Theron Genevieve L, de Waal Caroli, Barrett Spencer C H, Anderson Bruce
Department of Botany and Zoology Stellenbosch University Matieland South Africa.
Department of Ecology and Evolutionary Biology University of Toronto Toronto ON Canada.
Ecol Evol. 2019 Aug 20;9(18):10122-10134. doi: 10.1002/ece3.5457. eCollection 2019 Sep.
Geographic variation in the reproductive traits of animal-pollinated plants can be shaped by spatially variable selection imposed by differences in the local pollination environment. We investigated this process in (Iridaceae), an enigmatic species from the Western Cape region of South Africa. has evolved a specialized perch facilitating cross-pollination by sunbirds and displays striking geographic variation in perch size and floral traits. Here, we investigate whether this variation can be explained by geographic differences in the pollinator communities. We measured floral and inflorescence traits, and abiotic variables (N, P, C, and rainfall) and made observations of sunbirds in populations spanning the range of . In each population, we recorded sunbird species identity and measured visitation rates, interfloral pollen transfer, and whether the seed set of flowers was pollen limited. To evaluate whether competition from co-occurring sunbird-pollinated species might reduce visitation, we quantified nectar rewards in and of other co-flowering bird-pollinated species in local communities in which populations occurred. Variation in abiotic variables was not associated with geographical variation of traits in . Malachite sunbirds were the dominant visitor (97% of visits) and populations with larger-sized traits exhibited higher visitation rates, more between-flower pollen transfer and set more seed. No sunbirds were observed in four populations, all with smaller-sized traits. Sunbird visitation to was not associated with local sunbird activity in communities, but sunbird visitation was negatively associated with the amount of sugar relative to the availability of alternative nectar sources. Our study provides evidence that populations with larger floral traits are visited more frequently by sunbirds, and we propose that visitation rates to may be influenced, in part, by competition with other sunbird-pollinated species.
动物传粉植物繁殖性状的地理变异可能受到当地传粉环境差异所施加的空间可变选择的影响。我们在鸢尾科的一种植物（来自南非西开普地区的一个神秘物种）中研究了这一过程。该物种进化出了一种特殊的栖木，便于太阳鸟进行异花授粉，并且在栖木大小和花部性状上表现出显著的地理变异。在这里，我们研究这种变异是否可以用传粉者群落的地理差异来解释。我们测量了花部和花序性状以及非生物变量（氮、磷、碳和降雨量），并对该物种分布范围内的种群中的太阳鸟进行了观察。在每个种群中，我们记录了太阳鸟的物种身份，并测量了访花率、花间花粉转移情况，以及花朵的结实是否受花粉限制。为了评估与太阳鸟传粉的共存物种之间的竞争是否会减少访花，我们对该物种以及该种群所在当地群落中其他同时开花的鸟类传粉物种的花蜜回报进行了量化。非生物变量的变异与该物种性状的地理变异无关。铜色太阳鸟是主要访客（97%的访花），具有较大性状的种群表现出更高的访花率、更多的花间花粉转移且结实更多。在四个性状较小的种群中未观察到太阳鸟。太阳鸟对该物种的访花与群落中当地太阳鸟的活动无关，但太阳鸟的访花与该物种花蜜中糖分的含量相对于其他花蜜来源的可获得性呈负相关。我们的研究提供了证据，表明具有较大花部性状的该物种种群被太阳鸟访花的频率更高，并且我们提出对该物种的访花率可能部分受到与其他太阳鸟传粉物种竞争的影响。
