Biochemical and Morphological Evolution of Hawaiian Bonefishes (Albula)

Abstract

Biochemical and morphological evolution of Hawaiian bonefishes (Albula). Syst. Zool., 30:125–146.—Electrophoretic analysis of the protein products of 84 presumed gene loci for over 180 specimens reveals that two distinct species of bonefishes occur in Hawaiian waters. Both species are characterized by low levels of within-species variation (H = 0.005 and 0.022). However, the two species are well differentiated from each other; they possess fixed allelic differences at about 70% of the loci screened and have a calculated genetic distance of 1.16. There is no evidence that the two species hybridize although they co-occur on both a macro and a microgeographic scale. The magnitude of genetic differentiation between the two species suggests that they have been separate genetic units for approximately the last 20–30 million years. Although the two species of bonefishes in Hawaii are superficially very similar morphologically, there are a number of significant differences. The distributions of vertebral counts for the two species are completely non-overlapping, and the mean values for several meristic variables (including numbers of lateral-line scales, branchiostegal rays, and gill rakers) are significantly different in the two species. The single best field character for diagnosis is the shape of the lower jaw which is broadly rounded in one species and more angular and pointed in the other species. A number of traits associated with the head and feeding (lower jaw shape, number of gill rakers, shapes of tooth patches, and number of teeth) differ in the two species. Stepwise discriminant function analysis using 31 morphological characters demonstrates that the two species have distinctively different overall morphologies and that they can be distinguished with over 99% accuracy.