MatK and rbcL gene sequence data indicate that Saxifraga (Saxifragaceae) is polyphyletic

• Published in: American journal of botany Vol. 83; no. 3; pp. 371 - 382
• Main Authors: Soltis, D.E. (Washington State University, Pullman, WA.), Kuzoff, R.K, Conti, E, Gornall, R, Ferguson, K
• Format: Journal Article
• Language: English
• Published: Columbus American Botanical Society 01-03-1996; Botanical Society of America, Inc
• Subjects: Biological taxonomies; Botany; CHLOROPLASTE; Chloroplasts; Classification; CLOROPLASTO; ESPECE; ESPECIES; FILOGENIA; Flowers & plants; GENE; Genera; GENES; GENETICA; Genetics; GENETIQUE; Monophyly; Phylogenetics; PHYLOGENIE; Phylogeny; Plant morphology; SAXIFRAGACEAE; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE; Sisters; Systematics; Taxa; TAXONOMIA; TAXONOMIE; We they distinction
• ISSN: 0002-9122; 1537-2197
• DOI: 10.2307/2446171

The large genus Saxifraga, which consists of approximately 400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK-rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well-differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species-rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradora, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium-Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well-separated Saxifraga lineages