Effects of landscape characteristics on fragmented wetland plant communities and experimental metapopulations of Arabidopsis thaliana

Abstract

In my Ph.D. thesis, I conducted both observational and experimental studies on the effects of landscape patterns (habitat fragmentation and spatial structure) and landscape dynamics (changes in landscape patterns through time) on plant communities. Evolutionary and ecological process in spatially structured landscapes were investigated at different scales from natural landscapes to experimental microcosms and involved observation of large scale population processes as well as experimentally manipulated short-lived metapopulations. In the observational study, changes in the biodiversity of 36 species-rich, pre-alpine fen meadows in NE Switzerland over the last 10 years, has been studied. This study revealed that effects of landscape structure on plant biodiversity were more pronounced at the time of the second census in 2005/06, conservation planning should take into account the lag effect of habitat fragmentation, because populations and metapopulations may respond with a time lag to the structure of the landscape. Isolation measures (e.g. increasing distance, presence of barriers, reducing number of neighbouring habitats) have more serious consequences for regional plant species survival when occurring in combination than when occurring separately. In experimental study, we artificially created islands of suitable habitat embedded in an unsuitable matrix to simulate islands of natural habitats in nature, using Arabidopsis thaliana as a model species. We investigated selection on dispersal abilities of Arabidopsis thaliana over five generations in landscapes differing in the degree of habitat fragmentation and disturbance rate of patches. This study revealed that disturbance regime was more important than area of the habitat patches, thus, temporal change and landscape dynamics have also an important role and should be taken into account in landscape scales studies on biodiversity. Habitatfragmentierung, also die Zerstückelung grosser, verbundener Flächen in kleinere, isolierte Lebensräume wird als eine starke Bedrohung der globalen biologischen Vielfalt angesehen. Ich untersuchte die Auswirkungen von Habitatfragmentierung auf die Pflanzenvielfalt in einer vergleichenden Studie in artenreichen schweizer Flachmooren und in einem Fragmentierungs- und Störungs- experiment mit Arabidopsis thaliana (Acker-Schmalwand). Unsere Flachmooruntersuchungen ergaben, dass sich die Habitatfragmentierung mit Zeitverzögerung vor allem auf spezialisierte Arten auswirkt und die Kombination verschiedener Isolationsmechanismen den stärksten Effekt auf die Biodiversität hat. Unser Arabidopsis Experiment zeigte, dass Störung einen grösseren Einfluss auf die Populationsdichte und die Überlebenswahrscheinlichkeit hat als Habitatgrösse. Diese Ergebnisse sind unter anderem wichtig für die Naturschutzplanung