Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa.
Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
Plant Biol (Stuttg). 2020 Nov;22(6):992-1001. doi: 10.1111/plb.13159. Epub 2020 Aug 26.
Variation in plant breeding systems has implications for pollinator-mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self-compatibility and pollen limitation in different floral colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants are endemic to fynbos and renosterveld vegetation in the Cape Floristic Region of South Africa, and the species complex includes five floral colour forms (pink, purple, red, white and yellow), some of which are known to be pollinated by beetles. Controlled hand-pollination experiments were conducted in 15 populations of D. cistiflora s.l. (two to four populations per floral colour form) to test whether the colour forms vary in their degree of self-compatibility and their ability to produce seeds through autonomous self-fertilization. Yellow-flowered forms were highly self-incompatible, while other floral colour forms exhibited partial self-compatibility. Seed set resulting from autonomous selfing was very low, and pollinator dependence indices were high in all populations. Since hand cross-pollination resulted in greater seed set than open pollination in 13 of the 15 populations, we inferred that seed production is generally pollen-limited. Drosera cistiflora s.l. typically exhibits high levels of pollinator dependence and pollen limitation. This is unusual among Drosera species worldwide and suggests that pollinators are likely to mediate strong selection on attractive traits such as floral colour and size in D. cistiflora s.l. These results also suggest that the floral colour forms of D. cistiflora s.l. which are rare and threatened are likely to be vulnerable to local extinction if mutualisms were to collapse indefinitely.
植物繁殖系统的变化会影响传粉媒介对花部特征的选择以及种群的生态。本研究评估了不同花色形式的毛毡苔（茅膏菜科）中传粉者对种子产生、自交亲和性和花粉限制的贡献。这些肉食性多年生植物是南非开普植物区系的 fynbos 和 renosterveld 植被的特有种，该物种复合体包括五种花色形式（粉色、紫色、红色、白色和黄色），其中一些已知是由甲虫授粉的。在 15 个毛毡苔（广义）种群（每种花色形式两个到四个种群）中进行了受控的人工授粉实验，以测试花色形式在自交亲和性程度和通过自主自交产生种子的能力上是否存在差异。黄色花形式高度自交不亲和，而其他花色形式表现出部分自交亲和性。所有种群中，自主自交产生的种子数量非常低，传粉者依赖指数很高。在 15 个种群中的 13 个种群中，人工异交产生的种子数量比自然授粉产生的种子数量多，因此我们推断种子产生通常受到花粉限制。毛毡苔（广义）通常表现出高度依赖传粉者和花粉限制。这在全球茅膏菜属物种中是不常见的，这表明传粉者可能会对毛毡苔（广义）的吸引力特征（如花部颜色和大小）进行强烈的选择。这些结果还表明，如果互利关系无限期崩溃，毛毡苔（广义）的花色形式，即那些稀有和受到威胁的花色形式，可能容易局部灭绝。
