UBC Theses and Dissertations
Interactive effects of dispersal rate and disturbance synchrony on microarthropod diversity at multiple spatial scales : rescue effects do not increase regional richness Meldrum, Gennifer Eileen
Immigration from surrounding areas is known to benefit community recovery following disturbance. However, whether such rescue effects can increase regional diversity in landscapes subject to patchy disturbance has rarely been investigated experimentally. This study manipulated landscape connectivity and disturbance synchrony in moss patches, and examined the consequences for the embedded microarthropod communities. We assembled metacommunities with two patches connected by 0, 1, or 2 corridors. Patches were left undisturbed or were disturbed asynchronously or synchronously by Tullgren funnel extraction. We found evidence of rescue effects at the local-scale for microarthropods overall, especially for the oribatids and collembolans. However these rescue effects did not result in greater regional diversity for several reasons. First, rescue effects only occurred after one of the disturbances so they did not increase average local-scale diversity and any increase in local-scale diversity was offset by increasing compositional similarity across the landscape. Competitive and trophic interactions may have diminished the expected benefit of connectivity for diversity. Finally, disturbance and isolation did not always decrease local diversity as expected, suggesting a strong role for context-dependent dispersal behaviour and in situ recovery processes. Our results indicate that rescue effects mediated by habitat corridors can improve recovery of local community diversity following disturbance, but they may not be effective at maximizing regional diversity. Predator diversity may be more likely to benefit from rescue effects than prey diversity at the regional scale.
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