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Life History Variation Among Populations of an Amphipod (Hyalella Azteca)

1972; Wiley; Volume: 53; Issue: 6 Linguagem: Inglês

10.2307/1935422

1939-9170

Donald R. Strong,

Environmental Toxicology and Ecotoxicology

Inheritable differences in life history features are shown among three groups of populations of Hyallela azteca from Oregon. Hyallela individuals of coastal populations are relatively small as eggs, as young, and as adults. They grow slowly as young and adults, and the regression of clutch size on female size is relatively steep. Hyallela individuals from the Cascade Mountains are large as eggs, as young, and as adults. They grow rapidly as young and adults, and the regression of clutch size on female size is relatively less steep. A population of Hyalella from a hot springs is made up of animals that are intermediate in these characteristics. The maturation period and the rate of production of egg volume does not differ among the populations investigated. Selection for inconspicuousness, generated by visually orienting predaceous fish, is probably responsible for the small, slow—growing end of the character spectrum (coastal populations). Hyallela is a grazer and deposit feeder, it does not filter. Evidence indicates that larger Hyalella do not have a competitive advantage in predator—free environments, as do larger planktonic filter feeders.