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Angiosperm diversification through time¹

Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito de Ciudad Universitaria, Del. Coyoacán, México D.F. 04510 Mexico

ABSTRACT

The extraordinary diversity of angiosperms is the ultimate outcome of the interplay of speciation and extinction, which determine the net diversification of different lineages. We document the temporal trends of angiosperm diversification rates during their early history. Absolute diversification rates were estimated for order-level clades using ages derived from relaxed molecular clock analyses that included or excluded a maximal constraint to angiosperm age. Diversification rates for angiosperms as a whole ranged from 0.0781 to 0.0909 net speciation events per million years, with dates from the constrained analysis. Diversification through time plots show an inverse relationship between clade age and rate, where the younger clades tend to have the highest rates. Angiosperm diversity is found to have mixed origins: slightly less than half of the living species belong to lineages with low to moderate diversification rates, which appeared between 130 and 102 Mya (Barremian-uppermost Albian; Lower Cretaceous). Slightly over half of the living species belong to lineages with moderate to high diversification rates, which appeared between 102 and 77 Mya (Cenomanian-mid Campanian; Upper Cretaceous). Terminal lineages leading to living angiosperm species, however, may have originated soon or long after the phylogenetic differentiation of the clade to which they belong.

Key Words: crown group • diversification • extinction • fossils • molecular clock • penalized likelihood • stem group

Received for publication 15 February 2008. Accepted for publication 13 October 2008.

FOOTNOTES

¹ The authors are grateful to the editors of the "Darwin’s Abominable Mystery" issue for inviting them to contribute a manuscript. They thank L. Segovia for setting parallel-processing and providing computing resources, I. Cacho and P. Vinuesa for useful Bayesian suggestions, T. Hernández for help in compiling fossil first appearances, J. C. Aguilar for mathematical advice, and B. Moore for comments regarding the capabilities of SymeTREE. They also thank the editors and two anonymous reviewers for their thorough and careful editing and for helpful suggestions. This research was partially funded by the Consejo Nacional de Ciencia y Tecnología, México (CONACYT-2004-C01-46475). The Coordinación de la Investigación Científica, UNAM, provided postdoctoral funding to A.C.

² Author for correspondence (e-mail: s.magallon{at}ibiologia.unam.mx)

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