Panarctic Flora

500709a Saxifraga paniculata subsp. laestadii (Neuman) Karlsson

2n= 28 (4x). - Iceland, Greenland. - Löve and Löve (1951, 1956b); Jørgensen et al. (1958).

Geography: North American (NE) - amphi-Atlantic (W): ICE CAN GRL.

Notes: Elven: This section is one of the basal branches in the main Saxifraga group in the molecular phylogenies of Soltis et al. (1996, 2001), with good bootstrap support. It is well differentiated in molecular markers from the other groups of subg. Porphyrion.

Zhmylev: Except for Saxifraga tricuspidata, the arctic representatives of sect. Trachyphyllum are divisible on two groups: the S. bronchialis and the S. spinulosa aggregates. Together they consist of about 20 species distributed mainly in Siberia. The majority of botanists have traditionally followed Engler and Irmscher (1916-1919) and have regarded almost all of them as geographic races of S. bronchialis. In fact, the species of section Trachyphyllum are very similar. Among them, however, there are groups (subsections according to Khokhrjakov 1979; Zhmylev and Khokhrjakov 1985) of closely related species differing in shape of leaf and capsule and in colour of petals. Transitional forms between these two groups are very rare and probably due to hybridization.

Murray, Elven, and Solstad: We are not convinced that all the proposed species of the two aggregates should be accepted as species. We do not doubt the variation pattern described by Zhmylev, just its hierarchical representation. However, our opinion may be coloured by the comparatively small variation observed on the North American side (Calder and Savile 1959). Elven and Solstad observed some of the sympatric northern Siberian taxa in the field in 2004 and are now less reluctant to accept them (as species) than they were before.

It may be worth notice that some of the proposed species are reported to be diploids (S. bronchialis, S. stellerana, and S. omolojensis in the S. bronchialis aggregate, S. cherlerioides in the S. spinulosa aggregate, and S. tricuspidata) and some others to be polyploids (S. spinulosa and S. funstonii in the S. spinulosa aggregate and perhaps S. balandinii in the S. bronchialis aggregate). This implies that there might be a more complicated structure of basal diploids and merging allopolyploids that makes a division on two aggregates difficult. This could be a justification, when the genetic relationships between the taxa are analysed, for treatment as basal diploid species and a superstructure of (allo)polypolyploid species. Some combined morphological, cytological, and molecular investigation is needed. Zhmylev's proposal of two aggregates with several species is entered but partly in lack of alternatives.