Kin recognition in social insects and other animals- a review of recent findings and a consideration of their relevance for the theory of kin selection

Abstract

Kin selection is a widely invoked mechanism to explain the origin; evolution of social behaviour in animals. Proponents of the theory of kin selection place great emphasis on the correlation between asymmetries in genetic relatedness created by haplodiploidy; the multiple origins of eusociality in the order Hymenoptera. The fact that a female is more closely related genetically to her full sister than to her daughters makes it more profitable for a Hymenopteran female; in terms of inclusive fitness to raise full sisters rather than daughters or full siblings with a female biased sex ratio rather than offspring. This is sometimes referred to as the haplodiploidy hypothesis. In reality however, genetic relatedness between workers in social insect colonies, the reproductive brood they rear is far below 0.75, the value expected for full sisters, often below 0.5 the value expected between mother and daughter and not uncommonly approaching zero. Such values are on account of queen turnover multiple mating by queens or polygyny. This situation raises doubts regarding the haplodiploidy hypothesis unless workers can discriminate between full half sisters preferentially direct their altruism towards their full sisters only. This would still mean an effective coefficient of genetic relatedness of 0.75 between altruist and recipient. For this to be possible however, workers should be able to recognise their full sisters inspite of growing up with being habituated to an assortment of full sisters half sisters and perhaps other even less related individuals. Even outside the Hymenoptera, social animals may find themselvesg rowing up together in the company of individuals of varying degrees of relatedness. An ability to tell apart the more; less related individuals under such circumstances should favour kin selection. Much effort is now going into assessingth e abilities of animals to discriminate betweenk in; non kin. In every case studied carefully so far and animals appear to be capable of recognising their kin. Ants, wasps, sweat bees, honey bees, frogs, toads, mice, rats, voles, squirrels, monkeys and even humans appear to be able to recognise their kin in one circumstance or another. An ability to recognize true genetic relatedness requires genetically specified recognition labels; these must therefore be present. Recent findings of the role of the histocompatibility system provides some clues to the possible nature of recognition labels. An ability to recognise full sisters for example; inspite of being habituated to full; half sisters requires not merely genetically specified labels but also recognition templates which are based on the characteristics of the individual animals making the recognition; not templates based on all animals one grows up with. Some animals such as honey bees; tadpoles; ground squirrels appear to have such templates but others such as sweat bees; some mice appear not to. It is entirely possible that our inability to devise natural enough assays for recognition prevents us from understandingt he full potential of the kin recognition abilities of many animals peciesI.n any case; genetically specified labels; self based templates should greatly facilitate the evolution of social behaviour by kin selection.