Richness and structure of an Odonata larval assemblage from Rio Pinolapa, Tepalcatepec, Michoacán, Mexico in relation to their habitat characteristics

The odon. larval assemblage from Rio Pinolapa (RP) in the municipality of Tepalcatepec, Michoacan, is described. Sampling was conducted twice in each season (8 trips in total), and additionally some physicochemical variables of the river channel were recorded. Strata (shores, riffles and eddies) and seasonal variation of assemblages are described and compared using classical diversity measures such as Shannon’s diversity index, Simpson’s diversity index as a dominance measure, Margalef’s richness index and Pielou’s evenness index. For comparing strata and seasonal diversity the Renyi’s diversity profiles were used. A Cluster Analysis was performed on a Bray-Curtis similarity matrix to explore the faunal relationships among year seasons and strata. CCA was also performed to investigate the relationships between the physicochemical and species abundance matrixes. As results, 28 spp. (12 Zygoptera and 16 Anisoptera) were recorded as larvae. Most abundant species were Erpetogomphus elaps, Brechmorhoga praecox and Phyllogomphoides luisi. The highest number of spp. was registered in winter and the lowest in summer. Among strata the highest abundance was recorded in riffles, although the shoreline had the largest number of spp. The most similar assemblages were those of autumn and winter. Shore habitats were more heterogeneous than eddies and riffles and this could explain the larger number of species. The Clench’s model explains better the data. Additionally, we used the slope of cumulative number of spp. curve for assessing completeness of the RP list. CCA was significant, with pH, autumn, shoreline and riffles the most important variables. This means that species variation is related to physicochemical, temporal and strata conditions in RP.