Cretaceous origin of tropical rainforest in Africa and the Levant and the implications for modern climate predictions

• Applicant: Dr. Clément Coiffard
• Subject Area: Palaeontology ; Evolution and Systematics of Plants and Fungi
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 399895065

• Final Report Year: 2021

Final Report Abstract

Modern tropical rain forests (TRF) are one of the most important and species rich biomes on the planet. Rainforest environments have an enormous impact on the global water and heat circulation and play therefore a major role in the water distribution and the rainfall patterns. These forests are characterized by their stratified closed canopy, the presence of woody angiosperms at least in the understory, abundant rainfall and equable temperatures. This biome is supposed to have developed during the Late Cretaceous (100-65 Ma) but its origin and geographic distribution are unknown and much had been speculated about its emergence. Studies based on living plants suggest an earliest Late Cretaceous (100 Ma) appearance of the TRF but they are based on the assumption that modern taxonomic groups maintained the same ecology and they rely on limited fossil calibrations for their dating. In contrast, fossil TRF, characterized by their physiognomy (e.g. broad entire-margined leaves with drip tips), climate proxies and high diversity, usually about 25 sp. in a single quarry (as well as in a single modern TRF leaf litter sample) and more than 100 sp. in a regional assemblage, have not been identified so far before the latest Cretaceous (ca 72 Ma). Understanding of the early development of TRF has also been hampered by the fact that most of the information originate from fossil sites from mid- to high-latitudes reflecting more temperate climate conditions, while sites from low latitudes were hardly studied. The aim of this proposal was to explore the low latitude fossil record from the Late Cretaceous of Northeast Africa and the Levant in order to understand when and how TRF did emerge. Fossil assemblages show that, 80 Ma ago, Northeastern Africa was covered by species rich vegetation under a wet climate (ca 1800 mm rainfall per year) suggesting the early existence of TRF. In contrast, older assemblages, ca 90 Ma old, display a lower diversity and a physiognomy supporting a dryer climate (ca 900 mm rainfall per year), comparable to modern savannas. This dryer climate may be associated with the warmest part of the Cretaceous. Still older assemblages (ca 100Ma) need more sampling but their overall physiognomy suggest again a wet climate. In all these assemblages, angiosperm are nearly exclusive and the rise to dominance of angiosperms must have occurred earlier in these tropical areas. https://www.dailymail.co.uk/sciencetech/article-7240961/Worlds-oldest-lily-grew-115-million-year-sago-fossilised-flower-intact-cells.html

Publications

• (2018). Cretaceous tropical Alismatales in Africa: diversity, climate and evolution. Botanical Journal of the Linnean Society, 188(2), 117-131
  Coiffard, C., & Mohr, B. A.
  
• (2019). Fossil evidence of core monocots in the Early Cretaceous. Nature plants, 5(7), 691-696
  Coiffard, C., Kardjilov, N., Manke, I., & Bernardes-de-Oliveira, M. E.
  
• (2020). Montsechia vidalii from the Barremian of Spain, the earliest known submerged aquatic angiosperm, and its systematic relationship to Ceratophyllum. Taxon, 69(6), 1273-1292
  Gomez, B., Daviero‐Gomez, V., Coiffard, C., Barral, A., Martín‐Closas, C., & Dilcher, D. L.
  
• (2020). When and Why Nature Gained Angiosperms. In Nature through Time (pp. 129-158). Springer, Cham
  Kvaček, J., Coiffard, C., Gandolfo, M., Herman, A. B., Legrand, J., Mendes, M. M., ... & Wang, H.