Pollen Diversity and Evolution in Proteoideae (Proteales: Proteaceae)

Abstract

Proteoideae (27 genera, 655 species) are one of the largest clades in the early-diverging eudicot family Proteaceae and are distributed in Australia, New Caledonia, and Africa. New palynological observations using scanning and transmission electron microscopy are reported for 15 genera and 49 species, which complement previous work on the subfamily. These are integrated with an extensive review of all literature data available to provide a summary of pollen morphology and variation in each genus of Proteoideae, using a new rigorous method of character scoring. The results are discussed in the context of recent phylogenetic analyses of Proteaceae. The monophyletic Leucadendreae, comprising two Australian genera and a large clade of 10 southern African genera, appear to be relatively homogenous in pollen morphology, especially in ultrastructure of the apertural region. In addition, two other African genera, Faurea and Protea, share very similar pollen characters, some of which appear to be apomorphic, consistent with strong phylogenetic evidence for their sister group relationship. Beauprea, Eidothea, Faurea, Protea, and Stirlingia share a distinct pattern of foot layer disintegration at the apertural region and complete lack of endexine. The occurrence of the same apertural type in the early-diverging Persoonioideae suggests that it is plesiomorphic in Proteoideae and Proteaceae as a whole. 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.