Molecular phylogeny of cycads inferred from rbcL sequences

Abstract

The chloroplast gene rbcL was sequenced to elucidate the evolution of the gymnosperm plant order Cycadales. In accordance with traditional systematics, the order Cycadales and the corresponding genera cluster as monophyletic clades. Among them, the genus Cycas forms a basal group. The genetic distances within the genus Encephalartos and between the sister groups Encephalartos, Lepidozamia and Macrozamia, are unexpectedly small, suggesting that the extant species are the result of Miocene and Pliocene speciation. Their distribution in Africa or Australia, respectively, may therefore rather be due to long-distance dispersal than to Cretaceous continental drift, as had previously been assumed. The rbcL sequences also indicate that the colonisation of Madagascar by Cycas thouarsii occurred only recently as the sequences of C. thouarsii and Cycas rumphii from Indonesia are identical. In contrast, the divergence of the Cycadaceae and Zamiaceae apparently occurred in the Mesozoic.

Distribution of living Cupressaceae reflects the breakup of Pangea

“…Previous studies of gymnosperm radiations mostly have inferred Oligocene-age crown groups (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26), and a recent meta-analysis found a median crown age for gymnosperm genera of 32 Ma, younger than that found for angiosperm genera (25). Our dating of those genera with more than one species in the Cupressaceae similarly suggests relatively recent diversifications (Fig.…”

Gymnosperms from the Middle Triassic of Antarctica: The First Structurally Preserved Cycad Pollen Cone

“…Cycadaceae, with the single genus Cycas, has historically been interpreted as the most basal family, and this is supported in recent phylogenetic analyses (Stevenson 1990;Caputo et al 1991;Nixon et al 1994;Rydin et al 2002;Treutlein and Wink 2002). Zamiaceae is consistently regarded as the most derived, although relationships among the eight genera included in the family remain unresolved (Crane 1988;Stevenson 1990;Treutlein and Wink 2002). The monophyly of Stangeriaceae ( ) has recently been challenged on the basis Stangeria + Bowenia of molecular and cytological studies, and it appears that Stangeria may be more closely related to Zamia than to Bowenia (Kokubugata et al 2002;Treutlein and Wink 2002;Bogler and Francisco-Ortega, in press;Rai et al 2003).…”

“…Extant Cycadales include three families: Cycadaceae, Zamiaceae, and Stangeriaceae (Stevenson 1990(Stevenson , 1992. Cycadaceae, with the single genus Cycas, has historically been interpreted as the most basal family, and this is supported in recent phylogenetic analyses (Stevenson 1990;Caputo et al 1991;Nixon et al 1994;Rydin et al 2002;Treutlein and Wink 2002). Zamiaceae is consistently regarded as the most derived, although relationships among the eight genera included in the family remain unresolved (Crane 1988;Stevenson 1990;Treutlein and Wink 2002).…”

“…Zamiaceae is consistently regarded as the most derived, although relationships among the eight genera included in the family remain unresolved (Crane 1988;Stevenson 1990;Treutlein and Wink 2002). The monophyly of Stangeriaceae ( ) has recently been challenged on the basis Stangeria + Bowenia of molecular and cytological studies, and it appears that Stangeria may be more closely related to Zamia than to Bowenia (Kokubugata et al 2002;Treutlein and Wink 2002;Bogler and Francisco-Ortega, in press;Rai et al 2003). Nearly all phylogenetic analyses of seed plants based on morphology score cycads on the basis of characters of the extant taxa; only a few include any fossil representatives of the order (Doyle andDonoghue 1986, 1992;Doyle 1996).…”

Exposing the illegal trade in cycad species (Cycadophyta:Encephalartos) at two traditional medicine markets in South Africa using DNA barcoding

“…Lepidozamia Lehm. was used as the outgroup in the analysis as its phylogenetic placement has consistently been resolved as sister to Encephalartos (Treutlein and Wink 2002;Hill et al 2003;Bogler and Francisco-Ortega 2004;Chaw et al 2005;Sangin et al 2008;Zgurski et al 2008). Maximum parsimony using PAUP* v. 4.0b1 (Swofford 2002) was implemented to analyze the combined dataset (matK, rbcLa, trnH-psbA, and nrITS).…”