Polymorphism, Mimicry, and the Evolution of the Hamlets (Hypoplectrus, Serranidae)

The hamlets, small western Atlantic serranids in the genus Hypoplectrus, are poorly understood systematically. The 12 apparent species are broadly overlapping in ecology, distribution, and morphology; they differ almost exclusively in color pattern alone. Many of these color patterns are, in turn, subject to considerable geographic and sympatric variation. Apparent hybrids, fishes combining color characteristics of two or more other species, are also common. The primary color patterns are further unusual in that most duplicate, in detail, the color patterns of other common, but non-predatory, fishes, these members of several families. Evidence strongly suggests hamlets to be aggressive mimics of the latter species. The evolution of the hamlets is, therefore, seen as a combination of easy chromatic variation and stabilization of some patterns based on mimetic value. The diversity of hamlet species is the result of the population size of each mimic being limited to some fraction of the population size of its respective model species. Thus, no single mimic can achieve complete dominance and a stable balanced polymorphism is generated.