Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fishParamormyrops kingsleyae

Abstract

This study examines evolutionary causes underlying the maintenance of diversity in electric courtship signals (EODs) emitted by the mormyrid electric fish species Paramormyrops kingsleyae. P. kingsleyae are polymorphic for an EOD feature which characterizes interspecific signal diversity among the rapidly diverged Paramormyrops genus. We collected 338 specimens and recorded EOD signals from 9 populations distributed throughout Gabon, west central Africa, collected in 1999Africa, collected in -2009. First, we demonstrate using microsatellite genotyping a significant signature of isolation by distance between populations. Second, utilizing principal components analysis of 21 landmarks measured from EOD waveforms, we find that EOD duration and the magnitude of a small head negative pre-potential (P0) are highly correlated with patterns of spatial and genetic structure. Finally, utilizing a behavioral assay, we demonstrate that P. kingsleyae individuals can discriminate between P0-absent and P0-present EOD waveforms, although genetic and morphological analysis indicate no assortative mating between signal types. Together, these results support the hypothesis that patterns of signal variation in P. kingsleyae have resulted from genetic drift acting upon isolated populations. As P. kingsleyae represents a microcosm of signal diversity among mormyrids, these findings illustrate a potential mechanism by which interspecific patterns of EOD diversity may originate at the population level.

Selection, drift, and constraint in cypridinid luciferases and the diversification of bioluminescent signals in sea fireflies

“…Visual pigment genes (opsins) are a prime example of a gene family that underlies an organismal phenotype (colour sensitivity) with a shared genetic basis across species (Henze & Oakley, 2015; Spaethe & Briscoe, 2004; Yokoyama, 1997). While most genomic and single‐gene studies highlight how selection and/or epistasis impact phenotypic diversification (Brawand et al., 2014; Yokoyama et al., 2015), a role for neutral processes has been largely overlooked at causal loci, despite its theoretical prevalence (Mendelson et al., 2014; Shaw & Parsons, 2002) and known contribution at the phenotypic level (e.g., Campbell et al., 2010; Irwin et al., 2008; Martin & Mendelson, 2012; but see Picq et al., 2020, who explicitly consider the neutral alternative).…”