GENETIC RELATIONSHIPS OF THE COLOR MORPHS OF THE SERRANID FISH HYPOPLECTRUS UNICOLOR.

Abstract

Fishes of the genus Hypoplectrus, commonly known as hamlets, are small serranids limited to the New World tropics. Like other members of the subfamily Serraninae, they are synchronous hermaphrodites (Smith, 1965). Ten species are currently recognized, nine in the Atlantic and one in the Pacific. The eastern Pacific species H. lamprurus, of which only a few specimens exist, none collected recently, differs from Atlantic material both in relative scale size and gill raker number (Meek and Hildebrand, 1925). Robins and Starck (1961) suggested that H. lamprurus be placed in the genus Serranus, but Kendall (1977) has given reasons for maintaining it in Hypoplectrus. The number of species to be recognized in the Atlantic has long presented difficulties to systematists. Currently, nine named species are recognized, differentiable on the basis of color pattern (see Randall [1968] for color plates of eight of the nine) and at least three additional distinctive unnamed color types have been distinguished (Thresher, 1978). However, none of the color forms can be differentiated morphometrically or meristically (C. R. Robins, pers. comm.). Fischer (1979) did demonstrate some differences in body depth in five color types. However, no color type could be distinguished from all others, and allopatric populations of the same color type also differed significantly in body depth. The synchronously hermaphroditic hamlets are reported to spawn in pairs (Barlow, 1975). Although assortative mating by color form is usually the case, mixed pairs have been observed, and spawnings in such pairs have been seen (Barlow, 1975; Fischer, 1979). Whether such associations result in viable offspring is not known; however, several fish have been observed in the field which exhibit color markings characteristic of two or more color forms (Thresher, 1978; Fischer, 1979). Thresher (1978) has reviewed the problem. He concluded that hamlets are aggressive mimics, duplicating the color patterns of common, nonpredatory reef fishes. He suggested that a stable series of polymorphs could have evolved without complete speciation but that some degree of reproductive isolation was necessary. On the basis of the data then available, he did not directly address the question of the systematic status or genetic relationships of the color morphs. It was the purpose of our study to examine this question by means of an electrophoretic survey of protein polymorphism within and between the color morphs of Hypoplectrus. We have examined all nine named color morphs and an additional unnamed type. Inasmuch as our results support the hypothesis that the hamlets should be referred to a single species, we will use the common names to designate the color types in our discussion. The nominal species and common names of the color morphs examined by us are given in Table 1. In addition, Thresher (1978) has distinguished the Blueback hamlet and the Bicolor hamlet.