Habitat complexity predicts the community diversity of rock-dwelling cichlid fish in Lake Malawi, East Africa
Understanding the factors that regulate species diversity remains an important goal in ecology, conservation and evolutionary biology. Speciose communities, like the cichlid fishes in the East African Great Lakes, offer useful opportunities to examine these factors. For example, Lake Malawi supports well over 700 cichlid fish species which likely descended from a common ancestor within the past 2–4 million years. One consequence of this remarkable radiation is the high species diversity of Lake Malawi’s cichlid communities. However, the factors facilitating the assembly and maintenance of species rich cichlid communities have yet to be fully identified. In this study, we examine the diversity of Lake Malawi’s rock-dwelling cichlid communities and investigate the roles that several environmental variables have played in maintaining such high diversity. We surveyed 82 quadrats spanning seven sites and observed 54 species from 12 genera. Most environmental variables that we measured varied significantly within, but did not differ significantly among sampled sites, suggesting that habitat heterogeneity is locally high, but at the lake-wide scale habitats are uniformly heterogeneous. Community diversity was strongly influenced by habitat complexity, while community similarity was strongly dependent on the geographical distance between communities. At the genus level, no relationship between geographic distance and community similarity was found, but community composition was also determined by habitat complexity. Our findings demonstrate that habitat complexity predicts both cichlid species diversity and functional diversity, whereas geographic separation determines the similarities among communities at the species but not at the generic level.
KeywordsCichlids Community ecology Lake Malawi Rugosity Species richness
We are grateful to Dr. Ryan King for help with the experimental design. We want to thank Richard Zatha and Aimee Howe for their help with field work. We are grateful to Lake Malawi National Park, the Malawi Fisheries Department, and the University of Malawi—Chancellor College for their assistance in collecting this data set. Darrell Vodopich, Martin Genner, and two anonymous reviewers provided valuable comments on this manuscript. This research was funded by a Jordan Grant of the American Cichlid Association and a Glasscock Award to M. H., Folmar Awards to B. D. and M. H. and additional funding of the Department of Biology, Baylor University to P. D. D.
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