No severe genetic bottleneck in a rapidly range-expanding bumblebee pollinator

Abstract

Genetic bottlenecks can limit the success of populations colonizing new ranges. However, successful colonizations can occur despite bottlenecks, a phenomenon known as the genetic paradox of invasion. Eusocial Hymenoptera such as bumblebees ( Bombus spp.) should be particularly vulnerable to genetic bottlenecks, since homozygosity at the sex-determining locus leads to costly diploid male production (DMP). The Tree Bumblebee ( Bombus hypnorum ) has rapidly colonized the UK since 2001 and has been highlighted as exemplifying the genetic paradox of invasion. Using microsatellite genotyping, combined with the first genetic estimates of DMP in UK B. hypnorum , we tested two alternative genetic hypotheses (‘bottleneck’ and ‘gene flow’ hypotheses) for B. hypnorum 's colonization of the UK. We found that the UK population has not undergone a recent severe genetic bottleneck and exhibits levels of genetic diversity falling between those of widespread and range-restricted Bombus species. Diploid males occurred in 15.4% of reared colonies, leading to an estimate of 21.5 alleles at the sex-determining locus. Overall, the findings show that this population is not bottlenecked, instead suggesting that it is experiencing continued gene flow from the continental European source population with only moderate loss of genetic diversity, and does not exemplify the genetic paradox of invasion.

Predicting negative Effects of Climate Change on Taiwan’s endemic Bumblebee Bombus formosellus

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species, and climate change (Goulson et al 2015;Cameron and Sadd 2020). Of these factors, climate change is particularly detrimental to the high altitude bumblebee species, which have limited ecological amplitude and more negative effects than those experienced by more common species at lower altitudes (Biella et al 2021;Brock et al 2021). For example, high-mountain bumblebees usually prefer cold niches and lack tolerance to relatively high temperatures (Iserbyt and Rasmont 2012;Martinet et al 2021).

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