Abstract - Animal Conservation

The response of quantitative traits in translocated populations has not been well explored. Evolutionary shifts in quantitative traits, such as life history characteristics, are of particular interest because such traits contribute to our perception of biodiversity. In a recent survey, Stockwell (1995) examined life history variation of four populations of western mosquitofish (Gambusia affinis) that were derived from a common ancestral population 55-58 years earlier. Three life history traits differed considerably among the four sites and appeared to be correlated with local environmental conditions. To test whether these differences were due to plasticity or rapid evolution, fish from the four sites were maintained under common-garden conditions for two generations. After two generations, no differences among populations were observed for one of the three traits: offspring size. However, the other two (fat content and size at maturity) varied significantly among populations. Thus, differences observed in the field reflected phenotypic plasticity for offspring size but rapid evolution apparently occurred for size at maturity and fat storage for these recently established mosquitofish populations. These life history differences may have arisen by genetic drift and/or natural selection. These data, combined with data from a variety of other taxa, suggest that translocations may alter the evolutionary trajectory of the targeted taxa. Our findings provide additional impetus for the protection of species in their native range.

Last Updated : 7/23/99

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