Ecomorphological analysis of fish taxocenes in rainforest streams of northern Borneo

Abstract

Average species richness for fish taxocenes in the Nida River (Poland), Grand River (Ontario) and Baram River (Sarawak, Malaysia) was 7, 16 and 24 species respectively. Discriminant analysis of 15 morphological attributes indicated Baram fishes partitioned the habitat vertically into mainly surface, pelagic, benthic and substratum niche types. Attribute comparisons among the river systems revealed a progression towards more sedentary benthic morphologies with increasing average species richness. Similarly, niche compression as a consequence of increasing average species richness was indicated by a reduction in length of life and average size, and was associated with development of complex life‐history and reproductive styles. Total niche space occupied by the fish taxocenes was comparable in the three river systems despite differences in species richness. The amount of species packing and niche space occupied by Baram fish taxocenes were also not related to the numbers of species present. Fish community structure was apparently determined by the range of available resources and the associated specializations of the coexisting species.