Cold adaptation in the Asian tiger mosquito's native range precedes its invasion success in temperate regions

Abstract

Adaptation to environmental conditions within the native range of exotic species can condition the invasion success of these species outside their range. The striking success of the Asian tiger mosquito, Aedes albopictus, to invade temperate regions has been attributed to the winter survival of diapause eggs in cold environments. In this study, we evaluate genetic polymorphisms (SNPs) and wing morphometric variation among three biogeographical regions of the native range of A. albopictus. Reconstructed demographic histories of populations show an initial expansion in Southeast Asia and suggest that marine regression during late Pleistocene and climate warming after the last glacial period favored expansion of populations in southern and northern regions, respectively. Searching for genomic signatures of selection, we identified significantly differentiated SNPs among which several are located in or within 20 kb distance from candidate genes for cold adaptation. These genes involve cellular and metabolic processes and several of them have been shown to be differentially expressed under diapausing conditions. The three biogeographical regions also differ for wing size and shape, and wing size increases with latitude supporting Bergmann's rule. Adaptive genetic and morphometric variation observed along the climatic gradient of A. albopictus native range suggests that colonization of northern latitudes promoted adaptation to cold environments prior to its worldwide invasion.

Predicting the success of an invader: Niche shift versus niche conservatism

“…However, a previous analysis in Ae. albopictus revealed wing size clines among tropical, subtropical, and temperate native ranges (Sherpa, Blum, & Després, ). Furthermore, all temperate invasive and native populations differ from one of the European source located in more southern latitudes (China: 23.1°N), suggesting postintroduction changes in the size of individuals as Albanian populations were introduced from China (Sherpa, Blum, Capblancq, et al, ).…”

“…Following our initial reports on the role of genetic diversity in invasive populations (propagule pressure, genetic admixture) and preexisting adaptations within the native range (cold adaptation; Sherpa, Blum, Capblancq, et al, ; Sherpa, Blum, & Després, ), we evaluated whether niche characteristics could also be an essential predictor of Ae. albopictus invasive success in Europe.…”

“…Morphometric data were collected for 410 individuals from 25 invasive populations from Europe and 1 invasive population from United States (Table ). We also included morphometric data from 153 individuals from 4 native populations (China and Japan) reared in the same laboratory conditions, analyzed in a previous study (Sherpa, Blum, & Després, ).…”

“…Wing morphometrics were performed using landmark‐based (LM) geometric morphometrics. Twenty LM located at vein intersections and termini of left wings (Figure ; Sherpa, Blum, & Després, ) were digitalized using tpsUtil v1.76 (Rohlf, ) and tpsDig2 v2.31 (Rohlf, ). Variation due to scale, orientation, and position was removed by applying a Procrustes superimposition using IMP CoordGen8 (Sheets, ).…”

“…albopictus in Europe, by comparing the ecological characteristics of European invasive populations to the characteristics of their North American and Chinese source populations (Sherpa, Blum, Capblancq, et al, ). Because North American populations originated in Japan, where preexisting cold adaptation probably favored invasion in temperate regions (Sherpa, Blum, Capblancq, et al, ; Sherpa, Blum, & Després, ), we also included Japan in niche comparisons. The examination of niche shifts during the invasion process of Ae.…”