Vanishing chromosomal inversion clines in Drosophila subobscura from Chile: is behavioral thermoregulation to blame?

Chromosomal inversion clines paralleling the long-standing ones in native Palearctic populations of Drosophila subobscura evolved swiftly after this species invaded the Americas in the late 1970s and early 1980s. However, the new clines did not consistently continue to converge on the Old World baseline. Our recent survey of Chilean populations of D. subobscura shows that inversion clines have faded or even changed sign with latitude. Here, we investigate the hypothesis that this fading of inversion clines might be due to the Bogert effect, namely, that flies’ thermoregulatory behavior has eventually compensated for environmental variation in temperature, thus buffering selection on thermal-related traits. We show that latitudinal divergence in thermal preference (Tp) has evolved in Chile for females, with higher-latitude flies having a lower mean Tp. Plastic responses in Tp also lessen latitudinal thermal variation because flies developed at colder temperatures prefer warmer microclima...

染色体倒位梯度（chromosomal inversion clines）与暗果蝇（Drosophila subobscura）本土古北界（Palearctic）种群中长期存在的倒位梯度模式相似，该物种于20世纪70年代末、80年代初入侵美洲后，此类梯度迅速演化形成。然而，这些新形成的倒位梯度并未持续稳定地趋近于旧大陆的基准模式。我们近期对智利暗果蝇种群的调查显示，倒位梯度已随纬度梯度逐渐弱化，甚至出现了符号反转。本研究旨在验证这一假说：倒位梯度的弱化或许源于博格特效应（Bogert effect），即果蝇的体温调节行为最终抵消了环境温度的波动，从而缓冲了与温度相关性状所受的选择压力。研究结果表明，智利雌性暗果蝇的热偏好（thermal preference, Tp）已随纬度产生分化：高纬度种群的平均热偏好更低。此外，热偏好的可塑性响应同样缓解了纬度间的温度差异——在低温环境下发育的果蝇更偏好温暖的微生境……