Abstract
Evaluating components of landscape diversity is essential for the implementation of efficient conservation strategies. We evaluated the diversity of Odonata larval assemblages from the Coalcomán mountains (CM), Michoacán, Mexico, and related it to local (site-level) habitat variables. Larvae were collected from shores, riffles and pools in five streams, counted and identified to species, twice per season during 2005. The Shannon Diversity Index (H'), Margalef's Richness Index (R), Simpson's Index as a dominance measure (D) and Pielou's Equitability (J) were used to describe the assemblages, and Renyi's Diversity Profiles were used to order diversity. A Bray-Curtis Similarity Index (BC) was used to evaluate beta diversity. Theoretical richness was estimated using non-parametric and parametric methods. A Canonical Correspondence Analysis (CCA) was applied to explore the relationships of species with site-level environmental variables. A total of 12 245 larvae from 75 species, 28 genera and 8 families were recorded. Over all sites, the dominant species were Erpetogomphus elaps, Macrothemis pseudimitans and Argia pulla. The number of species per locality ranged from 18 to 36, and a high number of species (76%) occurred with relative abundances lower than 1%. A differential distribution of species and abundance in streams, time and strata was observed. Renyi's diversity profiles showed diversity was higher in spring and on shores. Most BC similarity values were smaller than 25%, indicating a high turnover rate in the CM. The high turnover rate reflects a differential distribution of the species along the altitudinal gradient, supporting the hypothesis of Mexico as a betadiverse country. According to the slope of Clench's curve, a reliable list of species was gathered. The CM larval assemblage is currently the largest reported for Mexico, and our results support previous proposals of the CM as a species-rich area for conservation.
Highlights
Given its topography, climatic diversity and geographical situation between two biogeographic regions (Neotropical and Nearctic), Mexico is a megadiverse country (Mittermeier et al 1998)
Physicochemical variables: Streams had significantly different gradients, and the Bonferroni paired t-test with multiple comparisons indicated that CL (Colorín) had the highest slope while Río Pinolapa (RP) (Pinolapa) and TZ (Ticuiz) had the lowest (Table 1)
There was a significant difference among streams for width, depth, current velocity and discharge
Summary
Climatic diversity and geographical situation between two biogeographic regions (Neotropical and Nearctic), Mexico is a megadiverse country (Mittermeier et al 1998). There are many taxonomic studies on larvae and imagoes of Mexican Odonata, but the ecological studies are relatively scarce, especially for short and long term evaluations on possible changes induced by human activities (e.g. climatic change). It is well known that Odonata larvae are dependent on habitat characteristics (Watson et al 1982), sensitive to abiotic factors, and play significant roles as predators and prey in the trophic structure of aquatic communities (Corbet 1999).
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