Shiner perch divergence and the phylogeny
of the Embiotocidae

Vicente Paulo Francisco Cassano
University of California, Los Angeles

Wednesday, July 28, 1999
3:00 p.m.—Pacific Forum

The shiner perch, Cymatogaster aggregata, is a small embiotocid from the northeastern Pacific. Viviparity, in association with their small size, and preference for protected environments, restricts their dispersal abilities. A second species in the same genus, C. gracilis, was erected for a slender allopatric form from Pelican Bay, Santa Cruz Island. Exactly how many distinct species of shiners are there in the California Bight? Allozymes were employed to survey genetic variation in geographic populations to verify if morphological divergence has a genetic analogue. The evidence discovered bears on the taxonomic treatment of this fish and will be discussed.

The phylogenetic relationships of 17 species of surfperches representing all living genera were estimated from a fragment of 486 nucleotides of the mitochondrial gene 16S rDNA. Maximum parsimony, maximum likelihood, and neighbor joining methods were employed to estimate relationships and yield identical results. The surfperches were divided in three groups: a group of amphisticins and two groups of embiotocins. The Japanese surfperch genera Ditrema and Neoditrema form a monophyletic group. Among four North-American genera represented by more than one species in this study, Embiotoca, Hyperprosopon, Micrometrus, and Rhacochilus, only Micrometrus is monophyletic. The arrangement of the species groups indicates that the embiotocid subfamilies, Amphisticinae and Embiotocinae, are monophyletic sister taxa. The phylogeny will be discussed.

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