Abstract
Biological invasions of pests into climatically unsuitable areas can be facilitated by human‐regulated environments, in which case there may be an impact on genetic structure through population processes and/or adaptation. Here, we investigated the population genetic structure of an invasive agricultural pest, Thrips palmi, in China, which has expanded its distribution range through using greenhouses. Early invaded populations showed a relatively higher level of genetic diversity than recently expanded greenhouse populations. Strong population genetic structure corresponded to a pattern of isolation by distance, with no recent gene flow and low historical gene flow among populations, reflecting limited ongoing dispersal. A genetic signature of population expansion was detected in early invaded populations and three northern populations from greenhouses, suggesting that the greenhouse environments facilitated expansion of this species. Redundancy analysis showed that the independent effects of environment and geography could explain 51.68% and 32.06% of the genetic variance, respectively. These findings point to climate‐ and greenhouse‐related spatial expansion, with the potential for adaptation by T. palmi. They emphasize the contribution of human‐regulated environments on the successes of this invasive species, a situation likely to apply to other invasive species that use greenhouse environments.
Highlights
Spatial spread of many small invertebrate species is often restricted by climatic extremes (Overgaard, Kearney, & Hoffmann, 2014; Wiens & Graham, 2005)
Several studies have shown ev‐ idence of evolutionary adaptation of species under natural climatic conditions (Csilléry, Rodríguez‐Verdugo, Rellstab, & Guillaume, 2018; Hoffmann, 2017). These factors are not necessarily indepen‐ dent, with many small invertebrates rapidly adapting to controlled environmental conditions when they are reared in the laboratory (Hoffmann & Ross, 2018), suggesting that species might adapt to controlled greenhouse conditions
Spatial spread of F. occidentalis seems not restricted by environmen‐ tal conditions, which contributes to its cosmopolitan status as a pest and its lack of population genetic structure in introduced areas
Summary
Spatial spread of many small invertebrate species is often restricted by climatic extremes (Overgaard, Kearney, & Hoffmann, 2014; Wiens & Graham, 2005). Spatial spread of F. occidentalis seems not restricted by environmen‐ tal conditions, which contributes to its cosmopolitan status as a pest and its lack of population genetic structure in introduced areas. Another important pest thrips, the melon thrips, Thrips palmi (Thysanoptera: Thripidae), was first described in tropical regions of Sumatra in Indonesia (Karny, 1925). By under‐ standing population genetic variation of T. palmi as well as evolution‐ ary processes affecting it, factors that facilitate the spread of this invasive species and its potential to become a wider pest can be iden‐ tified This is one of the few studies that focus on population genetic structure of an agriculture insect pest in greenhouse conditions. The results shed light on understanding the impact of artificial environ‐ ments on population genetic structure of pests more generally
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