Traits or species – space or environment : how to understand the spatial structure of springtail community composition

• How communities are structured and the processes shaping species composition are among the basic questions in ecology. Knowledge about these processes is essential to predict changes in community composition in response to changes in for example climate or land use practices. Soil communities are considered to be both remarkably species-rich and to have many generalist species with seemingly similar niche requirements. Soil fauna composition shows a large variation even at small spatial scales and both local environment and spatial configuration of habitats are regarded as important forces shaping the community composition. In this thesis, I examine the factors influencing small-scale community composition of springtails (Collembola) in two habitats, a variable and dynamic salt marsh and a more stable mature pine forest. The functional traits of species determine both their responses to the environment and their effects on ecosystem processes. The current knowledge on environment - species - traits relationship is limited in spite of its potential importance for ecosystem function. I show that by combining perspectives from two closely linked theoretical frameworks – metacommunity ecology and community assembly theory – we get a better understanding of the important ecological factors operating in this system. I found that the factors influencing community composition was context dependent, but in a predictable way. In the environmentally variable habitat, salt marsh, with spatial and temporal heterogeneity, there was evidence of strong environmental filtering. Small-scale topography was the strongest predictor of community composition, likely due to disturbances restricting where habitat-generalists can persist. In contrast, in the more stable habitat, mature pine forest, environmental filtering appeared weaker and biotic interactions seemed to have a stronger impact. Coexisting species were more similar in traits related to resource utilisation and sensory ability than expected, and variation in species composition was explained mainly by spatial factors like the distance between samples, i.e. each local community seemed to depend on the composition of the surrounding communities.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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