Correlated extinctions, colonizations and population fluctuations in a highly connected ringlet butterfly metapopulation |
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Authors: | Odette L Sutcliffe Chris D Thomas Tina J Yates J Nick Greatorex-Davies |
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Institution: | (1) Department of Biology, University of Leeds, Leeds, LS2 9JT, UK, GB;(2) Institute of Terrestrial Ecology, Monks Wood, Natural Environment Research Council, Abbots Ripton, Huntingdon, Cambridgeshire, PE17 2LS, UK fax: (01487) 773467, e-mail: O.Sutcliffe@ite.ac.uk, GB |
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Abstract: | The persistence of metapopulations is likely to be highly dependent on whether population dynamics are correlated among habitat
patches as a result of migration between patches and spatially-correlated environmental stochasticity (weather effects). We
examined whether population dynamics of the ringlet butterfly, Aphantopus hyperantus, were synchronous in an area of approximately 0.5 km2, with respect to extinction, colonization and population fluctuations. Monks Wood Butterfly Monitoring Scheme transect count
data from 1973 to 1995, revealed (A) a major environmental perturbation, the drought of 1976, which caused synchronized extinctions
of A. hyperantus in subsequent years, (B) synchronized recolonization in years following the large number of apparent extinctions, and (C)
population changes by A. hyperantus were highly correlated in many of the 14 sections of the transect, presumably reflecting similar responses to environmental
stochasticity, and the exchange of individuals among sections. However, extinction and population synchrony depended on habitat
type. Following the 1976 drought, A. hyperantus apparently became extinct from the most open and most shady habitats it occupied, with some persistence in habitats of intermediate
shading, thus showing retraction to core populations in central parts of an environmental gradient, albeit with an average
shift to relatively open habitat. Populations at extreme ends of the environmental gradient occupied by A. hyperantus fluctuated least synchronously, suggesting a potential buffering effect of habitat heterogeneity, but this was not crucial
to survival after the 1976 drought. Thus, not all habitats are equally important to persistence. Correlated temporal dynamics,
variation in habitat quality and the interaction between habitat quality and temporal environmental stochasticity are important
determinants of metapopulation persistence and should be incorporated in metapopulation models.
Received: 26 April 1996 / Accepted: 17 July 1996 |
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Keywords: | Environmental gradient Shade Drought Aphantopus hyperantus Population dynamics |
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