Oro Daniel, Freixas Lídia, Bartrina Carme, Míguez Silvia, Torre Ignasi
Ecology and Complexity Department Center of Advanced Studies (CEAB-CSIC) Blanes Spain.
BiBio Research Group Natural Sciences Museum of Granollers Granollers Spain.
Ecol Evol. 2024 Aug 16;14(8):e70104. doi: 10.1002/ece3.70104. eCollection 2024 Aug.
Marginal populations usually have low densities and are considered to be particularly vulnerable to environmental stochasticity. Using data collected in nest boxes, we analyzed the breeding performance of the edible dormouse (), an obligate hibernating rodent and a seed predator in deciduous forests, in two populations at the distribution range's edge. Despite being only 20 km apart from each other, Montseny is a large patch of mixed deciduous forests (oaks and beech), whereas Montnegre would be the harshest habitat, that is, a small, isolated patch with only oaks. First, we studied the differences in climate and tree cover change in the two populations. Second, we analyzed the direct and indirect roles of local climate conditions and seed availability on breeding performance over 10 years in each population. Finally, we explored the influence of tree cover change on the occupancy dynamics in the two populations. Our results showed contrasting responses between populations: in Montseny, asynchronous seed production between oaks and beech precluded skip breeding, and breeding performance increased with seed availability. Furthermore, dormice in Montseny may use pollen production to anticipate the amount of beech nut resources and adjust their breeding effort. Boxes showed higher occupancy and colonization and fewer extinctions in Montseny than in Montnegre, where seed availability did not drive breeding performance. Results from Montnegre suggest that skip breeding was an adaptive response to a more pulsed, harsher environment. Here, females produced a similar number of pups than at Montseny. Long-term studies dealing with population responses in marginal habitats can lead to a deeper understanding of the capacities of organisms to adapt to harsh environments. Although local adaptation is frequently documented across various taxa, studies at the distribution edge may shed light on our still limited comprehension of the underlying mechanisms responsible for its occurrence.
边缘种群的密度通常较低，被认为特别容易受到环境随机性的影响。我们利用在巢箱中收集的数据，分析了在分布范围边缘的两个种群中，食用睡鼠（一种专性冬眠啮齿动物和落叶林种子捕食者）的繁殖表现。蒙特塞尼和蒙特内格雷虽然彼此相距仅20公里，但蒙特塞尼是一大片落叶混交林（橡树和山毛榉），而蒙特内格雷则是最恶劣的栖息地，即一个只有橡树的小而孤立的斑块。首先，我们研究了这两个种群在气候和树木覆盖变化方面的差异。其次，我们分析了当地气候条件和种子可获得性在每个种群10年期间对繁殖表现的直接和间接作用。最后，我们探讨了树木覆盖变化对这两个种群占据动态的影响。我们的结果显示了种群之间截然不同的反应：在蒙特塞尼，橡树和山毛榉之间种子生产的不同步排除了跳过繁殖的情况，繁殖表现随着种子可获得性的增加而提高。此外，蒙特塞尼的睡鼠可能利用花粉产量来预测山毛榉坚果资源的数量，并调整它们的繁殖努力。与蒙特内格雷相比，蒙特塞尼的巢箱显示出更高的占据率和定殖率以及更低的灭绝率，在蒙特内格雷，种子可获得性并未驱动繁殖表现。蒙特内格雷的结果表明，跳过繁殖是对更不稳定、更恶劣环境的一种适应性反应。在这里，雌性产仔数与在蒙特塞尼时相似。处理边缘栖息地种群反应的长期研究可以使我们更深入地了解生物体适应恶劣环境的能力。尽管在各种分类群中经常记录到局部适应现象，但在分布边缘的研究可能有助于我们进一步理解其发生的潜在机制，目前我们对这些机制的理解仍然有限。
