Allozyme and Morphological Variation among Three Nominal Species of Ambloplites (Centrarchidae) Inhabiting the Ozarks Region

Abstract

A simple means for in situ identification of three species of Ambloplites occurring in Missouri's Ozarkian watersheds does not currently exist, presenting a difficulty for resource managers. Species distributions are not accurately documented because of an insufficient method of morphological identification. To address this difficulty, we examined allozyme and morphological variation to develop a method for identifying the species. Variation at 41 protein-coding loci and 21 morphometric and meristic characteristics was assessed for 50 collections representing the three species' ranges, including 36 sites in the Ozarks and adjacent Lowland region. Ozark bass Ambloplites constellatus displayed significant divergence from rock bass Ambloplites rupestris and shadow bass Ambloplites ariommus with both allozyme and morphological analyses. We observed little divergence between rock bass and shadow bass, although two collections of shadow bass from Florida and Alabama drainages displayed divergent genetic arrays from all other collections and from each other. Ozark bass, which has the most restricted distribution, had the lowest average heterozygosity. Patterns of genetic variation in the Gasconade River, a system of taxonomic concern in Missouri, supported historical information that Ambloplites had been introduced into that drainage. Analysis of allozyme and morphological variation provided an adequate means for identification of Ozark bass but did not allow for separation of rock bass and shadow bass. The status and distribution of the three species in the Ozarks cannot be documented until the taxonomic relationship of rock bass and shadow bass is resolved.