An analysis of life histories in freshwater bivalves (Mollusca: Pisidiidae)

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Abstract
A survey of patterns of covariation of six life history traits in 13 species (26 populations) of pisidiid bivalves was carried out using canonical discriminant analysis. The analysis separated the three genera of pisidiids into significantly different clusters. The traits that separated the genera have been called life history tactics and the genera have been placed along an r–K continuum. Univariate phenotypic correlation statistics were used to identify specific life history traits that covary at the genus and interspecific levels. The identifiable groupings of life history traits and traits that strongly covary appear to be influenced in part by phylogeny (size differences between genera), allometry (size differences within a cohort), and habitat (both localized and historical influences). At the present time there is a lack of the detailed intraspecific life history data necessary to sort out the causality behind the groupings of traits. It will be necessary to make detailed comparisons of life histories at the intraspecific level to attain an understanding of the proximal processes involved in causing life history variability.