Pollen, genes and the evolution of the Fagales

With the increasing specialisation in science it becomes more difficult to establish general hypotheses about evolution. The aim of this project is bridging the gap between palaeobotany and the fields of biogeography, molecular dating, and phylogenetics by integrating molecular phylogenetic and biogeographic hypotheses with the fossil pollen record of the Fagales. The Fagales have an extraordinarily rich fossil record of vegetative and reproductive organs. At the same time, the number of genera and species in the modern Fagales is workable and allows analysing molecular differentiation at low and high taxonomic levels. The Fagales originated in the Late Cretaceous and a number of early radiating, extinct lineages have unknown affinities to modern groups. Dispersed pollen, but also macrofossils, allow tracing modern genera back until the Palaeogene, providing an ideal opportunity to coalesce palaeo- and neobotanical methods and data. Despite their abundance, fossils of most genera have not been put in an evolutionary context, particularly the well-known and highly conserved pollen types have been largely ignored in neobotanical studies. During a period of 20 Ma (late Eocenemiddle Miocene) extinct and extant genera of Fagales coexisted, which offers an excellent opportunity to investigate evolutionary turn-over. Only some of their modern members are genetically well-studied, others are in urgent need of detailed investigations. The project aims at clarifying some of the enigmas of the evolution of the Fagales such as the nearly simultaneous emergence of modern genera, its unfolding in space and time, and to fill some of the white spots in morphological and molecular data sets. The ultimate goal is to integrate the rich fossil record of the Fagales, in particular recent and upcoming palynological evidence, with phylogenomic data of the extant members for the mutual benefit of palaeobotanical and neobotanical research.

With this Lise-Meitner Mobility grant we bridged the widening inter-disciplinary gap: a trained geologist, who became a geneticist and data analyst, collaborated closely with experienced palynologists on dispersed pollen floras from Earth's past. Science increasingly fragments into subdisciplines. The amount of data accessible for reconstruction of modern and past relationships between organisms, or the ecosystems they thrive in, increases every minute. Whereas the forefathers of evolutionary sciences, Charles Darwin, Alfred Wallace, and Ernst Haeckel, deducted everything based on their (holistic) observations of nature as it is (was), today, each field of science relies on highly specialised researchers and their unique methodological approaches. The huge amount of data is processed by (bio)informaticians, who can handle specialised and increasingly sophisticated computer programmes. Molecular systematicists use gene data to determine relationships between modern organisms. Biogeographers reconstruct migration pathways using the modern, and to a much lesser degree, past distribution of organisms. Statisticians and modellers apply simulations and mathematical models. But a decreasing amount of researchers work at the coal-face of organismal sciences: traditional botanists and zoologists spending their time in the field and existing collections to provide (identify the material, all other disciplines rely on. An even smaller group with unique knowledge are the palaeontologists, researchers familiar with the fossil record (the life that was), and palynologists, researchers studying tiny microscopic objects such as pollen and spores. Although often claimed, there is too little exchange between the different disciplines. Scientific papers typically treat a single topic. Anything else, such as cross-disciplinary research were different fields of science fertilise each other, is rare and difficult to publish. Partly because the so-called "peers", usually anonymous said-experts who judge the quality of a scientific paper, are, like far the most scientists, specialists with limited insight in other disciplines. We tried to bridge this gap. The results were a series of scientific publications including some truly cross-disciplinary ones that highlight the great value and potential of palynological data, fossil pollen, for other biological disciplines such as molecular dating and biogeography. We showed how the oldest record of beech trees and their relatives, such as oak and chestnut, agrees with evidence from molecular dating. We highlighted the importance of Greenland as ancient home of today equatorial and southern hemispheric plants and demonstrated the utility of pollen for better understanding of the evolutionary history of the Loranthaceae, a tropical- subtropical group of mistle-toes. The hope is that our studies will motivate other researchers to follow the path we laid out and take up similar research tasks, and try to bridge the widening gaps between different fields of science. The main message of our project is that it may be difficult, but it can be done, and it is worthwhile.