Well-hidden but still there: patterns of cryptic speciation in Dutch rotifer populations

Well-hidden but still there: patterns of cryptic speciation in Dutch rotifer populations

Aquatic Ecology

General context

Before the advent of molecular genetic techniques, zooplankton taxa were believed to be not exceedingly rich in species. Many species were also assumed to have a wide biogeographic distribution pattern. Recently, however, it has become more and more obvious that cryptic species (i.e. species that can not be morphologically distinguished) are actually rather common and that earlier biodiversity assessments have largely underestimated the number of species. This opens a lot of interesting avenues for evolutionary and ecological research, with questions such as: How long ago have these species come to existence? Did they evolve in sympatry or allopatry? Is there still hybridization going on? And to what extend do such species (and possibly their hybrids) differ from each other ecologically?

Project outline

The rotifer Brachionus calyciflorus is a rotifer species occurring in a wide variety of habitats, ranging from mesotrophic to hyper eutrophic ponds and lakes. A recent study in China has demonstrated the existence of potential cryptic species for this taxon. In this project, we want to genetically characterize natural populations of this species in The Netherlands and identify the potential existence of cryptic species. For this, we will sample and hatch resting eggs from numerous ponds and lakes, and analyze mitochondrial DNA to assess the geographic distribution of haplotypes, their degree of phylogenetic differentiation and their possible evolutionary age. In a later stage, we will also apply microsatellite analysis to test for patterns of hybridization and perform experiments to explore for ecological differences among the newly found species. This topic is suitable for both long and short term internships of MBO, HBO and master students.


3-9 months


Steven Declerck, S.Declerck@nioo.knaw.nl