The phoretic mite (Arachnida: Acari) assemblage of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Curculionidae)

The phoretic mite assemblage of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Curculionidae) has not been as thoroughly documented as that of some other ecologically and economically important bark beetle species. Phoretic mites can impact individual fitness and population dynamics of their hosts and documenting the mite assemblage associated with a bark beetle may provide information on their ecological and interactive roles. We caught Douglas-fir beetles over two summers in central British Columbia, Canada and sorted the associated mites into morphospecies. Representatives of the morphospecies were DNA barcoded (cytochrome oxidate I barcode region) which indicated at least nine distinct Operational Taxonomic Units (OTUs). There was a mean of 50.5 {+/-} 4.7 mites per beetle with both females and males carrying similar numbers of most mite species. However one OTU (Sarcoptiformes: Hemisarcoptidae) was found in substantially higher numbers than all other OTUs, and was always clustered in large aggregations in an anterior pocket on the sub-elytral surface. When B1 was removed from the mean, there were only 1.3 {+/-} 0.2 mites per beetle. The consistent high numbers of that OTU in conjunction with its consistent anatomical aggregation suggests an important interaction between that mite species and the Douglas-fir beetle.