Wednesday, March 4, 2009

Introduction

All of life on earth is related, and the pattern of relatedness is shaped like a tree. Darwin realized this when he wrote in The Origin of Species:

"The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species. (...)

A phylogenetic tree: The only illustration in Charles Darwin's seminal work, The Origin of Species, published in 1859

The only illustration in Charles Darwin's seminal work The Origin of Species, published in 1859


As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications."


To reconstruct the Tree of Life - or fragments of it (Purvis, 1995; Bininda-Emonds et al., 2007) - is one of the goals of the field of phylogenetics, not just because of its intrinsic beauty, but also because the phylogenetic context allows us to test hypotheses on the origin and generation of biological diversity.


Well-resolved trees that include estimates of divergence dates allow more powerful tests of a wide range of hypotheses. Although large numbers of these phylogenies have been and are being published, they still cover only a small fraction of all the diversity of life, and each of these phylogenies usually describes the evolutionary relationship of few taxa from a relatively narrow taxonomic range. Our knowledge of 'the' tree of life is fragmented.


The challenges to overcome are wide-ranging: inferring large phylogenies poses great computational difficulties, some of which I have discussed in my dissertation. In my ongoing research I am working on developing new tools to integrate the ever-growing amount of comparative data from molecular, morphological and other sources in more and more detailed and comprehensive estimates of phylogeny.


We are Primates. We're animals, vertebrates, part of biodiversity. To understand where we come from we must also understand where everything else comes from. By studying our origins within a comparative framework we will be able to characterize the selective forces that shaped us into what we are. I am therefore interested in applying phylogenetic techniques to the Order we belong to and to use this information to answer questions about our place within the multidimensional space of genes, genomes, morphology and ecology.