Comparison of metrics for identifying Key Biodiversity Areas

Achieving global biodiversity targets requires reliable identification of Key Biodiversity Areas (KBAs). The KBA Standard defines six metrics to identify KBAs for threatened (criterion A1) or geographically restricted (criterion B1) species, one as a measure of population size: (i) number of mature individuals, and four proxies for population size: (ii) area of occupancy, (iii) extent of suitable habitat, (iv) range, and (v) number of localities. The sixth parameter, (vi) distinct genetic diversity, explicitly captures genetic variation. We compared the performance of these metrics using a geographically restricted model species ( Ariagona margaritae , Insecta: Orthoptera). In our model species, KBA identification varied substantially depending on the metric used. The number of localities turned out to be the best proxy for population size, while other metrics were influenced by spatial dimensions of proposed KBAs. When calculating distinct genetic diversity for each area separately it picked the most diverse but genetically similar areas. The complementarity-based approach using ∆ + distinct genetic diversity best ensures comprehensive coverage of several genetic lineages and the species' evolutionary trajectory. This suggests that the inclusion of distinct genetic diversity in the KBA Standard would be better placed in a new subcriterion than as a metric under criteria A1 and B1. Our results will help to inform further development of the KBA Standard.