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

• Main Authors: Quinn, Tom P., Gowell, Conrad P., Taylor, Eric B.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2012
• Subjects: Fish; Morphometrics; Phylogeography; Population genetics; diet analysis; stable isotopes; Pygmy whitefish; Alaska
• Online Access: http://hdl.handle.net/10255/dryad.43222; https://doi.org/10.5061/dryad.7pd82

Ecologically, morphologically, and genetically distinct populations within single taxa often co-exist in postglacial lakes and have provided important model systems with which to investigate ecological and evolutionary processes such as niche partitioning and ecological speciation. Within the Salmonidae, these species complexes have been well studied, particularly within the Coregonus clupeaformis-C. laveratus (lake and European whitefish, respectively) group, but the phenomenon has been less well documented in the other whitefish genera, Prosopium and Stenodus. 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.