Impact of forest size on parasite biodiversity: implications for conservation of hosts and parasites

Studies of biodiversity traditionally focus on charismatic megafauna. By comparison, little is known about parasite biodiversity. Recent studies suggest that co-extinction of host specific parasites with their hosts should be common and that parasites may even go extinct before their hosts. The few studies examining the relationship between parasite diversity and habitat quality have focused on parasites that require intermediate hosts and pathogens that require vectors to complete their life-cycles. Declines in parasite and pathogen richness in these systems could be due to the decline of any of the definitive hosts, intermediate hosts, or vectors. Here we focus on avian ectoparasites, primarily lice, which are host specific parasites with simple, direct, life-cycles. By focusing on these parasites we gain a clearer understanding of how parasites are linked to their hosts and their hosts’ environment. We compare parasite richness on birds from fragmented forests in southern China. We show that parasite richness correlates with forest size, even among birds that are locally common. The absence of some ectoparasite genera in small forests suggests that parasites can go locally extinct even if their hosts persist. Our data suggest that the conservation of parasite biodiversity may require preservation of habitat fragments that are sufficiently large to maintain parasite populations, not just their host populations.