At this week’s journal club we discussed a paper by Mason and Tyler about genetic differentiation in Common, Hoary (or Arctic) and Lesser Redpolls that was published in Molecular Ecology earlier this year. ddRAD and RNA-seq indicate very small differences despite phenotypic variation and differentiation in several traits. There was a correlation between general gene expression profile and general morphology and plumage variation, but the direction of cause and effect is difficult to disentangle. The authors conclude that the patterns observed may reflect “high levels of ongoing gene flow between polymorphic populations, incomplete lineage sorting accompanying very recent or ongoing divergence, variation in cis-regulatory elements, or phenotypic plasticity, but do not support a scenario of prolonged isolation and subsequent secondary contact.”
Figure showing the distribution and phenotypic differences between the three Redpoll species analysed by Mason and Tyler (their Figure 1a,b).