Population structure and genetic differentiation of tea green leafhopper, Empoasca (Matsumurasca) onukii, in China based on microsatellite markers

Abstract

The tea green leafhopper, Empoasca (Matsumurasca) onukii Matsuda, is one of the dominant pests in major tea production regions of East Asia. Recent morphological studies have revealed variation in the male genitalic structures within and among populations. However, the genetic structure of this pest remains poorly understood. This study explores the genetic diversity and population structure of this pest in nineteen populations from the four main Chinese tea production areas using microsatellite markers, with one Japanese population also examined. The results show low to moderate levels of genetic differentiation with populations grouped into four clusters, i.e. the Jiangbei group, the Southwest group 1, the Southwest group 2 and the South China group. Populations from China have a close phylogenetic relationship but show significant isolation by distance. Lower genetic diversity and genetic differentiation of E. (M.) onukii were found in the Kagoshima population of Japan. Evidence for genetic bottlenecks was detected in the South China and Jiangnan populations. Population expansion was found in the Southwest, Jiangbei and Kagoshima populations. This is the most extensive study of the population genetics of this species and contributes to our understanding of its origin and evolutionary history.

Figure 1

Structure of E. (M.) onukii populations in China revealed by Bayesian analysis implemented in Structure. Each individual is represented by a vertical bar broken into different colored genetic clusters, with length proportional to probability of assignment to each cluster. Analysis of 19 populations, 570 individuals, with possible numbers of clusters ranging from 2–4, indicated that the most likely number of clusters was 4.

Figure 2

Neighbor-joining tree based on Nei’s genetic distances for 20 populations of E. (M.) onukii with allelic frequencies obtained from 18 microsatellite markers. Numbers on nodes represent bootstrap support values (values below 50% not shown). The colors indicate the major clusters inferred by Structure analysis when K = 4.

Figure 3

PCoA at population level generated from 18 microsatellite markers in 20 populations in China and Japan. The first two principle component factors, PC1 and PC2, account for 33.54% and 14.76% of total variance. Colors are coded as in Fig. 2.

Figure 4

Geographic distribution and Bayesian model-based cluster analysis of E. (M.) onukii. Population codes are listed in Table 3; the pie chart in each population represents the proportion of individuals from four clusters inferred by Structure analysis. SimpleMappr was used to produce a distribution map based on the geographical coordinates in Table 3. URL: http://www.simplemappr.net/#tabs=0.