Evaluating diversity of chironomid (Insecta: Diptera) communities in alpine lakes, Retezat National Park (Romania)
Cogălniceanu, Dan; Tudorancea, Monica; Preda, Elena; Gâldean, Nicolae.
We analysed the species and genus richness of chironomid larvae from benthic samples taken from 18 alpine lakes in the Retezat National Park, Romania, at both regional and local scales. We identified 86 species in 49 genera, with most taxa having restricted and clumped distributions. We estimated the sampling effort needed to identify a certain percentage of the total number of taxa based on species accumulation curves. While a good estimate of genus richness can be obtained with a relatively small number of samples, a greater sampling effort is necessary for estimating species richness. Our results indicate that genus richness can be well predicted with relatively few samples, suggesting a different approach in species-richness estimation: genus richness can be estimated through extrapolation. Regression analysis allows subsequent estimation of species richness from genus richness. There was little correlation between local and regional richness indicating that chironomid larval communities in alpine lakes of the Retezat National Park are saturated and largely limited by ecological processes. Since the species accumulation curves did not reach a plateau we tested the utility of eight estimators, of which seven non-parametric. All estimators showed higher values than the observed species richness, but lower than the total number of species. The sampling effort was best predicted by samples than by the number of individuals. Four estimators (Jackknife 2, ICE, Chao2 and Michaelis-Menten model) tended to reach an asymptote after an initial peak. The Michaelis-Menten model reached an asymptote very rapidly, and therefore is strongly recommended for this type of study. We suggest that the use of estimators of species richness can help improve cost-effectiveness as the expectation of detecting additional species is reduced, by providing a comparable basis for redirecting sampling to taxa-rich sites, evaluating effectiveness of sampling methods or timing of sampling.