While habitat loss and fragmentation are frequently thought to most severely affect rare species and species at higher trophic levels, they can also have drastic effects on ecosystems’ more cryptic and less charismatic creatures: parasites. Previously understudied, parasites are recognized more frequently as central figures in driving some ecological processes, notably, host population regulation. The way that habitat fragmentation and parasites interact to influence intermediate and definitive host populations is still unclear. Previously, we determined that landscape-scale experimental habitat fragmentation removed parasitic nematode (Hedruris wogwogensis) pressure from intermediate amphipod host (Arcitalitrus sylvaticus) and skink definitive host (Lampropholis guichenoti) populations in remnant Eucalyptus fragments and introduced pine matrix. We asked how these host populations responded to the loss of parasites and how that changed over time in different parts of the landscape at the large-scale, long-term Wog Wog Habitat Fragmentation Experiment in New South Wales, Australia.
Results/Conclusions
Following fragmentation, 16% of skinks in fragments and 7% of skinks in the matrix were infected with at least one nematode compared to 59% infected skinks in undisturbed, continuous forest. The fragmentation-driven reduction in nematode prevalence resulted when the amphipod intermediate host decreased in fragments and went locally extinct in the matrix. With a release from parasite pressure, skink abundance increased in fragments and, to a smaller degree, in the matrix compared to continuous forest. Skinks and nematodes exhibited strong seasonal population cycles while all three species also showed longer (3-4 years) cycles. Habitat fragmentation altered these cycles in fragments, creating mismatches in peak parasite and host abundances. These results underscore the important role that parasites play in the regulation of host populations. Additionally, they show how habitat fragmentation can alter host-parasite dynamics leading to unimpeded growth of host populations and the potential for cascading effects throughout the ecosystem.