title: Fine-scale spatial genetic structure of common and declining bumble bees across an agricultural landscape.
abstract: Land-use changes have threatened populations of many insect pollinators, including bumble bees. Patterns of dispersal and gene flow are key determinants of species' ability to respond to land-use change, but have been little investigated at a fine scale (<10 km) in bumble bees. Using microsatellite markers, we determined the fine-scale spatial genetic structure of populations of four common Bombus species (B. terrestris, B. lapidarius, B. pascuorum and B. hortorum) and one declining species (B. ruderatus) in an agricultural landscape in Southern England, UK. The study landscape contained sown flower patches representing agri-environment options for pollinators. We found that, as expected, the B. ruderatus population was characterized by relatively low heterozygosity, number of alleles and colony density. Across all species, inbreeding was absent or present but weak (FIS  = 0.01-0.02). Using queen genotypes reconstructed from worker sibships and colony locations estimated from the positions of workers within these sibships, we found that significant isolation by distance was absent in B. lapidarius, B. hortorum and B. ruderatus. In B. terrestris and B. pascuorum, it was present but weak; for example, in these two species, expected relatedness of queens founding colonies 1 m apart was 0.02. These results show that bumble bee populations exhibit low levels of spatial genetic structure at fine spatial scales, most likely because of ongoing gene flow via widespread queen dispersal. In addition, the results demonstrate the potential for agri-environment scheme conservation measures to facilitate fine-scale gene flow by creating a more even distribution of suitable habitats across landscapes.
authors: Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK; School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK.
authors: Stephanie
authors: S
authors: Dreier
authors: John W
authors: JW
authors: Redhead
authors: Ian A
authors: IA
authors: Warren
authors: Andrew F G
authors: AF
authors: Bourke
authors: Matthew S
authors: MS
authors: Heard
authors: William C
authors: WC
authors: Jordan
authors: Seirian
authors: S
authors: Sumner
authors: Jinliang
authors: J
authors: Wang
authors: Claire
authors: C
authors: Carvell
mesh_terms: D000383:Agriculture; D000818:Animals; D001516:Bees / Q000235:genetics*; D003247:Conservation of Natural Resources; D017753:Ecosystem; D004739:England; D005260:Female; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population; D007178:Inbreeding; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D017422:Sequence Analysis, DNA
keywords: Bombus; conservation; isolation by distance; microsatellite; queen dispersal; relatedness