Saturday, January 07, 2006

Cats Climb New Family Tree

Top Cat from HERE.

The Late Miocene Radiation of Modern Felidae: A Genetic Assessment. W. E. Johnson et al. Science vol. 311: 73-77.

Abstract: Modern felid species descend from relatively recent (<11 million years ago) divergence and speciation events that produced successful predatory carnivores worldwide but that have confounded taxonomic classifications. A highly resolved molecular phylogeny with divergence dates for all living cat species, derived from autosomal, X-linked, Y-linked, and mitochondrial gene segments (22,789 base pairs) and 16 fossil calibrations define eight principal lineages produced through at least 10 intercontinental migrations facilitated by sea-level fluctuations. A ghost lineage analysis indicates that available felid fossils underestimate (i.e., unrepresented basal branch length) first occurrence by an average of 76%, revealing a low representation of felid lineages in paleontological remains. The phylogenetic performance of distinct gene classes showed that Y-chromosome segments are appreciably more informative than mitochondrial DNA, X-linked, or autosomal genes in resolving the rapid Felidae species radiation.

From Shaoni Bhattacharya at New comes this article:
Despite their occasional fierceness, the domestic cat diverged from its “roaring” cousins, such as lions, jaguar and tigers, 10.8 million years ago – just after the evolution of the ancestor of all modern cats. The revelation comes from a thorough new genetic analysis of the cat family tree.
Cats are “one of the world’s most successful carnivore families, inhabiting all continents except Antarctica”, say the researchers, but modern species evolved only relatively recently – about 11 million years ago.

Originating in Asia, they successfully traversed and colonized the globe, with the periodic rise and fall of the sea level facilitating their spread and evolution into new species, the new study suggests. The cat family tree has been notoriously difficult to decipher because there are few dated cat fossils and because most of today’s species appeared so recently.

Johnson’s team managed to piece together a tree by analysing DNA sequences from the 37 living cat species. They used DNA from the sex chromosomes, X and Y, and from mitochondria – structures in the cell which provide energy and are inherited only via the mother.

They suggest that after modern cats arose in Asia, the eight main lineages diverged during the course of at least 10 migrations across continents. The felines used geographical features such as the Bering land bridge, which once connected Eurasia to North America, and the Panamanian land bridge, connecting North and South America, to spread across the world. The team also suggests that 60% of the modern species arose in just the last million years.