Oenothera Section Calylophus population genetic study

Premise: Animal pollinators play an important role in pollen dispersal. Differences in foraging patterns, flight distances and grooming behaviors are assumed to have consequences for genetic diversity of plants but are rarely tested explicitly. Here, we assess the role of pollinator functional groups with different foraging behaviors (hawkmoth and bee) in generating patterns of genetic diversity over similar geographic ranges for two closely related taxa.

Methods: This study focuses on two members of Oenothera section Calylophus that co-occur on gypsum outcrops throughout the Chihuahua Desert but differ in floral phenotype and primary pollinator: Oenothera gayleana (bee) and O. hartwegii subsp. filifolia (hawkmoth). We measured breeding system and floral traits in the greenhouse and conducted a population genetic study at the local (<13km; four populations) and landscape (60–440km; five populations) scales using 10–11 nuclear (pollen dispersal) and three plastid (seed dispersal) microsatellite markers. 

Key Results: Both taxa were self-incompatible and floral traits were consistent with expectations for different pollinators. We found no evidence of genetic structure at the local scale, but at the landscape scale, O. gayleana showed greater differentiation and significant isolation by distance than O. hartwegii subsp. filifolia. The plastid data were consistent with gravity dispersal of seeds and suggest that pollen dispersal is the principal driver of genetic structure in both species.

Conclusions: We demonstrate that pollinator functional groups can impact genetic differentiation in different and predictable ways. Hawkmoths, with larger foraging distances, can maintain gene flow across greater spatial scales than bees.

Methods
Floral morphology and leaf tissue for genetic samples were collected in wild populations in New Mexico and Texas, USA.

Floral morphology data and the breeding system assessment were conducted on plants grown in a growth chamber at the Chicago Botanic Garden, Illinois, USA.

Additional details of methods used can be found in the published manuscript (to be updated upon publication).

研究背景：传粉动物在花粉传播过程中发挥着关键作用。现有研究推测，不同传粉类群的觅食模式、飞行距离以及梳理行为差异，会对植物的遗传多样性产生影响，但此类假设鲜少得到明确验证。本研究针对两个近缘类群，在相似的地理分布范围内，探究具有不同觅食行为的传粉功能群——天蛾（hawkmoth）与蜂（bee）——对其遗传多样性格局的塑造作用。

研究方法：本研究聚焦于奇瓦瓦沙漠石膏露头生境中共存的两个月见草属卡拉月见草组（Oenothera section Calylophus）类群，二者具有差异化的花部表型与主要传粉者：盖尔月见草（Oenothera gayleana，以蜂为主要传粉者）与哈特维格月见草细叶亚种（O. hartwegii subsp. filifolia，以天蛾为主要传粉者）。我们在温室中测定了繁育系统与花部性状，并分别在局域尺度（<13km，共4个种群）与景观尺度（60–440km，共5个种群）下，利用10~11个核微卫星标记（nuclear microsatellite markers，用于推断花粉传播过程）以及3个质体微卫星标记（plastid microsatellite markers，用于推断种子传播过程）开展了种群遗传学研究。

核心结果：两个类群均为自交不亲和（self-incompatible），花部性状与对应传粉者的适配预期相符。我们未在局域尺度上检测到显著的遗传结构，但在景观尺度上，盖尔月见草较哈特维格月见草细叶亚种表现出更高的遗传分化水平与显著的距离隔离效应。质体遗传数据符合种子重力传播的特征，同时表明花粉传播是两个物种种群遗传结构的主要驱动因素。

研究结论：本研究证实，传粉功能群可通过不同且可预测的方式影响种群遗传分化。天蛾的觅食距离更远，因此相较于蜂，能够在更大的空间尺度上维持基因流（gene flow）。

补充实验方法：花部形态样本与用于遗传分析的叶片组织采集自美国新墨西哥州与德克萨斯州的野生种群。花部形态数据与繁育系统评估基于美国伊利诺伊州芝加哥植物园生长箱内栽培的植株完成。本研究的详细方法可参见已发表论文（出版后将更新完整细节）。