From primary forest to pasture: Diversity and distribution of fruitfeeding butterflies of the Western Andes, Colombia

Abstract

Tropical forests are under immense pressure from agricultural expansion and other human disturbances, and the deforestation leads to forest fragmentation and accelerated biodiversity loss. The tropical Andes of Colombia, a global biodiversity hotspot, is an area that has undergone severe land-use change and where the remaining primary forest is highly fragmented. Previous studies show that this land-use change and fragmentation of primary forest have severely affects a variety of different taxonomic groups. Yet, apart from for dung beetles, no study to date has assessed the impacts of land-use change on insects in the Colombian Andes. Fruit-feeding butterflies are good candidates to study effects of land-use change because they are easy to capture, and they are relatively well known taxonomically and ecologically. Butterflies are also an indicator taxon, used to measure ecosystem health. Here I examine the patterns of fruit-feeding butterfly assemblage structure and composition along an altitudinal gradient (1319-2683 masl) in primary forest, secondary forest and pasture in the western Andes of Colombia. Fruit-feeding butterflies were sampled using baited butterfly traps in 400 x 400m squares distributed across the three habitats. Each square contained 10 traps and a total of 30 squares were sampled. I found that pasture contained the highest species richness and abundance, largely dominated by Satyrinae butterflies. However, primary and secondary forests were more diverse and had a similar species composition. Pasture assemblages were significantly different to those of primary and secondary forest. Altitude significantly affected butterfly abundance, but not richness, across the habitats. In addition, several species had a very narrow altitudinal range at the very lowest elevations, perhaps suggesting that these species belong to the lowlands and are at their altitudinal limits. The results show that butterfly assemblages are severely affected by land-use change. However, the fact that secondary forests contain a similar species composition to that of primary forest suggests that secondary forest retain significant biodiversity and plays a vital role in supporting biodiversity in regions where most of the primary forest has been lost. It also suggests that secondary forests are recovering towards a primary forest state. I therefore conclude that primary forests should be a conservation priority in the region, but investing in secondary forest recovery by reforesting marginally profitable cattle pastures may be a good way to aid the protection of the highly endangered biota across the Andes.