Sanger Lab Collaborative Project:
The Evolution and Development of the Lizard Skull
T
he lizard skull is remarkably diverse. There are species with long faces which likely evolved to quickly snap prey out of the air. In contrast, there are species with short jaws and large muscles that exhibit a powerful bite. Then there are species with horns, ornaments, and accessory ossifications that adorn the skull. Although most of these species have been known to science for decades, but the broad evolutionary patterns of skull diversification have not been as widely explored.
As many of you know, our lab specializes on Anolis lizards, a textbook model of adaptive diversification. Prior works suggests that the Anolis exploded in morphological diversity and species richness as this clade moved out of South America into the Caribbean islands that, which were absent ecological competitors and predators. However, this idea has not been fully tested. First, most studies have focused on the post cranium. Rarely have studies directly compared Anolis lizards to their distant relatives. The goal of this large study is to test whether the skull of Anolis lizards has diversified in novel ways compared to these relatives.
To accomplish this goal we will analyze the shape of three-dimensional skull models based on data collected on CT scanners. Some of this data we have collected from specimens borrowed from the Field Museum and the Museum of Comparative Zoology at Harvard. Other of these data have come from public repositories. In total, I hope that we will compare head shapes among approximately 350 species. Roughly half will be anoles and the other half from families closely related to anoles (left). This project will be one of the largest analyses of lizard skull shape conducted to date once complete.
At our roots we remain a developmental biology lab. Once we understand where the largest transitions in skull shape occurred we will be better equipped to analyze developmental patterns on either side of that transition. This analysis will allow us to pick the extremes of morphological diversity and use that to determine the developmental changes that lead to those differences. Although this is an exciting project on its own, it will set the stage for many future investigations in our lab.
Collecting and analyzing this much data is no small feat. We all need to work together and use the same protocols to make sure that all of our data are comparable. We cannot sacrifice working quickly for maintaining a high quality of data. We will work through each of the following steps sequentially:
1) Learn how to use the modeling software.
2) Create 3D models of all the skulls.
3) Choose morphometric landmarks that can be found on all of the species.
4) Collect data for all species.
5) Check data for quality and consistency.
6) Analyze shape data in an evolutionary context.
Go on to the next page to find the links to the software, data, and project management.