Dalea bicolor var. orcuttiana Barneby
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1977. Daleae Imagines, an illustrated revision of Errazurizia Philippi, Psorothamnus Rydberg, Marine Liebmann, and Dalea Lucanus emen. Barneby, including all species of Leguminosae tribe Amorpheae Borissova ever referred to Dalea. Mem. New York Bot. Gard. 27: 1-892.
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Family
Fabaceae
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Scientific Name
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Type
Holotypus, NY- isotypi, F, NY, UC, US . — Dalea seemanni sensu Wats., Proc. Amer. Acad. 22: 470, pro parte (Orcutt 1329, GH), exclus. typ.
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Synonyms
Dalea seemanni S.Watson, Parosela megalostachys Rose, Dalea macrostachya Ruiz ex Pav. & Moric.
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Description
Latin Diagnosis - Dalea bicolor Humb. & Bonpl. ex Willd. var. orcuttiana (Charles Russell Orcutt, 18641929) Barneby, var. nov., a var. bicolori imprimis spica conferta simul ac bracteis cum calycibus dense plumoso-pilosulis ciliatisque necnon patria peninsulari (nec continentali) abstans. — Baja California (Edo): Socorro, 14 Apr 1886, C. R. Orcutt.
Species Description - Erect or diffuse shrubs 3-12 dm tall; leaves 1-3.5 (4.5) cm long; leaflets 4-10 (11) pairs either softly gray-tomentulose or -pilosulous both sides or glabrous and green above and pilosulous to thinly puberulent beneath; spikes moderately dense to greatly congested and conelike, permanently ovoid or becoming cylindroid, without petals or androecia (8) 9-15 mm diam, the axis (1) 1.5-6 cm long; bracts densely pilose; calyx 4.3-5.6 (6.8) mm long, pilose or pilosulous with ascending-spreading hairs up to 0.5-1.2 mm long, the tube 2.3-3 (3.2) mm, the dorsal tooth 1.6-3 mm long (exceptionally up to 0.8 mm longer than tube, usually at least a trifle shorter); keel 6.8-9.1 (10) mm long, the blades (4.5) 5-6.2 (7) mm long, (2.5) 2.7-3.6 mm wide; n = 7 (Spellenberg, 1973). — Collections: 41 (o).
Distribution and Ecology - Desert washes, rocky crests, boulder-strewn hillsides and canyon-terraces, sometimes on cliff-ledges, near sea-level up to 1250 m (4170 ft), widely but interruptedly dispersed through Baja California in lat. 25°-31° N, from San Matias Pass at n. end of Sierra San Pedro Martir s. (sometimes with Idria) through the deserts and detached mountain ranges toward the Gulf side of the Peninsula the length of Sierra de la Giganta. — Flowering February to May and (especially s.-ward, following summer rains) August to October.
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Discussion
(Plate CI)
A small xerophytic, drought deciduous shrub of desert washes and canyons, with either gray or green foliage and many ovoid or oblong heads of handsome rose-purple flowers. It is the common fruticose true dalea of the middle peninsular region of Baja California, sympatric with several species of Marina but only one species of Dalea, the rare D. pur- pusii, very distinct by reason of its few leaflets and long feathery calyx-teeth. Two related congeners, D. brandegei and D. trochilina, endemic to the region of Magdalena Bay and the Cape mountains respectively, are in many respects similar but in practice set off by truly glabrous stems and foliage.
Variation in var. orcuttiana follows the same general course as in its continental counterpart, var. bicolor: leaves densely gray-pilosulous to green and glabrescent; leaflets variable in number, ± 4-10, rarely 11 pairs; spikes variable in length, diameter, and density; calyx-hairs variable in length; and relative proportion of calyx-tube and -teeth unstable. As in var. bicolor the variations are not all of random nature. The populations in Sierra de la Giganta, so well collected by Carter, have green, thinly pubescent foliage and (nearly always) numerous leaflets, in primary leaves usually 6-10, rarely only 5 pairs; northward the leaflets are usually gray-pubescent and mostly 4-6 pairs. An incipient racial differentiation can be demonstrated, but not as yet any substantial morphological discontinuity. In this green southern form, interpreted by Wiggins (1940, p. 53) as transitional to D. trochilina (q.v.), the spikes are moderately dense, mostly 1.5-6 cm long and (without petals) 10-12 mm diameter.
North from latitude 27° N consistently ashen foliage is associated with a great variability in density and diameter of the spikes, which may be exactly as in Sierra de la Giganta or contracted into a conelike head up to 13-15 mm diameter by only 1-3 cm long. The range of the densely spicate phase is discontinuous and lies entirely within that of the narrow-spiked form. It has been collected in San Pedro Martir (Providencia Canyon; Los Emes; Arroyo Agua Amarga), in Sierra San Borja (28° 43' N), and shortly south of the territorial boundary at San Pablo (Purpus 99, ARIZ, UC, US). The typus of Dalea megalostachya, from San Esteban (27° 20' N, ± 50 km w. of San Ignacio; cf. Moran, 1952, p. 254) is thought to be no more than an extreme form in which the calyx, corolla, and androecium simultaneously attain a size approached but not really matched elsewhere in var. orcuttiana as now known. Wiggins (1940) has treated D. megalostachya as a narrow endemic known only from the vicinity of the type-station, but in light of the many collections made recently in the central peninsula by Moran and others this interpretation seems hardly tenable. If D. megalostachya indeed deserves taxonomic recognition and the same standards were applied to continental populations of D. bicolor, there would be no visible end to the segregation of individual populations unique in some particular combination of qualities. However, since the typus of D. megalostachya does transcend expected limits of variability and may, after all, represent a genetically differentiated form of some stature, its name is best preserved in abeyance for it alone, and not stretched to cover all of its common relatives on the peninsula, which have passed as D. seemanni Wats. I here exercise the privilege of applying to D. seemani auct. (= Parosela seemani sensu Rydb., 1920, p. 88, pro parte, as to the Baja Californian element) a new varietal epithet, reserving in case of need for the form with conelike spikes of large flowers the formula D. bicolor var. orcuttiana fma. megalostachya (Brandg.) Barneby, stat. nov.
The existence of a concept equivalent to the original D. seemani, based on a mixture of var. bicolor from Durango and var. orcuttiana from San Pedro Martir, and its subsequent acceptance by Rydberg, speak eloquently of the close essential similarity between these peninsular and continental expressions of their species. Indeed they seem to differ in no one firmly reliable morphological character but rather in a combination of several which tend together to exceed in a given direction the extreme recorded for the other. In habit, foliage, and pubescence the two are fully confluent. The coincidence of relatively dense spikes, densely villous calyces, and relatively long calyx-teeth, fortified by a disjunct range at desert elevations, nevertheless points to a biological parting of the ways in time and in adaptation.
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Objects
Representative: Baja California (Edo): Harbison 21,816 (SD); Wiggins 5257 (F, NY, UC, US); Raven et al. 12,487 (GH, UC), 12,646 (GH); J. H. Thomas 7983 (NY); Moran 9656 (SD, NY), 11,424 (SD), 7975 (NY, SD), 7889 (NY, SD). Baja California (Terr. Sur): Moran 11,587 (SD); Gentry 4162 (ARIZ); Carter & Moran 5351 (NY); Carter 4396, 4807, 4891, 5033 (all NY, UC).
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Distribution
Baja California Mexico North America| Mexico North America|