| Alternative colony founding behaviors are associated with a large number of important traits in social insects. Colonies are initiated either by queens dispersing to found on their own (independently) or queens entering established colonies (dependently). Some species have both modes in the same population. Often polymorphic queens occur, in which large queens found independently while small queens found dependently. I studied colony-founding behavior in the cavity-nesting ant Temnothorax longispinosus. I found three queen morphs in Wisconsin populations. The largest morph had long wings, high fat content, and was produced in large numbers per nest. Another large morph had low fat levels but was also produced in large numbers. A third queen morph was small, had very little fat, and few were produced per nest. Small queens were more likely to return to their natal nest after mating, though some large queens returned. Both large morphs flew more during mating, suggesting they were more likely to disperse. Small gynes (winged, unmated queens) developed when an adult queen was present. Workers only responded to queens they could directly contact. Queen presence increased biting behavior. Large larvae that were scarred pupated earlier as workers in queenright nests, suggesting that biting diverts females to worker development. Queen size varied among forest patches. In patches with lower nest densities, large queens and gynes were more common. Large gynes from a low-density patch had greater independent-founding abilities than large gynes from a high-density patch and small gynes. Nesting units from the high-density site produced fewer large gynes per nest. There were no differences in small gyne production. The differences in large gyne phenotypes and abilities among patches, particularly in those raised under identical lab conditions, suggest that high nest-density selects against independent founding. This has led to specialization for dependent founding without changing the developmental response to queen presence. Colony-founding behavior in species with only one mode of founding may have evolved in this manner. Developmental plasticity would have facilitated changes in multiple traits associated with each mode of founding, easing the shift to the alternative form. |
