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Distributions of odonate richness and diversity with elevation depend on windward or leeward aspect: implications for research and conservation planning


Dr. W. Bruce Campbell, c/o Dr Silvia López Ortiz, Colegio de Postgraduados, Campus Veracruz, Apartado Postal 421, Veracruz, Veracruz, Mexico, C.P. 91700. E-mail:


Abstract.  1. Assessing species richness (SR) and diversity along environmental gradients is important to see whether abiotic differences alter patterns of species distribution and composition.

2. We examined distributions of odonate SR, average taxonomic distinctness (ATD) and functional diversity (FD) (using the Shannon Index on proportions of plant-dependent and non-dependent species) with elevation and slope provided from an exploratory survey along a transect in the Sierra de Coalcomán Mountains, Michoacán State, Mexico. Adults were collected along both sides of a 500 m stream segment for 6 h day−1 site−1 in each of eight sites, and these species lists were complemented by collecting mature larvae.

3. Species richness and FD declined with elevation among windward sites, while ATD increased. Among leeward sites, SR peaked at mid-elevation, and there was no trend for FD or ATD with elevation. Leeward sites were similar in species composition, whereas windward sites were dissimilar. Slope was correlated with elevation among windward sites, and influenced most variables, but not among leeward sites. FD was negatively correlated with ATD among sites along both aspects. Mean values of SR, ATD and FD between aspects were similar.

4. The Energy-Richness Hypothesis best explained the species distributions along the windward aspect. Local abiotic influences appeared more important in community assembly among windward sites. Among leeward sites, the potential for Mid-Domain and Rapoport Effects suggest interspecies interactions control community assembly; providing greater potential for expansion of species elevational ranges, and an increase in range expansion of alien and non-endemic species along this aspect.

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