Data from: Testing adaptive hypotheses for an evolutionarily conserved trait through slow-motion videos of pollinators

Traits conserved across evolutionary time often provide compelling examples of key adaptations for a given taxonomic group. Tetradynamy is the presence of four long stamens plus two short stamens within a flower and is conserved across most of the roughly 4000 species in the mustard family, Brassicaceae. While this differentiation in stamens is hypothesized to play a role in pollination efficiency, very little is known about the potential function of the two stamen types. The present study sheds new light on this mystery using wild radish (Raphanus raphanistrum), a widespread and well-studied tetradynamous plant. We used data collected from slow-motion videos of pollinators visiting wild radish flowers to test three non-mutually exclusive adaptive hypotheses: 1) short and long stamens are specialized for either feeding or pollinating, 2) short and long stamens are specialized for different pollinator taxa, and 3) the presence of short and long stamens increases pollinator movement and thus effectiveness. We find evidence consistent with hypothesis three, but no evidence for hypotheses one or two. Thus, tetradynamy may be an adaptation for generalized pollination, enabling effective visits by the variety of pollinators visiting most species of Brassicaceae.

历经演化时间仍保守保留的性状，往往能为某一分类群的关键适应性演化提供极具说服力的例证。四强雄蕊（tetradynamy）指一朵花中具4枚长雄蕊与2枚短雄蕊的雄蕊排列方式，在十字花科（Brassicaceae）约4000个物种的绝大多数类群中均保守存在。尽管学界推测这种雄蕊分化有助于提升传粉效率，但针对两类雄蕊各自的潜在功能，目前仍知之甚少。本研究以广泛分布且被充分研究的四强雄蕊植物——野萝卜（Raphanus raphanistrum）为研究对象，为这一谜题提供了新的见解。我们通过采集传粉者造访野萝卜花的慢动作视频数据，检验了3个非互斥的适应性假说：1）长、短雄蕊分别特化为取食或传粉器官；2）长、短雄蕊分别适配不同类群的传粉者；3）长短雄蕊的存在可提升传粉者的运动能力，进而增强传粉有效性。研究结果支持假说3，但未发现支持假说1和2的证据。据此推测，四强雄蕊可能是一种适应泛化传粉的性状，能够让造访十字花科多数物种的各类传粉者均实现高效传粉。