Decline in the Diversity of Bivalvia Ninnescah River, Kansas

At least 22 species of bivalve mollusks historically have occurred in the Ninnescah River Basin. Fifteen native unionacean species are extirpated and six exist in low numbers. The exotic species, Corbicula fluminea, is the most abundant and widespread bivalve in the system. Slow climatic changes from cool-moist to warm-dry following the last glacial period and rapid changes in stream regimen initiated by EuroAmerican settlement of the region in the 1880's are proposed as factors in this decline.