Patterns in Body Size, Population Dynamics, and Regional Distribution of Bracken Herbivores

Publisher Website
Google Scholar
Abstract
The "reassembly" of community patterns from detailed knowledge of the local dynamics of component species and the analysis of broad patterns of local and regional dynamics of species are two possible approaches to understanding community structure. Here, the latter approach is applied to data for the herbivorous insect community feeding on bracken in Great Britain. A number of previously reported qualitative patterns, relating local population dynamics (average population sizes and fluctuations in population size of component species in two adjacent habitats over 7 yr), body size of each species, regional distribution (at 216 sites throughout the British Isles [UK]), and feeding specificity are analyzed using bracken insect data. Previously, these patterns had never been examined together in one community. The results are encouraging, with several predicted patterns confirmed, despite the relatively small number of species considered (a maximum of 21). Species'' body size appears to underlie many of the observed patterns, emphasizing its ecological importance. Species of small body size are more widely distributed nationally, have higher average population densities, and have populations that fluctuate more than those of large species. Hence, locally abundant populations and widely fluctuating populations are also more widespread nationally. Small species also tend to be host-plant specialists, whereas larger species are generalists, and small specialist species have local populations that are larger and more variable. The interaction and theoretical bases of the patterns and difficulties in disentangling artifact from cause and effect are discussed.