Habitat conversion and fragmentation are pervasive impacts of humans on landscapes worldwide and are leading threats to biodiversity and species persistence. While parasites are increasingly recognized as diverse and important components of ecosystems, and are particularly at risk of extinction from human impacts, the impacts of fragmentation on parasitism have been largely overlooked. Complex life cycles, varied responses to fragmentation, and confounded landscape factors make it difficult to make general predictions on the effects of fragmentation on parasites. However, fragmentation experiments provide an opportunity to better understand the effects of fragmentation while controlling for confounding factors. Here we asked how habitat fragmentation affects a host-parasite interaction between a skink (Lampropholis guichenoti) and parasitic nematode (Hedruris wogwogensis) with a crustacean intermediate host in a large-scale, long-term fragmentation experiment.
We found that the prevalence of nematodes was higher in the guts of skinks from continuous eucalypt forest than eucalypt fragments and that the nematode was absent from skinks in the cleared matrix between fragments (change in deviance = 46.7; df = 2; P < 0.001). Similarly, we found that the prevalence of terrestrial amphipods (Arcitalitrus sylvaticus), the presumed intermediate host, was higher in the guts of skinks from continuous forest than fragments and that amphipods were absent from skink guts in the matrix (change in deviance = 14.6; df = 2; P < 0.001). Amphipod abundances from pitfall traps mirrored this pattern. These findings indicate that fragmentation can disrupt a host parasite interaction by altering the abundance of intermediate hosts. Relating these findings to those of similar studies suggests that fragmentation commonly disrupts host-parasite dynamics by altering the distribution and abundance of the intermediate host.