Nest suitability, fine-scale population structure and male-mediated dispersal of a solitary ground nesting bee in an urban landscape

PLoS One. 2015 May 7;10(5):e0125719. doi: 10.1371/journal.pone.0125719. eCollection 2015.

Abstract

Bees are the primary pollinators of flowering plants in almost all ecosystems. Worldwide declines in bee populations have raised awareness about the importance of their ecological role in maintaining ecosystem functioning. The naturally strong philopatric behavior that some bee species show can be detrimental to population viability through increased probability of inbreeding. Furthermore, bee populations found in human-altered landscapes, such as urban areas, can experience lower levels of gene flow and effective population sizes, increasing potential for inbreeding depression in wild bee populations. In this study, we investigated the fine-scale population structure of the solitary bee Colletes inaequalis in an urbanized landscape. First, we developed a predictive spatial model to detect suitable nesting habitat for this ground nesting bee and to inform our field search for nests. We genotyped 18 microsatellites in 548 female individuals collected from nest aggregations throughout the study area. Genetic relatedness estimates revealed that genetic similarity among individuals was slightly greater within nest aggregations than among randomly chosen individuals. However, genetic structure among nest aggregations was low (Nei's GST = 0.011). Reconstruction of parental genotypes revealed greater genetic relatedness among females than among males within nest aggregations, suggesting male-mediated dispersal as a potentially important mechanism of population connectivity and inbreeding avoidance. Size of nesting patch was positively correlated with effective population size, but not with other estimators of genetic diversity. We detected a positive trend between geographic distance and genetic differentiation between nest aggregations. Our landscape genetic models suggest that increased urbanization is likely associated with higher levels of inbreeding. Overall, these findings emphasize the importance of density and distribution of suitable nesting patches for enhancing bee population abundance and connectivity in human dominated habitats and highlights the critical contribution of landscape genetic studies for enhanced conservation and management of native pollinators.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bees / genetics
  • Bees / physiology*
  • Female
  • Genetic Variation*
  • Genotype
  • Humans
  • Male
  • Microsatellite Repeats
  • Models, Genetic
  • Pollination*
  • Population Density
  • Population Dynamics
  • Urban Renewal

Grants and funding

Funding was provided by grants from the Andrew W. Mellon Foundation at Cornell University (MMLU), the Sarah Bradley Fellowship (MMLU), the Cornell Biology Research Fellowship Program (CKS), and awards from the National Science Foundation (DEB-0814544 and DEB-0742998 to BND). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.