Prof. Dr. Jutta Schneider
Jutta M Schneider currently works at the Institute of Zoology in the Department of Biology, University of Hamburg. Jutta does research in Behavioural Ecology. Her focus is on mating strategies in sexually cannibalistic spiders.
Abstract:
Sex roles in cannibalistic spiders: Loyal males and cheeky females
While female polygamy is now generally accepted as the rule in animals rather than the exception, male monogamy appears counterintuitive, particularly in the absence of paternal care. In monogynous mating systems, which evolved repeatedly within highly diverse taxa, males actively limit their investment to a single female. Such a strategy contradicts classical views on sex roles which assume that male fitness increases with the number of mates. How can we explain the existence of such an unexpected mating system? Theory revealed that a male biased sex ratio is necessary for monogyny to evolve but field data to test this argument are scarce. Monogyny in spiders is generally associated with sexual cannibalism, genital plugging, and a strong female-biased sexual size dimorphism. Males attempt to monopolise fertilisation of their single female, but females resist monopolisation. We have studied several species that show variations of a monogynous mating system but in this talk, I will focus on the wasp spider, Argiope bruennichi. Females of this species are highly aggressive and restrict most males to a single copulation by attacking and cannibalising them at the onset of genital contact. Female aggression limits the male’s option to monopolise paternity and allows females the possibility to remate and execute cryptic female choice. This is because the genitalia of these spiders are paired and a single copulation by a male into one genital opening leaves the second spermatheca free for another mating by the same or another male. Males have evolved counter strategies in response to female aggression to retain some control over their fate, which include using pheromonal signals to choose the best females and modifying the length of copulation to survive their first copulation and mate with another female. Opportunistic bigyny in concert with a modest male biased sex ratio maintain monogyny in this spider.
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Dr. Joël Meunier
Joël Meunier currently works at the Institut de Recherche sur la Biologie de l'Insecte in Tour. He is an evolutionary biologist studying multiple aspects of social life and social evolution in insects.
Abstract:
The unexpected costs and benefits of family life: lessons from the European earwig.
Family life is a ubiquitous phenomenon in animals. From vertebrates to arthropods, this form of social life has long been characterised by the importance of parental care for offspring and parents, fostering the idea that its emergence and maintenance depend largely on the benefits it brings to all family members. But what if this long-held assumption is incorrect? Is it possible that factors other than parental care are essential to the emergence of family life from an ancestral state of solitary living, or even that family life evolved despite the costs of having parents around for offspring? In this talk, I will present the results of 10 years of research into these questions in the European earwig, an insect in which maternal care takes many forms, but is still facultative for the development and survival of the juveniles. Using a variety of experimental approaches, I will first show that the presence of a mother during family life is not always beneficial for earwig juveniles and that under certain conditions it can even be lethal. I will then show that earwig juveniles can gain important benefits from cooperative behaviour with their siblings, especially when their mother is not providing enough care. Finally, I will present data suggesting that mothers may also benefit from interacting with their offspring. To conclude, I will discuss how these demonstrations that parental care should not be considered the sole evolutionary driver of family life opens up new perspectives in our general understanding of the early emergence and maintenance of social life in animals.
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