Browsing by Subject "mate choice"

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  • Teerikorpi, Pauliina Elisabet; Sirkiä, Paivi Maria; Laaksonen, Toni (2018)
    Environmental shifts may induce sudden reversals in the relative quality or sexual attractiveness of mates (ecological crossovers) leading to non-directional sexual selection. Studies on such ecological crossovers induced by environmental shifts during the nonbreeding season are particularly rare. We studied the interactive effects between nonbreeding conditions and a male white wing patch on the breeding success of breeding pairs and the local survival of females in a migratory passerine population over a 32-year period. After dry winters, females paired with large-patched males were more likely to survive than those paired with small-patched males, and vice versa after moist winters. Moreover, after dry winters, large-patched males succeeded in attracting females that laid large clutches, while small-patched males bred with females that laid small clutches, and vice versa after moist winters. This phenomenon led to a difference in fledgling numbers only during years with dry winters and high precipitation during the breeding season. The selection on this male trait and its signaling value to females thus depended on a complex interaction between conditions both at the nonbreeding and breeding grounds. We show that it is important to consider conditions during the nonbreeding season when examining the effects of sexual ornaments on fitness.
  • Kokko, Hanna; Jennions, Michael D; Houde, Anne (2007)
    The diversity of sexual traits favoured by females is enormous and, curiously, includes preferences for males with rare or novel phenotypes. We modelled the evolution of a preference for rarity that yielded two surprising results. First, a Fisherian 'sexy son' effect can boost female preferences to a frequency well above that predicted by mutation-selection balance, even if there are significant mortality costs for females. Preferences do not reach fixation, however, as they are subject to frequency-dependent selection: if choosy females are too common, then rare genotypes in one generation become common, and thus unattractive, in the offspring generation. Nevertheless, even at relatively low frequency, preferences maintain polymorphism in male traits. The second unexpected result is that the preferences can evolve to much higher frequencies if choice is hindered, such that females cannot always express their preferences. Our results emphasize the need to consider feedback where preferences determine the dynamics of male genotypes and vice versa. They also highlight the similarity between the arbitrariness of behavioural norms in models of social evolution with punishment (the so-called 'folk theorem') and the diversity of sexual traits that can be preferred simply because deviating from the norm produces unattractive offspring and is, in this sense, 'punished'.
  • Pettay, Jenni E.; Lummaa, Virpi; Lynch, Robert; Loehr, John (2021)
    Because sex ratios are a key factor regulating mating success and subsequent fitness both across and within species, there is widespread interest in how population-wide sex ratio imbalances affect marriage markets and the formation of families in human societies. Although most modern cities have more women than men and suffer from low fertility rates, the effects of female-biased sex ratios have garnered less attention than male-biased ratios. Here, we analyze how sex ratios are linked to marriages, reproductive histories, dispersal, and urbanization by taking advantage of a natural experiment in which an entire population was forcibly displaced during World War II to other local Finnish populations of varying sizes and sex ratios. Using a discrete time-event generalized linear mixed-effects model, and including factors that change across time, such as annual sex ratio, we show how sex ratios, reproduction, and migration are connected in a female-dominated environment. Young childless women migrated toward urban centers where work was available to women, and away from male-biased rural areas. In such areas where there were more females, women were less likely to start reproduction. Despite this constraint, women showed little flexibility in mate choice, with no evidence for an increase in partner age difference in female-biased areas. We propose that together these behaviors and conditions combine to generate an "urban fertility trap" which may have important consequences for our understanding of the fertility dynamics of today including the current fertility decline across the developed world.
  • Pärssinen, Varpu; Kalb, Nadine; Vallon, Martin; Anthes, Nils; Heubel, Katja (2019)
    Nests play a critical role for offspring development across the animal kingdom. Nest quality may contribute to the builder's extended phenotype and serve as an ornament during mate choice. We examined male and female nest choice in the common goby (Pomatoschistus microps), a benthic fish with male-only parental care where females deposit eggs in male-built nests. Using prebuilt nest models, we independently manipulated two candidate nest quality traits: (a) nest entrance width with a role in oxygen ventilation, and (b) extent of sand cover with a role in camouflage. In simultaneous choice trials, male gobies exhibited no preference for any nest model type. This suggests that initial characteristics of a nesting substrate have minor importance for males, which usually remodel the nest. Females were given a choice between two males occupying either entrance- or cover-manipulated nests. The same pair of males was then exposed to a second female but now with alternated nest types assigned. Most females were consistent in choosing the same, typically the heavier male of the two regardless of nest properties. However, the females that chose the same nest regardless of the male preferred low over high sand coverage and narrow over wide nest entrance. Our results indicate that females base their mating decision on a combination of male phenotype and nest traits. While we found no indication that females are attracted to highly decorated nests, our study is the first in fishes to disentangle a preference for narrow (and thus more protective) nest entrances independent of nest coverage.
  • Candolin, Ulrika; Jensen, Irene (2021)
    When environments change rapidly, evolutionary processes may be too slow to rescue populations from decline. Persistence then hinges on plastic adjustments of critical traits to the altered conditions. However, the degree to which species harbour the necessary plasticity and the degree to which the plasticity is exposed to selection in human-disturbed environments are poorly known. We show that a population of the threespine stickleback (Gasterosteus aculeatus) harbours variation in plasticity in male courtship behaviour, which is exposed to selection when visibility deteriorates because of enhanced algal growth. Females in clear water show no preference for plastic males, while females in algal-rich, turbid water switch their mate preference towards males with adaptive plasticity. Thus, while the plasticity is not selected for in the original clear water environment, it comes under selection in turbid water. However, much maladaptive plasticity is present in the population, probably because larger turbidity fluctuations have been rare in the past. Thus, the probability that the plasticity will improve the ability of the population to cope with human-induced increases in turbidity-and possibly facilitate genetic adaptation-depends on its prevalence and genetic basis. In conclusion, our results show that rapid human-induced environmental change can expose phenotypic plasticity to selection, but that much of the plasticity can be maladaptive, also when the altered conditions represent extremes of earlier encountered conditions. Thus, whether the plasticity will improve population viability remains questionable.
  • Elgert, Christina Barbro Cecilia; Hopkins, Juhani; Kaitala, Arja Leena; Candolin, Ulrika (2020)
    The amount of artificial light at night is growing worldwide, impacting the behaviour of nocturnal organisms. Yet, we know little about the consequences of these behavioural responses for individual fitness and population viability. We investigated if females of the common glow-wormLampyris noctiluca-which glow in the night to attract males-mitigate negative effects of artificial light on mate attraction by adjusting the timing and location of glowing to spatial variation in light conditions. We found females do not move away from light when exposed to a gradient of artificial light, but delay or even refrain from glowing. Further, we demonstrate that this response is maladaptive, as our field study showed that staying still when exposed to artificial light from a simulated streetlight decreases mate attraction success, while moving only a short distance from the light source can markedly improve mate attraction. These results indicate that glow-worms are unable to respond to spatial variation in artificial light, which may be a factor in their global decline. Consequently, our results support the hypothesis that animals often lack adaptive behavioural responses to anthropogenic environmental changes and underlines the importance of considering behavioural responses when investigating the effects of human activities on wildlife.
  • Elgert, Christina Barbro Cecilia; Lehtonen, Topi Kasperi; Kaitala, Arja Leena; Candolin, Ulrika (2021)
  • Karvonen, Anssi; Lindström, Kai (2018)
    Parasitism is considered a major selective force in natural host populations. Infections can decrease host condition and vigour, and potentially influence, for example, host population dynamics and behavior such as mate choice. We studied parasite infections of two common marine fish species, the sand goby (Pomatoschistus minutus) and the common goby (Pomatoschistus microps), in the brackish water Northern Baltic Sea. We were particularly interested in the occurrence of parasite taxa located in central sensory organs, such as eyes, potentially affecting fish behavior and mate choice. We found that both fish species harbored parasite communities dominated by taxa transmitted to fish through aquatic invertebrates. Infections also showed significant spatiotemporal variation. Trematodes in the eyes were very few in some locations, but infection levels were higher among females than males, suggesting differences in exposure or resistance between the sexes. To test between these hypotheses, we experimentally exposed male and female sand gobies to infection with the eye fluke Diplostomum pseudospathaceum. These trials showed that the fish became readily infected and females had higher parasite numbers, supporting higher susceptibility of females. Eye fluke infections also caused high cataract intensities among the fish in the wild. Our results demonstrate the potential of these parasites to influence host condition and visual abilities, which may have significant implications for survival and mate choice in goby populations.
  • Mannerla, Miia (Helsingfors universitet, 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.