Citril finch wing length changes along >25 years: natural selection under climate

Abstract

In recent years, rapid changes in the wing length of several bird species, apparently due to climate change, have been reported. However, none of these studies has shown whether the changes detected are due to directional natural selection processes. Here we use an extensive capture-recapture (CR) database of Citril Finches (Carduelis citrinella) sampled from 1991-2017. Survival estimation in relation to wing length showed that wing length was under positive directional selection from 1991 to 2009. From 2009 on, wing length remained constant, and survival analyses showed that wing length was under fluctuating stabilising selection. Results show therefore, for the first time, that changes in wing length under the scenario of climate change are under natural selection processes. However, in birds getting to a stabilization in wing length variation in more recent years, suggests that the change in wing length cannot be explained only by climate change.