Intracolonial distribution and phylogeny of kin recognition in ants

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Although intracolonial kin recognition was tested in various species of ant, no evidence of kin discrimination was obtained. However, only one species Pachycondyla sublaevis suggested that they may be able to discriminate each nestmate from others within a colony as follows :This and species had small colonies (2-18 workers) and no morphologically distinct queens. Instead, it exhibited a well-defined dominance hierarchy in which only the top-ranked worker was inseminated by males and had a well-developed ovary with matured oocytes. The dominance order was related to the age of workers but not their body size. That is, the top rank was occupied by young workers in most colonies and newly eclosed callows always filled the position next to the top. The high-ranked workers were engaged in extranidal tasks such as hunting and nest defende.The existence of kin recognition was suggested when demotion within the hierarchy occurred occasionally. For instance, when the top-ranked worker was artificially removed in a colony, second-ranked worker immediately became top as usual. Soon later, however, some workers helped new third and aggressively attacked new top and second until the third finally monopolized the top position.It is suggested that the dominance hierarchy of this ant species has evoloved as a consequence of intra-colonial competition for reproduction, and it is also likely that close kins can help each other even with a colony to raise their addaptive fitness.