séminaire du pôle évolution du vivant – vendredi 8 mars 2013

Diversity patterns and dispersal processes in riverine metacommunities

Florian Altermatt, Swiss Federal Institute of Aquatic Science and Technology, Department of Aquatic Ecology, Dübendorf, Switzerland


Understanding the effect of spatial habitat structure on population dynamics and diversity is one of the most challenging and active domains in ecology. Until recently, studies on dispersal or invasions have only considered minimally the specific structure of landscapes, or were done in landscapes with a simplified spatial structure. The spatial structure of many natural systems, however, is complex. In rivers for example, individual linear habitat segments are arranged in a spatially hierarchical, dendritic structure. Since rivers are (relative to their area) among the most diverse habitats on earth, the understanding of factors affecting diversity is of high priority.

We studied how biased dispersal kernels and restricted dispersal along different network structures affect community composition, using a combination of mathematical models and experiments with protist microcosms. In a first step, we developed a general simulation model for competing species in linear metacommunities to evaluate the role of directionally-biased dispersal on species diversity, abundance and traits. In the parallel experiment, we manipulated dispersal direction and distance in linear metacommunities. We found that dispersal directionality affects diversity patterns but not local abundances of species. We then extended our studies to complex, river-like networks, using an optimal channel network approach. We found that community composition and diversity patterns on the landscape level depended on the network structure and specific species traits. Specifically, we found that localized dispersal in dendritic networks resulted in diversity patterns (alpha and beta) commonly observed in rivers, and that these patterns were significantly different compared to lattice landscapes. Finally, we compared our experimental and theoretical results with data on macroinvertebrate diversity from a large monitoring project. We analysed species diversity of may-, stone-, and caddisflies and genetic diversity of Amphipods, with respect to local habitat characteristics and connectivity within the aquatic metacommunity. Together, our results may help to better understand and protect diversity in natural metacommunities, specifically in river systems.