/absence of the female preference for the call using phonotaxis tests in which female responses to test calls broadcast from speakers at opposite ends of an acoustic chamber are scored. These tests demonstrate that females from calling and non-calling populations have the preference for the call. Phylogenetic analyses recover an extreme case of mitochrondrial-nuclear discordance but nevertheless reveal that calling populations are a distinct species that inherited the ability to call from a calling ancestor.