Meeting Abstract
103.1 Wednesday, Jan. 7 PHENOTYPIC PLASTICITY IN ALLIGATORINAE EVOLUTION & VISUALIZING 3-D SHAPE CHANGE SADLEIR, R.W.*; LEE, S.; Field Museum & Univ. of Chicago; Univ. of Illinois, Chicago rsadleir@uchicago.edu
During ontogeny, organisms can display different phenotypes as a result of living under different environmental conditions. Recent research suggests such environmentally induced phenotypic plasticity can promote evolutionary diversification among populations. The growing Alligator mississippiensis agroindustry provides a unique opportunity to investigate whether different environmental conditions through ontogeny can induce cranial shape variability and whether the magnitude of variability corresponds to or exceeds species boundaries. In various species of crocodilians, captive-raised populations have been casually recognized to have cranial morphologies very different from wild populations. In a 2D geometric morphometric analysis of extant crocodilian variation, farm-raised A. mississippiensis specimens cluster closer to A. sinensis suggesting that differences in shape due to ontogenetic environment transcend species morphospace boundaries. Inferential power improves when fossil taxa are included. Results reveal the morphospace range of wild and captive A. mississippiensis is nearly inclusive of its taxonomically closest extinct taxa A. olseni. Captive A. mississippiensis occupy a novel region of morphospace orthogonal to the wild populations ontogenetic shape change. This suggests the phenotypic plasticity in A. mississipiensis is large enough to account for the scale of evolutionary differentiation among Alligator species back to the Miocene. This hypothesis is explored at higher analytical resolution using a greater fossil sample, and presents a new method of visualizing and animating geometric morphometric shape change in 3-D using the freeware Blender. A sample of 16 farm-raised A. mississippiensis of known age and ontogenetic environmental condition was compared to a post-hatchling size range of 22 wild specimens from the same geographic range.
