The Invertebrate Fauna

Abstract

The invertebrate community of lotic ecosystems is, with some specific exceptions, a remarkably conservative assemblage of types that recur in similar biotopes regardless of geographical location. Similar environ mental niches (physical/chemical/biotic) harbour analogous taxa, often of the same familial or generic group, wherever such habitats are found (see Botosaneanu 1960, Illies 1961b, Hynes 1970). The fauna of the upper Gombak River, in its essential features, has few differences from and considerable affinities with the rheophile rain forest assemblages of Africa, Ceylon and tropical America, while the lower river shares many features with lowland ‘potamon’ reaches of rivers throughout the world. Structurally, the community parallels that found in more temperate streams with the notable difference that species diversity in many groups is greater and the population of any particular species comparatively smaller. Asynchronous and non-seasonal life cycles combine to keep population densities low and this, with the variety of relatively constant, but not necessarily stable, microhabitats available, permits multiple congeneric combinations or groups of unrelated invertebrates apparently exploiting the same feeding niches to occur.