Differential pollinator effectiveness and importance in a milkweed (Asclepias, Apocynaceae) hybrid zone.
Differential pollinator effectiveness and importance in a milkweed (Asclepias, Apocynaceae) hybrid zone.
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马利筋（萝藦属、夹竹桃科）杂交区中不同传粉媒介的有效性和重要性。
DOI：
10.3732/ajb.1100272
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发表时间：
2012
影响因子：
3
通讯作者：
M. Fishbein
中科院分区：
文献类型：
--
作者：
T. Stoepler;Andrea A. Edge;A. Steel;R. O’Quinn;M. Fishbein
研究前提
在不同的植物、动物和真菌群体中，物种之间完全生殖隔离的理想状态是常见的，但通常对致病的生态过程知之甚少。在开花植物中，杂交的结果部分取决于传粉者在种间花粉运输中的有效性。在Asclepiasexaltata和A.在弗吉尼亚州谢南多厄国家公园的夹竹桃科（夹竹桃科）杂交区，已经记录了广泛的渐渗。本研究的目的是：（1）确定传粉者重叠的程度在A。exaltata，A.和它们的杂交种;（2）鉴定负责杂交和渐渗的昆虫类群。
方法
我们观察了焦点植物的亲本物种和杂交种，以测量访问率，访问持续时间，和每次访问花粉去除和沉积，我们计算传粉有效性和重要性。
关键成果
访问率变化显着之间的2年的研究。总的来说，意大利蜜蜂，熊蜂，和单棘瓢虫是最重要的传粉者。然而，熊蜂是唯一的访客，观察到双方删除和插入花粉的亲本物种以及杂交。
结论
我们的结论是，熊蜂可能是一个关键的代理商的杂交和渐渗在这些同域马利筋种群，杂交种既不首选，也不选择对传粉者。因此，我们已经确定了一个潜在的机制，如何杂交作为桥梁，基因流之间的A。exaltata和A.叙利亚。这些结果提供了深入了解前合子隔离机制的崩溃。
PREMISE OF THE STUDY
Exceptions to the ideal of complete reproductive isolation between species are commonly encountered in diverse plant, animal, and fungal groups, but often the causative ecological processes are poorly understood. In flowering plants, the outcome of hybridization depends in part on the effectiveness of pollinators in interspecific pollen transport. In the Asclepias exaltata and A. syriaca (Apocynaceae) hybrid zone in Shenandoah National Park, Virginia, extensive introgression has been documented. The objectives of this study were to (1) determine the extent of pollinator overlap among A. exaltata, A. syriaca, and their hybrids and (2) identify the insect taxa responsible for hybridization and introgression.
METHODS
We observed focal plants of parental species and hybrids to measure visitation rate, visit duration, and per-visit pollinia removal and deposition, and we calculated pollinator effectiveness and importance.
KEY RESULTS
Visitation rates varied significantly between the 2 yr of the study. Overall, Apis mellifera, Bombus sp., and Epargyreus clarus were the most important pollinators. However, Bombus sp. was the only visitor that was observed to both remove and insert pollinia for both parent species as well as hybrids.
CONCLUSIONS
We conclude that Bombus may be a key agent of hybridization and introgression in these sympatric milkweed populations, and hybrids are neither preferred nor selected against by pollinators. Thus, we have identified a potential mechanism for how hybrids act as bridges to gene flow between A. exaltata and A. syriaca. These results provide insights into the breakdown of prezygotic isolating mechanisms.