Flora of North America species comparison

Subspecies 6 (5 in the flora).

Pedicularis sudetica is a difficult complex. Hultén employed the degree of lobing on subtending floral bracts, length of corolla tubes, and inflorescence vestiture in recognizing eight infraspecific taxa. U. Molau and D. F. Murray (1996) emphasized presence or absence of spots on the abaxial lip, inflorescence vestiture, length of petioles and calyx, and ecological features to define four species, subsuming several of Hultén’s other subspecific taxa into these species. According to Molau and Murray, P. sudetica in the narrow sense is a morphologically distinct, disjunct taxon endemic to the Sudeten Mountains of central Europe, but part of the broader circumscription by Hultén (1961, 1964), which is treated here as the sixth subspecies.

U. Molau and D. F. Murray (1996) did not include subsp. scopulorum in their analysis, noting only that teeth are virtually absent on the galea of Pedicularis scopulorum. Presence or absence of apical teeth on the margins of the galea often distinguishes species in other Pedicularis taxa. Because teeth are sometimes present in this taxon, it is treated here as one of the five North American subspecies in the broad sense of P. sudetica. A recent molecular study confirms its close relationship to other members of the complex (B. W. Robart et al. 2015).

When comparing the two alternative taxonomies, the treatment by U. Molau and D. F. Murray (1996) is easier to apply. Close inspection of specimens identified as these species often reveals combinations of traits attributable to more than one taxon; Molau and Murray reported finding hybridization common between Pedicularis albolabiata and P. arctoeuropaea, and P. albolabiata and P. pacifica where habitats overlap, indicating that reproductive isolation is not complete. Recognition of these taxa as varieties may be more appropriate considering the broad geographic overlap where the few distinguishing features tend to intergrade. They are treated here, however, as subspecies. The following key is modified from Molau and Murray.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera ca. 100, species ca. 2000 (27 genera, 292 species in the flora).

Orobanchaceae are now defined to include both the holoparasitic members traditionally included in the family (A. Cronquist 1981) and the hemiparasitic genera formerly included in Scrophulariaceae. Although multiple research groups focus on members of the Orobanchaceae, a widely accepted infrafamilial classification of the family in the sense of Angiosperm Phylogeny Group (2016) has not yet appeared.

The classification by J. R. McNeal et al. (2013), who found that Orobanchaceae comprise six clades, is followed herein (their named clades are roughly equivalent to tribes). The autotrophic Lindenbergia Lehmann (12 species in the Old World) corresponds to the basal clade sister to the rest of the clades. Species in our region are distributed among the remaining five clades: Cymbarieae D. Don (genus 1), Orobancheae Lamarck & de Candolle (genera 2–6), Rhinantheae Lamarck & de Candolle (genera 7–12), Buchnereae Bentham (genera 13 and 14), and Pedicularideae Duby (genera 15–27). Within the family, genera are arranged alphabetically within tribes, or within Pedicularideae, in subgroups within the tribe.

Parasitic plants attach to their hosts via haustoria (L. J. Irving and D. D. Cameron 2009). Haustoria are produced by both hemiparasitic and holoparasitic Orobanchaceae (E. Fischer 2004). In hemiparasitic taxa, haustoria usually tap their host’s xylem, mostly taking up water, mineral nutrients, and nitrogen from their host, and sometimes also carbon. Holoparasitic taxa derive all of their growth requirements predominantly from the host’s phloem (Irving and Cameron).

Parasitism has evolved once in the family (N. D. Young et al. 1999; J. R. McNeal et al. 2013); holoparasitism has arisen independently three times from the hemiparasitic condition (J. R. Bennett and S. Mathews 2006; McNeal et al.).

Some Orobanchaceae are serious pests, primarily on legume and grain crops in warmer and drier areas, especially in sub-Saharan Africa. Striga is a particularly serious pest that parasitizes mostly monocots; S. gesnerioides attacks eudicots (K. I. Mohamed et al. 2006). Orobanche parasitizes eudicot crops primarily in temperate parts of the world (E. S. Teryokhin 1997). All Striga species and non-native species of Orobanche in the flora area are listed on the Federal Noxious Weed List (http://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/weedlist.pdf) in the United States.

(Discussion copyrighted by Flora of North America; reprinted with permission.)