Meeting Abstract

P2.11  Monday, Jan. 5  Sexual dimorphism of electrocommunication signals across populations of the weakly electric fish Apteronotus albifrons RACK, J.M.*; HO, W.W.; SMITH, G.T.; Slippery Rock Univ., PA; Indiana Univ., Bloomington; Indiana Univ., Bloomington jmr9439@sru.edu

Weakly electric fish produce electric organ discharges (EODs) for electrolocation and communication. Both EOD frequency (EODf) and EOD modulations (chirps) vary across species, sexes, and individuals. EOD modulations can also vary across populations of the same species (Turner et al. 2007). The focus of this study was to examine population-level variation in the sexual dimorphism of electrocommunication signals. We characterized EODs in four populations of A. albifrons, and used mtDNA cytochrome-b sequence to examine genetic relationships between populations. Individuals from populations in the Orinoco drainage (CO-oc and CO-jn) or the Amazon drainage (PE and BR) were presented with playbacks of synthetic conspecific EODs, and their EODs and chirps recorded. EODf was sexually dimorphic in both CO populations, but did not differ significantly between the sexes in the PE and BR populations. Consistent with previous studies (Dunlap et al. 1998; Kolodziejski et al. 2005), chirp rate did not differ between sexes in any of the A. albifrons populations. Chirp frequency modulation and duration were also sexually dimorphic in the Orinoco, but not the Amazon populations. Overall, populations from the same river systems were more genetically and behaviorally similar than populations in separate river systems. This is consistent with the hypothesis that diversity in sexually dimorphic EOD behavior has evolved in allopatry, with South American watersheds acting as barriers for reproductive isolation.