COS 7-4
Functional diversity and the fragility of avian assemblages in the Solomon Archipelago
The fragility or robustness of biotic assemblages is an important and complex property of ecological systems. While many studies have examined the connection between biodiversity and ecosystem function (BEF), the relationship between diversity and assemblage fragility—the relative abundances of species prone to extinction—remains poorly understood. We ask two questions: first, using relevant ecological traits, is it possible to predict species’ IUCN threat status? Second, is community-level functional diversity an emergent property that makes constituent species more or less vulnerable to extinction? To address these questions we focus on the avifauna of the Solomon Archipelago, a diverse and insular system characterized by increasing human impact. We created a dataset of over 1,000 morphological measurements of ecological traits of interest, and have mined the literature for relevant life history data. In addition to species traits, we quantified the extrinsic characteristics of assemblages’ habitats using GIS. Understanding the importance of ecological traits in determining species-level extinction risk will improve conservation prioritization efforts. In addition, understanding the emergent properties of communities that may arise from different dimensions of diversity within an assemblage can unify studies of ecosystem properties that maintain biodiversity with the developing field of BEF.
Results/Conclusions
In order to evaluate the relationship between ecological traits and IUCN threat status, we used an ordered logistic regression to test for relationships between body size, dispersal ability, and clutch size and the IUCN threat category of each species. These traits are not significantly related to extinction risk (p>0.1). In addition, we modeled the average IUCN threat status for all species occurring on each of 31 islands as a function of the functional diversity of the birds on each island, and the area and isolation of each island. We find that both the functional diversity of the community and island area are significantly associated with IUCN threat level (p<0.05). Surprisingly, both of these variables are positively related to IUCN threat level, suggesting that more functionally diverse assemblages, and those that occur on larger islands, are occupied by species with higher average levels of threat. Our results show that threat at the species level may be divorced from ecological traits thought to be important determinants of extinction risk. Additionally, the same species that expand functional diversity may be those most threatened, which has important implications when viewed through the BEF framework.