The history of European Paleogene flower-insect interactions unraveled using fossil flowers and insects and their associated pollen grains

Author(s): Christian Geier, Johannes Martin Bouchal, André Nel, V. Ngo-Muller, Jürg Schönenberger, D. Uhl, Silvia Ulrich, Torsten Wappler, S. Wedmann, Fridgeir Grimsson
Abstract: The interaction between flowers and visiting insects is evident on every continent except Antarctica. Despite the current close relationship between angiosperms and insects, little is known about flower-insect interactions through the geological record. While some exceptional findings have been reported that spotlight individual insect taxa and their potential pollen source, large-scale investigations comprising complete fossil faunas and floras from the same sedimentary units are missing. Even more, investigations on successive assemblages of different ages comprising fossil flowers and insects have
until now not been conducted in relation to flower-insect interactions. Here we report some preliminary results from ongoing studies on Paleogene flower-insect interactions using in-situ/adhered pollen from fossil flowers and insects. So far, we have studied flowers and insects from four Paleogene localities in
France and Germany, including Menat (middle-late Paleocene, Selandian-Thanetian, 61–56 Ma), Messel (middle Eocene, early Lutetian, c. 48 Ma), Eckfeld (middle Eocene, middle Lutetian, c. 44 Ma), and Enspel (late Oligocene, late Chattian, c. 24 Ma). As representatives for the manifold discoveries we have made so far, three examples are presented herein. 1) Our study revealed a close relationship between bees (Apoidea) and the plant subfamily Tilioideae (comprising the genera Craigia, Mortoniodendron, and Tilia) spanning over 30 million years. We have identified Apoidea bees with adhering Tilioideae pollen from all four localities. In addition, we have discovered several fossil flowers
from Enspel with in-situ Tilioideae pollen enabling a morphological/anatomical comparison with extant flowers of the subfamily. 2) During our work, Parthenocissus (Vitaceae) pollen keeps surfacing in various samples. Pollen from this genus has now been discovered inside the guts of several fossil insects and/or adhering to their exterior. Parthenocissus pollen has been found in association with various Coleoptera, Diptera, and Hymenoptera, and it is currently one of the most frequently occurring pollen types found in association with fossil Paleogene insects from Europe. 3) By extracting in-situ pollen from anthers of fossil compressed flowers, we have identified several rare plant taxa, one of them a unique Onagraceae flower bud. This middle Eocene fossil from Eckfeld, Germany, represents the first and only pre-historic Ludwigia flower record ever discovered. We also found Ludwigia pollen adhering to the exterior of two different fossil beetles, one belonging to Buprestidae and the other to Scarabaeidae, from the same sediments/locality. These fossils provide the first-ever direct evidence for paleo-flower-insect visitation in Ludwigia/Onagraceae. Interestingly, we did not discover any Ludwigia pollen on the several hymenopteran fossils investigated, although hymenopterans being the main flower visitors and pollinators of living Ludwigia. These findings might suggest that beetles were the main flower visitors and potential pollinators of European Ludwigia during the Eocene and that there has been a shift in primary pollinators for Ludwigia over time.
Organisation(s): Department of Botany and Biodiversity Research
External organisation(s): Museum national d'Histoire Naturelle, Université de Paris, Senckenberg Biodiversity and Climate Research Centre, Rheinische Friedrich-Wilhelms-Universität Bonn
Pages: 21-22
Publication date: 2023
Austrian Fields of Science 2012: 105117 Palaeobotany, 106008 Botany
Portal url: https://ucrisportal.univie.ac.at/en/publications/486215b4-86c2-414c-8b6b-481a92835ad6