Ol. Sutcliffe et al., CORRELATED EXTINCTIONS, COLONIZATIONS AND POPULATION FLUCTUATIONS IN A HIGHLY CONNECTED RINGLET BUTTERFLY METAPOPULATION, Oecologia, 109(2), 1997, pp. 235-241
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 environm
ental stochasticity (weather effects). We examined whether population
dynamics of the ringlet butterfly, Aphantopus hyperantus, were synchro
nous in an area of approximately 0.5 km(2), with respect to extinction
, colonization and population fluctuations. Monks Wood Butterfly Monit
oring Scheme transect count data from 1973 to 1995, revealed (A) a maj
or environmental perturbation, the drought of 1976, which caused synch
ronized extinctions of A. hyperantus in subsequent years, (B) synchron
ized recolonization in years following the large number of apparent ex
tinctions, and (C) population changes by A. hyperantus were highly cor
related in many of the 14 sections of the transect, presumably re flee
ting similar responses to environmental stochasticity, and the exchang
e of individuals among sections. However, extinction and population sy
nchrony depended on habitat type. Following the 1976 drought, A. hyper
antus apparently became extinct from the most open and most shady habi
tats it occupied, with some persistence in habitats of intermediate sh
ading, 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 gradie
nt occupied by A. hyperantus fluctuated least synchronously, suggestin
g 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, v
ariation in habitat quality and the interaction between habitat qualit
y and temporal environmental stochasticity are important determinants
of metapopulation persistence and should be incorporated in metapopula
tion models.