Thursday, May 3, 2007

Bininda-Emonds et al. 2007

Bininda-Emonds, O.R.P., M. Cardillo, K.E. Jones, R.D.E. MacPhee, R.M.D. Beck, R. Grenyer, S.A. Price, R.A. Vos, J.L. Gittleman and A. Purvis. 2007. The delayed rise of present-day mammals. Nature. 446:; 507-512.

This paper uses a species-level phylogeny of extant Mammalia to answer the question of did the end-Cretaceous mass extinction event trigger the evolutionary radiation of present day mammals. They conclude that no, it did not.

The phrase that caught my eye while reading this paper was "phylogenetic fuses". The authors define phylogenetic fuses as: where lineages persist at low diversity for some time after their initial origins before undergoing evolutionary radiations (explosions).

Long fuse model= a long time period between the Cretaceous origins of the orders and the first split among their living representatives (crown groups) immediately after the KT boundary.
Short fuse model= diversity occured before the KT boundary

The long- and short fuse models are two competing hypotheses for when mammalian crown groups evolved.

Their hypothesis: there was a significant increase in the net per-lineage rate of extant mammalian diversification, r (the difference between the per-lineage speciation and extinction rates), immediately after the K/T mass extinction.

Methods: -only used extant mammals (this is probably a big problem in their study)
-2, 500 partial estimates (whatever that means)
-66 gene alignment w/ 30 calibration points

Results: They found low rates of extant mammalian diversification during the Cenozoic and little evidence for the long fuse model, indicating that the extinction of dinosaurs and other taxa had a major effect on mammalian diversification. However I noticed that their supertree is only 46.7% resolved. I wouldn't trust that tree.

Tuesday, May 1, 2007

Dobler & Muller 2000

Dobler, S. and J.K. Muller. 2000. Resolving phylogeny at the family level by mitochondrial Cytochrome Oxidase sequences: phylogeny of carrion beetles (Coleoptera: Silphidae).

In this paper the authors use COI, COII, and tRNA-leu to reconstruct the phylogeny of the Silphidae. Important points:

1) used 23 species from 13 genera
2) the Agyrtidae is justified as a separate family based on the phylogeny
3) the genus Silpha was not monophyletic
4) Pseudosilphites triassicus, a coleopteran fossil from the Triassic, is morphologically similar to silphids and possibly an ancestor of the Staphylinoidea (Zeuner, 1930)
5) compared parsimony and likelihood trees

This paper also briefly discusses the biogeography of the family:
-Silphidae 'apparently' originated in Palearctic because it has the most genera and highest # of species (Peck and Anderson 1985). [center of origin criteria #'s 1 and 2].
The phylogeny in this paper also agrees with a Palearctic origin.

*This is the first published phylogeny of the Silphidae.