Macroevolutionary Diversification of Multivariate Body Plan in a Prominent Lizard Adaptive Radiation

<p>Natural selection theory predicts that similar ecological pressures can result in similarphenotypes evolving in distantly related species through a process known as convergentevolution. Although there are many described cases of species adaptively evolving similarphenotypes in response to the same habitats (i.e., “ecomorphs”), this is not a universaloutcome of natural selection. Liolaemus lizards embody an exceptional example ofadaptive radiation where, thus far, studies have not identified any evidence ofecomorphological evolution. Why some lineages display such signals of convergentevolution while others do not remains an open question. Here, shape was more accuratelyquantified by using geometric morphometrics (as opposed to the linear measures ofmorphology used previously) to address the question of whether Liolaemus lizards haveundergone convergent evolution in body morphology and to conduct phylogeneticmodelling to quantify patterns and rates of multivariate morphological evolution in thisradiation. Further to this, the effect of diet and parity mode on morphology were explored.The morphometric analysis produced three principal component (PC) axes that explainedover 10% of variance. Each axis captures different changes in shape; PC1 shows areduction in relative head size when the body becomes wider and more elongated andvice versa. PC2 shows changes in the width of the body, with little change in the lengthof the body and of changes in the head. PC3 shows lengthening in the posterior of thebody while there is a pinching towards the front of the body and an increase in relativehead size and vice versa. Results generally showed no significant separation in bodyshape between microhabitat groups, and thus suggest ecomorphs are not present. Diet andparity groups were significantly separated, however, not when phylogeny was includedin the analyses. Phylogenetic macroevolutionary analyses were used to develop anunderstanding of the evolution of biodiversity. OU models of evolution were found to bethe best fitting evolutionary models in explanation of the evolution of shape withinLiolaemus when BM, OU, ? and ? models were fit. Phenotypic rate variation showedsome increases in rate of evolution on PC1 whereas PC2 and PC3 showed decreases.PGLS showed a significant relationship between SVL and PC1 and for SVL and PC2when microhabitat, parity and diet were included. Pairwise comparisons showed asignificant difference between insectivorous and herbivorous species for SVL and PC1open-ground shrubs and open ground species for SVL and PC2. The best fitting model 9for PC1 and PC2 included microhabitat and diet, but not parity, for PC3 the best fittingmodel included diet and parity, but not microhabitat. Results suggest the lack of anecomorphological relationship could be a consequence of other ecological factorsexerting a stronger pressure on the evolution of morphology or that the adaptations arepresent but methodologies are not appropriate to identify them.</p>