Flora of the Canadian Arctic Archipelago
English: Crowberry family,
Empetraceae, Crowberry family.
Vegetative morphology. Plants 5–10(–30) cm high; shrubs; dwarf shrubs, or low shrubs. Horizontal stems at ground level, branching extensively to shape plant habit as mats. Aerial stems prostrate, or ascending. Aerial stem trichomes spreading, or erect. Leaves distributed along the stems; alternate; persistent. Petioles absent (leaf blade attenuate). Leaf blades simple. Leaf blade bases attenuate. Blades 2–6 mm long, 0.5–1 mm wide, spreading or divaricate, linear, revolute (hollow), with inconspicuous veins. Blade adaxial surface glabrous or hairy, hairs glandular. Blade abaxial surface hairy. Blade margins entire, with non-glandular hairs (these overlapping along the revolute leaf margins making a still air pocket on the abaxial surface of the leaf); apices acute, or obtuse.
Reproductive morphology. Plants monoecious, or dioecious, or bisexual. Flowering stems with leaves (single flowers are on short shoots that arise laterally from the main axis and bear only scale leaves below the flower). Flowering stem glandular hairs present. Flowers solitary (in leaf axils). Bisexual spike(s) with empty bracts at the base. Flowers small; radially symmetrical (actinomorphic); unisexual (subsp. nigrum), or bisexual (subsp. hermaphroditum). Sepals conventional (as tepals); 3; free; 0.08–0.12 mm long; 0.2–0.3 mm wide (tiny); green (green at the base), or purple (towards the apex); petaloid. Calyx without sessile glands; glabrous. Petals conventional (as tepals); free; 3; purple; unlobed; 1–2 mm long. Stamens 2. Anthers ovoid (without appendages); 0.6–0.8 mm long. Nectaries absent. Ovary superior; carpels (2–)4–9; syncarpous. Ovaries sub-globose; glabrous. Styles variable, reflexed; partially fused. Placentation axile. Ovules per ovary 2–5. Fruit sessile; with calyx persisting; fleshy; a berry, or a drupe; spherical; black, or purple, or blue; 3–8 mm long; 3–8 mm wide; glabrous; surface appearing veinless; indehiscent. Seeds 2–9; 1.6–1.8 mm long; brown; surfaces verrucose.
General notes. The world monographer of Empetrum, Vassiljev (1961), accepted 18 species in the genus, whereas many other authors accept only two: the southern hemisphere red-fruited E. rubrum Vahl ex Willd. and the northern hemisphere black-, purplish, or very rarely red-fruited E. nigrum L. Seven of Vassiljev's species are reported by him from the Canadian Arctic Archipelago and surroundings (for publications, see the synonymy under the species below): the three purplish fruited species E. atropurpureum Fernald and Wiegand mainly from eastern North America north to Labrador, E. purpureum Raf. from Labrador, Ellesmere, and western Greenland, and E. eamesii Fernald and Wiegand from eastern North America north to Labrador; and four black-fruited species, E. nigrum L. s.s. from southern Labrador, E. hermaphroditum Lange ex Hagerup from a broadly amphi-Atlantic range including most of the Canadian Arctic Islands, E. subholarcticum V.N. Vassil. from a very broadly amphi-Beringian range including Alaska, Yukon, and northernmost Ungava, and E. arcticum V.N. Vassil. from an amphi-Beringian range but also including the Canadian Arctic Islands.
Later Russian authors have partly merged some of Vassiljev's species (i.e., E. arcticum and E. subholarcticum), partly reduced them to subspecies. Tzvelev (2001) recognised six subspecies within E. nigrum. Subspecies hermaphroditum is widely amphi-Atlantic, whereas a subsp. subholarcticum mainly replaces subsp. hermaphroditum from Polar Ural throughout Siberia and Far East to Northern Canada. Elven and other botanists find these very difficult to separate consistently and are very reluctant to accept several subspecific taxa.
In northeastern North America, D. Löve (1960) treated the eastern North American and arctic plants as different from the European E. nigrum s.s. She recognised E. eamesii Fernald and Wiegand (Rhodora 15: 215, 1913) with three subspecies: (i) the non-arctic subsp. eamesii, (ii) subsp. atropurpureum (Fernald and Wiegand) D. Löve, Rhodora 62: 289, 1960, and (iii) the circumpolar subsp. hermaphroditum. This approach is not reflected in Tzvelev's account. At species level E. eamesii (1913) has priority before E. hermaphroditum (1927).
In 2001, when Elven and Murray tried to apply Tzvelev's treatment to Alaskan material (ALA) where at least subsp. subholarcticum, subsp. arcticum, and possibly subsp. sibiricum should occur, according to Tzvelev's draft, a very significant group combined characters across the criteria given by Tzvelev. Elven and Murray concluded that there is probably significant taxonomic variation, but that the current treatment by Russian botanists is unsatisfactory and does not adequately fit the observed variation.
In Europe, the two taxa treated as subsp. nigrum and subsp. hermaphroditum in Flora Europaea, by Tutin, are often treated as separate species, largely because of their difference in chromosome number; but the correlation between number and reproductive pattern, though good, is not perfect (the latter being possibly susceptible to environmental influences), and the differences in vegetative characters show some overlap, shown by Mirré (2004).
In a recent combined molecular, ploidy (successful flow cytometry on herbarium material), and morphological study, Mirré (2004) set out to test the classification of Vassiljev, mainly based on samples from the Atlantic, Pacific-Beringian, and southern hemisphere ranges. She found a comparatively distinct group of diploids in Europe (E. nigrum s. str.) and two separate groups of diploids in the amphi-Pacific regions (one perhaps corresponding to E. sibiricum, the other possibly an unnamed western American group). She also found some separation between amphi-Beringian and amphi-Atlantic tetraploids (supporting a possible recognition of the entities 'hermaphroditum' and 'subholarcticum' at some level), but the structure found was not very robust. Each of the proposed tetraploid taxa may have multiple and complex origins from the diploids. Two other problems are that all the eastern Canadian plants (tetraploids from Quebec and Baffin) were unstable in all classifications (the Baffin plants often connected to Beringia), and that the entity named as 'hermaphroditum' may have at least two quite different origins, one in Europe north to Iceland and Jan Mayen, another in Greenland (type area), Svalbard, and arctic Russia. Her conclusion, which is supported by Elven (personal communication, 2005), is that it is premature to recognise taxa within the Empetrum nigrum aggregate. This also includes 'hermaphroditum'.
Illustrations. • Close-up of fruit. Mature blue Iqaluit blackberries with cylindrical leaves. The leaf margins almost meet and surround an internal air space. A leaf showing the underside is above the piece of fluff on the rock. Nunavut, Baffin Island, Iqaluit. Aiken 97–005.
This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.
Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.
Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa..