Evaluation of species richness estimators in studies of diversity involving two larval digenean communities parasitizing snail hosts

Abstract

The nonparametric estimators of species richness are some of the most widely used extrapolation methods in studies of biodiversity. These studies need relative large samples to achieve total diversity (including rare species), and estimators are routinely used to alleviate this problem. In the existing literature, parasite communities have received little attention. In fact, the present study is the first dealing with parasites in invertebrate hosts. Real data on seasonal diversity of larval digeneans in the snails Heleobia conexa and Heleobia australis from Mar Chiquita coastal lagoon (Argentina) were used to evaluate seven nonparametric estimators of species richness, observing the behavior of each method and its ability to estimate the richness using different subsample sizes. In addition, estimated species richness was compared with the previously observed species richness in the parasite component communities of both snail hosts, and the minimum sample size, necessary to include all the observed species of larval digeneans, was estimated using the nonparametric estimators. The bootstrap method had the best overall performance in the two communities. Although this estimator required large subsamples to estimate sample richness, it was in general the least biased and most accurate, and it presented the most similar curve shapes with lack of erratic behavior through the seasons. The results obtained from the comparison between the minimum sample sizes estimated in previous studies of both snail hosts and those suggested by the estimators also support the use of species richness estimators as methods to calculate the minimum sample size in studies of diversity.

Can the studies at a spatial scale of 100s meters detect the spatiotemporal fluctuations of a parasite assemblage?

“…Density of H. australis at each core was calculated as the number of snails by cm 3 . The sample size was calculated according to the methodology developed in Merlo et al (2010), and a total of 3600 randomly selected snails were isolated individually and exposed to a 100 W incandescent lamp for 48 h to stimulate shedding of cercariae. Finally, all gastropods were dissected under a stereomicroscope in order to detect the presence of sporocysts, rediae and developing cercariae (prepatent infections; Curtis and Hubbard, 1990).…”

Characterising the phytophagous arthropod fauna of a single host plant species: assessing survey completeness at continental and local scales

“…Total species richness was estimated in ESTIMATES version 9 (Colwell 2013). Three nonparametric estimators were used due to ambiguities as to which estimator is more accurate: the incidence-based second order jacknife [jack2, recommended by Melo and Froehlich (2001)], bootstrap [boot, recommended by Merlo et al (2010)], and the Chao 2 method (Chao 1987). Survey completeness occurs when all of the species in the study range have been collected.…”

Evaluation of a new sampling method for assessing Cladocera richness (Crustacea, Branchiopoda) in macrophyte-rich wetlands

“…Currently, several studies about diversity have used and recommended the non-parametric estimators of species richness to minimize the effects of biased sampling on the final results for the number of species (e.g., Petersen et al, 2003;Caterino, 2007;Merlo et al, 2010;Zagmajster et al, 2010). These methods for estimation can be used for comparisons of the analysis of ecological assemblages, since they are obtained through abundance or incidence data (Magurran, 2004); they can also be applied to biotic groups where the number of individuals is difficult to assess, especially in modular organisms, colonies and clones (Williams et al, 2007;Cruz et al, 2008;Gotelli and Colwell, 2010).…”