Williams’ Principle: An Explanation of Parental Care in Teleost Fishes

Abstract

Parental care may be defined as an association between parent and offspring after fertilisation that enhances offspring survivorship. This phenomenon has attracted the attention of evolutionary biologists since Darwin; however, it was not until the recent insurgence of behavioural ecology and sociobiology (e.g. Williams 1966a; Trivers 1972; Alexander 1974; Wilson 1975) that the variety of parental care patterns in animals has attracted such rigorous study. Perhaps because we ourselves are mammals, we tend to think of parental care as being the principal occupation of females, possibly with some help from males. A survey of the vertebrates, however, reveals that mammals are merely at one end of the spectrum, with predominantly female care, and fishes are at the other end, with predominantly male care (Table 11.1; see also Chapter 10 by Turner, this volume). Within teleost fishes with external fertilisation (about 85 per cent of all teleost families), one finds that the four states of parental care, ranked in descending order of their frequencies, are: no care, male care, biparental care, and female care. This seemingly peculiar trend has attracted considerable attention from evolutionary biologists, who have proposed several hypotheses about the origins of parental care in fishes (see reviews by Maynard Smith 1977; Blumer 1979; Perrone and Zaret 1979; Baylis 1981; Gross and Shine 1981; Gross and Sargent 1985).