Declines in biodiversity and the abundance of pest species across land use gradients in Southeast Asia

Context Changes in land use have disruptive effects on community structure, causing many species to disappear, though a few thrive and become pests. Objectives To gain understanding on how anthropogenic activity changes spatial patterns of native species diversity while favoring pests, we conducted rapid biodiversity assessments of dacine fruit flies across eight regions in Southeast Asia. Methods Male lure traps were maintained for 2 days along transects at 233 sites, in forest, agricultural and urban environments. Results A total of 8393 individuals were collected, belonging to 57 described and 4 new or unidentified species. The majority (78 %) of individuals belonged to 14 pest species, dominated by Bactrocera dorsalis (Hendel). The 57 species represent 38 % of those recorded from the region, indicating effective sampling. Individual flies were collected in highest numbers in urban and agricultural sites, but species diversity was low. Forest samples yielded fewer specimens but highest species diversity, suggesting a shift in community structure after disturbance, benefiting a few pest species at the expense of the broader community, even in the same genus and ecological guild. Conclusions Dacine fruit flies may be useful in assessing habitat quality and bait systems permit the execution of rapid biodiversity and multi-species conservation assessments. Our results apply to broader patterns concerning biodiversity loss and the emergence of pest species under increasingly intensive land use gradients, and demonstrate the remarkable loss of biodiversity over very narrow distances as forest is converted into agricultural use, hence the importance in maintaining a mosaic of native habitats.