Research Article

Conservation Genetics

, Volume 14, Issue 5, pp 1099-1110

First online:

Landscape heterogeneity predicts gene flow in a widespread polymorphic bumble bee, Bombus bifarius (Hymenoptera: Apidae)

  • Jeffrey D. LozierAffiliated withDepartment of Biological Sciences, University of Alabama Email author 
  • , James P. StrangeAffiliated withUnited States Department of Agriculture-Agricultural Research Service, Pollinating Insects Research Unit, Utah State University
  • , Jonathan B. KochAffiliated withUnited States Department of Agriculture-Agricultural Research Service, Pollinating Insects Research Unit, Utah State UniversityDepartment of Biology, Utah State University

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Abstract

Bombus bifarius is a widespread bumble bee that occurs in montane regions of western North America. This species has several major color pattern polymorphisms and shows evidence of genetic structuring among regional populations, and the taxonomic status of regional populations has repeatedly been debated. We test whether observed structure is evidence for discrete gene flow barriers that might indicate isolation or instead reflects clinal variation associated with spatially limited dispersal in a complex landscape. We first consider color pattern variation and identify geographical patterns of B. bifarius color variation using cluster analysis. We then use climate data and a comprehensive set of B. bifarius natural history records with an existing genetic data set to model the distribution of environmentally suitable habitat in western North America and predict pathways of potential gene flow using circuit theory. Resistance distances among populations that incorporate environmental suitability information predict patterns of genetic structure much better than geographic distance or Bayesian clustering alone. Results suggest that there may not be barriers to gene flow warranting further taxonomic considerations, but rather that the arrangement of suitable habitat at broad scales limits dispersal sufficiently to explain observed levels of population differentiation in B. bifarius.

Keywords

Landscape genetics Isolation by distance Isolation by resistance Environmental niche model Microsatellites Circuit theory Color polymorphism