Rebutia
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Notes
The circumscription of Rebutia s.l. vs. a suite of proposed segregates (including Aylostera, Digitorebutia, Mediolobivia, Sulcorebutia and Weingartia) has been the subject of continued debate in the past 30 years. The wide circumscription (including these taxa) was adopted by Anderson & al. (2001) and Hunt (2006), but not by Anderson (2005) who recognized Sulcorebutia and Weingartia. The broad concept goes back to the consensus Cactaceae classification as summarized by Hunt & Taylor (1986), and some participants of the discussions at that time even argued that Rebutia sensu latissimo should be placed in the synonymy of an even more expanded Echinopsis.
Recent molecular phylogenetic studies showed, however, that Rebutia does not belong into the Echinopsis clade (Ritz & al. 2007; Mosti & al. 2011; Schlumpberger & Renner 2012), and that the genus in this broad concept is an untenable polyphyletic assemblage, as first noted by Lendel & al. (2006). In the molecular phylogeny of Ritz & al. (2007), three independent clades with taxa of Rebutia s.l. are found, namely Weingartia (incl. Sulcorebutia and Cintia), "Rebutia I" (including the segregates Aylostera, Digitorebutia and Mediolobivia), and "Rebutia II" (conforming to Rebutia s.str.). While Rebutia s.str. is placed as sister to Browningia, Aylostera is placed in a clade with Cereus and Stetsonia (Ritz & al. 2007; Mosti & al. 2011). Therefore it appears reasonable to abandon the concept of Rebutia s.l., to restrict Rebutia to the "true" rebutias, and to accept both Aylostera as well as Weingartia as separate genera. Most of the necessary new combinations have been published for Aylostera (Mosti & al. 2011) and Weingartia (Hentzschel & Augustin 2008).A
A. Hernández-Ledesma, P., Berendsohn, W.G., Borsch, T., von Mering, S., Akhani, H., Arias, S., Castañeda-Noa, I., Eggli, U., Eriksson, R., Flores-Olvera, H., Fuentes-Bazán, S., Kadereit, G., Klak, C., Korotkova, N. & Nyffeler, R. 2015: A taxonomic backbone for the global synthesis of species diversity in the angiosperm order Caryophyllales. – Willdenowia 45(3): 281-383
Recent molecular phylogenetic studies showed, however, that Rebutia does not belong into the Echinopsis clade (Ritz & al. 2007; Mosti & al. 2011; Schlumpberger & Renner 2012), and that the genus in this broad concept is an untenable polyphyletic assemblage, as first noted by Lendel & al. (2006). In the molecular phylogeny of Ritz & al. (2007), three independent clades with taxa of Rebutia s.l. are found, namely Weingartia (incl. Sulcorebutia and Cintia), "Rebutia I" (including the segregates Aylostera, Digitorebutia and Mediolobivia), and "Rebutia II" (conforming to Rebutia s.str.). While Rebutia s.str. is placed as sister to Browningia, Aylostera is placed in a clade with Cereus and Stetsonia (Ritz & al. 2007; Mosti & al. 2011). Therefore it appears reasonable to abandon the concept of Rebutia s.l., to restrict Rebutia to the "true" rebutias, and to accept both Aylostera as well as Weingartia as separate genera. Most of the necessary new combinations have been published for Aylostera (Mosti & al. 2011) and Weingartia (Hentzschel & Augustin 2008).A