On the 14th of September 2020, I started a PhD at the University of Edinburgh with the Smiseth lab exploring the parental cooperation in Nicrophorus vespilloides. Despite being excited about the project, I was struggling with how overwhelming starting is, so, I decided to introduce the beetles and my project to you.
N. vespilloides is widespread beetle species which is common in the UK. It is part of the Silphidae beetle family and the Nicrophorinae sub-family. They can be recognised by their bright orange and black wing cases and distinguished from other British Nicrophorus beetles by their black, club-shaped antennae (the other species have orange antennae).
Their common name, the sexton beetle, hints at their role as one of the undertakers and recyclers of the animal kingdom. The life-cycle of N. vespilloides is centred around the carrion they feed and breed on. They tend to favour small vertebrates, like mice, which they remove all of the fur from, roll into a ball and shallowly bury in the ground. N. vespilloides provide their offspring with biparental care which is a rare trait among beetles and is one of the main reasons I am interested in them. The female lays her eggs in the soil nearby the carcass and when the larvae hatch they crawl into the carcass and live in a small crater created by their parents. Both parents contribute towards caring for the offspring in multiple ways: feeding the offspring predigested carrion, spreading antimicrobials on the carcass and guarding the offspring. The parents also use the nutrient-rich carcass as a food source whilst breeding. About a week after the larvae hatch, the parents then desert the offspring (normally the male slightly earlier than the female) to search for new mating opportunities. The offspring then disperse into the surrounding soil to complete their development.
The aim of my PhD is to continue building upon previous work done by the Smiseth lab which has started to explore how state (factors such as size, inbreeding status, handicapping and nutrition) can affect cooperation among burying beetle parents. This research focus stems from the sexual conflict between males and females when it comes to caring for offspring. Both parents want their offspring to survive and be of good quality. The conflict arises from how much each parent should contribute towards facilitating this. It is in the interest of each parent to provide as little care as possible, since caring requires an investment of their own resources and time, whilst still ensuring that the offspring are adequately looked after. The personal costs of parental investment (resources and time) in relation to the joint benefit (the offspring) lead to a necessity for compromise between males and females in species that provide biparental care.
The state of each parent may be an important factor in deciding how the conflict is resolved. For example, previous work has shown that parents in a worse state provide less care than parents in a better state since they may be physically less able to invest in care. There is also evidence that parents change the amount of care they provide in response to the state of their partner in addition to their own state. Some research shows that parents increase the amount of care they provide when paired with a disadvantaged partner to compensate. In contrast, there is also evidence that parents reduce the amount of care they provide when paired with a partner in a worse state, potentially due to the partner being less desirable.
Whether a state is temporary or permanent may also influence individual parental investment. Permanent states, such as size or inbreeding status, cannot be altered whereas temporary states, such as malnutrition or infection, have the potential to improve. Biparental care may facilitate this by allowing the temporarily disadvantaged parent to invest in improving their own state whilst the other parent cares for the offspring. In burying beetles, for example, a parent suffering malnutrition may spend less time providing care and more time feeding on the carcass whilst the other parent spends disproportionately more time caring for offspring. However, there may be social consequences associated with investing in oneself rather than the offspring.
There are lots of interesting routes I could choose for my project. Initially, I have decided to think about ‘state’ more broadly than just physiological features. I am currently interested in how previous experiences, such as breeding experience, may alter the amount of care parents provide for their offspring. I can’t wait to get going properly!
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