SOCIOGENETIC ORGANIZATION OF THE RED ANT MYRMICA-RUBRA

Knowledge of the sociogenetic organization determining the kin structu re of social insect colonies is the basis for understanding the evolut ion of insect sociality, Kin structure is determined by the number and relatedness of queens and males reproducing in the colonies, and part itioning of reproduction among them. This study shows extreme flexibil ity in these traits in the facultatively polygynous red ant Myrmica ru bra. Relatedness among worker nestmates varied from 0 to 0.82. The mos t important reason for this variation was the extensive variation in t he queen number among populations, Most populations were moderately or highly polygynous resulting in low relatedness among worker nestmates , but effectively monogynous populations were also found. Polygynous p opulations also often tend to be polydomous, which is another reason f or low relatedness. Coexisting queens were positively related in two p opulations out of five and relatedness was usually similar among worke rs in the same colonies. Due to the polydomous colony organization and short life span of queens, it was not possible to conclusively determ ine the importance of unequal reproduction among coexisting queens, bu t it did not seem to be important in determining the relatedness among worker nestmates. The estimates of the mating frequency by queens rem ained ambiguous, which may be due to variation among populations. In s ome populations relatedness among worker nestmates was high, suggestin g monogyny and single mating by queens, but in single-queen laboratory nests relatedness among the worker offspring was lower, suggesting th at multiple mating was common. The data on males were sparse, but indi cated sperm precedence and no relatedness among males breeding in the same colony. A comparison of social organizations and habitat requirem ents of M. rubra and closely related M. ruginodis suggested that habit at longevity and patchiness may be important ecological factors promot ing polygyny in Myrmica.