Evidence for multiple introductions of an invasive wild bee species currently under rapid range expansion in Europe

Abstract

Background Invasive species are increasingly driving biodiversity decline, and knowledge of colonization dynamics, including both drivers and dispersal modes, are important to prevent future invasions. The bee species Megachile sculpturalis (Hymenoptera: Megachilidae), native to East-Asia, was first recognized in Southeast-France in 2008, and has since spread throughout much of Europe. The spread is very fast, and colonization may result from multiple fronts. Result To track the history of this invasion, codominant markers were genotyped using Illumina sequencing and the invasion history and degree of connectivity between populations across the European invasion axis were investigated. Distinctive genetic clusters were detected with east–west differentiations in Middle-Europe. Conclusion We hypothesize that the observed cluster formation resulted from multiple, independent introductions of the species to the European continent. This study draws a first picture of an early invasion stage of this wild bee and forms a foundation for further investigations, including studies of the species in their native Asian range and in the invaded range in North America.

Nesting, Sex Ratio and Natural Enemies of the Giant Resin Bee in Relation to Native Species in Europe

“…This result is in agreement with the high proportion of males (83%) found by Geslin et al in southern France [21]. A recent research on the genetic variability of the giant resin bee provides insights into the skewed male sex ratio, as it detected a high percentage of diploid males among individuals sampled in Vienna (Austria) [48]. Diploid males are probably the consequence of a founder effect in new colonized areas.…”

“…Furthermore, it has been discovered that a low genetic diversity and the associated skewed sex ratio, even if temporarily limiting the performance of invasive species, do not always limit their spread over time, as theoretically expected [49,50]. In particular, in invading social species, the haplo-diploid system is capable of overcoming the issue through multiple introductions [48,51] and natural selection mechanisms, which increases average heterozygosis at the sex locus over time [49].…”

Early-phase colonization by introduced sculptured resin bee (Hymenoptera, Megachilidae, Megachile sculpturalis) revealed by local floral resource variability

“…Therefore, source(s) of these presumed long-distance jumps within SE-Europe could have been any of the populations from the earlier-established W-European range, even the overseas origins cannot be excluded (Kovács 2015). The recent estimates of genetic relatedness suggest that the introduction into NE-Austria represents the independent colonization event in Europe, i.e., not originating from populations established in France and Switzerland (Lanner et al 2021).…”

“…Lanner et al, 2021). Generally, human-aided secondary introductions among the recently established but widely isolated locations within SE-Europe are not likely, since the initial low-abundances…”

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“…À cela s'ajoute la dispersion liée au transport de marchandises, bois ou autre support pouvant contenir des larves, qui peut conduire à des déplacements sur de longues distances et qui explique probablement les « bonds » de plusieurs centaines de kilomètres que semble faire l'espèce (LANNER et al, 2020a). Par ailleurs, l'analyse génétique de plusieurs populations européennes a récemment suggéré que plusieurs hhhhh hhh hhhh hhh hhhh hhh hhhh hhhh hhh hhhh hhh hhhh hhh hhhh hhh hhhh hhh hhhh hhh hhhh hhh hhhh hhhh hhh hhhh hhh h évènements d'introduction indépendants pouvaient également être un facteur explicatif de la progression rapide de M. sculpturalis en Europe (LANNER et al, 2021). Des individus provenant du sud et du centre de la France, de Suisse et de Vienne (Autriche) ont été génotypés.…”