Brachionus calyciflorus is undoubtedly the most studied freshwater monogonont rotifer taxon. Although it has been identified to be a cryptic species complex since more than a decade, its four hitherto known species (B. calyciflorus, B. dorcas, B. elevatus and B. fernandoi) have been (re)described only recently, based on a combination of a molecular phylogenetic and morphological analysis. Considering the close relationship, the ecological differentiation of these species complex were largely unknown. We here conducted comparative life table and population demographic experiments using genotypes isolated from multiple natural populations in The Netherlands. In addition, we applied cross-mating experiments between the two sibling species B. elevatus and B. calyciflorus to test for reproductive isolation.
Results/Conclusions
The life table experiment revealed substantial life history strategy differentiation among species. Traits such as investment in sexual reproduction, juvenile and embryonic development time were found to be species-specific and also translated into divergent population demography structures. The results of cross mating experiments suggest both pre- and post-zygotic isolation although formation of hybrids still possible. This is consistent with the occasional observation of hybrid and introgressed genotypes in natural populations. Our results demonstrate that besides of phylogenetic and morphological divergence, there’s strong ecological differentiation among B. calyciflorus species complex and correct identification is essential for the study of ecological dynamics in communities with ‘cryptic’ species.