Fitness Differences Among Remnant Populations of the Endangered Sonoran Topminnow

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Abstract
Four correlates of fitness were measured in three stocks of the endangered Sonoran topminnow, Poeciliopsis occidentalis, from Arizona. Survival, growth, early fecundity, and developmental stability were greatest in laboratory-reared fish from the most heterozygous natural population studied. Conversely, all four traits were poorest in fish from a population with no electrophoretically detectable genetic variation. These results emphasize the need for genetic as well as demographic information for the development of comprehensive species recovery programs.