Ant-associated mite communities are sensitive to ant colony neighborhoods, habitat, and seasonality in grasslands
Ants have significant interactions with above and belowground communities and can act as ecosystem engineers, creating biodiversity hot spots in soil in and around their nests. Mites are frequently found in ant nests and also riding on ants (phoresy) for dispersal. We conducted three studies to tease apart the effects of ant community, habitat, seasonality, and nest proximity on phoretic mite diversity and community composition. To test surrounding nest community effects, mites were collected from workers in a central nest and all ant nests within 10m2 were identified. We used non-metric multidimensional scaling (NMDS) to characterize the surrounding nest community, and then used axis scores in general linear models predicting mite abundance and richness. To test the role of habitat on mite communities we compared mites from the cosmopolitan ant, Myrmica americana, using nests inside a constructed prairie and bordering mowed lawn edges. We used MDS to characterize the mite communities in the two habitats and a permutational ANOVA to test the effect of habitat. Lastly we sampled workers from 22 nests every three weeks and identified seasonal and proximity effects on mite communities in nests with general linear models and Mantel correlograms, respectively.
The results of our ant community study revealed that M. americana and Aphaenogaster rudis nests have lower mite abundance when the local nest community has many nests of small competitive ants (such as Monomorium minimum and Solenopsis molesta) (p<0.001, dev. expl= 33% and 14%, respectively). Richness and abundance for nests inside and outside of the grasslands were highly variable and did not show a significant relationship with habitat type. Mite community composition, however, was significantly different between the prairie and mowed habitats (R2=7.7, Fstat=5.37, p=0.002). In our seasonal and proximity study, mite communities were dominated by a few of very common species with greatest abundance in early summer and a second peak in abundance around the time of alate production (late summer). Mantel correlograms showed increasing similarity in mite communities of closer nests, but this relationship was not significant. Together, these studies suggest that within nests of the same host species, phoretic mite communities may be sensitive to multiple factors including surrounding ant nest community and proximity to other nests, nest habitat, and season.