Meeting Abstract
Climate change shifted the timing of reproduction of the great tit (Parus major) but not as much as the phenology of their caterpillar food, leading to a phenological mismatch. This mismatch of offspring needs and caterpillar abundance has major fitness consequences and, as females laying earlier in spring now do better, there is strong natural selection for earlier laying. Predicting the response to this selection is difficult as lay date is a complex trait; the outcome of a physiological cascade, triggered by photoperiod and temperature. To gain insight in how natural selection can act on timing of reproduction we need to assess the genetic variation in these different components. To study this, we created two selection lines for early and late laying birds. For this, we used genomic estimated breeding values calculated from 500.000 SNPs ‘trained’ on the lay date of 2000 genotyped great tits from our long-term population in the Netherlands. During two years, selection line birds were pairwise housed in climate controlled aviaries and subjected to two contrasting environments, mimicking a cold or a warm year. We measured phenotypes at three levels: (key reproductive) gene expression, circulating hormone levels and lay date. We aim to determine differences between the selection lines in these three levels in response to artificial selection and in this way understand which component(s) of the physiological mechanism could be affected by natural selection. This knowledge about the genetic basis of the mechanism(s) underlying variation in timing of reproduction is crucial to predict whether the great tit will be able to adapt to their warming world.
