Julie Horvath, Ph.D.
Lemur Phylogeny and Comparative Genomics
Fellowship period: October 2005-September 2007
Currently: postdoctoral researcher, Department of Biology and Institute for Genome Sciences & Policy, Duke University
There are more than 50 species of lemurs endemic to the island of Madagascar. A generally accepted phylogeny of prosimians, including a subset of lemur species, is shown in Figure 1. Many of these animals are endangered and discrepancies in taxonomic classification cause continuing problems for researchers attempting to compare past and present datasets. Numerous phylogenetic and chromosomal studies suggest that more lemur species exist than are currently recognized, which is confounding problems with taxonomic classification and conservation efforts.
Most lemur sequence comparisons are based upon mitochondrial sequences and nuclear sequences often exist for only a subset of lemur species, making large-scale sequence comparisons difficult. The grey mouse lemur now has 2X genome sequences available at NCBI. While these sequence data will provide a lot of information about this one species, deeper comparisons with many lemur species will be necessary to reconstruct nuclear phylogenies and to obtain information that is species specific.
As a collaboration involving Hunt Willard, Greg Wray, and Anne Yoder, we are in the process of collecting DNA samples from the more than 200 animals, representing at least 15 species, housed at the Duke Lemur Center. We have obtained orthologous nuclear sequence from each lemur species using conserved primer pairs and directly sequencing PCR products. Some of these species have been separated for more than 60 million years of evolutionary time and therefore present challenges to conserved primer pair design due to sequence divergence. The primer pairs will become part of a 'Lemur Genomic Toolkit' that will be available to all lemur researchers, making future comparisons to our data and among all species much easier. The sequences are being used to reconstruct the evolutionary history and determine the amount of genetic diversity of these lemurs to aid in captive breeding management of the Duke Lemur Center animals. We also plan to construct cDNA libraries from multiple different species in order to compare genic sequences among lemurs and to other sequenced primates. Our long-term goal is that through research studies, we will learn more about lemur biology and management while offering a basis upon which future lemur studies can build.