Adaptations in river fishes facilitate species richness

Abstract

The concept of environmental, feeding and reproductive adaptations refers to phenotypic-or genotypic related charecteristics that enable an organism to better cope with specific habitats including other biota and has wide application in understanding species richness and co-existence. Conditions and may facilitate high species diversity. The present study describes the physico-chemical qualities in a large number of river in central Thailand as well as those characteristics associated with the habitat occurrenced of species within two families, Cyprinidae and Balitoridae and one Order, Siluriformes. Adaptations occur also in feeding patterns by fishes occupying similar habitats allowing for resource sharing and species diversity and counter the theory of competitive exclusion. Small but perhaps important dietary differences amoung species further lessen competition and enhance opportunities for species diversity. Reproduction adaptations in fecundity and oocyte diameter among closely related species within the Familiy Balitoridae are suggestive of further adaptations for stability in overall fish population size.