Species composition and morphological structure of the bat fauna of Yucatan, Mexico

1. The relationship between regional and local assemblages of species can be analysed by comparing the composition of species and their morphological structure. 2. I made such a comparison using data of the bat fauna of Yucatan, Mexico and of a regional pool of species. Null models were constructed to test for differences in composition in terms of taxonomic affiliation and of feeding and roosting habits. Additionally, dispersal ability and species-to-genus ratios were compared. Morphological structure was analysed using nearest-neighbour distances and minimum spanning trees were constructed on a morphological plane determined by the first two principal components of external and skull measurements. 3. No significant differences were detected in the comparisons of species composition, except in the case of dispersal ability. The Yucatan bat fauna was a random subsample of the pool in terms of taxonomy, diet and roosting habits. However, species with a higher dispersal ability were better represented in the Yucatan fauna than expected by chance. 4. No clear pattern could be detected in the comparisons of morphological structure. Nearest-neighbour analyses and minimum spanning trees showed only unclear and inconclusive results. 5. The bat fauna of Yucatan is apparently formed by those species from the pool that possess a higher dispersal ability. The forces-that determine the composition and structure of this fauna are probably regional in nature, and the search for structuring factors at the local level might be a futile endeavour.