Habitat fragmentation can lead to species decline and extinction. Yet how fragmentation affects most populations and communities remains poorly understood, in part due to a lack of experimental tests. We studied domatia-dwelling mites within a large-scale landscape fragmentation experiment that manipulates patch connectivity with corridors. Domatia-dwelling mites are generally mutualistic with their host plant, providing services such as fungal removal, while the plant provides the mites with housing (via domatia, small structures on leaf undersides). We investigated how patch connectivity, edge-to-area ratio (manipulated through differently shaped patches), edge proximity, and number of domatia per leaf impact abundance and species richness of mite communities on leaves of Quercus nigra trees. To do so, we collected leaves within our experimental landscapes (n=4 trees/each of 4 patches x 7 experimental landscapes) and sampled mite populations present on them (n=1100 leaves). We determined total abundance and morphospecies richness of mites, as well as number of domatia present on each leaf. Our predictions were as follows: (1) that there would be higher mite abundance and richness on the edges of patches (where mites are exposed to lower temperatures and more shade, leading to lower rates of desiccation), (2) that there would be higher abundance and richness in patches with a higher edge-to-area ratio, (3) that there would be higher abundance and richness in connected patches (due to higher wind speeds, leading to the potential for greater dispersal rates), and (4) that there would be higher abundance and richness on leaves with greater numbers of domatia.
Results/Conclusions
We found an interaction between distance from patch edge and patch type (p=0.017) on domatia-dwelling mite communities: there were both more mite individuals and higher mite species richness at edges of isolated patches, but not of connected patches. There were also both more mite individuals and higher mite species richness on leaves with greater numbers of domatia (p<0.0001). We did not find evidence for a main effect of edge-to-area ratio or connectivity on either mite species richness or abundance (p>0.05). Our results match our initial prediction one, though not for all patch types, as well as four. Our experimental work shows that fragmentation can affect a community of mites through effects at different scales. Specifically, patch edges impact mite abundance and richness and this effect may be modified by the larger-scale influence of patch connectivity, but for the most part large-scale landscape effects have minimal impact on the mite community.