The Role of Habitat Complexity and Heterogeneity in Structuring Tropical Mammal Communities

Abstract

The relationship between mammal community structure and vertical variation in habitat physiognomy (complexity) and horizontal variation in habitat form (heterogeneity) was examined on five study areas in the llanos of Venezuela. Data on the small mammal (<1 kg) of the study sites were obtained through a mark—recapture trapping program of >38 000 trap nights from 1976—1978. Data on the distribution of large, nonvolant mammals were obtained during 24 mo of field observation. Measures of habitat complexity and habitat heterogeneity were derived using principal components analysis. There was little association between habitat structure and the richness, diversity, abundance, and biomass of small mammals. Abiotic factors, such as the degree of wet—season flooding, probably play an important role in patterns of small mammal distribution and abundance. The total number of mammal species was positively correlated with habitat complexity but not correlated with habitat heterogeneity. Increasing species richness across the complexity gradient was probably accommodated by increasing potential food resources. New species were added to complex communities primarily through guild expansion rather than guild addition.