title: Calla palustris(Araceae): New palynological insights with special regard to its controversial systematic position and to closely related genera.
abstract: Almost all systematic treatments agree thatCallais a puzzling case, being a highly autapomorphic taxon with obscure relationships. In molecular-based classifications the variable placements ofCallawithin Aroideae conflict strongly with those in morphologically and anatomically based systematic classifications, which treat the genus as a subfamily (Calloideae) of its own. We studied the pollen morphology and ultrastructure ofCallaby light and electron microscopy, and mapped the relevant pollen characters as well as some flower characters to the proposed placements ofCallawithin the Araceae as indicated in the various molecular phylogenies.Callapollen is extraordinary within the entire Araceae. Pollen grains are small, and basically disulcate or with a ring-like aperture. The ornamentation is psilate to perforate, and the pollen wall consists of a sporopolleninous tectate-columellate exine. These pollen characters are shared with those of several earlier-diverging aroid taxa, especially with those of subfamily Zamioculcadoideae, whereas pollen characters in members of subfamily Aroideae deviate significantly. These findings are in accordance with other floral characters. Therefore, we propose thatCallais best placed in a transition zone between either subfamily Zamioculcadoideae (Stylochaetonclade) and subfamily Aroideae (Aroideae clade) or between subfamily Zamioculcadoideae (Stylochaetonclade) and subfamily Lasioideae.
authors.affiliation: Department of Structural and Functional Botany, University of Vienna, Rennweg 14, 1030 Wien, Austria.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.affiliation: Department of Structural and Functional Botany, University of Vienna, Rennweg 14, 1030 Wien, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Hesse
authors.affiliation: Department of Structural and Functional Botany, University of Vienna, Rennweg 14, 1030 Wien, Austria.
authors.forename: David
authors.initials: D
authors.lastname: Bröderbauer
authors.affiliation: Botanischer Garten, Menzinger Strasse 63 & Botanische Staatssammlung, Menzinger Strasse 67, 80638 München, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Bogner
authors.affiliation: Department of Structural and Functional Botany, University of Vienna, Rennweg 14, 1030 Wien, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Weber
authors.affiliation: Department of Structural and Functional Botany, University of Vienna, Rennweg 14, 1030 Wien, Austria.
authors.forename: Heidemarie
authors.initials: H
authors.lastname: Halbritter
keywords: Araceae; flowering behaviour; pollen; sulcus; systematics; ultrastructure
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