| Little is known about how pelagic (open ocean) biodiversity is created and maintained. Yet, pelagic ecosystems represent 99% of the planet's living space and produce half of the planet's oxygen. Understanding evolutionary processes in the open sea is particularly difficult because barriers to migration are often obscure and fossil records are typically lacking. Marine species that drift with the currents all of their lives (plankton) are traditionally thought to have large populations and high levels of gene flow. Therefore, the classical interpretation is that the open sea harbours relatively few and slowly-evolving species. An important, yet untested, prediction from evolutionary theory however, states that natural selection should be stronger in large populations than in smaller ones, which may lead to elevated evolutionary rates in species with very large populations. In addition, the recent discovery of fixation of advantageous mutations in mitochondrial DNA driven by selection in small marine invertebrates and my own data showing remarkable divergence and adaptive evolution in populations of chaetognaths, force a careful re-evaluation of the tempo and mode of marine zooplankton evolution. With this VENI, I will address this issue by studying zooplankton isolated in marine lakes. Marine lakes provide an unprecedented opportunity to study the evolutionary history as well as evolutionary rates of zooplankton because of the existence of multiple independently derived populations in marine lakes with known dates of flooding, along with their ancestral populations in the adjacent sea. I will take an ecogenomics approach to develop new genetic markers for two key-stone components of European pelagic foodwebs, the copepod Calanus helgolandicus and the chaetognath Sagitta setosa. This research will lay the ground work for my own independent research line and has the potential to address important theoretical as well as practical questions (e.g. possible adaptation of zooplankton populations to climate change). |
