Source dataset and code: Comparing impacts of fragmentation on bird functional and phylogenetic diversity in primary and secondary rainforests

This is a supplementary dataset to a paper on bird biodiversity metrics of human-modified forests of PNG. It includes both the code and base data to perform core analyses. Abstract1.Avian biodiversity in tropical rainforests is threatened by increasing intensity of anthropogenic disturbances. Secondary forest birds can maintain ecosystem services that are otherwise lost with disappearing primary forests. However, stability of these services can be impeded by area effects reducing bird diversity.2.We compared the effects of fragmentation on avian ecosystem functions in both primary and secondary forests. We performed point count surveys in both continuous rainforests, as well as isolated forest fragments in lowland Papua New Guinea. We combined taxonomic diversity with functional and phylogenetic indices, and patterns of individual functional traits.3.Bird taxonomic diversity was lower in secondary forests, and decreased considerably due to fragmentation. In contrast, functional diversity was not affected by fragmentation, but increased in secondary forests. Phylogenetic diversity increased in all human-modified forests.4.Decreases in taxonomic diversity stemmed from the loss of forest-dependent birds. In contrast, decreases in functional and phylogenetic diversity were prevented by introduction of open-habitat species. This was demonstrated by shifts in trait composition, as bird phenotypes reliant on forest continuity became less prevalent. Specifically, we recorded a proportional decrease in insectivory and ground foraging; and an increase in nectarivory and dispersal ability. Increased dispersal ability was also observed in secondary forests, where it was associated with shifts towards frugivory and canopy foraging. Increases in phylogenetic diversity were likely amplified by high phylogenetic dispersion of introduced habitat generalists. 5.Policy implications. We show that compensatory patterns of species introduction fail to account for loss of ecosystem functions due to the decline of forest-dependent birds. As such, conservation policies should be targeted towards species that share traits associated with disturbance sensitivity, such as insectivory, ground foraging, and low dispersal ability. This could prevent biodiversity loss in poorly explored tropical landscapes in early stages of large-scale deforestation.