Systematics Section / ASPT
Sauquet, Hervé , Cantrill, David , Weston, Peter H. , Barker, Nigel , Mast, Austin , Savolainen, Vincent .
A phylogenetic approach to the evolution of pollen morphology in Proteaceae (Proteales).
FAMILY Proteaceae comprise 80 genera and over 1700 species of mostly woody angiosperms from a wide range of temperate and tropical habitats in the Southern Hemisphere. With a particularly rich fossil record of palynomorphs throughout southern Gondwana extending back to the mid-Cretaceous, they represent an ideal model to test biogeographic hypotheses, in particular with respect to the origin of biodiversity hotspots with a Mediterranean climate. Here we summarize the results of a family-wide survey of pollen morphological variation in the extant Proteaceae, integrating substantial new observations in 50 genera and over 130 species using electron microscopy (SEM and TEM). All Proteaceae appear to have triporate (or rarely diporate) pollen, presumably derived from tricolpate pollen, observed in most remaining early-diverging eudicots. However, pollen grains of Proteaceae vary remarkably in other characters including size and shape, tectal sculpture, and exine ultrastructure. A total of 35 palynological characters are evaluated and optimized onto a supertree of phylogenetic relationships within Proteaceae, constructed from several multi-locus molecular analyses. Several important synapomorphies are emerging from this study. In particular, the presence of abundant endexine in the apertural region coincides with the emergence of Grevilleoideae, the largest subfamily of Proteaceae, in contrast with a distinct plesiomorphic type observed in Persoonioideae and Proteoideae. This study highlights the phylogenetic potential of ultrastructural characters in Proteaceae and high levels of homoplasy and polymorphism in other characters including pollen shape and tectum sculptural patterns. These results have severe implications for understanding fossil palynomorph relationships to extant members of Proteaceae and choosing reliable calibration points in molecular dating analyses.[c.e.:srb]
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1 - Swedish Museum of Natural History, Department of Palaeobotany, Svante Arrhenius väg 7, P.O. Box 50007, Stockholm, SE-104 05, Sweden
2 - Swedish Museum of Natural History, Po Box 50007, Stockholm, SE-104 05, Sweden
3 - Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia
4 - Rhodes University, Department of Botany, Molecular Ecology & Systematics Group, Grahamstown, Eastern Cape, 6140, South Africa
5 - Florida State University, Department of Biological Sciences, Tallahasse, Florida, 32306-1100, USA
6 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Molecular Systematics Section, Richmond, Surrey, TW9 3DS, United Kingdom
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 9:00 AM