Form, function and environments of the early angiosperms: merging extant phylogeny and ecophysiology with fossils

Summary The flowering plants – angiosperms – appeared during the Early Cretaceous period and within 10–30 Myr dominated the species composition of many floras worldwide. Emerging insights into the phylogenetics of development and discoveries of early angiosperm fossils are shedding increased light on the patterns and processes of early angiosperm evolution. However, we also need to integrate ecology, in particular how early angiosperms established a roothold in pre‐existing Mesozoic plant communities. These events were critical in guiding subsequent waves of angiosperm diversification during the Aptian–Albian. Previous pictures of the early flowering plant ecology have been diverse, ranging from large tropical rainforest trees, weedy drought‐adapted and colonizing shrubs, disturbance‐ and sun‐loving rhizomatous herbs, and, more recently, aquatic herbs; however, none of these images were tethered to a robust hypothesis of angiosperm phylogeny. Here, we synthesize our current understanding of early angiosperm ecology, focusing on patterns of functional ecology, by merging recent molecular phylogenetic studies and functional studies on extant ‘basal angiosperms’ with the picture of early angiosperm evolution drawn by the fossil record. Contents Summary 383 I. Introduction 384 II. Previous images of early angiosperms and their habitats 385 III. Progress in understanding angiosperm phylogeny: extant ‘basal’ relations 386 IV. Early angiosperm ecology: inferences from extant plants and reflections from the fossil record 387 V. The ecology of angiosperm diversification: gaining a roothold and subsequent diversification 397 VI. The environmental context of early angiosperm evolution 399 VII. Conclusions 402 Acknowledgements 402 References 402