Community structure in Sarracenia purpurea microcosms and adjacent peatlands. Sarracenia Microbiome Project

Water-filled habitats in plants, so-called phytotelma, are widely used model systems in community ecology as they represent discrete miniature ecosystems (aka microcosms) that can quite precisely be observed in space, time and environment. The patterns of local- and regional diversity, species turnover, evenness, colonization and dispersal in these systems are poorly understood. In this thesis, the microbial communities inhabiting the pitcher-shaped leaves of Sarracenia purpurea ssp. purpurea were used to explain colonization, community structure and diversity patterns of metacommunities. This carnivorous plant grows only in peatlands, which renders its distribution nested in bog patches, where this plant, in turn, occurs in more or less dense clusters. This spatial configuration eases inference about α-, β- and γ-diversity across a landscape.From a regional species pool only a subset of species is able to reach and in consequence, establish in a given local community. Thus, community membership is limited by dispersal, abiotic- and biotic filters. The colonization of new habitats and subsequent community structuring is a core topic in community ecology. Yet, to-date, this topic is poorly understood, especially for habitats with a known colonization history. Over long distances, microbes mainly disperse passively and are thus thought to have higher dispersal capacity than larger organisms. Although microbes are usually motile, suggesting active dispersal capacities, little is known about short-distance dispersal in metacommunities and active colonization of new habitats.This thesis comprises three main parts: In chapter I, the main focus was the detection of colonization paths of new pitchers and unraveling community structure and its drivers.Chapter II dealt with the α-, β- and γ-diversity as well as evenness of the inquilines and the effect of space, time and the environment on these metrics. In chapter III, the effectof the environment on and the interactions within microbial peatland communities were examined.For this, microbial communities from 160 Sarracenia pitchers and 40 adjacent peatland moss samples were sampled from five peatlands in West Switzerland. Additionally, an extensive set of environmental variables was collected. Targeting pro- as well as eukaryotes, microbes were identified via 16S- and 18S rRNA metabarcoding.