Background Matching and Color-Change Plasticity in Colonizing Freshwater Sculpin Populations Following Rapid Deglaciation

Abstract

Anthropogenic-induced change is forcing organisms to shift their distributions and colonize novel habitats at an increasing rate, which leads to complex interactions among evolutionary processes. Coastrange sculpin (Cottus aleuticus) have colonized recently deglaciated streams of Glacier Bay in Alaska within the last 220 years. We examined divergence among populations in background matching coloration and tested the hypothesis that observed variation is due to morphological color plasticity. To examine how color-change plasticity has interacted with other evolutionary processes, we also determined the influence of colonization on neutral genetic diversity. We observed clinal variation in substrate-matching fish color along the chronological continuum of streams. Microsatellites provided little evidence of genetic subdivision among sculpin populations. Fish color was significantly correlated to substrate color, but was not correlated to neutral population genetic structure. Furthermore, a laboratory experiment revealed that morphological color plasticity could explain much, but not all, of the observed fish color divergence. Our study demonstrates that sculpin in Glacier Bay have colonized and adapted to recently deglaciated habitat and suggests that color change plasticity has aided in this process. This research, therefore, highlights the important role phenotypic plasticity may play in the adaptation of species to rapid climate change.

Social hierarchies override environmental conditions in determining body coloration of brook trout

“…Losers of territorial disputes display submissive darkening to avoid conflict with familiar dominants (H€ oglund et al 2000;O'Connor et al 2000) and thus allowing for stable groups to form social hierarchies through cooperative signaling (Hurd 1997). Previous research indicates that the basis of color change is morphologic plasticity with very little genetic control (Whiteley et al 2009;Westley et al 2013), and that skin darkening is positively correlated with stress hormones (Boddingius 1976;H€ oglund et al 2000).…”

Phenotypic plasticity in the Antarctic nototheniid fish Trematomus newnesi: a guide to the identification of typical, large mouth and intermediate morphs

“…Among taxonomically diverse benthic Wsh, there are many examples of 4-5 dark lateral blotches against a lighter background, a pattern imparting crypsis through disruptive colouration (Armbruster and Page 1996;Whiteley et al 2009). Benthic species are generally more cryptically coloured than pelagic species (Clarke and Schluter 2011), and intraspeciWc variation in colour and shorter upper jaw (arrows) and narrower gape width but has nearly the same head width across the opercles and the same U-shaped head proWle as the large mouth morph.…”

Assessing the distinctiveness of the Cultus pygmy sculpin, a threatened endemic, from the widespread coastrange sculpin Cottus aleuticus

“…Combined with the relatively recent time since postglacial colonization, large population sizes and high levels of dispersal, the amount of gene flow could be high enough to minimize the effects of genetic drift and explain the low interpopulation differentiation seen in sculpins across most of our study area (see also Whiteley et al 2009). The most geographically distant population, Lake Washington, however, was highly distinct in the microsatellite analyses, which suggests that these fish had a separate origin from those in Cultus Lake.…”

“…These results are consistent with the few other studies that have been conducted on freshwater sculpins. For instance, Whiteley et al (2009) Taylor et al unpubl.). Consequently, compared with the low values observed in other systems (e.g.…”

“…We genotyped 350 fish at 8 Cottus gobio dinucleotide microsatellite loci (Nolte et al 2005, Whiteley et al 2009). These loci were amplified by PCR using fluorescently-labelled primers (see Tables S1 & S2 in the Supplement at www.…”