Panarctic Flora

641015 Potentilla insularis Soják

• Soják, Bot. Jahrb. Syst. 106: 203 (1986). Holotype (O!): Svalbard: Spitsbergen, Hyperithatten, 28. Aug. 1908, leg. H. Resvoll-Dieset.
• Potentilla rubricaulis auct. eur., non Lehm. (1830).
• Potentilla pedersenii auct. eur., non Rydb. (1908).

Geography: European (N): NOR.

Notes: Elven, Hamre, Hansen, and Nyléhn: Soják (1986) proposed Potentilla insularis to be a hybrid species from P. arenosa subsp. chamissonis and P. lyngei. This origin, at least as concerns the type material, is improbable. Plants with semidigitate or semipinnate leaves occur as populations in numerous sites in Svalbard, mostly associated with P. pulchella, often with P. arenosa and sometimes with P. nivea. In addition to Svalbard, Soják (1986) reported occurrence in eastern Greenland. Soják's treatment of P. insularis as apart from the main Greenland plant of the same affinity, P. pedersenii, was based on his assumption of a parentage involving the Russian P. lyngei, by him also assumed to occur in Svalbard and in eastern Greenland. If these assumptions more or less fail, the major parts of the Svalbard plants should perhaps be compared again with Greenland P. pedersenii. Provisionally we have omitted Greenland records for both P. insularis and P. lyngei.

To our knowledge, P. insularis is the only experimentally investigated plant of the assumed sect. Niveae x sect. Pensylvanicae parentage, commented on by Elven and Elvebakk (1996) and subsequently studied by Eriksen and Nyléhn (1999), Hamre (2000), Hansen et al. (2000), and Nyléhn and Hamre (2002). The hypothesis of a hybrid origin from P. arenosa subsp. chamissonis x P. lyngei is countered by: (a) The proposed "Pensylvanicae" parent (P. lyngei), even if possibly present in Svalbard, is absent from the type area of P. insularis where it grows together with P. pulchella and with P. arenosa subsp. chamissonis. (b) The common "Pensylvanicae" species in Svalbard, P. pulchella, is not a relevant parent from morphological evidence (this also supported by Yurtsev) or from molecular data. (c) In molecular markers, P. insularis is closer to P. arenosa subsp. chamissonis than to P. nivea (the two other related taxa in Svalbard) but consistently different. And (d), in isoenzymes, P. insularis is not more varied than, e.g., P. arenosa subsp. chamissonis or P. nivea (see Nyléhn and Hamre 2002). It does not include markers indicative of a hybrid origin with partaking of a more distant parent than from the P. nivea-arenosa group. The molecular evidence currently points towards P. insularis, a morphologically characteristic member of Soják's "Pensylvanicae x niveae" intersectional hybrids, genetically to be a member of sect. Niveae. Section Niveae may have to be extended to include some of the digitate or semipinnate leaved plants. Our third assumption is that the hypothesis of Soják and Yurtsev of inter-section hybridity should not be accepted as a general explanation until it is experimentally supported in several cases. This is also stated by Eriksen and Yurtsev (1999: 216): "In most other cases except for [P. drymeja, see below], however, it is not obvious, and even unlikely, that the taxa described as hybrids descend from the suggested parents".