Sullivan Martin J P, Franco Aldina M A
1School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK.
2School of Geography, University of Leeds, Leeds, LS2 9JT UK.
Biol Invasions. 2018;20(5):1147-1159. doi: 10.1007/s10530-017-1616-9. Epub 2017 Nov 22.
The distributions of many species are not at equilibrium with their environment. This includes spreading non-native species and species undergoing range shifts in response to climate change. The habitat associations of these species may change during range expansion as less favourable climatic conditions at expanding range margins constrain species to use only the most favourable habitats, violating the species distribution model assumption of stationarity. Alternatively, changes in habitat associations could result from density-dependent habitat selection; at range margins, population densities are initially low so species can exhibit density-independent selection of the most favourable habitats, while in the range core, where population densities are higher, species spread into less favourable habitat. We investigate if the habitat preferences of the non-native common waxbill changed as they spread in three directions (north, east and south-east) in the Iberian Peninsula. There are different degrees of climatic suitability and colonization speed across range expansion axes, allowing us to separate the effects of climate from residence time. In contrast to previous studies we find a stronger effect of residence time than climate in influencing the prevalence of common waxbills. As well as a strong additive effect of residence time, there were some changes in habitat associations, which were consistent with density-dependent habitat selection. The combination of broader habitat associations and higher prevalence in areas that have been colonised for longer means that species distribution models constructed early in the invasion process are likely to underestimate species' potential distribution.
许多物种的分布与其环境并不平衡。这包括正在扩散的非本地物种以及因气候变化而发生分布范围变化的物种。在范围扩张过程中，这些物种的栖息地关联可能会发生变化，因为在扩张范围边缘不太适宜的气候条件会限制物种仅使用最适宜的栖息地，这违背了物种分布模型中平稳性的假设。或者，栖息地关联的变化可能是由密度依赖的栖息地选择导致的；在范围边缘，种群密度最初较低，因此物种可以表现出对最适宜栖息地的非密度依赖选择，而在范围核心区域，种群密度较高，物种会扩散到不太适宜的栖息地。我们研究了非本地普通梅花雀在伊比利亚半岛向三个方向（北、东和东南）扩散时，其栖息地偏好是否发生了变化。在范围扩张轴线上存在不同程度的气候适宜性和定殖速度，这使我们能够区分气候和居留时间的影响。与之前的研究不同，我们发现居留时间对普通梅花雀分布的影响比气候更强。除了居留时间的强烈累加效应外，栖息地关联也有一些变化，这与密度依赖的栖息地选择一致。在已被定殖较长时间的地区，更广泛的栖息地关联和更高的分布率相结合，意味着在入侵过程早期构建的物种分布模型可能会低估物种的潜在分布。
