Molecular Systematics of Selected Members of the Black Basses, Genus Micropterus, with Concentration on the Spotted Bass (M. punctulatus) Species Complex
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This study examined genetic relationships among selected populations of black basses. These centrarchid fishes, separated by both physical barriers (land formations) and distance, have shown varying degrees of differentiation, but retain many morphometric characters in common. Eight populations representing four taxa and geographical extremes in the genus Micropterus, with concentration on the spotted bass complex, were selected and evaluated for biochemical genetic characters. This study examined two species and two subspecies of spotted basses. The type species from Kentucky represented Micropterus punctulatus punctulatus; population from Alabama represented M. p. henshalli. A Texas population, previously classified as conspecific with spotted bass but now listed as a distinct species, was included. One primary objective of this study was where the Louisiana populations of M. punctulatus align within this group, as these populations are found at a central geographic position in the distribution of these differentiated basses. Since previous studies have revealed low levels of genetic variability, a technique more sensitive to genetic differences was used, and compared to results from allozyme analysis, the more traditional method for assessing genetic differentiation. Both allozyme analysis and random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) were used to assess genetic relationships.
These two techniques resolved very different relationships. The allozyme study showed the type species, Kentucky bass, as most divergent, but supported the predicted relationships among the remaining four populations. The RAPD-PCR results were in basic agreement with the expected taxonomy. Based on similarities at 302 polymorphic RAPD loci, the two Louisiana and Kentucky populations closely clustered, with the subspecies M. p. henshalli the next most divergent, and M. treculi, diverging next, but completing a cohesive cluster with the other spotted bass relative to the outgroups. A yet unnamed new form from Florida, the Chipola bass, was also analyzed with this technique. PCR results place this form approximately equal distances from the other two outgroup species and the punctulatus group. Therefore, this analysis would support species recognition for the Chipola bass, and regrouping the Texas strain of spotted bass in the M. punctulatus species complex.