Meeting Abstract
P2.130 Wednesday, Jan. 5 MicroRNAs support a Testudines-Lepidosaur clade LYSON, Tyler R.; SPERLING, Erik A.*; GAUTHIER, Jacques A.; HEIMBERG, Alysha M.; PETERSON, Kevin J.; Yale University; Yale University; Yale University; Dartmouth College; Dartmouth College erik.sperling@yale.edu
Understanding the evolution of a clade, either from a morphologic or genomic perspective, requires a correct topology, allowing for the polarization of traits and the ability to distinguish between homologies and homoplasies. Although great advances have been made in unraveling the tree of life, primarily based on the incorporation of molecular data and the discovery of new fossils, some areas of the tree still remain largely unknown. One contentious area in the vertebrate tree, in particular, is the interrelationships among the amniotes. Here, we propose that microRNAs, small non-coding regulatory genes, may be a new dataset that can resolve amniote relationships as they show three properties that make them excellent phylogenetic markers: 1) new microRNA families are continually being incorporated into metazoan genomes through time; 2) they show very low homoplasy, with only rare instances of secondary loss, and 3) they are almost impossible to evolve convergently. Sequencing of new small RNA libraries coupled with genomic searches reveals a likely sister group relationship between turtles and lizards, as they share 5 unique microRNA gene families that are not found in any other organisms’ genome or small RNA library. Further, no microRNAs were found in all diapsids but not turtles, or turtles and archosaurs but not in lizards. Other nodes including Amniota, Diapsida, Archosauria, Mammalia and Aves are each supported by one or more unique microRNA. If this result is true, it indicates that there have been numerous morphological convergences and reversals, including the loss of temporal fenestrae, coupled with the acquisition of several truly spectacular evolutionary novelties, in the early evolutionary history of the Testudines.
