Meeting Abstract
36.2 Jan. 5 Evolving to be short and stubby � orthogenesis and grades of evolution in body plan in lizards. BERGMANN, PJ*; MEYERS, JJ; IRSCKICK, DJ; University of Massachusetts at Amherst; University of Massachusetts at Amherst; University of Massachusetts at Amherst pjbergma@nsm.umass.edu
Evolutionary changes in body proportions are of central interest in evolutionary biology, as such changes can affect organismic function. Relative changes in limb and body lengths are particularly important in influencing locomotor performance and kinematics. Although the evolution of body elongation and limb reduction has received considerable attention, the evolution of a short and stocky body plan have not. The evolution of a short and stocky body plan may be affected through directional evolution, or orthogenesis; or alternately, through the evolution of a series of grades from a more typically proportioned body. The Phrynosomatidae is a lizard clade containing a diversity of body proportions, including the short, broad-bodied horned lizards (Phrynosoma spp). We document patterns of body proportion evolution among 23 species of phrynosomatids by examining head, limb and body dimensions. Our findings show positive associations between body length and front and hind limb lengths, but negative associations between those variables and body width. A phylogenetically uncorrected analysis indicates these associations scale differently with body size in each of the three main subclades (horned, sand and fence lizards) of phrynosomatids. In all of these subclades, stockier lizards are also larger. However, the degree of stockiness increases most dramatically with body size in sand lizards, and least dramatically in horned lizards. A phylogenetically corrected analysis supports the general association between body size and stockiness, but does not detect differences between subclades. The results indicate both a directional correlated evolution of body dimensions, and that the three major phrynosomatid subclades represent separate grades of evolution.
