Evaluating Biodiversity Through Functional Groups: A Comparison of Functional Groups and Biodiversity Measures

Abstract

Quantification of blodiversity is crucial to development of policy aimed at the conservation of flora and fauna, and ecologists are therefore under pressure to arrive at an agreed mode of evaluating biodiversity (Hunter 1996). However, difficulties arise in defining blodiversity because it is studied at different levels, usually distinguished as the genetic, species, community and landscape levels, each of which constitutes a different facet of the subject (Noss 1992). Where a decision is made to focus on the community level, further problems arise in quantifying biodiversity. Communities are to a greater or lesser extent multispecific, and taxonomic and time constraints prevent the identification of all species present. This has resulted in the adoption of indicator taxa and functional groups as a pragmatic means of approximating community biodiversity (McLaren et al. 1998, Williams 1998). Some studies have found relationships between functional groups, for example butterfly and vegetation communities, and have suggested that a single functional group may be used as an indicator of landscape-scale ecological processes (Oostermeljer and van Swaay 1998; Negi and Gadgil 2002). However, it has been argued that such functional groups are often selected on the basis of popular attractiveness and ease of survey, rather than on ecological criteria such as importance to ecosystem functioning (Hunter 1996), and that the outcomes of biodiversity quantification based on such indicators may relate more to functional group choice than to attributes of the community (Walker 1989). If it is decided to attempt quantification of the biodiversity of a community through a survey of indicator functional groups, then a method of quantification must be selected. Many such methods have been suggested, but perhaps the most frequently adopted methods are (1) to count the number of species and (2) to combine the number of species and the distnbution of individuals among species within a diversity index (Magurran 1988). This short commuunication aims to provide information relevant to answering the following two questions Does the choice of indicator functional group affect the estimation of blodiversity? Does the choice of quantification method affect the estimation of blodiversity?