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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - MACEA (Micro-botanical Analyses at Cenozoic fossil localities from East Africa: new insights into the evolution of savannas in Africa from 50 million years)

Teaser

Summary

My main objectives during the two years I spent at the University of Washington were to test and analyze the phytolith productivity of >100 fossil soil and sediment samples collected at seven (at least) different East African localities dated from 50 Ma to nowadays using methods and approaches developed by Prof. StrÃ¶mberg. Also, I aimed to go collecting part of these samples during one (at least) fieldwork season in Kenya. With the testing and analyzing of 336 samples from about 20 different East African localities using Prof. StrÃ¶mberg\'s protocols, including 99 samples I myself collected in July 2016 in Kenya, my main goals are completely fulfilled.

MACEA aimed to document the evolution of grass-dominated ecosystems in East Africa over the Cenozoic in a research context where very little was known about this story based on previous published paleoenvironmental proxies. Within MACEA, I studied the phytolith content of different fossil deposits from East Africa and compared it to a modern existing dataset I completed with new data. This latter step was preformed during the third year of the funding, while the fossil data production was mostly performed during the two first years hosted at the University of Washington.

Work performed

Timing for actions to be completed evolved for several tasks as MACEA started in Spring rather than Winter (fieldwork had to be absolutely done in the Summer), and also as the number of samples to be processed had to be re-evaluated as the phytolith productivity was not as high as it was expected.

WP1: Producing the fossil phytolith dataset.
I processed a total of 336 fossil soil and sediment samples from about 20* different East African localities. I myself collected 99 of these samples during a fieldwork in Kenya in July 2016, while the 237 other samples were sent to me by several collaborators who conducted fieldwork in East Africa before MACEA started. To do so, I learnt and used the phytolith extraction protocol developed by Prof. StrÃ¶mberg.
*(up to 25 if you consider Rusinga Island as divided up in different localities).
I went to Kenya in July 2016 in order to collect samples from the Early Miocene fossil deposits of the Rusinga and Mfangano Islands while accompanying the REACHE research group in one of their field seasons there. I was there as an invited researcher by the REACHE research group, which includes several of my main collaborators in MACEA. I collected there 99 samples, which were carried back to the University of Washington for phytolith processing and analyses at the end of the field season.
Associated milestones:
Milestone m1: The fieldwork was successful with sufficient samples collected (=99) (M6 instead of M3)
Milestone m2: I processed an adequate number of fossil samples to be processed and analyzed (=336 in total) (M22 instead of M8)
Milestone m3: I completed the fossil dataset by processing and analyzing all the samples I collected or that were sent to me (M24 instead of M20)
Associated deliverables:
Deliverable D1.1: The extracted fossil phytolith samples were all reposited at the University of Washington Burke Museum, as well as entered into the Burke Museum database, with slide duplicates of productive samples made for both partner organizations (M24 instead of M21).
WP2: Counting and taxonomical identification of the fossil phytoliths
Deliverable D2.2: An article* presenting part of my results was planned to be ready by M28 (according to the update made in the 1st report). The manuscript, however, is still in preparation because 1/ we made the choice to include in it the modern data collected during M31 so the final interpretations could be more robust; 2/ several stable carbon isotope analyses out of my field of expertise need to be re-done due to uncertain results. The new deadline depends on the good progression of the co-authors in charge of these analyses. A submission to the Science journal, along with a twin paper** also in preparation, is envisaged.
WP3: Estimating the role of grasses in East African paleovegetation (M25-M33)

My analyses indicate premises of forest fragmentation in East Africa at the very beginning of the Miocene (22-21 Ma), yet regionally asynchronous; while forests persisted in Ethiopia, northwestern Kenya and Uganda showed the development of mixed vegetation with a significant abundance of grasses, especially PACMAD grasses. My work also provided the oldest evidence for pharoid grasses(genus Leptaspis) â€“ a subfamily restricted to forest environments â€“ and bamboos in the all Africa. My analyses on modern material indicate that East African forest soil assemblages(first phytolith study on the Kakamega forest) do not include significant amounts of spherical rugose phytoliths, but rather high proportions as silicified sclereids to be used as woody indicators; this has to be taken into account for future comparative studies based on modern material from East Africa.
Over the three years of MACEA, I presented my results at four international conferences(Canada, US, France, Ireland) and during multiple seminars (University of Washington, South Methodist University, CEREGE in France, Darmstadt). Three articles in collaboration were submitted and are currently in the

Final results

MACEA proposes to address crucial evolutionary and paleoenvironmental questions in the field of African Cenozoic by using a tool combined with several approaches that had never been applied to such a context beforehand. Beyond the fact that the results produced through MACEA so far are unique, they are also pushing forward our previous knowledge about grass evolution and grass expansion in East Africa. They especially revealed that East African vegetation started to open about two million years earlier than what the previous studied had demonstrated, in addition to indicate that C4 grasses, although likely occurring in small amounts, were already part of the East African vegetation about 20-18 million years ago. These results are still being in the process of being formatted for publication. Besides, they have been already presented at different stages of their production at two main conferences in the field of paleontology (SVP) and geology (GSA) in the last past year, where I managed to reach a large audience, pursue and also start new collaborations to get MACEA growing
Impact for the researcher career and personal development
MACEA gave me the unrivalled opportunity to extent my research and social skills in a foreign country, the US, where facing a different culture than mine was a totally enriching experience as a researcher, but also primarily as a human being. As a researcher, I extended my expertise in phytolith analyses by learning and mastering new processing methods, in addition to improve significantly my previous skills in phytolith observation, description, and identification. I built up durable collaborations in the US, Kenya, and Europe by gathering accomplished and well renowned researchers and research teams around MACEA.