HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

First published online January 9, 2009; doi:10.3732/ajb.0800142 American Journal of Botany 96: 391-408 (2009) © 2009 Botanical Society of America, Inc.

What's this?

This Article Full Text Full Text (PDF) Supplementary Data All Versions of this Article: ajb.0800142v1 96/2/391    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ogburn, R. M. Articles by Edwards, E. J. Search for Related Content PubMed Articles by Ogburn, R. M. Articles by Edwards, E. J. Agricola Articles by Ogburn, R. M. Articles by Edwards, E. J. Social Bookmarking                            What's this?

Anatomical variation in Cactaceae and relatives: Trait lability and evolutionary innovation¹

² University of Missouri–St. Louis, 1 University Boulevard, St. Louis, Missouri 63121 USA ³ Missouri Botanical Garden, 4500 Shaw Boulevard, St. Louis, Missouri 63110 USA ⁴ Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman St., Box G-W, Providence, Rhode Island 02912 USA

ABSTRACT

The cacti have undergone extensive specialization in their evolutionary history, providing an excellent system in which to address large-scale questions of morphological and physiological adaptation. Recent molecular phylogenetic studies suggest that (1) Pereskia, the leafy genus long interpreted as the sister group of all other cacti, is likely paraphyletic, and (2) Cactaceae are nested within a paraphyletic Portulacaceae as a member of the "ACPT" clade (Anacampseroteae, Cactaceae, Portulaca, and Talinum). We collected new data on the vegetative anatomy of the ACPT clade and relatives to evaluate whether patterns in the distributions of traits may provide insight into early events in the evolutionary transition to the cactus life form. Many traits had high levels of homoplasy and were mostly equivocal with regard to infraclade relationships of ACPT, although several characters do lend further support to a paraphyletic Pereskia. These include a thick stem cuticle, prominent stem mucilage cells, and hypodermal calcium oxalate druses, all of which are likely to be important traits for stem water storage and photosynthesis. We hypothesize that high lability of many putative "precursor" traits may have been critical in generating the organismal context necessary for the evolution of an efficient and integrated photosynthetic stem.

Key Words: adaptation • Cactaceae • character evolution • homoplasy • Portulacaceae • Portulacineae • stem photosynthesis • vegetative anatomy

Received for publication 21 April 2008. Accepted for publication 6 October 2008.

FOOTNOTES

¹ The authors thank B. Leuenberger (Berlin Botanical Garden), H. Forbes (University of California Botanical Garden at Berkeley), P. Forster (Queensland Herbarium), R. Abbott, P. Schnebelen, and the Royal Botanic Gardens, Kew, for generously providing plant material for this study. They also thank P. Stevens, E. Kellogg, R. Keating, A. Doust, and M. Richardson for guidance in developing the project, comments on the manuscript, and assistance with technical aspects of the work.

⁵ Author for correspondence (e-mail address: mogburn{at}brown.edu); present address: Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman St., Box G-W, Providence, Rhode Island 02912 USA

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				D. J. Hearn Developmental patterns in anatomy are shared among separate evolutionary origins of stem succulent and storage root-bearing growth habits in Adenia (Passifloraceae) Am. J. Botany, November 1, 2009; 96(11): 1941 - 1956. [Abstract] [Full Text] [PDF]