Invasive Emerald Ash Borer (Agrilus planipennis- EAB) has killed hundreds of millions of ash (Fraxinus spp.) trees in North America, including >200 in the 8 ha Chance Creek Nature Preserve (Lorain Co, OH). The deaths have affected forest structure by opening canopy gaps that increase light reaching the forest floor, thus altering sub-canopy environments. We previously documented that increased light levels are significantly correlated with increased forb and graminoid abundances. Given that ants are critical seed dispersers for many spring ephemerals, we investigated the relationship between ant diversity and habitat characteristics in upland, slope, and floodplain habitats, which vary in ash loss (from high-loss plots to sites that lack ash trees). In summer 2016 we used 72 pitfall traps to sample diversity and abundances in eight 0.04 ha subplots. We hypothesized that disturbance patterns would drive ant diversity, and we therefore predicted that ant taxa would be non-randomly distributed with respect to plot history and disturbance. We used Percent Similarity, Shannon’s diversity index (H’), and the effective number of species (eH’) to compare plots; ANOVA to compare habitat types and ant distributions; and, Canonical Correspondence Analysis (CCA) to examine relationships between taxa and habitats.
Results/Conclusions
We recorded >500 ants from 11 genera, which included seven of the 10 genera known for our county and four previously unreported genera. As predicted, taxa were distributed in a highly non-random pattern (p < 0.0001). Percent Similarity connected sites according to disturbance history. Forbs and graminoids dominated disturbed plots, which had more ant genera, but fewer total ants (n.s.) as compared to undisturbed sites, which were dominated by Camponotus (56%) and Aphaenogaster (22%) the most abundant taxa. The latter is important for dispersing spring ephemerals, but nearly absent from the disturbed plots. Two genera (Tapinoma and Crematogaster) occurred only in the disturbed plots, so were most strongly associated with forbs and graminoids in the CCA, but these taxa also disperse seeds. Camponotus and Aphaenogaster may be more sensitive to disturbance, while Tapinoma and Crematogaster may be more resilient. The greater taxonomic diversity and higher effective number of genera (p < 0.05) in disturbed habitats indicates a feedback between ants and plant diversity that is not well understood. Given that the peak of local ash deaths occurred in 2009, we have the opportunity to document changes that will improve our understanding of forest responses to the invasive EAB.