Journal Article

Replacement of Species Along Altitude Gradients: The Role of Branch Architecture

Rubén Milla, Luis Giménez-Benavides and Gabriel Montserrat-Martí

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 6, pages 953-966
Published in print December 2008 | ISSN: 0305-7364
Published online October 2008 | e-ISSN: 1095-8290 | DOI:
Replacement of Species Along Altitude Gradients: The Role of Branch Architecture

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and aims

Plant species typical of cold and warm habitats differ in a suite of morpho-physio-phenological traits, although their evolutionary routes have been poorly explored. Here, it is advocated that traits typical of different climate regimes can be largely driven by contrasting branch architectures. This is explored within Saxifraga. First, an investigation was carried out to determine whether series Ceratophyllae (lateral inflorescences) is segregated to lowlands compared with Pentadactylis (terminal inflorescences). Then, two altitudinal vicariants, S. trifurcata (lowland, with lateral inflorescences) and S. canaliculata (highland, with apical inflorescences), were selected. It was hypothesized that apical flowering of S. canaliculata constrains its growth period, bringing with it traits typical of short growth season plants, and conversely for S. trifurcata.


The hypothesis was tested by measuring plant compactness and organ pre-formation in seven populations of these species along an altitude gradient.

Key Results

Most variables differed among species. Morphological variables at all scales support that the architecture of S. canaliculata generates a more compact habit. A higher number of primordia and earlier inflorescence pre-formation in S. canaliculata indicate that it begins organogenesis earlier. Data on organogenesis suggest that the different timing of inflorescence initiation may be the origin of the contrasting architectures. Within species, shoot compactness increased, and the length of lateral primordia decreased, as altitude increased. All other metrics were similar among locations of the same species at contrasting altitudes.


The hypotheses linking elevational segregation of species, architecture and pheno-morphological traits were validated at broad (gen. Saxifraga) and local (altitudinal vicariants) scales. This supports the initial idea that shoot architecture may to a large extent condition high altitude adaptive syndrome.

Keywords: Saxifraga; meristem activity; altitude; architecture; phenology; organogenesis

Journal Article.  8312 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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