Dispersal ability of male orchid bees and direct evidence for long-range flights

Male Neotropical orchid bees collect volatile chemicals from various sources in the environment in order to compose their characteristic perfume bouquets. Amongst other plants, over 600 species of orchids are exclusively pollinated by the bees during their quest for volatiles. Since the plants usually have a scattered distribution, it is assumed that orchid bees can transport the pollinaria across several kilometres due to their flight capabilities and a high dispersal potential. Until now, very long-range flight distances (up to 45 km) of male orchid bees have only been indirectly inferred from habitat requirements of orchids whose pollinaria were carried by captured males, whereas the distances established by direct measures (mark and recapture, radio telemetry) only span distances of up to around 6 km. The discrepancy between inferred and proven distances led us to readdress the question of dispersal ability of male orchid bees. In this study, we used tag, scratch and chemical marking of large numbers of bees to clarify two aspects: (1) the effect of moderate natural obstacles on dispersal and (2) the possibility of very long-range movements across a terrain lacking such obstacles. Our results suggest that a moderate natural obstacle (a valley separating opposite ridges) does not restrain orchid bee movements. Individual bees achieved extraordinary flight distances of more than 50 km across even terrain, extending the directly proven flight distances of male bees by more than an order of magnitude.