VARIABLE FORTUNES IN A PATCHY LANDSCAPE - THE HABITAT TEMPLET OF AN INSECT MIGRANT

摘要

Migration by flight is essential for insects living in patchy landscapes and knowledge about variability in habitat patch structure and quality is important for the development of theory concerning insect dispersal polymorphisms. However, few studies provide more than anecdotal evidence about habitat change in time and space and its effects on insect survival and reproduction. Here I show how habitats and resource density of a lygaeid bug, Lygaeus equestris, change in a patchy landscape over a seventeen year period. Although habitat patches per se are very stable, there are large temporal fluctuations in per capita food resources. Food seems to be limiting only in some years, and there may be periods of several years when populations change due to weather disturbance. Between patch variation in reproductive success is large. Furthermore, the relative favourability of patches changes between years. There are also distance effects; in some years distances to suitable hibernation sites affect reproductive success. Long fliers experience more variable success, and sometimes extreme success, when compared with short fliers. The importance of movements from outlying areas also changes with time. The insect is thus faced with a habitat templet which varies strongly on many temporal and spatial scales.