Diversity and distribution of Odonata (Insecta) larvae along an altitudinal gradient in Coalcomán mountains, Michoacán, Mexico

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. Rev. Biol. Trop. 59 (4): 1559-1577. Epub 2011 December 01.

Evaluar los componentes de la diversidad de paisaje es una tarea esencial para implementar estrategias eficientes de conservación. En este estudio se describe la variación geográfica, temporal y por hábitats de la diversidad de larvas de odonatos en un gradiente altitudinal en la sierra de Coalcomán, Michoacán, México, y se explora su relación con variables fisicoquímicas locales. Presentamos diferentes índices de diversidad y gráficos de perfiles de diversidad de Renyi, así como la riqueza teórica por métodos paramétricos y no paramétricos, el recambio de especies en la sierra y, mediante análisis canónico de correspondencias (ACC) la relación de las especies con las variables fisicoquímicas. Recolectamos un total 12 245 larvas de 75 especies, 28 géneros y 8 familias. En todos los hábitats un alto número de especies presentó una abundancia inferior al 1%. El número de especies en los arroyos varió entre 18 y 36, existe además un alto recambio en la sierra. La diversidad beta es un componente importante de la diversidad del paisaje; se apreció una alternancia en la dominancia estacional entre anisópteros y zygópteros y nuestros datos concuerdan con la hipótesis del Mexico betadiverso y también apoya propuestas previas de conservación de la sierra.