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A parallel study of the genetic structure of two oligophagous species associated with the same hosts was conducted to determine the main factors shaping the distribution of genetic diversity. The bark beetle Tomicus piniperda and the pine processionary moth (PPM) Thaumetopoea pityocampa are both associated with the genus Pinus and belong to different guilds (xylophagous vs defoliating species). The PPM is an ectophagous species that feeds on the needles of living trees, whereas T. piniperda is endophagous and bores galleries in the inner bark of weakened trees. Both species were sampled in the main regions of France, and their genetic structure was assessed after genotyping with five microsatellite markers. Populations of the PPM were significantly structured. A pattern of isolation by distance was found when distances were calculated as bypassing the Massif Central, whereas no such pattern could be found with raw geographic distances. On the contrary, most populations of T. piniperda were not differentiated. No effect of host species could be detected in either of the two species. We conclude that the two taxa have contrasting effective dispersal rates per generation, and we hypothesize that this reflects the different selection pressures acting on individual fitness via different strategies of host use.Heredity (2006) 97, 38–45. doi:10.1038/sj.hdy.6800836; published online 10 May 2006 [ABSTRACT FROM AUTHOR]

The pine shoot beetle Tomicus piniperda is present throughout Eurasia. In Europe, it is considered as a secondary pest that rarely causes tree mortality, while heavy damage is observed in Yunnan Province (China) where it exhibits a novel aggregative behaviour during shoot attack. To understand why the ecological characteristics of the European and Chinese populations differ so strongly, we conducted an analysis of population genetic structure on 12 populations in Yunnan and one in JiLin using mitochondrial (COI-COII) and nuclear (ITS2 and 28S rDNA) DNA sequences, and compared the results to those obtained in France. We showed that the Yunnan populations differed markedly from French and JiLin populations. For all three markers, the genetic distances measured between the Tomicus from Yunnan and those from France were similar to distances previously observed between species. Similar distances were found between Yunnan and JiLin populations. Conversely, the distances between French and JiLin individuals were substantially lower, falling in the intraspecific range. We concluded that the individuals sampled in Yunnan belong to a new, undescribed species (Tomicus sp. nov.). We also showed that some individuals belong to the species T. brevipilosus that had never been recorded from this region before. Evolution of the genus Tomicus is discussed in the light of these new results.Heredity (2004) 93, 416-422. doi:10.1038/sj.hdy.6800518 Published online 28 July 2004 [ABSTRACT FROM AUTHOR]