No abstract

Attempts to identify priority sites for conserving biodiversity are greatly hampered by a lack of good data on species' distributions. Recent work suggests one promising solution might be to use higher-level taxa (such as genera or families) which might be more easily surveyed, yet nevertheless still act as reliable surrogates for patterns of species richness. But evidence justifying this approach comes mostly from tem perate datasets or inventories over enormous areas, and a num ber of concerns remain unanswered about the use of higher-taxon richness for identifying key conservation sites in the tropics, where most diversity occurs. Here in the first of two papers addressing these points, we explored congruence between species and higher-taxon richness across protected areas in Indo-M alaya and the Pacific rim. O ur 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, the precision with which absolute species richness of reserves could be predicted from higher-taxon richness was often surprisingly low, particularly for rich sites where surveying higher taxa rather than species would save most time. The performance of higher taxa as surrogates also dropped sharply with increasing taxonomic rank, resulting in a trade-off between time saved by high-level surveys and the value of those surveys. Lastly, we found that species richness within individual higher taxa was potentially as powerful an indicator of the overall species diversity of a site as the num ber of higher taxa it contained.

Recent analyses confirm that urgent attempts to catalogue the distribution of biological diversity may be facilitated by focusing at the level of genera or families rather than species. However, questions remain over the application of higher-taxon surveys to identify networks of priority areas for conservation action. Is the close spatial match between species and higher-taxon richness at global and regional scales re iterated when sites are locally distributed? How much money is saved by the higher-taxon approach? And how does using genus or family information affect the efficiency with which spatial priorities for conservation are identified? We examined these issues using data on the diversity of woody plants in Sri Lankan forests. We found that at this local scale, the family and particularly generic richness of sites was closely linked to their species richness, independently of variation in site size. Moreover, fieldwork in an additional forest showed that targeting woody plant genera and families rather than species reduced survey costs by a minimum of 60 % and 85 % respectively. Most importantly, while using family data in site-selection algorithms led to the loss from reserve networks of around 7-10% of woody plant species, using genera rather than species had virtually no effect on the representation of species in priority sites. These results thus confirm that judicious use of the higher-taxon approach is indeed a valuable technique for improving the cost effectiveness of field surveys for local conservation planning in the tropics.