The secret life of pests

  Last updated November 8, 2018 at 4:14 pm

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Dr Megan Head didn’t expect her interest in evolution and ecology to lead to her becoming the manager of a Beetle Love Hotel.


Dr Megan Head

Dr Megan Head with one of her specimans.


Dr Head is a behavioural ecologist at the ANU Research School of Biology and is publishing a paper in Animal Behaviour on the costs and benefits of sexual conflict in seed beetles, and how the environment affects it alongside Dr Maider Iglesias, Dr Michael Jennions and PhB student Gizem Bilgin.


The research is based on many hours watching and recording the sexual behaviour of seed beetles. But to do so, Dr Head first had to set the mood.


“We put the beetles in those containers that you pee in when you go to the doctor, with a few holes in the top and with mung beans in the bottom of it, so it was like a tiny silo, where the beetles usually live.


“We then matched up the beetles individually so that each container would contain a female and one or four males and a dish of water, or no dish of water. We controlled the temperature at 25 degrees and set up stacks and stacks of these little pee jars, like a high-rise love hotel!”


But Dr Head wasn’t interested in romance, she was observing sexual conflict, which is as unpleasant as it sounds.


“Sexual conflict is basically when males and females have different evolutionary interests,” she explains.


“It pays for males to mate as many times as possible with as many different females as possible but for females it pays to mate just a couple of times to make sure they fertilise all their eggs.”


This discrepancy means that males and females evolve different adaptive traits and when they mate, females usually come off second best.


“What we’re interested in is how the environment affects this relationship,” Dr Head explains.


Her team chose to study how changing water availability had unintended consequences for the beetles’ sex lives.


Seed Beetle

Seed beetle


For seed beetles, water is the crucial resource that males have and females need. As adults, males carry water in their ejaculate so mating gives female access to that water to survive. Otherwise, they are left to try to absorb water from their dry surroundings to avoid desiccation.


In a drier climate, males are likely to carry less water and females will have to mate with more males to get the water sustenance she needs to survive and lay eggs.


But since male seed beetles come armed with spiny genitals that lock them into the females reproductive tract during mating, the more males a female has to mate with, the more likely she is to die during the process and not produce offspring. This is the world of sexual conflict.


“This is one of first papers that looks at the relationship between the environment and sexual conflict,” Dr Head says.


She believes that this research could be important to the biosecurity of Australia’s grain. Seed beetles are a pest, introduced from the tropical regions of India, and while their natural habitat is amongst the bark of trees, they have found a new home in grain silos. In a climate that is becoming hotter and drier, the microclimate of a grain silo will follow suit.


“Changing the environment to increase sexual conflict could keep the numbers of pests down.”


Speciman Jar

Speciman jar


This research could be expanded to other, bigger species that can be monitored in wild environments. Dr Head also works on reptiles, and hopes that the idea of understanding how a population changes with an increase or decrease in sexual conflict can help manage the challenges of climate change.


“It’s only by understanding how things work that we can conserve them. And unfortunately in the world today, we do have to manage the environment because we’ve had such a big impact on it.”


So, as the manager of a Love Hotel, what advice does Dr Head have for us humans based on the secret love lives of seed beetles?


“Don’t go to clubs with too many males, pick a partner in an environment where you’re comfortable, and it’s not always the best thing to do to go for more attractive males.”


Noted!




About the Author

Mitchell Sewter

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