title: Historical demography and phylogeography of a specialist bark beetle, Dendroctonus pseudotsugae Hopkins (Curculionidae: Scolytinae).
abstract: Contemporary distribution of North American species has been shaped by past glaciation events during the Quaternary period. However, their effects were not as severe in the southern Rocky Mountains and Northern Mexico as elsewhere in North America. In this context, we test hypotheses  about the historical demography of Dendroctonus pseudotsugae, based on 136 haplotypes of mitochondrial cytochrome oxidase I. The phylogenetic analysis yielded four haplogroups corresponding to northwestern United States and southwestern Canada (NUS), southwestern United States (Arizona, SUS),  northwestern Mexico (Sierra Madre Occidental, SMOC), and northeastern Mexico (Sierra Madre Oriental, SMOR). Predictions of demographic expansion were examined through neutrality tests against population growth and mismatch distribution. Results showed that the NUS and SMOC haplogroups have  experienced demographic expansion events, whereas the SUS and SMOR haplogroups have not. Divergence times between pairs of haplogroups were estimated from early to middle Pleistocene. The longer divergence time between NUS and all other haplogroups could be the result of refugia within the  Pacific Northwest and northern Rocky Mountains and long-term isolation from southernmost populations in Mexico. The results obtained in this study are in agreement with the evolutionary history of the host Douglas-fir, as the warmer climates of interglacial periods pushed conifers northward  of Colorado, New Mexico, and Arizona, whereas environmental changes reduced the population size of Douglas-fir and forced fragmentation of distribution range southward into northern Mexico.
authors.affiliation: Escuela Nacional de Ciencias Biológicas, Instituto Politecnico Nacional, Prolongación de Carpio y Plan de Ayala s/n, col. Santo Tomás, C.P. 11340, México, D.F., México. enrico_ruiz@yahoo.com
authors.forename: Enrico A
authors.initials: EA
authors.lastname: Ruiz
authors.forename: John E
authors.initials: JE
authors.lastname: Rinehart
authors.forename: Jane L
authors.initials: JL
authors.lastname: Hayes
authors.forename: Gerardo
authors.initials: G
authors.lastname: Zuñiga
mesh_terms: D000818:Animals; D002170:Canada; D003710:Demography; D003576:Electron Transport Complex IV / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D006239:Haplotypes; D008800:Mexico; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D028224:Pseudotsuga / Q000502:physiology; D017422:Sequence Analysis, DNA; D014481:United States; D048889:Weevils / Q000235:genetics*
chemical_list: D003576:Electron Transport Complex IV