Competitive interactions

Abstract

The idea that competition influences the distribution and abundance of stream-dwelling organisms has been invoked routinely for more than half a century. Natural populations often are observed to differ in one or more of their ecological requirements; that is, in their niches. As competition theory came to dominate ecology after the mid 1950s, studies of ecological differences flourished, resulting in an extensive literature on resource partitioning. These examples were viewed as evidence that competition was widespread and required a minimum level of niche partitioning to permit coexistence. By the late 1970s skepticism had set in concerning the relationship between niche differences and competition past or present, causing such interpretations to fall from favor. In its place ascended a counter view that also has a long history in stream ecology, that varying environmental conditions coupled with differences in species’ ecologies and life histories may play a greater role in determining species’ abundances than do interactions among species.