Origins of Animal Diversity:
By Ari Pani     Awards: Myers

All animals have descended from a common ancestor with a single set of genes, which gave rise to the staggering diversity of life. Understanding how this diversity has evolved is a major question for biologists but answers are often elusive. My research focuses on comparing the developmental and genetic processes that regulate embryonic development in distantly related animals with very different body plans.

Changes in genetic and developmental mechanisms are the underlying forces governing animal evolution. Understanding how these processes have shaped the origins of animal diversity requires detailed studies of multiple animals to reconstruct the processes that were present in common ancestors, and how those mechanisms changed during evolution of particular lineages. However, our current knowledge of how developmental genetic changes drive evolution relies heavily on data from a relatively small number of organisms representing only a few phyla. Studies on under-investigated groups in different positions in the tree of life have great potential to provide new insights into basic evolutionary processes.

My research focuses on the evolution of body patterning mechanisms – for example the genetic processes that distinguish head from tail, top from bottom, or muscle from skin as an animal develops from an egg into an adult. I use a number of molecular techniques to visualize where and when the same genes are activated in embryos of different animals and compare the patterns to identify how they might, or might not, be associated with changes in animal forms. Most of my research has focused on using hemichordates as a system to investigate the evolutionary origins of the vertebrate brain. Although hemichordates and vertebrates have very few comparable anatomical structures, they utilize surprisingly similar gene regulatory networks to define major regions of the hemichordate body and the vertebrate brain. In fact, my research has demonstrated that hemichordates possess several genetic mechanisms for body patterning that were previously considered to be vertebrate innovations based on their absence in the closest vertebrate relatives.

In addition to hemichordates, I am interested in investigating the genetic mechanisms that regulate mollusk development. Mollusks are the second most species-rich animal phylum and include animals as diverse as chitons, squid, oysters, and snails. Mollusks also occupy a phylogenetic position that makes them highly informative for understanding the genetic mechanisms that were present at some of the earliest branching points in the animal tree of life. Chitons are a group of plated mollusks that do not undergo embryonic torsion, a rotation of the body axes, making them more straightforward to compare to other phyla than existing mollusk model organisms. My work will involve characterizing patterns of gene activity in chiton embryos in relation to other animals such as sea anemones, flies, annelid worms, hemichordates, and vertebrates. These experiments will provide important data to help identify ancient genetic mechanisms shared by all animals and novel mechanisms that evolved in different groups.