USING HIGHER-TAXON RICHNESS AS A SURROGATE FOR SPECIES RICHNESS .1. REGIONAL TESTS

Attempts to identify priority sites for conserving biodiversity are gr eatly hampered by a lack of good data on species' distributions. Recen t work suggests one promising solution might be to use higher-level ta xa (such as genera or families) which might be more easily surveyed, y et nevertheless still act as reliable surrogates for patterns of speci es richness. But evidence justifying this approach comes mostly from t emperate datasets or inventories over enormous areas, and a number of concerns remain unanswered about the use of higher-taxon richness for identifying key conservation sites in the tropics, where most diversit y occurs. Here in the first of two papers addressing these points, we explored congruence between species and higher-taxon richness across p rotected areas in Indo-Malaya and the Pacific rim. Our results support the use of the higher-taxon approach in guiding tropical conservation , but with certain reservations. In all three groups examined, higher- taxon richness was quite closely related to species number. However, t he precision with which absolute species richness of reserves could be predicted from higher-taxon richness was often surprisingly low, part icularly for rich sites where surveying higher taxa rather than specie s would save most time. The performance of higher taxa as surrogates a lso dropped sharply with increasing taxonomic rank, resulting in a tra de-off between time saved by high-level surveys and the value of those surveys. Lastly, we found that species richness within individual hig her tars was potentially as powerful an indicator of the overall speci es diversity of a site as the number of higher taxa it contained.