Diversity of feeding and pollination strategies of Mesozoic beetles

Abstract

Beetles (Order: Coleoptera) as the most diverse and successful animals on the earth, comprise about 400,000 species, constituting almost 40% of described insects and a quarter of all animal species. They are distributed in almost every terrestrial natural habitat today, with various feeding preferences. Approximately 90% of the species in Coleoptera emerged in the Mesozoic, especially during the Jurassic-Cretaceous period. At the same time, vegetation type on the earth was shifting significantly — angiosperms (flowering plants) rapidly replacing the dominating gymnosperms, an event which Charles Darwin called the “Abominable Mystery”. The dramatic environmental and nutritional change could have impacted the interaction between beetles and related plant groups. The evolution of beetles may have also influenced the angiosperm radiation, e.g. through zoophilous pollination. <br /> The studies in this thesis demonstrate the remarkable feeding strategies and ecological diversity of Mesozoic beetles. Fourteen species of seven families from Karabastau Formation, Daohugou Biota, Burmese amber and Baltic amber are described, ranging from Early Jurassic to Eocene. The co-evolution between beetles and vegetation environments is discussed. Based on the continuous fossil records of the family Mordellidae, the early evolution trend of a typical beetle-flower ecology is outlined. Hypothetically, insect pollination contributes largely to the diversity of flowering plants, and is essential to the Cretaceous radiation of angiosperms. <em>Angimordella burmitina</em> Bao, 2019 and the associated tricolpate pollens provides direct evidence of insect pollination of Cretaceous eudicots ~99 million years ago, extending the record of insect mediated angiosperm pollination at least 50 million years earlier. The great angiosperm radiation in mid-Cretaceous acted as a driving force for the replacement of earth surface vegetation. By this time, nutrition groups as gymnosperms, fern, are also changed relatively, which also imply the associated beetle taxa. <em>Praezolodinus pilosus</em> and <em>Cretoptomaphagus microsoma</em> provide rare records of bottom forest ecosystem: an association of fern habited beetle and scavenger. Wood-borer and fungivorous beetles are abundant in Burmese amber, similar to the extant beetle species. With more and more flora and fauna inclusions discovered from Burmese amber, it is possible to draw a big picture of the Burmese forest back in. We can generally understand the forest vertical eco-components and the inner relationships of the ecosystem. The Waipoua forest could be the extant reference ecosystem. However, it should be pointed out that it is easy to underestimate the complexity of the ecosystem, when performing a comparative study of paleoecology in the future.