Late Lunch Talk: Weak geographical structure in sperm morphology of the willow warbler by Hanna Nyborg Støstad

Late Lunch Talk by Hanna Nyborg Støstad, Natural History Museum (UiO)

Sperm morphology has been shown to vary on all taxonomic levels, and is under selection pressure due to the important function of the sperm cells in reproduction. Geographical divergences in sperm traits might imply the formation of a reproductive barrier, which could be one of the first steps of speciation. Subspecies complexes are an interesting study system for this process, as sperm traits could be one of the factors maintaining the divide between the subspecies. Here we studied sperm morphology variation of 330 male willow warblers Phylloscopus trochilus in Norway (58o N – 69o N), across the range of two subspecies which are differentiated in morphology and migration routes. Birds showed a change in SNP allele frequencies and body morphology around 65o N, but we found no evidence of genetic structuring in neutral microsatellites. There was no geographical variation in sperm traits across Norway, except that sperm heads were on average longer in the south. This is consistent with a pattern of a shallow genetic divergence, and indicates that sperm morphology is not a reproductive barrier maintaining the narrow hybrid zone.

Published May 4, 2016 9:16 PM - Last modified Mar. 8, 2021 2:58 PM