Geographic variation in acoustic signaling in the guardian darter Etheostoma oophylax: effects of contemporary versus historical isolation

Abstract

Geographical variation in acoustic signals has been demonstrated in many taxa, including freshwater fishes. Previous studies have investigated variation in acoustic signaling between populations naturally isolated into separate drainages. However, the effect of man-made habitat modifications such as dams on the evolution of communication in fishes in unexplored. We used the guardian darter, Etheostoma oophylax to test for geographic divergence in acoustic signals in three streams in the Tennessee River Drainage. Panther and Sugar creeks were once linked by the Blood River but were isolated with the installment of the Kentucky Dam in 1930, while Anderson Creek was historically isolated from these two streams. This framework allowed us to test the effect of isolation on signal structure in these populations for both long and short timescales. We discovered significant variation in both the spectral and temporal components of E. oophylax vocalizations between sites isolated due to drainage locality, but not among sites isolated by the dam. We conclude that geographic isolation is contributing to signal divergence but it is likely that less than a century is not long enough of a timescale for signal divergence between Panther and Sugar Creek to become detectable.