title: Population genetics of bisexual and unisexual populations of the scaly-winged bark louse Echmepteryx hageni (Insecta: Psocoptera).
abstract: The scaly-winged bark louse, Echmepteryx hageni, exhibits a unique pattern of co-existence of apparently differnt reproductive modes. Unisexuality is widespread in eastern North America, while sexual populations are restricted to isolated rock out-croppings in southern Illinois and eastern Kentucky. Three of the four nuclear loci examined show greater genetic diversity in the unisexual form compared to the sexual form of E. hageni, in accordance with the pattern previously shown in mitochondrial genetic data. Neutrality tests of the nuclear loci indicate a consistent signal of demographic expansion in asexual populations, but not in sexual populations. There was evidence of inbreeding in the isolated sexual populations at three of the nuclear loci, and one locus had signs of gene specific balancing selection. However, there is no significant genetic differentiation between bisexual and unisexual populations, possibly due to the greater effective population size of nuclear loci relative to mitochondrial loci. The mitochondrial differentiation of E. hageni populations in the northwestern part of their range (Minnesota and Wisconsin) was also not reflected in the nuclear data. We present three hypotheses that may explain the disparity in observed nuclear and mitochondrial genetic diversity between the reproductive forms of E. hageni.
authors.affiliation: Department of Entomology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA, scott.shreve@centre.edu.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Shreve
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Johnson
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics; D000818:Animals; D019143:Evolution, Molecular; D005260:Female; D050259:Genes, Mitochondrial / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D006239:Haplotypes; D007178:Inbreeding; D019476:Insect Proteins / Q000235:genetics; D007658:Ketone Oxidoreductases / Q000235:genetics; D008297:Male; D008957:Models, Genetic; D009245:NADH Dehydrogenase / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D010445:Peptide Elongation Factors / Q000235:genetics; D008003:Phthiraptera / Q000145:classification / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction / Q000235:genetics; D017422:Sequence Analysis, DNA; D012726:Sexual Behavior, Animal; D014481:United States; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics
chemical_list: D019476:Insect Proteins; D009687:Nuclear Proteins; D010445:Peptide Elongation Factors; D000429:Alcohol Oxidoreductases; C021398:3-hydroxyisobutyrate dehydrogenase; D007658:Ketone Oxidoreductases; C053164:pyruvate dehydrogenase (NADP+); D009245:NADH Dehydrogenase; D025262:Vacuolar Proton-Translocating ATPases