Abstract
Leptocybe invasa Fisher et LaSalle is a global invasive pest that seriously damages Eucalyptus plants. Studying the genetic diversity, genetic structure and introgression hybridization of L. invasa in China is of great significance for clarifying the breeding strategy, future invasion and diffusion trends of L. invasa in China and developing scientific prevention and control measures. Genetic diversity and phylogenetic analyses of 320 L. invasa female adults from 14 geographic populations in China were conducted using 10 polymorphic microsatellite loci (SSRs) and mitochondrial DNA cytochrome oxidase I gene sequences (COIs). (1) The Bayesian phylogenetic tree and haplotype network diagram showed that only haplotype Hap3 existed in L. invasa lineage B in China, while haplotypes Hap1 and Hap2 existed in lineage A, among which haplotype Hap2 was found for the first time. The nucleotide and haplotype diversities of lineage A were higher than those of lineage B. (2) The SSR genetic diversity of the Wuzhou Guangxi, Ganzhou Jiangxi and Panzhihua Sichuan populations was higher than that of the other 11 populations, and the SSR genetic diversity of lineage A was higher than that of lineage B. (3) The AMOVA analysis of mitochondrial COI data showed that 75.55% of the variation was among populations, and 99.86% of the variation was between lineages, while the AMOVA analysis of nuclear SSR data showed that 35.26% of the variation was among populations, and 47.04% of the variation was between lineages. There were obvious differences in the sources of variation between the COI and SSR data. (4) The optimal K value of COI and SSR data in structure analysis was 2, and PCoA analysis also divided the dataset into two obvious categories. The UPMGA phylogenetic tree based on SSR data clustered 14 geographic species into two groups. The results of genetic structure analysis supported the existence of two lineages, A and B, in China. (5) Structural analysis showed that there was obvious introgressive hybridization in Wuzhou Guangxi, Ganzhou Jiangxi, Panzhihua Sichuan and other populations. These results suggest that lineage introgressive hybridization has occurred in the L. invasa population in China. The introgressive hybridization degree and genetic diversity of lineage A are obviously higher than those of lineage B. Lineage introgressive hybridization may be the driving force for further L. invasa invasion and diffusion in China in the future.
Highlights
With the development of international trade and economic globalization, biological invasion has become a serious concern within the international community
(5) Structural analysis showed that there was obvious introgressive hybridization in Wuzhou Guangxi, Ganzhou Jiangxi, Panzhihua Sichuan and other populations. These results suggest that lineage introgressive hybridization has occurred in the L. invasa population in China
A Bayesian phylogenetic tree and haplotype network were constructed using 831 605-bp cytochrome oxidase I gene sequences (COIs) gene sequences downloaded from GenBank
Summary
With the development of international trade and economic globalization, biological invasion has become a serious concern within the international community. There are 560 confirmed invasive alien species; 125 are insect pests, 92 of which damage the agricultural ecosystem. The estimated annual economic loss due to alien invasive species is more than $18.9 billion [1]. Leptocybe invasa Fisher et LaSalle (Hymenoptera: Apodemidae) is an invasive gall pest that damages more than 30 species of Eucalyptus and mainly harms the branches and leaves of eucalyptus, causing typical lumplike galls on the veins, petioles and shoots of new leaves. In 2014, it had spread to 29 countries on five continents [3]. L. invasa was first discovered in China in 2007 in Dongxing, Fangchenggang, Guangxi, which is near the border with Vietnam [5]. L. invasa has become an important invasive forest pest of eucalyptus worldwide with unprecedented scale and speed of invasion and spread
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