Meeting Abstract

67.3  Tuesday, Jan. 6  Polymorphic trap-jaws: intra- and interspecific scaling of jaw forces in trap-jaw ants SPAGNA, J.C.*; PATEK, S.N.; SUAREZ, A.V.; William Paterson University; Univ. of California, Berkeley; Univ. of Illinois, Urbana-Champaign SpagnaJ@wpunj.edu

Trap-jaw ants exhibit a remarkable range of mandible morphology from short and robust to elongate and spiny. One fundamental issue in this system is whether this variation is primarily caused by developmental or evolutionary factors. In one case, sisters in the trap-jaw ant species Odontomachus cephalotes exhibit within-colony variation in body and mandible size that exceeds cross-species differences in many other trap-jaw ants in this genus. Here, we measure size variation, acceleration, and modeled force generation within O. cephalotes, then compare this to size and strike force to model predictions derived from seven monomorphic trap-jaw ant species. Across a size range covering 92% of the range of 7 monomorphic species, O. cephalotes workers mandible length was negatively allometric relative to body length (mean slope 0.79, 95% CI 0.59-0.99), while mandible mass was positively allometric by mandible length (mean slope 4.38, 95% CI 3.88-4.90). The relatively short, massive jaws of the larger O. cephalotes workers contrasted with interspecific scalings, which were isometric. From these results, O. cephalotes largest workers should produce mandibular forces similar to those of large monomorphic species (~100mN), but at smaller sizes, O. cephalotes workers should strike with about twice as much force as similarly-sized species (60 mN vs. 30 mN). The lower variation found in the polymorphic species suggests that interspecific differences in strike forces are influenced by evolutionary as well as developmental factors.