McLaren James D, Schmaljohann Heiko, Blasius Bernd
Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, 26129, Oldenburg, Germany.
Institute for Biology and Environmental Sciences (IBU), Carl Von Ossietzky University of Oldenburg, 26129, Oldenburg, Germany.
Mov Ecol. 2023 Jul 5;11(1):37. doi: 10.1186/s40462-023-00406-0.
For many migratory species, inexperienced (naïve) individuals reach remote non-breeding areas independently using one or more inherited compass headings and, potentially, magnetic signposts to gauge where to switch between compass headings. Inherited magnetic-based migration has not yet been assessed as a population-level process, particularly across strong geomagnetic gradients or where long-term geomagnetic shifts (hereafter, secular variation) could create mismatches with magnetic headings. Therefore, it remains unclear whether inherited magnetic headings and signposts could potentially adapt to secular variation under natural selection.
To address these unknowns, we modelled migratory orientation programs using an evolutionary algorithm incorporating global geomagnetic data (1900-2023). Modelled population mixing incorporated both natal dispersal and trans-generational inheritance of magnetic headings and signposts, including intrinsic (stochastic) variability in inheritance. Using the model, we assessed robustness of trans-hemispheric migration of a migratory songbird whose Nearctic breeding grounds have undergone rapid secular variation (mean 34° clockwise drift in declination, 1900-2023), and which travels across strong geomagnetic gradients via Europe to Africa.
Model-evolved magnetic-signposted migration was overall successful throughout the 124-year period, with 60-90% mean successful arrival across a broad range in plausible precision in compass headings and gauging signposts. Signposted migration reduced trans-Atlantic flight distances and was up to twice as successful compared with non-signposted migration. Magnetic headings shifted plastically in response to the secular variation (mean 16°-17° among orientation programs), whereas signpost latitudes were more constrained (3°-5° mean shifts). This plasticity required intrinsic variability in inheritance (model-evolved σ ≈ 2.6° standard error), preventing clockwise secular drift from causing unsustainable open-ocean flights.
Our study supports the potential long-term viability of inherited magnetic migratory headings and signposts, and illustrates more generally how inherited migratory orientation programs can both mediate and constrain evolution of routes, in response to global environmental change.
对于许多迁徙物种而言，缺乏经验（天真）的个体利用一个或多个遗传的罗盘方向，以及潜在的磁路标，独立抵达偏远的非繁殖区域，以此来判断在何处切换罗盘方向。基于遗传磁性的迁徙尚未作为一种种群层面的过程进行评估，尤其是在强地磁梯度区域，或者长期地磁变化（以下简称长期变化）可能导致与磁方向不匹配的地方。因此，目前尚不清楚遗传的磁方向和路标在自然选择下是否有可能适应长期变化。
为了解决这些未知问题，我们使用一种结合全球地磁数据（1900 - 2023年）的进化算法对迁徙定向程序进行建模。建模的种群混合纳入了磁方向和路标的出生地扩散以及跨代遗传，包括遗传中的内在（随机）变异性。利用该模型，我们评估了一种迁徙鸣禽跨半球迁徙的稳健性，该鸣禽的近北极繁殖地经历了快速的长期变化（1900 - 2023年磁偏角平均顺时针漂移34°），并且它通过欧洲穿越强地磁梯度前往非洲。
在整个124年期间，模型进化出的磁路标迁徙总体上是成功的，在罗盘方向和测量路标的合理精度范围内，平均有60 - 90%的个体成功抵达。有路标的迁徙减少了跨大西洋的飞行距离，与没有路标的迁徙相比，成功率高达两倍。磁方向响应长期变化而发生可塑性变化（定向程序之间平均变化16° - 17°），而路标纬度的变化则受到更多限制（平均变化3° - 5°）。这种可塑性需要遗传中的内在变异性（模型进化出的标准差约为2.6°标准误差），从而防止顺时针长期漂移导致不可持续的公海飞行。
我们的研究支持了遗传磁迁徙方向和路标的潜在长期可行性，并更普遍地说明了遗传迁徙定向程序如何响应全球环境变化，既介导又限制路线的进化。
