Soil mites as bioindicators of disturbance in the boreal forest in northern Alberta, Canada: Testing taxonomic sufficiency at multiple taxonomic levels

Soil systems provide numerous ecosystem services but are often degraded due to anthropogenic and natural disturbances. Invertebrates can be used as biological indicators to provide information on soil health. Mites (Arachnida: Acariformes, Parasitiformes) constitute the majority of invertebrates in soil; however, their small size and diversity make them a challenging group to identify. Identification to levels coarser than species (e.g., genus, family) can alleviate some of the taxonomic difficulties. Here we test whether two groups of soil mites, Mesostigmata and Oribatida, can indicate three disturbance types (fire, forest harvest and linear features such as seismic lines and roads) in the boreal forest in northern Alberta. We assessed this at three taxonomic levels: species, genus and family. Samples were collected by the Alberta Biodiversity Monitoring Institute from 2010 to 2015 from across Alberta. We paired disturbed sites with nearby undisturbed sites while minimizing habitat and temporal differences (N pairs: fire = 13, harvest = 11, linear = 7). Mesostigmata were separated into two size categories, large only (> 300 mu m) and with small included (all mites > 50 mu m), while oribatid were analyzed only with individuals > 300 mu m. We used ANOVAs and PERMANOVAs to determine whether species richness, Shannon-Wiener diversity and assemblage structure differed significantly between disturbed and undisturbed sites. Compared to undisturbed habitats, we found that richness and diversity of Mesostigmata > 50 mu m were lower with fire disturbance at all three taxonomic levels; similarly, richness and diversity of Oribatida were lower with fire and harvest at all three taxonomic levels and richness was lower for linear disturbance at family-level. Assemblage structure of Mesostigmata > 50 mu m indicated fire and linear disturbance at all three taxonomic levels, while that of Mesostigmata > 300 mu m indicated all three-disturbance types at species-level, and harvest disturbance at genus and family. Assemblage structure of Oribatida indicated fire disturbance at all three taxonomic levels, and linear disturbance at genus and family. Our analyses showed that mesostigmatid and oribatid mites can indicate disturbance when identified to ranks coarser than species suggests that labour-intensive species-level identifications may not always be required for bioindicator studies using soil mites. The generality of these findings should be assessed in different regions and with different disturbances.