Fish life-history traits predict patterns of occurrence and assemblage composition in prairie streams

Prairie stream ecosystems have undergone dramatic changes since American colonization began in the mid-1800’s.  In the Kansas River basin for example, early extirpations (prior to 1920) of native fish species were associated with increased row-crop agriculture, whereas more recent changes to stream faunas (after 1960) are associated with species introductions and more stable hydrology due to river impoundment (favoring some native species as well as introduced species).  Using a long-term database of fish collections (1885-2003; n=603) across the Kansas River basin, we related trends in occurrences of 72 species to a suite of 17 life-history traits.  Traits included age and size at maturity, mean and maximum clutch size, mean and range of egg size, egg characteristics and time to hatching, duration of spawning season and number of bouts per year, maximum body size and longevity, indices of relative anadromy and parental care, and growth rates for larvae, YOY and adults.  PCA of these life-history variables explained approximately 90% of variation on the first two axes.  MANOVA of species scores on PC1 and PC2 did not distinguish native from non-native species (P=0.092), however differences among taxonomic families (p<0.001), habitat associations (p<0.001), and trophic groups (p=0.001) were observed.  Among sample differences in fish assemblage composition were explained by life-history traits (p=0.015), which correlated with a habitat template based largely on hydrology.  Understanding functional relationships among species population trajectories and anthropogenic impacts such as hydrological modification will aid in predicting how future changes will affect patterns of biological and functional diversity.