Effects of social and visual environments on female sexual signaling

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Remote link: https://oulu.zoom.us/j/61640053045

Topic of the dissertation

Effects of social and visual environments on female sexual signaling

Doctoral candidate

Master of Science Anna-Maria Borshagovski

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Faculty of Ecology and Genetics

Subject of study

Ecology

Opponent

Docent Markus Öst, Åbo Academi

Custos

Associate Professor Heikki Helanterä, University of Oulu

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Struggle for attractiveness in female glow-worms - how to be noticed in bright summer nights of the north

Mate choice and mate attraction are affected by competitors, preferences of potential mates, and environmental conditions. Commonly males attract females with conspicuous ornaments and females choose the most attractive male as their partner. However, females that visibly compete over males’ attention and matings are an evolutionary curiosity.

I studied in nature and laboratory how the attractiveness of a female glow-worm relative to another female affects its mate attraction strategy and how females secure their visibility in challenging light environments. Females produce yellow-green light at night to attract flying males, which favor the brightest and therefore largest and most fecund females. According to my results, when a female faces a brighter female than itself, it moves away from the competitor, which may increase its possibilities to attract a male. When a female faces a dimmer and smaller competitor than itself, its large size enables earlier onset of glowing.

Environmental conditions also set boundaries for the attractiveness of female glow. Although the glow is the most visible in darkness, females still glow at bright summer nights in the north. Glow-worms are widely distributed in Europe and Asia and therefore different populations live in very different light conditions. In the northernmost parts of the distribution range, that is, middle Finland, bright summer nights can restrict the visibility of females and the survival of the species. However, I noticed in my studies that Finnish females of northern populations are larger and their glow is brighter than their more southern conspecifics. This may require postponing maturation and therefore mating to the next summer.

Glow-worms are also in a race against time: their adulthood lasts only two weeks at best. During that time, they do not eat, losing the more eggs the longer they wait for mating. Small and dim females, especially, may be left without a male and lose all their eggs. Therefore, it is important to females to secure visibility and success in competition in the bright summer nights of the north.
Last updated: 21.4.2021