Dactylorhiza

Herbs, perennial, terrestrial, rather succulent, glabrous. Roots from base of stem fascicled tuberoids, usually palmately divided with 2–5 lobes, fleshy. Stems leafy. Leaves several, ascending to recurved, not enfolded around spike, with or without purplish spots; base sheathing in proximal leaves, distal leaves bractlike, not sheathing. Inflorescences terminal, spikes; floral bracts foliaceous, prominent. Flowers few to many, resupinate; dorsal sepal, sometimes lateral sepals, and petals connivent, forming hood distal to lip; petals ± obliquely dilated basally; lip 3-lobed, base spurred, margins occasionally entire, nectarless; pollinaria 2, each with 1 pollen mass; viscidia within single 2-lobed bursicle; stigma reniform or obcordate, concave with median ridge, hidden behind bursicle. Fruits capsules, ascending, ellipsoid.

Distribution

Alaska, Canada, mostly Eurasian.

Discussion

Species ca. 75 (2 in the flora).

Dactylorhiza is a taxonomically complex genus in which closely related species have been combined into species aggregates (P. Vermeulen 1947; R. M. Bateman et al. 1997). Recognition of the aggregate taxa alone reduces the number of species by more than half. Recent research synthesizing morphometric and allozyme data to circumscribe species (R. M. Bateman and I. Denholm 1983, 1985, 1989; M. Hédren 1996), and DNA sequences and chromosome studies to determine the relationships of those species (R. M. Bateman et al. 1997; A. M. Pridgeon et al. 1997), is shedding much light on the evolution of the genus. The diploid lineage (2n = 40) appears to have evolved in Asia, migrating and speciating to both the west and northeast. Several alloploidy events (hybridization followed by chromosome doubling) occurred recently in Europe, apparently between the distinct diploids D. fuchsii and D. incarnata. That generated a highly complex suite of poorly distinguishable “prospecies” of 2n = 80, treated as a single species by some authorities and as many species by others (L. V. Averyanov 1990). Of the two North American species, D. aristata is a native diploid originating during the northeasterly migration, and D. majalis is an allotetraploid that originated in Europe and presumably is naturalized in North America (H. J. Clase and S. J. Meades 1996).

Despite an extensive literature, much taxonomic work still remains to be done.

Selected References

Averyanov, L. V. 1990. A review of the genus Dactylorhiza. In: J. Arditti, ed. 1977+. Orchid Biology: Reviews and Perspectives. 7+ vols. Ithaca, N.Y. and New York. Vol. 5, pp. 159–206.

Bateman, R. M. and I. Denholm. 1983. A reappraisal of the British and Irish dactylorchids: 1. The tetraploid marsh orchids. Watsonia 14: 347–376.

Bateman, R. M. and I. Denholm. 1985. A reappraisal of the British and Irish dactylorchids: 2. The diploid marsh orchids. Watsonia 15: 321–355.

Bateman, R. M. and I. Denholm. 1989. A reappraisal of the British and Irish dactylorchids: 3. The spotted orchids. Watsonia 17: 319–349.

Bateman, R. M., A. M. Pridgeon, and M. W. Chase. 1997. Phylogenetics of subtribe Orchidinae (Orchidoideae, Orchidaceae) based on nuclear ITS sequences: 2. Infrageneric relationships and taxonomic revision to achieve monophyly of Orchis sensu stricto. Lindleyana 12: 113–141.

Hédren, M. 1996. Genetic differentiation, polyploidization and hybridization in northern European Dactylorhiza (Orchidaceae): Evidence from allozyme markers. Pl. Syst. Evol. 201: 31–55.

Pridgeon, A. M. et al. 1997. Phylogenetics of subtribe Orchidinae (Orchidoideae, Orchidaceae) based on nuclear ITS sequences: 1. Intergeneric relationships and polyphyly of Orchis sensu lato. Lindleyana 12: 89–109.

Stace, C. A. 1991. New Flora of the British Isles. Cambridge and New York. Pp. 1166–1173.

Tyteca, D. and J.-L. Gathoye. 1993. On the morphological variability of Dactylorhiza praetermissa (Druce) Soó (Orchidaceae). Belg. J. Bot. 126: 81–99.

Vermeulen, P. 1947. Studies on Dactylorchids. Utrecht.

Lower Taxa

Dactylorhiza aristata, Dactylorhiza majalis

Key

1	Sepals and petals awned; lip often magenta- to red-spotted.	Dactylorhiza aristata
1	Sepals and petals obtuse, hoodlike, or acute, not awned; lip with red-violet loops (continuous or discontinuous), dashes, and spots.	Dactylorhiza majalis