Rhamnus purshiana now Frangula

[Eric La Fountaine]

UBCBG accessions of Rhamnus purshiana are being relabelled as Frangula purshiana. This change is based on Generic limits in Rhamnus L. s.l. (Rhamnaceae) inferred from nuclear and chloroplast DNA sequence phylogenies by K. Bolmgren and B. Oxelman published in Taxon, Volume 53, Number 2, 1 May 2004 , pp. 383-1(-381)

Some easily recognizable morphological differences in the character complex separating Frangula from Rhamnus are, according to Grubov (1949; for English translation see Johnston & Johnston, 1978): (1) bud scales absent, (2) 5-merous hermaphroditic flowers, (3) erect and fleshy sepals, (4) well-developed and short- clawed petals, (5) unexserted and unbranched style, and (6) almost straight, pinnate leaf nerves. Another characteristic of Frangula, which in addition to bud scales being absent is probably the most important synapomorphy for Frangula, is (7) the protruding ‘beak’of the seed, i.e., a testa with a thickening “that protrudes from the opening of the endocarp in the shape of a beak-like rostellum” (Johnston & Johnston, 1978: 5).

[Michael F]

Frangula has been moved in and out of Rhamnus like a yo-yo over the last 240 years . . . I wonder if this will really be the last move??

Presume you're doing the same for Frangula californica and any others in this (sub)genus you have?

[Ron B]

Genetic analysis used this time may carry more weight.

[Eric La Fountaine]

The only other Rhamnus species listed in the garden's database is Rhamnus alnifolia. I am not quite sure about the placement of that species. It was not mentioned in the article and seems to remain in the genus Rhamnus according to GRIN and others.
http://www.ars-grin.gov/cgi-bin/npgs...plist.pl?10359

[Michael F]

Yep, Rhamnus alnifolia has always been placed in (sub)genus Rhamnus, so it won't be moved.