Am Nat. 2020 Dec;196(6):769-774. doi: 10.1086/711396. Epub 2020 Oct 28.
AbstractThe growth habit of mistletoes, the only woody, parasitic plants to infect host canopies, represents a key innovation. How this aerially parasitic habit originated is unknown; mistletoe macrofossils are relatively recent, from long after they adapted to canopy life and evolved showy, bird-pollinated flowers; sticky, bird-dispersed seeds; and woody haustoria diverting water and nutrients from host branches. Since the transition to aerial parasitism predates the origin of mistletoes' contemporary avian seed dispersers by 20-40 million years, this leaves unanswered the question of who the original mistletoe dispersers were. By integrating fully resolved phylogenies of mistletoes and aligning the timing of historic events, I identify two ancient mammals as likely candidates for planting Viscaceae and Loranthaceae in the canopy. Just as modern mouse lemurs and galagos disperse viscaceous mistletoe externally (grooming the sticky seeds from their fur), Cretaceous primates (e.g., ) may have transported seeds of root-parasitic understory shrubs up into the canopy of Laurasian forests. In the Eocene, ancestors of today's mistletoe-dispersing marsupials, , likely fed on the nutritious fruit of root-parasitic loranthaceous shrubs, depositing the seeds atop western Gondwanan forest crowns. Once mistletoes colonized the canopy, subsequent evolution and diversification coincided with the rise of nectar- and fruit-dependent birds.
摘要槲寄生是唯一感染树冠的木本寄生植物，其生长习性代表了一个关键的创新。这种空中寄生习性是如何起源的尚不清楚；槲寄生的宏观化石相对较新，是在它们适应树冠生活并进化出鲜艳的、靠鸟类传粉的花朵、粘性的、靠鸟类传播的种子以及从宿主树枝上分流水分和养分的木质吸器之后很久才出现的；由于向空中寄生的转变早于现代鸟类传播者的起源，因此，槲寄生的原始传播者是谁的问题仍然没有答案。通过整合已解析的槲寄生全系统发育关系，并对齐历史事件的时间，我确定了两种古代哺乳动物可能是将桑寄生科和列当科植物种植在树冠中的候选者。就像现代的鼠狐猴和丛猴外部传播粘性槲寄生种子（从它们的皮毛上梳理粘性的种子）一样，白垩纪灵长类动物（如）可能已经将根寄生的林下灌木种子运输到了劳亚古陆森林的树冠中。在始新世，当今传播槲寄生的有袋类动物的祖先，可能以根寄生的列当科植物的营养果实为食，将种子放置在西部冈瓦纳森林的树冠上。一旦槲寄生在树冠中定植，随后的进化和多样化就与依赖花蜜和果实的鸟类的兴起相吻合。
