Reproductive structure and reproductive roles in colonies of eusocial insects

Abstract Variation in the number of queens in colonies of social insects has become a subject of growing interest among sociobiologists. The increased concern with colony queen number is partly due to the discovery that multiple queen (polygynous) colonies are more common than previously recognized, especially among ants, in which polygyny may be the predominant social structure (Buschinger 1974; Rissing and Pollock 1988; Frumhoff and Ward 1992). More importantly, the mounting interest in polygyny stems from the realization that the origin and subsequent evolution of polygynous colonies from their presumed single-queen (monogynous) ancestors is an evolutionary enigma (Holldobler and Wilson 1977; Nonacs 1988), presenting many of the same theoretical challenges as does the origin and maintenance of eusociality (see Ross 1988a, 1989). For this reason, Rosengren and Pamila (1983) referred to the evolution of polygynous societies from monogynous ancestors as ‘sociality evolving a second time’. Thus research into the origin and evolution of polygyny and eusociality are highly complementary, with insights gained into one situation likely to shed light on the other.