Abstract Detail

Systematics Section / ASPT

Scotland, RW [2], Sanderson, MJ [1].

The significance of few versus many in the tree of life.

When classifications are examined in the context of species richness, a remarkable but consistent feature emerges. Namely, most taxonomic groups of organisms contain one or a few species and a few groups contain very large numbers of species, and the frequency distribution has the shape of a so-called "hollow curve". For example, one third of 13,000 angiosperm genera are monotypic whereas relatively few genera e.g. Astragalus, contain large numbers of species. Using birds and plants as examples we demonstrate that the disparity in species richness patterns across the tree of life - can be explained without invoking extinction, differential rates of speciation or fluctuations in rates of character evolution. Instead, very high levels of disparity can be generated by a constant rate of speciation and character evolution.

1 - University of California, Davis, Plant Biology, One Shields Ave., Davis, California, 95616, USA
2 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, OX1 3RB, United Kingdom

Keywords:
adaptive radiation
hollow curve
monotypic groups
stochastic
Simultaneous broken stick
Simulatneous broken tree
classifications
species richness
extinction.

Presentation Type: Paper
Session: 58-6
Location: Cottonwood B (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 2:45 PM
Abstract ID:206