Life‐history trait variation in a queen‐size dimorphic ant

Abstract

1. Size polymorphism is often connected to alternative life‐history traits, which may eventually lead to distinct size classes. In the ant Myrmica ruginodis, larger macrogyne and smaller microgyne queen morphs have been suggested to follow different reproductive strategies, which has presumably resulted in several differences in their key life‐history traits.2. In this study, we examine the association of queen‐size morphs with colony queen number (monogyny vs. polygyny), dispersal and queen recruitment patterns, as well as habitat associations of the queen morphs. We do this by sampling established queens from a large number of excavated nests from several populations, estimating genetic relatedness among coexisting queens and pitfall trapping free‐ranging wingless queens.3. Our results show that associations of queen morphs with colony queen number and nest‐founding strategy holds only partly. The morph frequencies vary widely across populations from practically pure macrogyne to more than 50% microgyne, but the expected association of macrogyne occurrence with monogyny and microgyne with polygyny is not universal. Dispersal and queen recruitment patterns also show that although most macrogynes participate in nuptial flights and most microgynes are recruited back to their natal nests, a fraction of both morphs use the alternative strategy.4. The polygynous microgyne morph has been suggested to specialize in stable habitats, but our results from Finnish mesic heath forests do not support this. This study shows that factors other than just queen size also influence life‐history trait variation and reproductive strategies in ants.