Constraining uncertainty in the timescale of angiosperm evolution and the veracity of a Cretaceous Terrestrial Revolution.

Ziheng Yang,Philip C J Donoghue,Harald Schneider,Mario Dos Reis,Jose Barba‐Montoya

doi:10.1111/nph.15011

Abstract

Summary Through the lens of the fossil record, angiosperm diversification precipitated a Cretaceous Terrestrial Revolution (KTR) in which pollinators, herbivores and predators underwent explosive co‐diversification. Molecular dating studies imply that early angiosperm evolution is not documented in the fossil record. This mismatch remains controversial.We used a Bayesian molecular dating method to analyse a dataset of 83 genes from 644 taxa and 52 fossil calibrations to explore the effect of different interpretations of the fossil record, molecular clock models, data partitioning, among other factors, on angiosperm divergence time estimation.Controlling for different sources of uncertainty indicates that the timescale of angiosperm diversification is much less certain than previous molecular dating studies have suggested. Discord between molecular clock and purely fossil‐based interpretations of angiosperm diversification may be a consequence of false precision on both sides.We reject a post‐Jurassic origin of angiosperms, supporting the notion of a cryptic early history of angiosperms, but this history may be as much as 121 Myr, or as little as 23 Myr. These conclusions remain compatible with palaeobotanical evidence and a more general KTR in which major groups of angiosperms diverged later within the Cretaceous, alongside the diversification of pollinators, herbivores and their predators.

Highlights

Angiosperms constitute one of the largest scions of the tree of life
Topology estimation and the effect of fossil calibration uncertainty We recovered a topology in which deep-level relationships among angiosperms are resolved with confidence and most branches are supported with bootstrap value of 100% (Figs. 1 and S3)
The results of these analyses demonstrate that calibration strategy has a strong impact on estimated divergence times (Figs. 3a, 4g-j, S1 and Table 2)

Summary

Introduction

Angiosperms constitute one of the largest scions of the tree of life. They dominate extant plant diversity, occupy almost every habitat on Earth, and are one of the principal components of modern biota playing crucial roles in terrestrial ecosystems (Augusto et al, 2014; Cascales-Miñana et al, 2016). Angiosperms rose to ecological dominance in the Cretaceous Terrestrial Revolution (KTR), when their apparently explosive radiation is believed to have underpinned the diversification of lineages that are key components of contemporary terrestrial environments, such as birds, insects, mammals, and seed-free land plants, foreshadowing modern terrestrial biodiversity (Dilcher, 2000; Benton, 2010; Meredith et al, 2011; Cardinal & Danforth, 2013; Augusto et al, 2014; CascalesMiñana et al, 2016) These hypotheses of co-diversification rest largely on the perceived coincidence in the radiation of angiosperms and the renewal of trophic networks in terrestrial ecosystems. It may be that molecular clock estimates are just unrealistically old, perhaps an artifact of their failure to accommodate dramatic accelerations that may have been associated with an explosive diversification of angiosperms (Magallón, 2010; Beaulieu et al, 2015; Brown & Smith, 2017)

Objectives

Methods

Results

Discussion

Conclusion