Data from: Coexistence and origin of trophic ecotypes of pygmy whitefish, Prosopium coulterii, in southwestern Alaskan lake

Here, we examined the morphology, feeding biology, and genetic structure of three putative forms of the pygmy whitefish, Prosopium coulterii, that were first reported from Chignik Lake, southwestern Alaska, over 40 years ago. Field collections and morphological analyses resolved a shallow water (< 5 m depth) low gill raker count form (< 15 first arch gill rakers), a deepwater (> 30 m), low gill raker form, and a deepwater, high gill raker count (> 15 gill rakers) form.

The two low gill raker count forms fed almost exclusively on benthic invertebrates (mostly chironomids), while the deepwater, high gill raker count form fed almost exclusively on zooplankton, differences in diet that were also reflected in differences both in δ13C and δ15N stable isotopes. All three forms were characterized by the same major mitochondrial DNA clade that has been associated with persistence in, and postglacial dispersal from, a Beringian glacial refugium.

Analysis of variation at nine microsatellite DNA loci indicated low, but significant differentiation amongst forms, especially between the two low gill raker count forms and the high gill raker count form. The extent of differentiation along phenotypic (considerable) and genetic (subtle) axes amongst the Chignik Lake forms is similar to that found amongst distinct taxa of Prosopium found in pre-glacial Bear Lake (Utah-Idaho, USA) which is probably at least ten times older than Chignik Lake.

Our analyses illustrate the potential for the postglacial differentiation in traits subject to divergent natural selection across variable environments. Usage notes microsatellite allele frequencies Microsatellite DNA allele frequencies in base pairs April113 Stomach contents proportional diet contents (range from 0 - 1.0) for pygmy whitefish dryad.xls Stable isotope data Stable isotope (C, N) for Chignik Lake pygmy whitefish collected in 2008, 2009 dryad.xls distancesfromlandmarks_dryad linear distances from landmark data for pygmy whitefish collected 2008, 2009 from Chignik Lake