Correlated extinctions, colonizations and population fluctuations in a highly connected ringlet butterfly metapopulation

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 km, 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.

Unexpected coherence and conservation

“…11). However, there are also examples of extinctions of butter£y metapopulations in response to climatic events that have synchronous e¡ects (Thomas et al 1996;Sutcli¡e et al 1997).…”

The re-expansion and improving status of the silver-spotted skipper butterfly (Hesperia comma) in Britain: a metapopulation success story

“…Managing habitats for a species based on a prescription that is out of date may even have detrimental affects on the populations the management is attempting to conserve. In this regard, habitat heterogeneity may be advantageous (Kindvall, 1996;Sutcliffe et al, 1997). A mosaic of grassland at various sward heights will provide the butterfly with ideal breeding conditions, whatever the prevailing temperature, and will improve the probability of a population surviving either extreme dry and hot, or cold and wet summers.…”

Empirical determinants of measles metapopulation dynamics in England and Wales

“…Metapopulation theory has focused mainly on the role of low level coupling in promoting the persistence of populations (Levins 1969;Gilpin & Hanski 1991;Hassell et al 1991;Allen et al 1993;Holt 1994;Ruxton 1994;Grenfell et al 1995b;Hanski et al 1996;Sutcli¡e et al 1997b). Understanding the balance between local and global dynamics is a central issue here, and a number of theoretical and empirical studies have recently addressed this question (Hanski et al 1995;BjÖrnstad et al 1995BjÖrnstad et al , 1996Hill et al 1996;Kuussaari et al 1996;Sutcli¡e et al 1996Sutcli¡e et al , 1997bRanta et al 1997). We can distinguish a continuum of spatial interaction strength: from completely separate local populations, via weakly coupled metapopulations, to globally interacting populations made up of strongly coupled patches (Sutcli¡e et al 1997a).…”