Phylogenetics and life history variation of the tree lizard, Urosaurus ornatu

Every organism shares an evolutionary history at some level because of the hierarchical relationships inherent in the fact that speciation is a lineage bifurcating process. Organisms are, thus, not evolutionarily independent units and the importance of the influence of phylogenetic history on variation of organisms cannot be overstressed. Phylogenetic relationships have been shown to have large effects on patterns of variation of life history traits at the genus and subfamily level in some iguanian lizards. Extensive variation in life history traits has been documented within many lizard species, but the effects of phylogenetic relationships on life history traits have never been examined at the population level. I developed a phylogeny of tree lizard, Urosaurus ornatus, populations to examine potential effects of phylogeny on life history variation among seven well studied populations of tree lizards. This was done for these seven populations alone and for a larger sample of 41 populations. These phylogenies are based on both molecular (mtDNA restriction site maps) and morphological (extemal scale) characters. Parsimony analysis of the combined data sets resulted in a single most parsimonious tree for seven populations with life history traits. One most parsimonious tree was also found using all 41 tree lizard populations. Because these hypotheses give slightly different relationships for the seven populations, both were used in the comparative analysis. Life history trait values for the seven populations were taken from published studies and phylogenetic effects on a set of life history traits were calculated using the phylogenetic autocorrelation model. All life history traits were negatively correlated with the hypothesized phylogenetic relationships of these populations. Negative phylogenetic autocorrelations imply that the more closely related populations actually differed more with respect to their life history traits than did more distantly related populations. The results of this study indicate that most if not all the observed between-population variation in life history traits of these tree lizard populations is due to local factors such as adaptation to local conditions or phenotypic plasticity.