Redpolls one species
A newly published paper suggests that the redpoll complex is better treated as one species, rather than the three currently recognised.
The findings suggest that variation in the birds’ appearance stems from a specific chromosomal inversion (when a chromosome undergoes breakage and rearrangement within itself).
Within this inversion, Erik R Funk and his team of researchers found multiple candidate genes related to melanogenesis (the production of melanin pigments), carotenoid colouration and bill shape, suggesting the inversion acts as a supergene controlling multiple linked traits in redpolls. The varying redpoll forms are described in the paper as ‘ecotypes’, which are more akin to morphs than qualified subspecies (let alone species), citing that the observed differences in ecotype across redpolls’ range (including plumage colour and bill morphology) are likely driven by environmental factors, which maintain the variations in the supergene.
The researchers found that redpolls lack population genetic structure by either geography or ecotype boundaries, and that genetics failed to differentiate each individual according to its current specific classification.
Three species – Lesser, Common and Arctic Redpolls – and a range of distinctive subspecies are currently recognised across the Holarctic range of redpolls. However, the genetic evidence provided suggests that they are best treated as conspecific. ■