Browsing by Subject "kin selection"

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  • Hakala, Sanja Maria; Seppä, Perttu; Helanterä, Heikki (2019)
    The extreme diversity of dispersal strategies in ants is unique among terrestrial animals. The nature of ant colonies as social, perennial, and sessile superorganisms is the basis for understanding this diversity, together with the inclusive-fitness framework for social evolution. We review ant dispersal strategies, with the aim of identifying future research directions on ant dispersal and its evolution. We list ultimate and proximate determinants of dispersal traits and the ecological and evolutionary consequences of dispersal for population structures and dynamics, as well as species communities. We outline the eco-evolutionary feedbacks between the multitude of traits affecting dispersal evolution and the likely evolutionary routes and ecological drivers in transitions among the diverse ant dispersal strategies. We conclude by presenting a research framework to fill the gaps in current knowledge, including comparative studies of colony life histories and population structures and theoretical models of the eco-evolutionary dynamics affecting dispersal, in an inclusive-fitness framework.
  • Rautiala, Petri; Helantera, Heikki; Puurtinen, Mikael (2019)
    Evolution of altruistic behavior was a hurdle for the logic of Darwinian evolution. Soon after Hamilton formalized the concept of inclusive fitness, which explains how altruism can evolve, he suggested that the high sororal relatedness brought by haplodiploidy could be why Hymenopterans have a high prevalence in eusocial species, and why helpers in Hymenoptera are always female. Later it was noted that in order to capitalize on the high sororal relatedness, helpers would need to direct help toward sisters, and this would bias the population sex ratio. Under a 1:3 males:females sex ratio, the inclusive fitness valuation a female places on her sister, brother, and an own offspring are equalapparently removing the benefit of helping over independent reproduction. Based on this argumentation, haplodiploidy hypothesis has been considered a red herring. However, here we show that when population sex ratio, cost of altruism, and population growth rate are considered together, haplodiploidy does promote female helping even with female-biased sex ratio, due the lowered cost of altruism in such populations. Our analysis highlights the need to re-evaluate the role of haplodiploidy in the evolution of helping, and the importance of fully exploring the model assumptions when comparing interactions of population sex ratios and social behaviors.
  • Haapanen, Saara-Maria (Helsingin yliopisto, 2019)
    Objective. Motives for childbearing are poorly understood, but it is well-renowned that fertility behavior runs in families. There is no agreement on mechanism of intergenerational fertility transmission. First in Finland, the aim of this study is to examine the relationship between the numbers of full and half-siblings (and maternal and paternal half-siblings) and fertility, and the association between half-siblings and timing of fertility. Since full and half-siblings differ in terms of relatedness and childhood backgrounds, it is possible to get better insights into mechanisms of fertility transmission, and better consider today’s heterogeneity in families. Methods. The current study utilized nationally representative registry data (FINNFAMILY). The sample (n = 35 063) consisted of women (49.1 %) and men in four birth cohorts (1955, 1960, 1965, 1970) which had completed fertility. Poisson regression analyses were used to examine relationships between the numbers of siblings (all siblings, full and half-siblings, maternal and paternal half-siblings) and children. Associations between half-siblings and fertility timing were examined by regressing the cumulative number of children over the participants’ reproductive age by the number of half-siblings. Results and discussion. The findings showed intergenerational fertility transmission in Finland. Half-siblings were differently associated with fertility between sexes. The number of half-siblings increased only women’s fertility, and women with half-siblings had higher completed fertility and earlier entry to parenthood. Maternal half-siblings were associated with women’s fertility, but not men’s. The findings support the idea of women as family kin keepers. Future research should further examine the role of sibling rivalry and mutual investments in fertility transmission.