Springtails in space : factors structuring Collembola populations and communities, revealed by trait-based analyses

• The relative influence of environmental conditions, biotic interactions and dispersal limitation for community structure and diversity patterns is a reoccurring theme in community ecology. In studies of soil fauna communities, small-scale horizontal and vertical variations in environmental variables and biotic interactions have often been disregarded, despite these being key factors to understanding the diversity of soil fauna communities. In this thesis I examined the spatial distribution patterns of springtail (Collembola) species and communities in three different ecosystems: a salt marsh, mature pine forests and a high Arctic tundra meadow. The different systems consisted of a, to the human eye, homogeneous habitat. Still, they had different regimes and small-scale heterogeneity in environmental variables. In the three first studies the focus was on species and trait composition and diversity, at scales from 10 cm to 300 km. In the fourth paper I question the use of species-level analyses of distribution patterns, as different age classes within a species might be structured by different factors. I found that when habitat conditions were kept as similar as possible, the pine forest Collembola communities had similar functional diversity, although there was a high species turnover both between samples within study sites and between sites. The functional similarity between samples was lower in the salt marsh habitat, a habitat characterized by frequent inundation events. The small-scale variation in species and trait composition was best explained by spatial variables in the stable mature pine forest floor, while in the dynamic salt marsh environmental variation was most important. Coexisting species showed a higher difference in traits than expected in the pine forest, while coexisting species were similar in traits in the salt marsh. This indicates that species interactions can have a large impact on the community composition of springtails at small spatial scales. Small-scale niche partitioning may be one explanation for the high local diversity observed in many soil communities. I found that incorporating species-specific trait information in studies greatly helps our understanding of the mechanisms structuring communities, despite the finding that in some species of collembolans different age classes may use space differently. To improve our understanding of Collembola communities both these factors should be considered in future studies.

Ämnesord

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

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

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