ASSESSING THE INDICATOR PROPERTIES OF SPECIES ASSEMBLAGES FOR NATURAL AREAS MONITORING

The diversity of organisms and complexity of ecosystems prevent thorough inventory and monitoring of protected areas, yet sound databases are needed to manage ecosystems for long-term persistence. One strategy is therefore to focus monitoring on indicator organisms, but guidelines are lacking for selecting appropriate species or groups. This paper presents a simple protocol based on ordination techniques for establishing the indicator properties of a group of organisms and for selecting an indicator species subset for more intensive monitoring. Use of ordination allows inclusion of many more taxa than have been traditionally used for natural areas monitoring, and need not rely on detailed knowledge of species biology. As an example, I studied the indicator properties of a butterfly taxocene in a rain forest in Madagascar. Butterflies have been suggested as particularly good environmental indicators due to their sensitivity to micro-climate and light level changes, and their interactions as larvae and adults with different sets of host plants. The indicator properties of butterfly assemblages were evaluated in this study with respect to a known pattern of environmental heterogeneity along topographic/moisture and disturbance gradients. Butterfly assemblages were found to be excellent indicators of heterogeneity due to the topographic/moisture gradient, limited indicators of heterogeneity due to anthropogenic disturbance, and poor indicators of plant diversity. The protocol defined in this study is widely applicable to other groups of organisms, spatial scales, and environmental gradients. By examining the environmental correlates of the distribution of species assemblages, this protocol can assess the indicator proper-ties of target species groups.