Genetic connectivity is maintained in two insect pollinators across a human-altered landscape

1. Population genetics is a valuable tool for assessing the impact of human -altered landscapes on genetic connectivity in various species. However, when applied to insects, challenges arise due to potentially large effective population sizes (Ne), high dispersal capacities and the recency of anthropogenic impacts. 2. This study assessed the population genetic structure of two pollinators across a human -altered landscape in Luxembourg. Samples from the ashy mining bee (Andrena cineraria, N = 201) and the greater bee fly (Bombylius major, N = 637) were genotyped at 25 microsatellite loci, including a genotyping-by-ampliconsequencing approach for A. cineraria. 3. Despite high statistical power of FST > 0.002 in B. major and FST > 0.0025 in A. cineraria, no deviations from genetic homogeneity were detected. For both species, there was no evidence for isolation -by -distance or genetic clustering. Genetic homogeneity was most likely the result of high levels of gene flow that compensate for the effects of genetic drift. 4. Estimates of Ne ranged between several thousand to tens of thousands, although precision was low. Simulations highlighted that genetic lag times can substantially affect our ability to detect recent (<50 generations) population differentiation when Ne is very large. Lag times were shorter with data from 25,000 simulated di -allelic loci, but only when sample sizes remained high. 5. Insect genetic studies should consider lag times due to large Ne and ensure sample size and markers offer adequate power to reject the null hypothesis of no landscape effect on genetic connectivity.