Alchemilla glomerulans

GROWTH FORM

Moderately mat-forming herb with very stout, horizontal rhizome densely covered with blackish remains of petioles and marcescent leaf sheaths. Rhizome branching at irregular intervals, resulting in an open clone of shoots at ground level. Aerial shoots with 2—4 or more basal leaves and (in Svalbard only occasionally) stems ascending from the caudex just beneath the leaf rosettes. Stems with appressed hairs. Stem leaves 2—4, smaller and more short-petiolate than the basal leaves.

LEAF

Leaves alternate, with petioles up to 10 cm and blades nearly orbicular in outline, up to 8—9 × 9—10 cm, slightly plicate, with palmate venation and ca. 9 rounded, dentate lobes. Appressed hairs on petiole, blade lower surface (especially on veins) and sparsely on blade upper surface. Each blade lobe with (11)13(15) teeth, acute but not acuminate and curved.

INFLORESCENCE

Inflorescence a composite cyme of rather dense primary cymes (clusters, 'glomeruli', note the scientific name), each cluster with 10—30 flowers on short pedicels. Main branches in the inflorescence with appressed hairs, secondary branches and pedicels glabrous.

FLOWER

Flowers radially symmetric, epigynous (perianth attached above the gynoecium) with an urn-shaped, glabrous hypanthium, with 4 short epicalyx bractlets and sepals, no petals, yellowish green. Sepals short and triangular, with a few apical hairs or glabrous. Stamens 4. Gynoecium of one carpel. Style basal, short, surrounded by a ring-formed discus.

FRUIT

Fruit a nut enclosed in the hypanthium.

REPRODUCTION

Asexual reproduction by seeds (agamospermy); local vegetative reproduction by fragmentation of rhizome. Seed production depends on pollination for development of the endosperm that furnishes nutrients for embryo development (a phenomenon named pseudogamy). The entire colony on Bjørnøya consists of two clones, at the same locality but being too far apart from each other to be due to vegetative growth alone. Hence, some seed reproduction must have taken place. Whether regular seed reproduction occurs is unknown but unlikely; the plants have been observed flowering, approaching fruit maturation, at the end of August.

Fruits have no special adaptation to dispersal, probably spread very locally by wind and animals.

COMPARISON

Alchemilla glomerulans differs from the introduced A. subcrenata (on Spitsbergen and Bjørnøya) in hairs on stems and petioles appressed, in dense flower clusters ('glomeruli'), and in leaves with a very sparse pubescence. Alchemilla subcrenata has stems and petioles with patent to retrorse hairs, more open flower clusters, and leaves more densely pubescens, on the upper surface with concentrations of hairs in the folds between leaf lobes.

HABITAT

Snowbed depressions with a meadow character. A herbarium labels says "at the bottom of a ravine, in herb meadow" (translated here from Norwegian). Very little else is known of the site where the species occurs.

DISTRIBUTION

Found in the middle arctic tundra zone and the weakly oceanic section. One stand with two clones is known on the northeast coast of Bjørnøya, close to the radio station at Tunheim, the site of the longest inhabitation on the island. The plant is, however, assumed native. See Engelskjøn & Schweitzer (1970).

COMMENTS

The genus Alchemilla is one of the larger agamospermous groups of Rosaceae with 400—500 reported species (or microspecies) in Europe (Kurtto et al. 2007). It is nearly confined to Europe and W Siberia (with some shrubby species or a related genus in the E African high mountains), but a few species transgress the Atlantic to Iceland and Greenland and 1—2 species to Jan Mayen and Bjørnøya. As all investigated European and North Atlantic species are agamospermous, only a single fruit is needed to start a new population. The source area of every Atlantic Alchemilla is Europe (there are no endemic species in Iceland, Greenland or the arctic islands). This vouches for a rather efficient dispersal across the sea. As no species of Alchemilla have fruits with any floating ability, this is an indirect support for the importance of bird dispersal.

LITERATURE

Engelskjøn, T. & Schweitzer, H.J. 1970. Studies on the flora of Bear Island (Bjørnøya). I. Vascular plants. – Astarte 3: 1–36.

Kurtto, A., Fröhner, S.E. & Lampinen, R. 2007. Atlas florae europaeae. Distribution of vascular plants in Europe. 14. Rosaceae (Alchemilla and Aphanes). – The Committee for Mapping the Flora of Europe and Societas Biologica Fennica Vanamo, Helsinki.