Conclusion
We found strong evidence that selection – acting through both survival and (to a lesser degree) reproduction, was associated with TLR3 locus variation in the contemporary Cousin population. This suggests that an unknown pathogen is present in the Seychelles warbler population, driving evolution at this TLR3 locus. It is possible that this current positive selection may be part of a much longer-term pattern of balancing selection, but only further monitoring will be able to determine this.