The rise of angiosperms to ecological dominance and the breakup of Gondwana during the Mesozoic marked major transitions in the evolutionary history of insect-plant interactions. To elucidate how contemporary trophic interactions were influenced by host plant shifts and palaeogeographical events, we integrated molecular data with information from the fossil record to construct a time tree for ancient phytophagous weevils of the beetle family Belidae. Our analyses indicate that crown-group Belidae originated approximately 138 Ma ago in Gondwana, associated with Pinopsida (conifer) host plants, with larvae likely developing in dead/decaying branches. Belids tracked their host plants as major plate movements occurred during Gondwana's breakup, surviving on distant, disjunct landmasses. Some belids shifted to Angiospermae and Cycadopsida when and where conifers declined, evolving new trophic interactions, including brood-pollination mutualisms with cycads and associations with achlorophyllous parasitic angiosperms. Extant radiations of belids in the genera Rhinotia (Australian region) and Proterhinus (Hawaiian Islands) have relatively recent origins.
Keywords: angiosperms; beetles; biogeography; evolutionary biology; gymnosperms; host shifts; phytophagy.
For over 400 million years, insects and plants have evolved alongside one another, shaping each other’s development while adapting to major environmental changes. Studying fossils can provide clues about how ancient interactions between plants and insects developed as well as how environmental changes influenced these relationships. During the Mesozoic era (around 252 to 66 million years ago) two events led to major changes in how insects and plants interacted. Firstly, flowering plants began to replace gymnosperms – plants whose seeds are not enclosed in a protective case – such as conifers, which were dominant at the time. Secondly, the supercontinent Gondwana split into the separate land masses of today, including South America, Africa, Antarctica and Australia. To understand how these changes affected insect-plant relationships, Li et al. studied the evolutionary history of the Belidae family of beetles. During the Jurassic period (around 200-150 million years ago) these beetles lived off gymnosperms, but later they began to feed on flowering plants. By combining genetic information from the DNA of 38 species of Belidae beetles with information from fossils, Li et al. constructed a timeline of the beetles’ evolution. This revealed that Belidae beetles first appeared around 138 million years ago in Gondwana. Their larvae likely developed in the dead and decaying branches of the conifer plants on which they fed. As Gondwana split, these insects remained with their conifer hosts on the newly formed land masses. However, when conifers became less common, some of the beetles switched to feeding and developing larvae on flowering plants instead, diversifying again. Understanding how changes in the availability of plants and the Earth’s geography have affected insects in the past can help scientists understand evolutionary history as well as current ecosystem stability and biodiversity. With further research, this may help scientists to devise strategies to better manage and preserve ecosystems.
© 2024, Li et al.