A novel SARS-CoV-2 variant, VOC 202012/01 (lineage B.1.1.7), emerged in southeast England in November 2020 and is rapidly spreading toward fixation. Using a variety of statistical and dynamic modelling approaches, we estimate that this variant has a 43–90% (range of 95% credible intervals 38–130%) higher reproduction number than preexisting variants. A fitted two-strain dynamic transmission model shows that VOC 202012/01 will lead to large resurgences of COVID-19 cases. Without stringent control measures, including limited closure of educational institutions and a greatly accelerated vaccine roll-out, COVID-19 hospitalisations and deaths across England in 2021 will exceed those in 2020. Concerningly, VOC 202012/01 has spread globally and exhibits a similar transmission increase (59–74%) in Denmark, Switzerland, and the United States.

■ Abstract Although best known for cooperation, insect societies also manifest many potential conflicts among individuals. These conflicts involve both direct reproduction by individuals and manipulation of the reproduction of colony members. Here we review five major areas of reproductive conflict in insect societies: (a) sex allocation, (b) queen rearing, (c) male rearing, (d) queen-worker caste fate, and (e) breeding conflicts among totipotent adults. For each area we discuss the basis for conflict (potential conflict), whether conflict is expressed (actual conflict), whose interests prevail (conflict outcome), and the factors that reduce colony-level costs of conflict (conflict resolution), such as factors that cause workers to work rather than to lay eggs. Reproductive conflicts are widespread, sometimes having dramatic effects on the colony. However, three key factors (kinship, coercion, and constraint) typically combine to limit the effects of reproductive conflict and often lead to complete resolution. INTRODUCTIONObservation of an insect society readily reveals cooperation. Workers actively work for the good of the colony as they forage, guard, build, and nurse. Detailed study reinforces this impression. Workers cooperate to forage and defend by means of sophisticated communication signals (56,113). In some species cooperation includes extreme altruism, with defending workers sacrificing their lives as they deploy detachable stings or chemical-filled exploding abdomens to deter intruders (56,113). However, sophisticated cooperation in one area of social life does not preclude conflict in another. Egg laying, brood rearing, and queen-worker caste development, for example, can all be associated with significant conflict. Indeed, potential conflict in insect societies is inevitable because insect societies are almost always families, not clones. Nevertheless, conflict in insect colonies is less obvious 0066-4170/06/0107-0581$20.00 581 Annu. Rev. Entomol. 2006.51:581-608. Downloaded from arjournals.annualreviews.org by University of Massachusetts -Amherst on 10/14/09. For personal use only. 582RATNIEKS FOSTER WENSELEERS than cooperation, which suggests that conflict may often be resolved or weak. What factors enable insect societies to resolve their conflicts? In this review, we discuss the large body of work devoted to this question, which has focused primarily on the eusocial Hymenoptera (bees, ants, and wasps). INCLUSIVE FITNESS THEORY: EXPLANATION FOR BOTH COOPERATION AND CONFLICTInclusive fitness theory (47) provides a general explanation for reproductive division of labor in eusocial insects, with some individuals forgoing direct reproduction to help rear the offspring of other colony members. The intermediate levels of relatedness typically found in insect societies provide a strong incentive for altruism, and kin are also close at hand and can readily be helped by defense or food collection. Ironically, the same theory also led to the realization that insect societies are subject to internal conflic...

A major evolutionary transition to eusociality with reproductive division of labor between queens and workers has arisen independently at least 10 times in the ants, bees, and wasps. Pheromones produced by queens are thought to play a key role in regulating this complex social system, but their evolutionary history remains unknown. Here, we identify the first sterility-inducing queen pheromones in a wasp, bumblebee, and desert ant and synthesize existing data on compounds that characterize female fecundity in 64 species of social insects. Our results show that queen pheromones are strikingly conserved across at least three independent origins of eusociality, with wasps, ants, and some bees all appearing to use nonvolatile, saturated hydrocarbons to advertise fecundity and/or suppress worker reproduction. These results suggest that queen pheromones evolved from conserved signals of solitary ancestors.

The evolution of mutualisms presents a puzzle. Why does selection favour cooperation among species rather than cheaters that accept benefits but provide nothing in return? Here we present a general model that predicts three key factors will be important in mutualism evolution: (i) high benefit to cost ratio, (ii) high within‐species relatedness and (iii) high between‐species fidelity. These factors operate by moderating three types of feedback benefit from mutualism: cooperator association, partner‐fidelity feedback and partner choice. In defining the relationship between these processes, our model also allows an assessment of their relative importance. Importantly, the model suggests that phenotypic feedbacks (partner‐fidelity feedback, partner choice) are a more important explanation for between‐species cooperation than the development of genetic correlations among species (cooperator association). We explain the relationship of our model to existing theories and discuss the empirical evidence for our predictions.