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x affomarcoi (Gallo & Afferni) Afferni, 2013

Petrosedum xaffomarcoi at Monte Secchieta, Italy (photo Massimo Afferni)

A new combination of a natural hybrid of Sedum series Rupestria A.Berger = Petrosedum Grulich (Crassulaceae). Massimo Afferni   Until quite recently it is not uncommon to find articles in the literature using the generic name Sedum when speaking of taxa belonging to the series Rupestria Berger. However, a molecular study by Mort (2001) has shown that plants of this series have a closer affinity to Sempervivum than they have to Sedum, confirming the view already predicted by Grulich (1984). He therefore created a new genus, Petrosedum, to accommodate those species belonging to Berger's series Rupestria. Grulich also provided all the necessary new combinations for the taxa of series Rupestria known at the time, including one natural hybrid, Petrosedum × luteolum  Chaboiss. ex Grulich, 1984.   Recent authors now accept that Petrosedum is worthy of recognition at the rank of genus, and Eggli (pers. comm.) has indicated that it will be accepted in the next edition of the standard reference work, The Illustrated Handbook of Succulent Plants, currently in preparation.   The authors 't Hart (1978, 1979, 1987) and Gallo (2009, 2012) have described new natural hybrids of this group of sedums belonging to Sedum series Rupestria rather than in the genus Petrosedum, and these will need new combinations in due course. In particular, I wish to recombine the nothospecies that I jointly named for my late son, died prematurely, in the paper of Gallo (Gallo 2012). This is a natural hybrid of Sedum montanum Songeon & E.P.Perrier and Sedum reflexum L. (S. rupestre auct. non L.) from the Italian regions of Piedmont, Liguria, Tuscany and Abruzzo, which we first published as Sedum ×affomarcoi Gallo & Afferni (Gallo 2012). A new combination for this is now published here:   Petrosedum ×affomarcoi (Gallo & Afferni) Afferni comb. nov. [= P. montanum (Songeon & E. P. Perrier) Grulich × P. reflexum (L.) Grulich]. Basionym: Sedum ×affomarcoi Gallo & Afferni, Natural hybrids in Sedum series Rupestria Berger (Crassulaceae): A review of taxonomy and nomenclature, Forum Geobot. 6: [2]. 2012 ).

Petrosedum xaffomarcoi at Passo della Collina, Italy (photo Massimo Afferni)

I am indebted to Margrit Bischofberger, Roy Mottram and Urs Eggli for their kind assistance in the preparation of this paper.

Literature cited :

Afferni, M. (2008) Sedum montanum × Sedum rupestre un ibrido naturale in Toscana (Italia). Sedum Soc. News. (87): 16-18. (Oct)

Gallo, L. (2009) Sedum ser. Rupestria Berger (Crassulaceae): work in progress toward a checklist of taxa and their distribution. Bocconea 23: 203-205.

Gallo, L. (2012) Natural hybrids in Sedum series Rupestria Berger (Crassulaceae): a review of taxonomy and nomenclature. Forum Geobotanicum 6: [1-13].

Grulich, V. (1984) Generic division of Sedoideae in Europe and the adjacent regions. Preslia 56(1): 29-45.

Mort & al., (2001) Phylogenetic relationships and evolution of Crassulaceae inferred from matK sequence data, Amer. J. Bot. 88(1): 76-91.

‘t Hart, H. (1978) Biosystematic studies in the acre-group and the series Rupestria Berger of the genus Sedum L. (Crassulaceae). Drukkerij Elinkwijk, Utrecht.

‘t Hart, H. (1979) Sedum × hegnaueri nov. hybr. Danseria 16: 28-33.

 First publisched in CactusWorld Vol. 31(1), 67-68, 2013.

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