title: Microsatellites reveal a strong subdivision of genetic structure in Chinese populations of the mite Tetranychus urticae Koch (Acari: Tetranychidae).
abstract: BACKGROUND
  Two colour forms of the two-spotted spider mite (Tetranychus urticae Koch) coexist in China: a red (carmine) form, which is considered to be native and a green form which is considered to be invasive. The population genetic diversity and population genetic structure of this organism were unclear in China, and there is a controversy over whether they constitute distinct species. To address these issues, we genotyped a total of 1,055 individuals from 18 red populations and 7 green populations in China using eight microsatellite loci.
  
  
  RESULTS
  We identified 109 alleles. We found a highly significant genetic differentiation among the 25 populations (global FST = 0.506, global FST {ENA} = 0.473) and a low genetic diversity in each population. In addition, genetic diversity of the red form mites was found to be higher than the green form. Pearson correlations between statistics of variation (AR and HE) and geographic coordinates (latitude and longitude) showed that the genetic diversity of the red form was correlated with latitude. Using Bayesian clustering, we divided the Chinese mite populations into five clades which were well congruent with their geographic distributions.
  
  
  CONCLUSIONS
  Spider mites possess low levels of genetic diversity, limit gene flow between populations and significant and IBD (isolation by distance) effect. These factors in turn contribute to the strong subdivision of genetic structure. In addition, population genetic structure results don't support the separation of the two forms of spider mite into two species. The morphological differences between the two forms of mites may be a result of epigenetic effects.
authors.affiliation: Department of Entomology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Jing-Tao
authors.initials: JT
authors.lastname: Sun
authors.forename: Chunlan
authors.initials: C
authors.lastname: Lian
authors.forename: Maria
authors.initials: M
authors.lastname: Navajas
authors.forename: Xiao-Yue
authors.initials: XY
authors.lastname: Hong
mesh_terms: D000818:Animals; D002681:China; D014644:Genetic Variation; D005828:Genetics, Population; D006801:Humans; D018895:Microsatellite Repeats; D058974:Phylogeography; D040102:Tetranychidae / Q000235:genetics*