Natural selection on flower size in invasive Cytisus scoparius along an elevation gradient

Aims Established invasive plant species have more diverse gene pools than single populations in their home range.This genetic and often phenotypic variation allows for natural selection to act and produce rapid adaptations as an invasive species interacts with other members of the community.For an invasive flowering plant,interactions with pollinators may lead to adaptations to a heterogeneous pollinator community.The variation in the pollinator community in the invaded range is similar to variation in the native range,suggesting that adaptations may mirror patterns seen in the home range.In this study,we investigated variation in flower size in Cytisus scoparius,an invasive leguminous shrub,along an elevation gradient.Methods This study took place in the Capitol State Forest in Washington State.We measured flower widths and the proportion of visited flowers,using 10 plants per field site.Sites were located along an elevation gradient and were visited three times to measure phenological variation on a per-plant basis.Important Findings We saw positive selection for flower size,albeit without a distinct pattern of higher selection at higher elevations.The pattern of natural selection could be seen both in terms of pollinator visitation rates and in seed production.We also found that the largest contributor to changes in seed production was not elevation or flower size but management practices.

已建群的入侵植物物种在其本地生长范围内比单一种群具有更多样化的基因库。这种遗传和表型变异可以使入侵植物与群落的其他成员相互作用,从而进行自然选择,并形成快速适应机制。对于入侵的开花植物,与传粉者的相互作用可能使其适应异质性的传粉者群落。入侵地内传粉昆虫群落的变化与本地范围内的变化相似,这表明适应性可能反映了在本地范围内看到的模式。在本论文中,我们研究了在华盛顿州的国会国家森林公园内的一种入侵豆科灌木金雀儿(Cytisus scoparius)花的大小沿海拔梯度的变化。我们在每个样地中测量了10株植物花的宽度和传粉花的比例。我们对沿海拔梯度分布样地的金雀儿在单株水平下的物候变化进行三次测定。研究发现,尽管没有呈现出明显的高海拔具有高选择性的规律,但对于花的大小呈现正选择效应。从授粉昆虫的造访率和种子产量两方面,可以看出自然选择的模式。我们还发现,造成种子产量变化的最大因素不是海拔高度或花的大小,而是管理措施。