The Ecology and Evolution of Deep-Sea Copepods: Niche Separation in a Three-Dimensional Habitat

Specialisation and niche separation are key processes for minimising or avoiding competition between co-occurring species. This study aimed at elucidating these processes for co-occurring meso- and bathypelagic representatives of two copepod families (Euchaetidae and Aetideidae) from the Arctic Fram Strait and the Southern Ocean by characterising their respective ecological niches based on ecological, bioà ¬chemical and molecular phylogenetic aspects. Phylogenetically closely related species are rather similar in ecological characteristics. They are generally characterised by similar trophic niches and minimise inter-specific competition by vertical partitioning. Species with similar vertical distribution ranges occupy different trophic niches. Arctic species strongly preyed on the abundant calanid copepods, as indicated by trophic markers (fatty acids and stable isotope ratios). Even deep-sea species benefit from these seasonally vertically migrating copepods as food items, which provide a short-cut in the food web and accelerate the vertical transport of organic matter into the deep sea.