Gnetales

While the topology of the Gnetales as sister to the rest of the gymnosperms may be considered unconventional, it is quite interesting to note that this topology has been retrieved from individual gene trees such as

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

Many current studies support the placement of Gnetales and conifers as closely-related groups, either as sister clades (Panel B), or with Gnetales as a nested group within the conifers (Panel D).

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

When the unicellular green alga Chlamydomonas and/or the moss Physcomitrella are included, cycads and Ginkgo nest within the conifers, and Gnetales appear basal.

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

In contrast, most molecular studies postulate gymnosperms as a monophyletic group sister to all angiosperms, and place the Gnetales as a sister group to the conifers (Panels B and D).

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

Moreover, the analysis represents a substantial data set that is not only consistent with a basal position for Gnetales either as sister to all other seed plants or as sister to the rest of the gymnosperms but also when analyses include bryophyte, lycophyte and pteridoyphyte outgroups as for example in the analysis of rbcL data [56].

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

Gnetales and conifers are separate, monophyletic groups, (i.e. not nested within one another).

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

Additionally, our results suggest Gnetales may indeed be the sister group to the rest of the extant gymnosperms.

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

Figure 2, together with our observations in serial addition experiments, supports the basal placement of Gnetales within the gymnosperms.

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

[11], which placed cycads as the earliest diverging branch followed by Ginkgo, and then the Gnetales and conifers as sister taxa deeper in the gymnosperm clade (i.e., a pectinate gymnosperm clade).

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009

[23] has generally remained marginal and controversial, places the Gnetales as basal gymnosperms, with conifers and Conflicting phylogenetic hypotheses on the evolution of seed plants.

PLoS ONE Alerts: New Articles Jose Eduardo de la Torre-Bárcena et al. 2009