title: Evidence for gene flow in parasitic nematodes between two host species of shrews.
abstract: We describe the genetic structure of populations of the intestinal nematode Longistriata caudabullata (Trichostrongyloidea: Heligmosomidae), a common parasite of short-tailed shrews (genus Blarina, Insectivora: Soricidae). Parasites and hosts were collected from a transect across a contact zone between two species of hosts, Blarina brevicauda and B. hylophaga, in central North America. An 800-base pairs (bp) fragment of the ND4 mitochondrial DNA (mtDNA) gene was sequenced for 28 worms and a 783-bp fragment of the mtDNA control region was analysed for 16 shrews. Phylogenetic analyses of mtDNA sequences revealed reciprocal monophyly for the shrew species, concordant with morphological diagnosis, and supported the idea that the transect cuts through a secondary contact zone between well-differentiated B. brevicauda and B. hylophaga. In contrast to this pattern, the parasitic nematode mtDNA phylogeny was not subdivided according to host affiliation. Genealogical discordance between parasite and host phylogenies suggests extensive gene flow among parasites across the host species boundary.
authors.affiliation: School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0118, USA. sbrant1@lsu.edu
authors.forename: Sara V
authors.initials: SV
authors.lastname: Brant
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ortí
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000235:genetics; D014644:Genetic Variation; D005843:Geography; D006790:Host-Parasite Interactions; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009329:Nebraska; D010802:Phylogeny; D011157:Population Dynamics; D017422:Sequence Analysis, DNA; D012788:Shrews / Q000235:genetics* / Q000469:parasitology*; D014251:Trichostrongyloidea / Q000235:genetics* / Q000502:physiology*
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial