Morphological correlates of ecological specialization in darters

TL;DR: While competition from established taxa undoubtedly has prevented additional habitat invasions, some darters appear to have overcome barriers through feeding site diversification and sexually selective characteristics, correlated with type of reproductive behavior and habitat, often make the male more conspicuous and therefore are constrained by predation.

Abstract: Darters feed on small benthic organisms, primarily insects, and evolutionarily have become increasingly small and benthic; most species are less than 80mm in standard length. Constraints on decreasing body size include living in midwater and territoriality. Lineages of darters have arisen as new habitats were invaded. Consequently, members of different lineages often vary in characteristics correlated with specific habitat variables. While competition from established taxa undoubtedly has prevented additional habitat invasions, some darters appear to have overcome these barriers through feeding site diversification. Living in various habitats has lead to a variety of reproductive strategies, termed egg-burying, -attaching, -clumping, and -clustering. Sexually selective characteristics, correlated with type of reproductive behavior and habitat, often make the male more conspicuous and therefore are constrained by predation.