Update, Aims and Rational for My Research

Dr. Kondrashov's laboratory is primarily concerned with discovering more about the diversity and evolutionary history of animal life. Documentation of the diversity of life is accomplished by describing the anatomy of animals and the evolutionary history is addressed by performing phylogenetic analyses. These specific aspects are studied in the laboratory by: i) describing newly discovered fossils, which provides dates as to when the animal existed and documents the anatomical characters at that time in history; and ii) inferring the phylogenetic relationships of animals based on their anatomical characteristics. With this knowledge a picture of how animals have changed through time can be pieced together. It shows where and when in history unique animal features evolved. It also allows groups of related animals to be constructed. This organizes the bewildering array of characters found in nature into hierarchical groups.

The focus of this project is to better understand the phylogenetic relationships of animals grouped in the superorder Xenathra. Every species in Xenarthra need not be included in the study. Only animals that represent each of the major evolutionary lineages in this group should be included. Anatomical characters will be used to infer the phylogenetic relationships among Xenathrans. We will be using established cladistic methodology it infer phylogenetic history from the subject animal’s anatomy. These methods have been verified by the long history of used in the field of systematics and phylogenetics.

Specific Aim 1 Monophyletic lineages or clades are the desired outcomes of phylogenetics. They are groupings of animals based solely on their evolutionary relatedness. I wish to determine if i) Xenathra is in fact a clade and ii) if each of the three major clades in Xenathra that are repeatedly found in more recent phylogenetic studies emerge using different anatomical data. Every study by necessity uses an incomplete set of anatomical characters for analysis. The inclusion of all data is impossible. The inclusion of different or additional data often results in different conclusions. Further studies that include different sets of characters allow more and more data to be analyzed. This will decrease assumptions and ensure more correct conclusions.
Specific Aim 2 The addition of taxa may alter the topology of a phylogenetic tree and thereby alter our understanding of phylogenetic relationships. Additional taxa, in particular extinct taxa, make the sample size more representative of what is or was found in nature and thus brings us closer to knowing how changes in animals has happened through time. Current phylogenetic analyses based on nucleic acid and amino acid sequence data are blind to extinct taxa. This is why morphological analyses are vital to understanding the full diversity and evolutionary history of animal life. The addition of novel taxa, including extinct taxa, will be utilized to realize these benefits.

Xenarthra is an ancient lineage of Eutheria or commonly called placental mammals. They are one of the first major clades that evolved in the Mesozoic era, over 100 million years ago. This unique place in placental mammal evolution means their phylogenetic history is vital to the correct interpretation of phylogenetic history of all placental mammals. This is of particular importance humans and Xenathrans are both grouped in Eutheria meaning they are important to our understanding of our own ancestry.