Evolutionary distinctness of Important Bird Areas (IBAs) of Sri Lanka: Do the species-rich wet zone forests safeguard Sri Lanka’s genetic heritage?

Abstract

Different components of biodiversity cannot be treated equally due to the limitations of knowledge and resources, and the heterogeneity in the distribution of biodiversity in the landscape. Therefore, biodiversity should be prioritized in effective site-based conservation. Parameters related to ecology, sociology and economics are primarily used for this prioritization process. Genetic and evolutionary history is broadly ignored. Using Important Bird Areas (areas of high avian diversity or density, defined based on several key criteria of species richness and abandons) as a model, here we attempted to use several key evolutionary tools in biodiversity prioritization with the aim of testing their applicability in an island nation where evolutionary relationships of species are yet to be fully appreciated. We developed a DNA-based phylogenetic tree for the 342 total species of birds recorded in Sri Lanka’s 71 IBAs. We used DNA sequence archives at www.birdtree.org for closely-related crown nodes of Sri Lankan species and higher-order phylogenetic backbone for represented taxonomic orders to construct the phylogenetic tree. Using this tree, we calculated the Phylogenetic Diversity (PD), Evolutionary Distinctness (ED) and the extinction risk of deep lineages (EDGE scores) for each IBA. Batrachostomus moniliger (Ceylon Frogmouth) is the most ED species while Otus thilohoffmanni (Serendib Scopes-owl) is the most EDGE species for Sri Lanka. Sri Lanka’s premier dry zone National Parks, Yala, Bundala and Udawalawe are the top ranked IBAs in PD, ED and EDGE scores. Except Sinharaja MAB Reserve and Knuckles, all other wet zone IBAs, which are characterized by their high endemicity and biodiversity were not ranked among the top ten IBAs for above evolutionary parameters. Mixing of both continental and insular lineages in the dry zone due to its proximity to mainland, the presence of wetlands that support migratory lineages and the movement of wet zone taxa along the riverine forests towards the dry zone could have increased the PD and ED scores in dry zone IBAs. However, wet zone IBAs are better at keeping the avian genetic composition that is unique to Sri Lanka by holding most of the avian endemics. For islands like Sri Lanka, global indices do not reflect the local evolutionary and conservation status. Effective site-based conservation programs that are aimed at preventing local extinctions therefore, must recognize the heterogeneity of biodiversity across the landscape. Our results show that the evolutionary parameters such as PD, ED and EDGE score are effective tools to refine the conventional indices used in habitat prioritization for Sri Lanka.

Keywords

• conservation prioritization, evolutionary distinctness, important bird areas, in-situ conservation, phylogenetic diversity, risk of extinction, sri lanka