Data from: Floral paedomorphy leads to secondary specialization in pollination of Malagasy Dalechampia (Euphorbiaceae)

The traditional evolutionary interpretation of Von Baer’s “laws” of embryology is that retention of early developmental forms into adulthood (paedomorphosis) leads to the evolution of simpler or more generalized morphology and ecology. Here we show that paedomorphosis can also be involved in an increase in ecological specialization, in this case of plant-pollinator relationships. A paedomorphic transition from generalized pollination (by several functional types of pollinators) to specialized pollination (by one or a few species in one functional type) occurred in a clade of endemic Malagasy vines (Dalechampia spp., Euphorbiaceae). This evolutionary transition involved staminate flowers that fail to develop “normally,” instead holding mature pollen inside virtually unopened, bud-like flowers. This paedomorphic morphology restricts reward access to “buzz-pollinating” bees, specifically Xylocopa sp. (carpenter bees), which can remove pollen by sonication. This is one of very few reports of paedomorphic specialization, and, as far as we are aware, the first documented case of a rapid reversal to specialized pollination in a lineage of plants that had previously switched from specialized to generalized pollination in conjunction with dispersing to a new region.传统演化论视角下，对冯·贝尔（Von Baer）胚胎学“法则”的经典解读认为，幼态持续（paedomorphosis）——即早期发育形态保留至成年阶段——会促使生物演化出更为简化或泛化的形态与生态特征。本研究证实，幼态持续亦可推动生态特化程度的提升，本次研究的案例为植物-传粉者互作关系的特化演化。在一支马达加斯加特有藤本类群——大戟科戴克利亚属（Dalechampia spp.，Euphorbiaceae）的演化支中，发生了一次幼态持续型的传粉系统转变：从泛化传粉（由多种功能类群的传粉者介导）转向特化传粉（由单一功能类群中的一种或少数几种物种介导）。该演化转变涉及雄花的“异常”发育：成熟花粉被包裹在几乎完全未开放的芽状花朵之中。这种幼态持续形态仅允许振翅授粉（buzz-pollinating）蜜蜂获取报酬，其中尤以木蜂属（Xylocopa sp.，carpenter bees）为代表——这类蜜蜂可通过声波振动移除花粉。本案例是目前为数不多的幼态持续型生态特化报道之一，且据我们所知，这是首个被记录的、曾因扩散至新区域而从特化传粉转向泛化传粉的植物支系，又快速逆转回归特化传粉的案例。