Trine Bilde


Trine Bilde
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Research Interests - Spider Lab Aarhus University

Evolution of cooperation - social spiders

A main aim of our research group is the study evolution of cooperation using social spiders as study organism. The social spiders are unique among group living animals, as the transition to permanent sociality is associated with strong inbreeding and highly female-biased sex ratios. Our research aims to understand 1) selective forces underlying the transition to sociality, 2) costs and benefits of group living, and 3) causes and consequences of inbreeding. Our research is mainly performed on the genus Stegodyphus, this genus contains both social and subsocial (pre-social) spiders, which makes it ideal for comparative studies. We do field work in South Africa, Nambia, India and Israel.

Left: Colonies of the social spider Stegodyphus dumicola (Eresidae) in Namibia, December 2003. The dense silk nests may contain several hundred spiders and are often interconnected with prey capture webs. Right: Individuals of the social spider Stegodyphus dumicola (Eresidae) foraging on a grasshopper. South Africa, January 2001.

Evolutionary ecology of inbreeding

We are particularly interested in the evolutionary consequences of inbreeding for population genetic diversity, evolutionary potential, and sex-ratio. We have sequenced the transcriptome of several of our study species to develop genetic tools to investigate these questions. Our current aims are to conduct large-scale population genetic studies, comparative studies of genetic variation, and investigate the evolution of female biased sex rations in relation to genetic and environmental factors.

Stegodyphus lineatus, matriphagy.

Kin cooperation

Young of the subsocial spider Stegodyphus lineatus (Eresidae) consume the female (matriphagy) 2 weeks after hatching. The suicidal maternal care by the female increases the survival chance of the young and may be a pre-condition for cooperation among siblings prior to dispersal.
Kin selection theory predicts that cooperation among individuals is favoured when relatedness within groups increases, we test these predictions by studying the effect of genetic relatedness on cooperation experimentally.

Ecology and phylogeography of social spiders

We apply macro-ecological modelling to understand distribution patters of social spiders and identify ecological factors that shape distribution patterns of social spiders. Furthermore, we apply phylogenetic and phylogeographic analyses to gain insights to biotic and abiotic factors that facilitate sociality and may drive the transition to group living.

Sexual selection and evolution of mating systems

Females of many species mate with multiple males (polyandry). The evolution of polyandry is continuously debated since the costs of polyandry to females can be large. We use invertebrate model systems to study the evolution of female multiple mating, specifically we study: 1) direct and indirect benefits of polyandry; 2) sexual conflict, where female multiple mating result from conflicting interests between males and females over mating rate; and 3) inbreeding avoidance, where polyandry allows females to exert post-mating sexual selection in favour of unrelated males. We perform behavioural studies and use genetic markers in studies of parentage and population genetic variation in relation to mating system.

One of our study animals is the nuptial gift giving spider Pisaura mirabilis. We study the evolution of male mating strategies and female co-evolutionary responses.

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