Am. J. Bot. Botany 2008 Ad
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (4)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lahaye, R.
Right arrow Articles by Rowe, N. P.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Lahaye, R.
Right arrow Articles by Rowe, N. P.
Agricola
Right arrow Articles by Lahaye, R.
Right arrow Articles by Rowe, N. P.
(American Journal of Botany. 2005;92:1381-1396.)
© 2005 Botanical Society of America, Inc.

Systematics

Evolution of shrub-like growth forms in the lianoid subfamily Secamonoideae (Apocynaceae s.l.) of Madagascar: phylogeny, biomechanics, and development1

Renaud Lahaye2,4,5, Laure Civeyrel2, Thomas Speck3 and Nick P. Rowe4

2Laboratoire Dynamique de la Biodiversité, UMR 5172, 118 rte de Narbonne, 4R3, F-31062, Toulouse, France; 3Plant Biomechanics Group, Institute for Biology II, Botanical Garden of the Albert-Ludwigs-Universität, Schänzlestrasse 1, D-79104 Freiburg, Germany; 4Botanique et Bioinformatique de l'Architecture des Plantes, UMR 5120 CNRS, TA40/PS2, Boulevard de la Lironde, F-34398 Montpellier, France

ABSTRACT

Lianas are common in the Apocynaceae s.l. and are predominant in the subfamily Secamonoideae. Shrub-like taxa are rare within this subfamily but occur in Malagasy genera such as Secamone, Secamonopsis, and Pervillaea. We explored the evolutionary appearance of shrub-like growth forms in Malagasy Secamonoideae through a molecular phylogeny using chloroplastic sequences. The phylogeny revealed several independent appearances of shrub-like growth forms within the Secamonoideae. Biomechanics and development of the shrub-like growth form were detailed in one species, Secamone sparsiflora, which has upright and self-supporting young stems that become procumbent in older stages of development. Biomechanical investigations revealed characteristics atypical of both lianas and self-supporting shrubs. Anatomical development in S. sparsiflora is initially similar to lianas in the same clade but shows potentially neotenic retention of juvenile wood development for most of the growth trajectory. The results suggest that evolution of lianescence can carry a high degree of specialization and developmental burden that might limit evolution back to self-supporting growth forms. Under certain geographic and ecological conditions, such as geographic isolation, xeric conditions and/or reduced biotic competition, escapes from lianescence to other growth forms can occur in some angiosperm groups via relatively simple heterochronic shifts of mechanically significant growth processes.

Key Words: Biomechanics • heterochrony • liana • molecular phylogeny • Secamone sparsiflora • Secamonoideae • shrub-like growth form






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2005 by the Botanical Society of America, Inc.