Browsing by Subject "adaptation"

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  • Mannerla, Miia (2009)
    The Baltic Sea suffers from eutrophication caused by the increased use of nitrogen- and phosphorus based fertilizers in agriculture. When these nutrients end up in the water ecosystem, they increase the growth of filamentous algae causing turbidity at many locations. The three-spined stickleback (Gasterosteus aculeatus) breeds at the shallow coastal waters of the Baltic Sea, which are often eutrophied. In these locations turbidity of the water may interfere with the mating cues used by the three-spined stickleback, which in turn may lead to decreased fitness of the population. I attempted to find out how turbidity alters the use of visual and olfactory cues in the mate choice of the three-spined stickleback, as well as to see if these changes decrease the viability of the following generation. Female three-spined sticklebacks choose their mates based on visual and olfactory cues. During the reproductive season stickleback males turn bright red and attract females to their nests by a conspicuous courtship dance. Females use males’ red colouration, size and courtship intensity as visual cues when choosing an appropriate mating partner. They also pay much attention to olfactory cues. Female sticklebacks are able to smell MHC-encoded peptides which are secreted to the males’ skin. The allelic combination of MHC determines which pathogens the individual has resistance for, and this resistance may be inherited by the offspring. I empirically tested the use of olfactory and visual cues in the mate choice of the three-spined stickleback using turbid and clear water as treatments. In mate choice tests a female was made to choose from two males in circumstances where she was allowed to use only one of the cues (visual or olfactory) or both cues simultaneously. The redness and size of the males was measured. Artificial inseminations were performed to produce offspring, whose growth rate was measured to evaluate fitness. Based on the results of these experiments, turbidity alters the use of mating cues of the three-spined stickleback. Visual cues seem to be important in clear water, whereas in turbid water olfactory cues increase in importance in relation to visual cues. The sample size was limited to reliably test offspring fitness effects, but it seems that the alteration in the use of mate choice cues may influence population viability in the long term. However, additional research is needed to determine this.