Final Report Summary - GRASSLANDS (The evolution of the Grassland biome: exploring past events to predict future scenarios) Knowledge of the evolution of the grassland biome throughout the Earth's environmental history is important for the reconstruction of links between diversification/extinctions events and climate. Biomes are now being impacted by anthropogenic environmental change on an unprecedented scale, and one mean of understanding how component species will react is to study the effects of past environmental changes. Hence, understanding the evolutionary history of grassland ecosystems in the context of past biotic and abiotic changes is relevant to the way we will manage them under future environmental change. A new perspective on the history of the grassland biome is beginning to emerge from key developments in palaeontology and molecular phylogenetics that will be integrated in the present project for the first time. GRASSLANDS aimed at exploring the origin and the radiation of the grasslands biome by examining the spatio-temporal origin of two of their main components, the grasses (Poaceae) and the daisies (Asteraceae) with a particular focus on the latter. We achieved this through the combination of fossil data, molecular phylogenetics and computational approaches. The potential contribution of GRASSLANDS to our understanding of the evolutionary history of these families and grassland ecosystems in general is significant and certainly provide new insights into the rise of flowering plants as the dominant components of almost every terrestrial ecosystems.There is a widespread belief that the origin and diversification of Poaceae and Asteraceae were roughly simultaneous with the expansion of the grassland biome, although this statement has never been empirically tested using an interdisciplinary and multidisciplinary approach. Whereas the virtual absence of unambiguous fossils of Poaceae and Asteraceae in the early Palaeogene favours a Neogene radiation, startling new discoveries from the Cretaceous seem to imply that Poaceae and Asteraceae diversified far earlier (Palaeogene) than the expansion of true grasslands (Neogene). GRASSLANDS aimed to determine which of these two hypotheses -Neogene versus Palaeogene diversification of Poaceae and Asteraceae- is best supported on the basis of an independent analysis of DNA sequence data and a reassessment of the fossil record used as time constraints. A comprehensive phylogenetic framework for the family Asteraceae was produced and divergence time estimates were obtained using new fossil records found in the Cretaceous period of Antarctica as well as more recent fossil inflorescence from the Eocene of Patagonia, which were previously described in a publication in which the Fellow is a co-author. We infer that the Cretaceous remain represent an extinct branch of the family Asteraceae, associated with extant members of subfamily Barnadesioideae, the earliest-diverging lineage of Asteraceae, sister to the remainder of the family. An important review of the fossil record of the daisy family was performed, which helped their assessment as potential calibration points to obtained divergence time estimates for the family. Overall, we found that the crown of family Asteraceae (i.e. the most recent common ancestor of the family plus all extant and extinct lineages that descended from it) have been present since the Late Cretaceous, estimated at 85.9 Mya. This new molecular dating analysis contradicts in part previous assumptions about a geologically recent origin of Asteraceae, indicating instead that the most recent common ancestor of the family existed far back into the Cretaceous (Objective 1, 3), during a time when the last dinosaurs roamed the Earth. This study was published in the high-impact factor journal Proceedings of the National Academy of Sciences of the USA (2015; 112: 10989-10994) and received international media coverage, including a mention in Nature Plants (Vol 1, Sept 2015). It involved colleagues from the UK (Royal Botanic Gardens, Kew), Argentina (CONICET) and New Zealand (Department of Palaeontology, GNS Science). Work is almost completed (publications to be completed by the end of the funding period, i.e. 31 July 2016) that is investigating the extinction and diversification rates within the Daisy and grass families, and the identification of shifts in diversification rates and their potential causal factors. We found evidence to support a Miocene increased diversification of the daisy and grass families, in agreement with a steep reduction in carbon dioxide during the earliest Miocene. This evidence will have important implications in how and under which circumstances open-habitat ecosystems evolved and ultimately help predicting how these important grassland systems will respond to future climate changes. Such information will be crucial to protect some of the richest repositories of biodiversity on the planet.
