Journal Article

Branching habit and the allocation of reproductive resources in conifers

Andrew B. Leslie

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 4, pages 915-921
Published in print September 2012 | ISSN: 0305-7364
Published online July 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs150
Branching habit and the allocation of reproductive resources in conifers

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

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Background and Aims

Correlated relationships between branch thickness, branch density, and twig and leaf size have been used extensively to study the evolution of plant canopy architecture, but fewer studies have explored the impact of these relationships on the allocation of reproductive resources. This study quantifies pollen cone production in conifers, which have similar basic reproductive biology but vary dramatically in branching habit, in order to test how differences in branch diameter influence pollen cone size and the density with which they are deployed in the canopy.

Methods

Measurements of canopy branch density, the number of cones per branch and cone size were used to estimate the amount of pollen cone tissues produced by 16 species in three major conifer clades. The number of pollen grains produced was also estimated using direct counts from individual pollen cones.

Key Results

The total amount of pollen cone tissues in the conifer canopy varied little among species and clades, although vegetative traits such as branch thickness, branch density and pollen cone size varied over several orders of magnitude. However, branching habit controls the way these tissues are deployed: taxa with small branches produce small pollen cones at a high density, while taxa with large branches produce large cones relatively sparsely.

Conclusions

Conifers appear to invest similar amounts of energy in pollen production independent of branching habit. However, similar associations between branch thickness, branch density and pollen cone size are seen across conifers, including members of living and extinct groups not directly studied here. This suggests that reproductive features relating to pollen cone size are in large part a function of the evolution of vegetative morphology and branching habit.

Keywords: Corner's Rules; plant architecture; reproductive allocation; conifer; pollen cone

Journal Article.  4583 words.  Illustrated.

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

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