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Trine Bilde

Billede af Trine Bilde
Dr. Trine Bilde

Evolution of cooperation

The evolution of cooperative societies where some individuals reproduce while others act as helpers or workers in the colony is intriguing, because of the costs of helping behaviour to the performer who sacrifices own reproduction. Kin selection is one possible explanation for this problem, if helpers gain inclusive fitness benefits from raising the offspring of relatives.
We study the evolution of permanent sociality and cooperation in social spiders. Sociality in spiders has evolved repeatedly across the spider phylogeny, and is a system with multiple independent origins of permanent sociality. Sociality is likely derived from subsocial ancestors, and is always associated with a transition to regular inbreeding and female-biased sex-ratios.
We aim to understand the selective forces underlying the transition to and maintenance of permanent sociality, and the consequences of regular inbreeding for population genetics, lineage persistence, and patterns of gene flow. We also work on the evolution of reproductive division of labour and task differentiation, and on macro-ecology of social spiders.
Our main study system is Stegodyphus spiders that contain multiple social and subsocial lineages which makes them ideal for comparative studies.

Eco-genomics of inbreeding 

The evolution of regular inbreeding in highly structures populations is expected to have profound consequences for population genetic structure, effective population size and efficacy of selection. We do comparative genetic and genomic studies to understand short and long term evolutionary consequences of inbreeding mating systems and female biased sex-ratios,

Sexual selection and evolution of mating systems

Stegodyphus: the genus Stegodyphus contains both permanently social and periodic-social species, and these spiders experience philopatry, limited dispersal and regular inbreeding. In such a system, females multiple mating can evolve as an inbreeding avoidance strategy. We aim to understand whether polyandrous females gain indirect genetic benefits by reducing the risk of fertilizing their eggs with sperm from closely related males, or whether polyandry result from conflict between males and females over optimal mating rate.
Pisaura: the courtship behaviour of the nursery web spider Pisaura mirabilis involves a nuptial gift, where males capture an insect prey which they wrap in white silk and offer to the female. When the female accepts and consumes the gift, the male copulates with her exploiting the female natural foraging motivation. If the female attempts to steal the gift without copulation, the male perform thanatosis – or death feigning - and is dragged along the substrate whilst holding onto the gift with his chelicerae. We are investigating the function and the ultimate courses underlying these behaviours, and also whether male exploitation leads to deceptive use of nuptial gifts suboptimal mating rates for females.

Contact: Trine Bilde