Morphological and genetic variation of the pine shoot tunnel beetle Placusa pinearum (Staphylinidae) in China.

Placusa pinearum, a newly described beetle species found living in pine shoot tunnels bored by the pine tip moth, Dioryctria rubella (Pyralidae), has potential as a vector to transport biological agents for controlling this moth pest of pine trees because of the high degree of niche overlap (co-occurrence) between them. In order to help determine the suitability of potential biological control vectors, it is useful to obtain knowledge concerning the intraspecific variation of the vector. We examined P. pinearum collected from 14 different geographical populations in China using morphological and molecular markers. An UPGMA dendrogram based on morphological characters showed divergence of populations of P. pinearum in a comparison of beetles from southwestern and 3 other geographic regions (central, northwestern, and eastern regions). We also compared 965-nucleotide sequences of the mitochondrial cytochrome oxidase subunit I gene from 56 individuals; 19 haplotypes were identified based on 28 polymorphic sites in this region. A Bayesian phylogenetic tree showed significant genetic divergence among the different populations in eastern China. In addition, absence of shared haplotypes, coupled with high pairwise FST values, demonstrated significant genetic divergence between the populations from the southwest and the other 4 main geographical regions (eastern, southern, central, and northwestern regions). Generally, we found the morphological divergence to be congruent with genetic divergence in these P. pinearum populations. This information should be useful for selection of suitable source materials in the species gene pool for future biological control programs.