Mat-forming herb with numerous short subterranean runners (rhizomes) that end in short shoots with crowded leaves resembling rosettes. Stems ascending singly from the short leafy shoots, up to 10–15(20) cm, without or with 1–2 small leaves, sometimes branched in the upper part, slender, slightly pubescent.
Leaves alternate. Early formed basal leaves with petioles 0.7–1.6 cm, longer than the blades, and with blades 0.2–0.4 × 0.4–0.6 cm, obcordate (heart shaped), indistinctly crenate (with rounded teeth), persisting throughout most of the growth season. Later basal leaves lanceolate with short or no petioles. The smaller leaves upwards on the stem are linear.
A single flower or a few-flowered cyme.
Flowers radially symmetric. Calyx with 5(7) linear lobes, spreading to reflexed during flowering. Corolla of 5(7) blue (occasionally albino) petals fused into a bell, 1–1.5(1.8) cm long. Stamens 5(7), free. Gynoecium of 5(7) fused carpels with 5(7) free styles.
A nodding, bell-shaped capsule with one room, basal pores and numerous seeds. Mature fruits are nodding so that the pores are situated at the top and seeds are spread ballistically. Mature fruits have not been observed in Svalbard.
Sexual reproduction by seeds; efficient local vegetative reproduction by clonal growth, may be more frequent than reproduction by seeds. The plant flowers late in the season (mid August – mid September). Insect pollinatied but may also self pollinate. No ripe seeds or seed bank have been found in Svalbard, although the relatively high level of genetic diversity found there suggests that the species occasionally has successful sexual recruitment (Alsos et al. 2002, 2003).
There is no special adaptation to seed dispersal, probably efficient only locally.
The two species of Campanula in Svalbard differ in numerous features. Campanula rotundifolia is mat-forming, has leaves obcordate to linear (two different shapes, i.e., ‘heterophylly’), flowers large and broadly bell-shaped, and capsules pendulous with pores basal on the capsule. Campanula uniflora grows more solitary, has leaves lanceolate or elliptic (i.e., of mainly one shape), flowers small and narrowly funnel shaped, and capsule erect with pores apical on the capsule. They can hardly be mistaken for each other or for any other Svalbard plants.
Campanula rotundifolia is found only on a single, climatically favourable, south-facing slope but with several stands over some distance. Typical growth places are sparsely vegetated and with fine textured soil in otherwise rocky and well drained environments. Occurs on moderately exposed to moderately sheltered locations. Seems to resist minor instability in the substrate. Probably indifferent as to soil reaction (pH). Not much grazed by reindeers or geese in its only known locality.
Clearly thermophilous. The locality is in the middle arctic tundra zone and the weakly continental section. Only found with a few stands or colonies within a very small area in Colesdalen by Isfjorden (Nordenskiöld Land) on Spitsbergen.
Campanula rotundifolia s. lat. is circumpolar in the southern arctic, boreal and northern temperate zones. Subspecies gieseckiana is amphi-Atlantic, reaching from NE Canada and Greenland across the North Atlantic to N Europe and NW Siberia.
Campanula rotundifolia ssp. gieseckiana belongs to a taxonomically intricate complex that includes several subspecies and species in a circumpolar pattern (see, e.g., Hultén 1971; Elven et al. 2011). The variation within the complex is expressed in, e.g., the number and shape of the flowers and the ploidy levels. The chromosome numbers 2n = 34 and 2n = 68 are the most common ones. Individuals with 2n = 34 are often referred to as diploids although isoenzyme studies suggest that they are secondary diploids (Alsos et al. 2002). Campanula rotundifolia ssp. gieseckiana was described from Greenland and has 2n = 34. In Svalbard, both 2x = 34 and 51 (3x) have been found (Alsos et al. 2002, 2003). No critical morphological or genetic comparison of the Svalbard populations with the type material has been undertaken but the characters of the Svalbard plants conform to those reported for Greenland and type ssp. gieseckiana.
Three other races of C. rotundifolia are described: ssp. roundifolia is tetraploid (2n = 68) and usually with numerous and smaller flowers, probably restricted to Europe; ssp. groenlandica (Berlin) Á.Löve & D.Löve is very similar to ssp. gieseckiana and with the same general range, but is tetraploid (2n = 68); whereas ssp. langsdorffiana (Fisch. ex Trautv. & C.A.Mey.) Vodop. is rather different morphologically, diploid (2n = 34), and restricted to Siberia and the Russian Far East.
The flower shape varies among the few stands in Svalbard, with small, narrow flowers nearest Coles Bay and larger, broader flowers in the larger stands 3–4 km inland in Colesdalen. These differences are consistent when grown in a phytotron. Also, individuals from the coastal stands flower two weeks earlier than individuals from the larger inland stand when grown in the phytotron (Alsos & Lund, pers. obs.). The stands are genetically distinct (Alsos et al. 2002). At a small location between these two, a third morphological type characterized by flowers with mainly 6, sometimes 5 or 7 petals with backwards curved petal lobes and short calyx lobes is found (Alsos, pers. obs.) but this one has not been investigated in the phytotron or genetically.
Alsos, I.G., Engelskjøn, T. & Brochmann, C. 2002. Conservation genetics and population history of Betula nana, Vaccinium uliginosum, and Campanula rotundifolia in the arctic archipelago of Svalbard. – Arctic, Antarctic, and Alpine Research 34: 408–418.
Alsos, I.G., Spjelkavik, S. & Engelskjøn, T. 2003. Seed bank size and composition of Betula nana, Vaccinium uliginosum, and Campanula rotundifolia habitats in Svalbard and northern Norway. – Canadian Journal of Botany 81: 220–231.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/
Hultén, E. 1971. The circumpolar plants. II. Dicotyledons. – Handlingar Kungliga Svenska Vetenskaps-akademien, ser. 4, 13(1). 463 pp.