Responses of a forest damselfly to differences in landscape structure arising from habitat fragmentation.

摘要

I examine responses of the forest-dwelling damselfly, Calopteryx maculata to differences in landscape structure arising from habitat fragmentation. I compare populations across two kinds of landscapes: forest, where resources for oviposition/mating and foraging are adjacent; and pasture, where resources are separated in space.;I examine the dispersion of individuals in the two landscape types and show that in pasture landscapes, C. maculata are distributed farther from the edges of the streams than they are in forest landscapes. I then show experimentally that pasture habitat is not a barrier to flight for C. maculata; individuals from either forest or pasture landscapes are equally able to fly through forest and pasture habitats when experimentally displaced from the edge of the stream where mating/oviposition occurs.;I then examine three responses of C. maculata to the differences in landscape structure. I show that the incidence and level of parasitism by a midgut gregarine is significantly lower in pasture landscapes than it is in forest landscapes. That C. maculata are distributed over a greater area in pasture landscapes may account for this difference. I then show that the wings of C. maculata in pasture landscapes are longer and wider than those in forest landscapes. Changes in wing morphology may reflect different micro-scale selection forces acting upon C. maculata in pasture that may be related to the additional flights made for foraging. Finally, differences in foraging results are examined and found to differ inconsistently across sites. Foraging rates vary widely even in a single site, and so these data are difficult to interpret.;Differences in landscape structure arising from habitat fragmentation influence the natural history of C. maculata in several widely different ways. Most importantly, the species is able to persist in a moderately fragmented landscape because it exhibits behavioral, physiological and morphological flexibility. These results have consequences for the study of habitat fragmentation in general.