Gene frequency clines at X-linked or haplodiploid loci

Area of Science:

• Population Genetics
• Evolutionary Biology
• Genetics of Sex-linked Traits

Background:

• Gene frequency clines describe how allele frequencies change across geographic space.
• Understanding clines is crucial for predicting evolutionary trajectories and species adaptation.
• X-linked and autosomal loci have different inheritance patterns, potentially affecting cline formation.

Purpose of the Study:

• To derive equations for gene frequency clines at X-linked and haplodiploid loci.
• To identify conditions under which X-linked clines mirror autosomal clines.
• To analyze clinal variation in a specific bumble bee species to infer selection intensity.

Main Methods:

• Mathematical derivation of gene frequency cline equations for sex-linked loci.
• Analysis of clinal variation patterns in the bumble bee Bombus melanopygus.
• Estimation of selection intensity required to maintain observed clinal patterns.

Main Results:

• X-linked clines match autosomal clines only under strict conditions: no dominance, equal dispersal, and equal allele effects in both sexes.
• Deviations from these conditions lead to divergent gene frequencies between males and females.
• Clinal variation in Bombus melanopygus color morphs suggests a low selection intensity (≤1%) is sufficient for cline maintenance.

Conclusions:

• Sex-linked inheritance significantly influences gene frequency cline formation, often creating differences between sexes.
• The study provides a framework for analyzing clines at X-linked and haplodiploid loci.
• Minimal selection can maintain observable clinal variation, as demonstrated in Bombus melanopygus.