Biological Inventory Using Target Taxa: A Case Study of the Butterflies of Madagascar

Abstract

Biotic inventories provide critical data for conservation planning, but frequently, conservation decisions are made without surveys, due to lack of time, funds, or appropriate methodology. A method, target taxon analysis, is therefore proposed for streamlining regional biotic inventories, while simultaneously increasing their taxonomic coverage and spatial resolution. In this method, regional inventories focus on a number of narrowly defined target taxa, chosen to represent collectively an array of higher taxa. Such target taxa should be information rich; in other words, the pattern of species distributions in these taxa should correlate either with patterns of environmental heterogeneity or with distributional patterns of species in unrelated taxonomic groups. It is suggested that clades that experienced an evolutionary radiation within the region are likely to be information rich for conservation planning at or within this regional scale. Such clades will be identifiable as low—ranking, species—rich taxa with high endemism. The information richness of these potential target clades can then be evaluated by direct gradient methods of analysis that relate community compositional change to environmental factors, or by correlating distributional patterns of species among separate target clades. To assess this approach to biological inventory, a species—rich genus and subgenus of endemic butterflies from the island of Madagascar were chosen as target taxa and were evaluated for information richness in comparison to the entire butterfly fauna of Madagascar. Using canonical correspondence analysis and other analytical techniques, the subgenus of Malagasy Henotesia species (Satyrinae) proved to be as good or better than the entire butterfly fauna at delineating a variety of environmental gradients at both local and landscape scales. The endemic genus Strabena (Satyrinae) was only able to delineate such patterns under a restricted set of conditions. However, this genus, while species rich in Madagascar, was not exceptionally diverse nor were its species members abundant within the study area. It is concluded that target taxon analysis is a potentially useful tool for providing high—quality data while expanding coverage of taxonomic diversity for conservation planning.