Abstract
BackgroundAbiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are also influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system.ResultsEvery species responded to at least one of three local environmental factors measured: water volume, leaf litter mass, and presence of a top predator. Several species were affected by water volume, and a non-exclusive group of species were influenced by leaf litter mass. Relative abundance of Aedes triseriatus was higher in treeholes with higher volumes of water, and relative abundances of three out of six other species were lower in treeholes with higher volumes of water. Leaf litter mass positively affected densities of Aedes triseriatus and relative abundance of several dipteran species. The density of the top predator, Toxorhynchites rutilus, affected the relative abundance of the two most common species, A. triseriatus and Culicoides guttipennis. Treeholes with T. rutilus had an average of two more species than treeholes without T. rutilus. We found little evidence of synchrony between pairs of treeholes, either spatially or temporally. There were high levels of spatial and temporal turnover, and spatial turnover increased with distance between patches.ConclusionThe strong effects of water volume, leaf litter mass, and presence of a top predator, along with the high temporal turnover strongly suggest that species presence and density are determined by local factors and changes in those factors over time. Both low water volume and high predator densities can eliminate populations in local patches, and those populations can recolonize patches when rain refills or predators exit treeholes. Population densities of the same species were not matched between pairs of treeholes, suggesting variation in local factors and limited dispersal. Distance effects on spatial turnover also support limitations to dispersal in the metacommunity, and we conclude that the weight of evidence favors a strong influence of local factors relative to regional factors.
Highlights
Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are influenced by regional factors such as immigration and colonization
Environmental variation Aedes triseriatus relative abundance increased with increasing water volume, C. guttipennis and Systenus sp. relative abundances decreased with increasing water volume and leaf litter mass, and relative abundance of H. pulchella decreased with increasing water volume only (Fig 1; Table 1)
The probability of M. posticata presence was higher in treeholes with higher water volumes, and the probability of H. pulchella presence was higher in treeholes with higher leaf litter masses (Table 2)
Summary
Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system Consideration of both local and regional processes is essential in studies of communities found in discrete and spatially separated habitat patches [1,2,3], such as phytotelmata, ponds, lakes, decomposing logs, rock pools, and fragmented habitats. Metacommunity ecology is the study of the factors that influence the dynamics in such spatially-structured communities Populations in these habitats may persist for a time or go locally extinct, after which they be rescued from extinction by colonization events [1]. Metacommunities have been shown to be affected both by abiotic and biotic conditions within a local habitat, as well as regional factors, such as distance between patches and dispersal ability of species
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