E&E PhD Exit Seminar: Systematics and Evolutionary Biology of the Weevils Associated with Cycads in Australia (Coleoptera: Curculionidae)

Cycads are subtropical and tropical palm-like gymnosperms, commonly known as “living fossils” as they arose in the late Paleozoic and were much more diverse and dominant during the Mesozoic. Modern cycads underwent a recent global diversification in Miocene (ca. 11–20 mya). Even though cycads were long thought to be wind-pollinated, it has been recently shown that cycads are dominantly pollinated by insects, especially beetles. Australia is one of the main centres of cycad diversity, comprising four genera and approximately 90 named species. While it is now established that Australian cycads are largely weevil-pollinated, the systematics and phylogeny of the cycad-associated weevils are poorly known, and it is consequently unknown how host-specific the pollinators are and the evolution of cycad-weevil association in Australia. In this thesis, mitochondrial genomes were sequenced from museum specimens to reconstruct the first molecular phylogeny to investigate on the monophyly, systematic placement and sister groups of Australian cycad weevils and relationships among species. The combination of morphological studies and molecular species delimitation were conducted for estimating putative species number of Australian cycad weevils and host specificity is determined based on the taxonomic information. To investigate on the origin of cycad-association of Australian cycad weevils, divergence dating using fossil calibration data was performed. We also conducted co-speciation analysis to compare phylogenies of cycads and weevils to identify any potential pattern of co-evolution. The present thesis also provides first-hand observations in the wild and during laboratory rearing, new host plant records and developed a method for rearing mature larvae of cycad weevils in the laboratory. This thesis improves our understanding of the phylogeny, systematics, evolution and natural history of the Australian cycad weevils, a unique group of Australia’s insect fauna evolving specific mutualistic interaction with the "living fossil" plants.