An evaluation of crustacean and rotifer diversity and composition in a temporary pond metacommunity: Comparing results from field samples and a hatching experiment

Many aquatic invertebrates that inhabit temporary ponds produce resting forms to overcome the dry period, building up the egg bank. When the wet phase returns, the resting forms hatch and the community is restored, and then pioneer species may have a major influence on how the pond community will assemble. We aimed to evaluate the diversity of an initial pond metacommunity by comparing the early active metacommunity collected in the field and the egg bank metacommunity (by carrying out a hatching experiment) of 32 Mediterranean temporary ponds. We hypothesised that both metacommunities would be similar but also that species turnover may play an important role, and that gamma diversity would be similar with both approaches. After the identification and counting of rotifers and crustaceans in both metacommunities (i.e. the field vs. the experiment) we performed a Partial Triadic Analysis comparing the field metacommunity with those corresponding to each of the eight times the hatching experiment was checked for hatchlings. Furthermore, we compared the field and experimental metacommunities with a PROTEST analysis and identified the taxa responsible for differences between metacommunities with a SIMPER analysis. We assessed gamma diversity using a size-based rarefaction curve and an evenness profile and explored beta diversity and its components (turnover and nestedness) for the two metacommunities. Our experimental results showed differences in the temporal pattern of emergence between groups of organisms, with copepods, rotifers, and anostracans appearing first, but ostracods and rotifers reaching the highest diversity at the end of the experiment. The active and experimental pioneer metacommunities were similar according to a Procrustes analysis. Nevertheless, beta diversity was high in both metacommunities and the differences among ponds and between both assemblages were mostly explained by species turnover. Both the active and experimental pond metacommunities showed some exclusive species that may be more difficult to uncover with only one type of approach. Furthermore, the high beta diversity observed indicates that each temporary pond is an important contributor to gamma diversity in the metacommunity. These results show that hatching experiments provide information that is complementary to standard sampling of the active community, and consequently is a useful tool to uncover pond biodiversity.