Landscape influence on pollinator population genetic connectivity

Insect pollinators face numerous threats, including habitat loss and population fragmentation. The effects of human-altered landscapes on population connectivity need to be better understood to inform effective mitigation measures. We examined the literature on the effects of landscape heterogeneity on population genetic connectivity in two key pollinator groups: bees (Hymenoptera: Anthophila) and hoverflies (Diptera: Syrphidae). We identified 113 studies from 59 countries, covering 96 bee and 21 hoverfly species. However, biased taxonomic and geographical coverage limited broad conclusions regarding species susceptibility to genetic isolation. Notably, hoverflies remain significantly understudied, hampering comprehensive assessments of genetic connectivity patterns. While some species demonstrated genetic differentiation across tens of kilometres, others maintained connectivity across entire continents. Various landscape features, including water bodies and mountain ranges, often acted as barriers to gene flow, while the impacts of deforestation, agriculture, and urbanisation on genetic connectivity were mixed. Biological traits like body size, resource specialisation, and effective population sizes were found to influence susceptibility to population isolation. However, contrasting results and limited species coverage precluded conclusive findings. Future research should include evaluations of genetic time lags and statistical power to determine the appropriateness of selected genetic tools for testing hypotheses of recent genetic effects of human-altered landscapes on pollinators. Owing to increased interest in pollinator habitat corridors, population genetic research encompassing a wider range of species, habitats, and improved study designs, is needed to provide an evidence-based framework for conservation measures.