Phylogeographic patterns of Lygus pratensis (Hemiptera: Miridae): Evidence for weak genetic structure and recent expansion in northwest China
April
Phylogeographic patterns of Lygus pratensis (Hemiptera: Miridae): Evidence for weak genetic structure and recent expansion in northwest China
Li-Juan Zhang 1 2 3
Wan-Zhi Cai 0 1 3
Jun-Yu Luo 1 2 3
Shuai Zhang 1 2 3
Chun-Yi Wang 1 2 3
Li-Min Lv 1 2 3
Xiang-Zhen Zhu 1 2 3
Li Wang 1 2 3
Jin-Jie Cui 1 2 3
0 Department of Entomology, China Agricultural University , Beijing , China
1 Natural Science Foundation of China (31601888) and the National Special Transgenic Project of
2 State Key Laboratory of Cotton Biology, Institute of Cotton Research of CAAS , Anyang , China
3 Editor: Tzen-Yuh Chiang, National Cheng Kung University , TAIWAN
Lygus pratensis (L.) is an important cotton pest in China, especially in the northwest region. Nymphs and adults cause serious quality and yield losses. However, the genetic structure and geographic distribution of L. pratensis is not well known. We analyzed genetic diversity, geographical structure, gene flow, and population dynamics of L. pratensis in northwest China using mitochondrial and nuclear sequence datasets to study phylogeographical patterns and demographic history. L. pratensis (n = 286) were collected at sites across an area spanning 2,180,000 km2, including the Xinjiang and Gansu-Ningxia regions. Populations in the two regions could be distinguished based on mitochondrial criteria but the overall genetic structure was weak. The nuclear dataset revealed a lack of diagnostic genetic structure across sample areas. Phylogenetic analysis indicated a lack of population level monophyly that may have been caused by incomplete lineage sorting. The Mantel test showed a significant correlation between genetic and geographic distances among the populations based on the mtDNA data. However the nuclear dataset did not show significant correlation. A high level of gene flow among populations was indicated by migration analysis; human activities may have also facilitated insect movement. The availability of irrigation water and ample cotton hosts makes the Xinjiang region well suited for L. pratensis reproduction. Bayesian skyline plot analysis, star-shaped network, and neutrality tests all indicated that L. pratensis has experienced recent population expansion. Climatic changes and extensive areas occupied by host plants have led to population expansion of L. pratensis. In conclusion, the present distribution and phylogeographic pattern of L. pratensis was influenced by climate, human activities, and availability of plant hosts.
Introduction
Cytoplasmic and nuclear data combined with coalescent theory are commonly used for
phylogeographic studies. They are powerful tools for evaluating the possible influence of climate
China (2016ZX08011−002). The funders had no
role in study design, data collection and analysis,
decision to publish, or preparation of the
manuscript.
changes, geological events, environmental changes and hosts on extant population structure
and tracing the possible evolutionary history of species [
1
]. Molecular phylogeographic results
have been used to reconstruct the evolutionary history of species by revealing colonization
history, range expansion, and spatial and temporal genetic variation [
2, 3
]. The phylogeographic
patterns of many organisms, whose evolution was affected by vicariance [4±6], climatic
changes [7], hosts [8] and human interference events [9±11] have been studied using
molecular data.
High levels of genetic diversity occur in many species, partially due to proper habitats and
sufficient food. However, the level of genetic variation varies widely between species.
Compared to the genetic distinctiveness often found in wild montane species, low genetic
differentiation of agricultural and public health insect pests is more common (e.g. Bactrocera dorsalis
[12]; Aedes albopictus [
13
]; Plutella xylostella [14]). Weak genetic structure is usually related to
habitat changes or to human activities that promote gene flow between populations. In
addition, lineage sorting, resulting from short-term coalescence, helps to weaken genetic
differentiation [
15
].
Vicariance is an important factor influencing the geographic pattern of organisms.
Vicariance isolates populations, reduces gene flow, and promotes genetic differentiation. As such, it
often results in the evolution of distinct genetic lineages. However, when a species possesses
high dispersal capacity [
9
] combined with migration [
16
], this greatly increases gene flow and
reduces the genetic differentiation of populations.
In addition to the role of vicariance, the contribution of climate conditions to
phylogeographic structure can be important. Lygus pratensis (L.) is a species of `continental' adaptation,
drier climate with greater seasonal variation. According to the characteristic biogeographical
patterns of continental taxa, we expected that the Lygus pratensis population should have more
extensive distributions, experience population expansion during parts of the (...truncated)