Experimental habitat fragmentation disrupts nematode infections in Australian skinks

Habitat conversion and fragmentation threaten biodiversity and disrupt species interactions. While parasites are recognized as ecologically important, the impacts of fragmentation on parasitism are poorly understood relative to other species interactions. This lack of understanding is in part due to confounding landscape factors that accompany fragmentation. Fragmentation experiments provide the opportunity to fill this knowledge gap by mechanistically testing how fragmentation affects parasitism while controlling landscape factors. In a large‐scale, long‐term experiment, we asked how fragmentation affects a host–parasite interaction between a skink and a parasitic nematode, which is trophically transmitted via a terrestrial amphipod intermediate host. We expected that previously observed amphipod declines resulting from fragmentation would result in decreased transmission of nematodes to skinks. In agreement, we found that nematodes were absent among skinks in the cleared matrix and that infections in fragments were about one quarter of those in continuous forest. Amphipods found in gut contents of skinks and collected from pitfall traps mirrored this pattern. A structural equation model supported the expectation that fragmentation disrupted this interaction by altering the abundance of amphipods and suggested that other variables are likely also important in mediating this effect. These findings advance understanding of how landscape change affects parasitism. Habitat conversion and fragmentation are widespread impacts of humans on landscapes that drive biodiversity loss and disrupt species interactions (Wilcove et al. 1998, Tylianakis et al. 2008, Butchart et al. 2010). Parasites have been suggested to be particularly at risk due to cascading effects of species loss (i.e., coextinction; Dunn et al. 2009, Lafferty 2012). While there is a growing realization that parasites play important roles in food webs and ecosystem processes (Hudson et al. 2006, Dobson et al. 2008, Kuris et al. 2008, Lafferty et al. 2008), the effects of fragmentation on parasitism vary among studies (Taylor and Merriam 1996, Allan et al. 2003, Mbora and McPeek 2009, Sullivan et al. 2011, Gottdenker et al. 2014, Bordes et al. 2015) and the underlying mechanisms are poorly understood compared to other species interactions (Hagen et al. 2012, Martinson and Fagan 2014). Limited understanding of fragmentation effects on parasitism could be attributed to a scarcity of experimental studies (Gottdenker et al. 2014) as well as the complexity of parasite life cycles, variation in species