THE IMPACT OF PREDATION ON LIFE HISTORY EVOLUTION IN TRINIDADIAN GUPPIES (POECILIA RETICULATA).

Abstract

Theoretical studies have demonstrated the potential importance of demographic selection in molding life history patterns. Some of the factors which have been examined include density-dependent versus density-independent mortality (MacArthur and Wilson, 1967), fluctuations in the survivorship of some or all age classes (Murphy, 1968; Schaffer, 1974; Hirshfield and Tinkle, 1975), and changes in the mean survivorship of specific age classes (Gadgil and Bossert, 1970; Law, 1979; Michod, 1979; reviewed by Stearns, 197 6a). Empirical studies have sought correlations between life histories and potential sources of demographic selection and, in some cases, have attempted to determine if the organisms have evolved as predicted by theory (reviewed by Stearns, 1977). These studies have found interand intraspecific life history variations that are often consistent with theory. However, in interpreting these variations as the product of evolution and relating them to theoretical predictions, one must both demonstrate that the observed differences have a genetic basis and characterize the type of natural selection. Few empirical studies have achieved either goal. Other criteria for adequately testing life history models are presented by Stearns (1977). Natural populations of guppies (Poecilia reticulata Peters) provide an opportunity to resolve many of the difficulties in empirical life history studies. They are easy to breed and have a short generation