Male Cone Evolution in Conifers: Not All That Simple

Christian Schulz, Kristina Vanessa Klaus, Patrick Knopf, Marcus Mundry, Veit Dörken, Thomas Stützel

Botanischer Garten Rombergpark, Dortmund, Germany.
Evolution and Biodiversity of Plants, Ruhr-Universit?t Bochum, Bochum, Germany.
Fachbereich Biologie M 613, Universit?t Konstanz, Konstanz, Germany.
Heisenberg Gymnasium, Dortmund, Germany.

DOI: 10.4236/ajps.2014.518300                

Abstract

Despite the simple structure of male conifer cones, there is an enormous variability in cone properties observed upon more careful examination. The diversity ranges from simple cones to compound cones. Moreover, cones can be distinguished according to different spatial distributions on the tree. Simple cones are distributed either as solitary cones or as fascicular or clustered aggregations, while compound cones only exhibit fascicular or clustered aggregations. Here, we demonstrate that these different spatial distribution patterns correlate with distinct leaf types and variable branching frequencies. Furthermore, we provide new insights into the evolution of the sporangiophore, particularly in Taxaceae. Two notably important and fast-evolving characters of conifers are the number of sporangia per sporangiophore and the number of sporangiophores per cone. We demonstrate, across many species and types of cones, how these characters are able to adjust according to the optimal amount of pollen.

Keywords

Pollen Cone, Phylogeny, Gymnosperms, Compound Cone, Microsporophyll

Conflicts of Interest

The authors declare no conflicts of interest.

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