Cycads aren't quite living fossils

[Dave-Vero]

Here's the abstract:

Published Online October 20 2011

Science DOI: 10.1126/science.1209926

• Report

Recent Synchronous Radiation of a Living Fossil

1. N. S. Nagalingum,,,*,
2. C. R. Marshall,
3. T. B. Quental,,
4. H. S. Rai,,
5. D. P. Little,
6. S. Mathews,*

+ Author Affiliations

1. ¹Arnold Arboretum of Harvard University, 22 Divinity Ave, Cambridge, MA 02138, USA
2. ²University of California Museum of Paleontology, 1101 Valley Life Sciences Building, University of California Berkeley, Berkeley, CA 94720–4780, USA
3. ³National Herbarium of New South Wales, Royal Botanic Garden Sydney, Mrs Macquaries Road, Sydney NSW 2000, Australia
4. ⁴Departamento de Ecologia, Universidade Estadual de São Paulo (USP), São Paulo - SP, Brazil
5. ⁵Department of Wildland Resources, 5230 Old Main Hill, Utah State University, Logan, UT 84322–5230, USA
6. ⁶Cullman Program for Molecular Systematics, The New York Botanical Garden, Bronx, NY 10458–5126 USA

1. *To whom correspondence should be addressed. E-mail: nathalie.nagalingum@rbgsyd.nsw.gov.au (N.S.N.); smathews@oeb.harvard.edu (S.M.)

Abstract

Modern survivors of once more diverse lineages are regarded as living fossils, particularly when characterized by morphological stasis. Cycads are often cited as a classic example, reaching their greatest diversity during the Jurassic-Cretaceous (199.6 to 65.5 million years ago), then dwindling to their present diversity of ~300 species as flowering plants rose to dominance. Using fossil-calibrated molecular phylogenies, we show that cycads underwent a near synchronous global rediversification beginning in the late Miocene, followed by a slowdown toward the Recent. Although the cycad lineage is ancient, our timetree indicates that living cycad species are not much older than ~12 million years. These data reject the hypothesized role of dinosaurs in generating extant diversity and the designation of today's cycad species as living fossils.

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I would add that I suspect that everyone who's encountered the genus Zamia (Florida's coontie and 70 or so Caribbean and Central American species) suspects that there's been a lot of pretty recent speciation, like over the past few million years.

[Patricia-CR]

Quite interesting, thank you!

[virtualpalm]

In some cases, Dave, speciation within Zamia may have occurred in as little as 5-10,000 years:

http://www.cycadconservation.org/publications/Taylor-et-al-Zamia-skinneri-complex-BOJ-2008.pdf

Jody

[XYZ]

Jody:

Thank you for pointing this out. Mesoamerican phytogeography and geological record suggests explosive speciation of many plant and animal families in recent periods. Also note that evidence confirms that even "prehistoric" organisms of ancient lineage such as American saber-tooths (Smilodon cf. fatalis) occupied much of the region within the past 15 K years for sure. Fan of intelligent design/Biblical timeline or not (I am not), we all need to unstuff our ears and get with the program. Many extant cycads may, indeed, be quite modern.

Cheers,

J

[Ampli]

Thanks for this revolutionary news.