Spatial and temporal variation in patch occupancy and population density in a model system of an arctic Collembola species assemblage

• Published in: Oikos
• Main Authors: Ims, Rolf A., Petter Leinaas, Hans, Coulson, Steve
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2004
• Subjects: Arctic; Svalbard
• Online Access: http://dx.doi.org/10.1111/j.0030-1299.2004.12634.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.0030-1299.2004.12634.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0030-1299.2004.12634.x

We employed an experimental model system to investigate the mechanisms underlying patterns of patch occupancy and population density in a high arctic assemblage of Collembola species inhabiting a sedge tussock landscape on Svalbard. The replicate model systems consisted of 5 cores of the tussocks (habitat patches) imbedded in a barren matrix. Four of the patches were open so that animals could migrate between them, while there was one closed patch per system to test the effect of migration on extinction rate. There were model systems of two types: one with long and one with short inter‐patch distances to test the effect of patch isolation on colonisation and extinction rates. Each of the four most common collembolan species at the field site were introduced to two open patches per system (source patches), with the other two functioning as colonisation patches for the species. The experiment was run in an ecotrone over three identical, simulated arctic summers separated by winters of 3 weeks. Six replicates of systems with short and long inter‐patch distances were sampled at the end of each summer. The species varied markedly in their performance in both open arenas and closed patches, indicating differential responses to patch humidity, consistent with their differential distribution along the moisture gradient in the field site. The extinction – colonisation dynamics differed markedly between species as predicted from our field studies. This could partly be ascribed to differential dispersal and colonisation ability, but also to different tolerance to spatially variable patch quality and/or tendency for aggregative behaviour. Three of the species exhibited dynamics that superficially resemble what could be expected from classical metapopulation dynamics. However, there was a striking discrepancy between what would be expected from the effect of migration on the extinction rate of isolated patches (in particular closed patches) and the observed rates. Thus, metapopulation processes, such as stochastic ...