Meeting Abstract
With many advantages, vocalization is perhaps the most common form of communication used by vertebrates. Anurans use advertisement calls to acquire mates, thereby affecting both male fitness and premating reproductive isolation. Anaxyrus fowleri or Fowler’s toads, are abundant on the coastal plain of the eastern USA and inhabit both the mainland and barrier islands of the Atlantic Coast. Previous studies reported island dwarfism in populations of A. fowleri on mid-Atlantic Coast barrier islands. Our goal was to test for an association between the small body size of island toads and vocal characteristics of island males. The advertisement calls for 31 mature males were recorded during the breeding seasons of 2010 and 2012, from both island and mainland sites along the Eastern Shore of Virginia. Calls were imported into RavenPro 1.4 to extract data on 12 different call variables. These variables were analysed by principal components analysis (PCA) to study the relationships among the call characteristics. Each call characteristic was also analysed with repeated measures nested ANOVA, to test for differences between island and mainland toads. The PCA indicated that the first two components were responsible for explaining 43% of the total variation in advertisement calls among sites. Six variables loaded on the Principal Component (PC) 1: resonance bandwidth, intensity modulation, lower delta side band, detuning parameter, call length, and the damping parameter. Fundamental frequency, resonant frequency, frequency range, and beginning pulse duration loaded on PC 2. The ANOVA tests indicated differences in resonant frequency between the island and mainland populations. These results support the hypothesis that island dwarfism affects the advertisement calls of these toads.
