Microsatellites reveal a strong subdivision of genetic structure in Chinese populations of the spider mite Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract The population genetic diversity and population genetic structure of the two-spotted spider mite were unclear in China. In addition, two colour forms of the two-spotted spider mite coexist in China. The red (carmine) form is considered to be native while the green variant is considered to be invasive. Whether they constitute one or two species has been debated for a long time. To address these issues, we genotyped a total of 1055 individuals from 18 red populations and 7 green populations in China using eight microsatellite loci. We identified 109 alleles. We found a highly significant genetic differentiation among the 25 populations (global FST=0.566; P < 0.0001) and a low genetic diversity in each population. Using Bayesian clustering, we divided the mite populations in China into five clades. Geographic distance emerged as a major factor in the genetic structure. Pearson correlations between statistics of variation (AR and HE) and geographic co-ordinates (latitude and longitude) showed that the genetic diversity of the red spider mite was correlated with increasing latitude. We infer that the characters of population genetic structure and genetic diversity of the native red mite populations are due to the current climatic regimes and their colonization in a south–to–north process during the Holocene. In addition, our genetic data don’t support the separation of the two forms of spider mite into two species. The morphological difference between the two forms of mites may be due to adaptive radiation.