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Participants: Dr Matthew Symonds (PI), Dr Greg Holwell (University of Auckland), A/Prof John Arnould
Aims and Background: Harem polygyny is a mating system where individual males monopolise access to groups of females either by defending a resource that the females require, or by directly preventing other males from mating with those females. Whilst well studied examples of harem polygyny are found in vertebrates including elephant seals, gorillas and zebras, this mating system also occurs among a diverse range of insects including some bees, beetles, bugs, crickets, flies, thrips and dragonflies. As a mating system, harem polygyny poses a number of interesting questions as to how and why it has evolved across so many diverse insects. Are there specific ecologies that favour the evolution of this mating system? What are the consequences for sexual selection on males and females? Why do females join harems? What determines harem size? We shall address these questions, and others, using a comparative analysis across insects and experimentally by focussing on two very different harem polygynous insect species found in Australia and New Zealand: the bark beetle Ips grandicollis, and the weta, Hemideina thoracica.
Scientific significance and innovation: The novelty of this project derives from its focus on a mating system in insects that is surprisingly common but little understood. Most of the theory on the evolution of polygynous mating systems derives from studies of vertebrates, but they have only been cursorily tested on insects. This is surprising because insects offer not only an extremely diverse range of species by which to examine general evolutionary trends in the evolution of harem polygyny but also provide excellent opportunities for experimental manipulation of the conditions surrounding harems. The project will help address fundamental questions regarding the evolution of polygynous mating systems and the reproductive ecology of insects.
Potential national benefit and strategic alignment with the aims of the CIE: The key benefits from the research will be i) a greater understanding of the conditions under which a key mating system has evolved, and ii) identification of the ecological factors that influence reproductive success of males and females in this mating system. The two species that the project will focus on are respectively an important pest of forestry in Australia and a highly charismatic and iconic part of the native fauna of New Zealand. The former is an invasive species that has been causing increasing problems to the pine industry in Australia in recent years and for which control measures have not been adequate. Better understanding of its reproductive ecology therefore ties in with the National Research Priority: Safeguarding Australia (Priority Goal: Protecting Australia from invasive diseases and pests). The project ties in to the aims of CIE in its focus on how the environment and ecological processes influence the reproductive strategies and output of insects on both long-term (evolutionary) and short-term (immediate) time scales.