Explore the vast range of titles available.

We studied the effect of forest fragmentation on the insect community inhabiting an old-growth forest specialist bracket fungus, Fomitopsis rosea, in eastern Finland. Samples of the fungus from large non-isolated control areas were compared with samples from forest fragments in two isolation time classes; 2-7 yr and 12-32 yr since isolation. Fomitopsis rosea hosted a species-rich community with relatively many specialized old-growth forest insects. The numerically dominant food chain consisted of F. rosea, the tineid moth Agnathosia mendicella and the tachinid fly Elfia cingulata, a specialist parasitoid of A. mendicella. The frequency of F. rosea on suitable fallen spruce logs and the frequency of A. mendicella in fruiting bodies were significantly lower in the forest fragments than in the control areas. The median number of trophic levels decreased from three in the control areas to one in the fragments that had been isolated for the longest period of time. The parasitoid was completely missing from the fragments isolated for 12-32 yr. Our results show that in boreal forests habitat loss and fragmentation truncate food chains of specialized species in the course of time since isolation.

This paper explores the correspondence between the parameters of an extinction model analysed by Lande, Foley and Middleton et al. and the parameters of the incidence function model of metapopulation dynamics. The parameters of the extinction model, the intrinsic rate of population increase (r), its variance (v) and the population ceiling (K), can be mapped to the parameters of the incidence function model describing the scaling of the probability of local extinction (E) with patch area (A), E=e/Ax, via the equations s = x and r=eDs/s, where s = 2r/v, D is population density and K = DA. I explore this correspondence with two empirical examples, a mainland- island metapopulation of the European common shrew (Sorex araneus) on islands in lakes and a classical metapopulation of the American pika (Ochotona princeps). The most robust result is the correspondence x = 2r/v, which value decreases with increasing strength of environmental stochasticity. Thus the impact of environmental stochasticity on population dynamics can, in principle, be inferred from the pattern of habitat patch occupancy in a metapopulation.

We describe an extensive metapopulation study on the Glanville fritillary Melitaea cinxia, in a network of 1502 discrete habitat patches, comprising the entire distribution of this butterfly species in Finland. A thorough survey of the easily detected larval groups revealed a local population in 536 patches (dry meadows). We demonstrate that this system satisfies the four necessary conditions for a species to persist in a balance between stochastic local extinctions and recolonizations. Patterns of patch occupancy support several qualitative and quantitative model predictions. With decreasing regional density and average area of habitat patches, the butterfly occurs in a diminishing fraction of suitable habitat. To our knowledge, this is the first conclusive demonstration, based on a comparison of many conspecific metapopulations, of declining habitat occupancy and hence of increasing threat to survival caused by increasing habitat fragmentation.

We surveyed the densities of small mammals on 17 islands in Lake Inari in Finnish Lapland during 5 yr to estimate the degree of spatial synchrony in the dynamics of microtine rodents (Clethrionomys, Microtus) and shrews (Sorex). Microtine rodents have a 4-5 yr population cycle in Lapland. Most island populations of microtine rodents were in complete synchrony with the mainland populations and each other, and the same-island rodent and shrew populations showed largely synchronous population changes. The few exceptions included small and isolated populations of Microtus oeconomus fluctuating out of synchrony. The generally high level of spatial synchrony is unlikely to be caused by predation by nomadic avian predators, as has been suggested previously, because they are very scarce in the study area. We present and discuss results suggesting that the synchrony is due to predation by small mustelids, especially the stoat, which may also be the primary cause of the large-amplitude rodent oscillations.