Using indicator families for vegetation classification in species-rich Neotropical forests

Vegetation studies in species-rich Neotropical forests are greatly hampered by high species numbers, identification difficulties, and large sample are as necessary to adequately cover species-rich woody plant communities as we ll as by logistic, financial, personal, and temporal limitations. In the pr esent study we assessed the representativeness and usefulness of 65 plant f amilies as indicator groups for such studies. Generally speaking, we found that the species associations in any family provided substantially more inf ormation about the relationship between vegetation plots than would be indi cated by the percentage value of species number of the respective family. T hus, the loss of information from not considering the whole flora was more than outweighted by the possibility to increase sample sizes, and by easier and more complete identification. This effect varied greatly between plant families (mainly in relation to biogeographic differences) as well as with coral species number (being more pronounced in species-rich communities). Usefulness of the 65 plant families was evaluated based on seven criteria: a) specialization of individual species to habitat; b) diversity of life fo rms in family; c) recognizability of morphospecies in the field; d) minimum area; e) wide ecological and geographical distribution; f) family easily r ecognized physiognomically; g) well-known and stable laxonomy. These criter ia revealed considerable differences between families but varied regionally and between habitats, so that no indicator families could be recommended a s useful for all studies. We provide guidelines for selecting indicator gro ups for vegetation studies in the Neotropics. A further analysis revealed t hat full floristic samples loose fairly little information if the plants ar e only identified to genus level, raising the possibility to base vegetatio n classification studies on comparatively easy genus identification.