Hydrologic controls on ecological processes : River networks as corridor for biodiversity and populations

Protist species cover a very broad range of body sizes and biological diversity (courtesy of Regula Illi and Florian Altermatt, Eawag).

A major aim in community ecology is the understanding of the origin and maintenance of biodiversity and identifying processes that define large-scale biodiversity patterns. Biodiversity has been strongly affected by humans over the last decades. In many systems, diversity has been declining at all levels, with major consequences on ecosystem functioning and services. Biological communities often occur in spatially structured habitats where connectivity directly affects dispersal and metacommunity processes. For simplified landscapes, described geometrically by linear or lattice structures, a variety of local environmental factors have been brought forward as the elements creating and maintaining diversity among habitats. Many highly diverse landscapes, however, exhibit hierarchical spatial structures that are shaped by geomorphological processes and neither linear nor two-dimensional environmental matrices may be appropriate to describe biodiversity of species living within dendritic ecosystems. Riverine ecosystems, among the most diverse habitat on Earth, represent an outstanding example of how local and regional factors interact in controlling population demography and community composition. Recent theoretical work suggests that dispersal constrained by the connectivity of specific habitat structures, such as dendrites like river networks, can explain observed features of biodiversity, but direct evidence is still lacking. The present proposal addresses the study of biodiversity in the river basin: observational data, theoretical models and laboratory experiments will be analyzed within a unified framework. The use of protists as model systems, representing a useful bridge between theory and nature, have contributed several breakthroughs in ecological understanding of population, metapopulation and metacommunity dynamics. This opens up the possibility to use laboratory experiments to test theory, develop new models to explain experimental results, in an iterative manner.  Protists cover a wide range of body sizes, and span different phyla in the tree of evolution. These species have rapid generation times, covering substantial biological complexity in terms of movement ability, trophic levels and species interactions. All these properties can be determined in detail with a stereo-microscope and a cell counter, over a wide range of conditions. By manipulating nutrients level and in general habitat quality, temperature, and the species pool, it is possible to resemble different stress conditions that species might face in natural situations, as human massive land use, climate change, habitat fragmentation and species invasions. Dispersal, which refers to the pathway constrained by the particular habitat connectivity, can be manipulated, opening the possibility to test directly predictions provided by spatially explicit theory, at different spatial and temporal scales. The timescales involved into such type of experiments rarely exceed one month, as systems relaxation times to equilibrium after perturbations happen in few Appliquer days. Thus, such combination of theory with realistic model systems is needed to understand general ecological principles that act in natural systems and at larger spatiotemporal scales.


Funding agencie(s) :
Period : 2010-2013
Contact person(s) : PhD: F. CarraraProf. A. Rinaldo