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Mitochondrial DNA markers reveal high genetic diversity and strong genetic differentiation in populations of <i>Dendrolimus kikuchii</i> Matsumura (Lepidoptera: Lasiocampidae)

<div><p><i>Dendrolimus kikuchii</i> Matsumura, 1927 is a serious forest pest causing great damage to coniferous trees in China. Despite its economic importance, the population genetics of this pest are poorly known. We used three mitochondrial genes (COI, COII and Cytb) to investigate the genetic diversity and genetic differentiation of 15 populations collected from the main distribution regions of <i>D</i>. <i>kikuchii</i> in China. Populations show high haplotype and nucleotide diversity. Haplotype network and phylogenetic analysis divides the populations into three major clades, the central and southeastern China (CC+SEC) clade, the eastern China (EC) clade, and the southwestern China (SWC) clade. Populations collected from adjacent localities share the same clade, which is consistent with the strong relationship of isolation by distance (r = 0.74824, P = 0.00001). AMOVA analysis indicated that the major portion of this molecular genetic variation is found among the three groups of CC+SEC, EC and SWC (61.26%). Of 105 pairwise FST comparisons, 93 show high genetic differentiation. Populations of Puer (PE), Yangshuo (YS) and Leishan (LS) are separated from other populations by a larger genetic distance. Distributions of pairwise differences obtained with single and combined gene data from the overall populations are multimodal, suggesting these populations had no prior population expansion in southern China. The nonsignificant neutral test on the basis of Tajima’ D and Fu’s Fs, and the lack of a star-shaped haplotype network together with the multiple haplotypes support this hypothesis. Pleistocene climatic fluctuations, combined with the host specificity to <i>Pinus</i> species, made these regions of south China into a refuge for <i>D</i>. <i>kikuchii</i>. The high level of population genetic structuring is related to their weak flight capacity, their variations of life history and the geographic distance among populations.</p></div

Sampling information of <i>D</i>. <i>kikuchii</i> in China.

<p>Sampling information of <i>D</i>. <i>kikuchii</i> in China.</p

Parameters of the neutral test based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.

<p>Parameters of the neutral test based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.</p

Sample locations for the 15 <i>D</i>. <i>kikuchii</i> populations from China, the codes for <i>D</i>. <i>kikuchii</i> populations are explained in Table 1; the gray region represents the geographic distribution of five <i>D</i>. <i>kikuchii</i> populations in Anhui.

<p>Sample locations for the 15 <i>D</i>. <i>kikuchii</i> populations from China, the codes for <i>D</i>. <i>kikuchii</i> populations are explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179706#pone.0179706.t001" target="_blank">Table 1</a>; the gray region represents the geographic distribution of five <i>D</i>. <i>kikuchii</i> populations in Anhui.</p

Parameters of genetic diversity based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.

<p>Parameters of genetic diversity based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.</p

Pairwise FST (below diagonal) and genetic distance (above diagonal) based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.

<p>Pairwise FST (below diagonal) and genetic distance (above diagonal) based on mitochondrial sequence data of 15 populations of <i>D</i>. <i>kikuchii</i>.</p

Median-Joining network based on the single genes of COI, COII and Cytb haplotypes.

<p>Each circle represents a haplotype, and the area of a circle is proportional to the number of observed individuals. Colors within the nodes refer to the <i>D</i>. <i>kikuchii</i> sampling regions.</p

Unrooted NJ phylogenetic tree of <i>D</i>. <i>kikuchii</i> based on the combination of the three gene sequences, estimated with PHYLIP using Kimura-2-parameter (1000 replications).

<p>The bootstraps were shown near the nodes. A, southwestern China clade; B, central and southeastern China clade; C, eastern China clade.</p

Observed and expected mismatch distributions for <i>D</i>. <i>kikuchii</i> in China, based on COI, COII, Cytb, and combined gene sequences.

<p>Observed and expected mismatch distributions for <i>D</i>. <i>kikuchii</i> in China, based on COI, COII, Cytb, and combined gene sequences.</p