Quantitative assessment of the dispersal of soil-dwelling oribatid mites via rodents in restored heathlands

1. Heathland restoration using topsoil removal requires the
re-colonisation of above- and belowground communities. Oribatid mites play
a key role in the comminution of organic matter and are frequently early
colonizers during succession despite their limited mobility. Whereas the
assembly of their communities may take decades, passive dispersal likely
dominates colonisation processes, but especially dispersal via other
animals (phoresy) remains poorly studied. Compared to other potential
hosts, movement habits and ecology of small rodents may provide dispersal
advantages to oribatid communities. 2. We studied dispersal of oribatid
mites via small rodents in restored heathland sites of different age. We
measured movement patterns of small rodents and extracted mites from their
pelts and nests to estimate annual contributions of these rodents to the
dispersal of oribatids. We also discussed phoretic estimates reported on
other host groups as a reference. 3. Probability estimates of oribatids in
pelts and nests showed lower occurrence frequencies compared to other
reported phoretic hosts. However, local rodent communities may aid the
dispersal of up to 41,000 oribatid mites per year. We highlight the high
diversity of oribatid species mounting rodents, unlike strong
species-specific filters reported in other passive pathways. We found that
over  half (58%) of the oribatid species reproduced asexually and
over a third (34%) had a soil-dwelling lifestyle. We also observed that
rodents often travel short distances below 40m, but occasionally reach
distances of up to 100m, especially in earlier successional stages. 4.
Synthesis and applications. Our results suggest that rodents may
contribute to assembly processes of soil-dwelling oribatid communities
given the slow turnover rate of this group in heathlands. This is
accomplished through short-distance dispersal, and especially in sites at
early stages of succession. To our knowledge, we are the first to
quantitatively assess the potential dispersal of oribatid mites via
rodents.