An example of spite comes from bacteriocins toxins that are secreted by many

An example of spite comes from bacteriocins toxins

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An example of spite comes from bacteriocins, toxins that are secreted by many bacteria and that kill susceptible bacteria [7] . Bacteriocin-producing genotypes are resistant to the toxin because of a resistance gene that is tightly linked to the gene for the toxin. Producing bacteriocin reduces growth. However, genotypes that make bacteriocins increase in laboratory cultures [8] . By killing susceptible cells, they free up resources and enhance the growth of relatives that also carry the producer gene As with intraspecific cooperation, there is always the potential for conflict within mutualisms because a genotype that “cheats” by exploiting its partner without paying the cost of providing a benefit in exchange is likely to have a selective advantage. Several possible factors can reduce the fitness of cheater genotypes, and thus maintain a mutualistic relationship. One is simply punishment of cheaters (“sanctions”), to prevent overexploitation [1] . Another possibility is that one or both partner species may be able to choose to reward the most cooperative or beneficial individuals of the other species, or exclude cheaters. • parent-sibling conflict i n a colony of hymenopterans, there is evolutionary conflict over which individuals should reproduce. A worker can gain more fitness by raising her own sons (related to her by r = 0.5) than by helping to raise the queen’s sons (the worker’s brothers, related to her by r = 0.25). But the queen gains more inclusive fitness through her own sons (related to her by r = 0.5) than through her daughters’ sons (related to her by r = 0.25). Queens of many species therefore destroy their workers’ eggs, and in some species (including honeybees, Apis mellifera ) workers destroy the eggs of other workers [12, 14] . This is one of the best examples of policing of non cooperators in social species, and it illustrates that kin selection can underlie the evolution not only of altruism, but also of selfishness. How did eusociality originate? In some species of bees, some females rear offspring with help from older offspring, while other females are solitary and receive no help. Compared with the reproductive fitness of single females, the inclusive fitness of daughters that help their mother is higher in some cases but lower in others (e.g., [6, 7]). So some origins of hymenopteran eusociality may well have been facilitated by kin selection. But ecological and behavioral factors were also important [8, 9] . Eusociality probably evolved frequently in Hymenoptera (com- pared with other
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insects) because single females of solitary wasps and bees construct a nest such as a burrow, which requires hard work but provides shelter for the young, and the offspring are helpless larvae that the mother must feed. These hymenopterans were predisposed to sociality because they already had the habit of caring for offspring and because the nest provided a safe place—a fortress—for grown offspring to stay and to interact with their mother and younger siblings [8] . In the case
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