How (much) do flowers vary? – The floral morphospace of Ericales

Marion Chartier, Sylvain Gerber, Stefan Löfstrand, Anna Maria Louise von Balthazar-Schönenberger, Florian Jabbour, Hervé Sauquet, Peter Crane, Jürg Schönenberger

Morphospaces are mathematical descriptions used for studying the evolution of morphological diversity (disparity) and for the evaluation of evolved shapes and trait combinations among theoretically possible ones in groups of extinct and extant taxa. To do so, a common procedure is the calculation of disparity indexes that allow quantifying and comparing morphological disparity among groups. In addition, reduced (2- or 3-dimensional) representations of the space can be built where similar morphologies fall close to each other. Although widely used in zoology, morphospaces – with a few exceptions – have been neglected in plant science in general and in the study of broad-scale patterns of floral structure and evolution in particular. Here, we use a morphospace approach to describe and quantify the morphological diversity of flowers in the angiosperm order Ericales. The order belongs to the asterid clade and with more than 11,000 species comprises ca. six per cent of the eudicot species diversity. The 22 currently recognized families include among many other well-known taxa tea (Camellia sinensis,Theaceae), kiwi (Actinidia deliciosa, Actinidiaceae), persimmon and ebony (Diospyros, Actinidiaceae), pitcher plants (e.g. Sarracenia, Sarraceniaceae) and many horticulturally important genera (e.g. Impatiens, Balsaminaceae; Primula, Primulaceae; Rhododendron, Ericaceae). Ericales are highly variable in their ecology, their vegetative morphology, and in particular their floral structure. For our morphospace analysis, we describe and quantify the distribution of floral morphological disparity among and within the families of Ericales as well as the morphological variation of the different parts of the flower (sterile, male, and female organs). To do so, we have built a dataset containing 40 floral characters for more than 350 species (259 genera) representative of the entire order, using the PROTEUS database. Character information was retrieved from earlier morphological studies, original species descriptions, taxonomic revisions, and online floras. Characters include, e.g., the number, position, and insertion of organs, and the degree of fusion among organs of the same type or of different types. As our dataset is composed of different types of descriptive variables (continuous, ordered and unordered categorical data), we used non-parametric representations and statistics methods based on distance matrices to build and analyse a morphospace in which we compare the relative position of the different ericalean families. We quantify and interpret the disparity among these groups in the light of their taxonomic diversity, their evolutionary history, and their ecology.

Department für Botanik und Biodiversitätsforschung
Externe Organisation(en)
University of Cambridge, Museum national d'Histoire Naturelle, Université Paris XI - Paris-Sud, Yale University
ÖFOS 2012
106042 Systematische Botanik, 106008 Botanik, 106012 Evolutionsforschung
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