Publication Date:
2011-10-25
Description:
Modern survivors of previously 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 timetrees indicate 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nagalingum, N S -- Marshall, C R -- Quental, T B -- Rai, H S -- Little, D P -- Mathews, S -- New York, N.Y. -- Science. 2011 Nov 11;334(6057):796-9. doi: 10.1126/science.1209926. Epub 2011 Oct 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Arnold Arboretum of Harvard University, 22 Divinity Avenue, Cambridge, MA 02138, USA. nathalie.nagalingum@rbgsyd.nsw.gov.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22021670" target="_blank"〉PubMed〈/a〉
Keywords:
Bayes Theorem
;
*Biological Evolution
;
Climate Change
;
*Cycadophyta/anatomy & histology/classification/genetics
;
Extinction, Biological
;
*Fossils
;
Genes, Plant
;
*Genetic Speciation
;
Molecular Sequence Data
;
Phylogeny
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
