Tests of biological corridor efficacy for conservation of a Neotropical giant damselfly

Deforestation and forest fragmentation are important drivers of global biodiversity loss and negatively impact ecosystem health and landscape continuity. One approach to reducing these impacts is the establishment of biological corridors. Studies on corridor efficacy have been limited to a small subset of taxa; while important, these data can rarely be extrapolated to other systems. I tested whether Megaloprepus caerulatus, a giant tree-hole breeding damselfly adapted to mature Neotropical forests, can and does disperse from mature forest to fragments that are components of an established corridor. I monitored presence of M. caerulatus in four secondary forest fragments of the San Juan-La Selva biological corridor network and in the contiguous La Selva forest. I compared densities of adult M. caerulatus and larval presence in artificial and natural breeding sites over the course of one year. None of the artificial holes in fragments were colonized by M. caerulatus whereas at La Selva 25% of artificial holes and 63% of natural tree holes were colonized. I tested M. caerulatus's ability to fly over pasture between fragments with a dispersal challenge experiment. Although the damselfly successfully crossed gaps of 25 m, it had difficulty traversing gaps as narrow as 50-100 m. Based on analysis of 360° photos taken from each release distance, the forest edge was less distinguishable from distances ⩾50 m. These results suggest limited conservation utility of existing biological corridor networks for M. caerulatus.