Catry Paulo, Campos Ana R, Granadeiro José Pedro, Neto Júlio M, Ramos Jaime, Newton Jason, Bearhop Stuart
MARE, Marine and Environmental Sciences Centre, ISPA-Instituto Universitário, Rua Jardim do Tabaco 34, 1149-041, Lisbon, Portugal.
MARE, Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal.
Oecologia. 2016 Dec;182(4):985-994. doi: 10.1007/s00442-016-3725-z. Epub 2016 Sep 16.
Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ H) in robin Erithacus rubecula feathers across Europe. We then use δ H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.
在迁徙物种中，经常会发现来自不同种群或地理起源的个体共享停歇地或越冬地。鉴于它们不同的生活史，生态理论预测不同群体的个体应该表现出一定程度的生态位分化。由于难以将迁徙个体与繁殖地对应起来，这一点很少得到研究。在这里，我们首先记录了欧洲知更鸟（欧亚鸲）羽毛中氢同位素（δH）的广泛地理梯度。然后，我们使用δH以及翼尖形状，作为在伊比利亚越冬鸟类广泛迁徙起源的替代指标，来研究种群的生态分化。已知不同性别、年龄和体型的越冬知更鸟在伊比利亚的栖息地之间存在分化。这被归因于优势个体将劣势竞争者从最佳区域专制性地排除。我们发现，在羽毛δH或翼尖形状方面，栖息地之间没有分化，这表明不同起源的迁徙知更鸟之间不存在主要的竞争能力不对称。营养级（从血液中的氮同位素推断）与羽毛中的δH以及翼尖形状都相关，表明来自不同地理起源的个体在共享的越冬地表现出一定程度的生态分化。同位素混合模型表明，来自更北方种群的越冬鸟类消耗更多的无脊椎动物。我们的多尺度研究表明，营养生态位分化可能源于（在特定种群的繁殖地产生的）特化，这些特化被迁徙者带到共享的越冬地。
