Dalea bicolor Humb. & Bonpl. ex Willd. var. bicolor
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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
"Habitat in America meridionali. Dalea bicolor de Humb. & Bonpland." - No typus seen, but a spm is to be sought in herb. Willd., B.-D. bicolor sensu Bonpl., PI. Rar. Malm. 142, tab. 58. 1819, the locality there corrected to Mexico. — Parosela bicolor (H.
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Synonyms
Parosela bicolor (Humb. & Bonpl. ex Willd.) Rydb., Dalea tuberculata Lag., Parosela tuberculata (Lag.) Rose, Dalea thymoides Cham. & Schltdl., Dalea laevigata A.Gray, Dalea verrucosa G.Don, Dalea comosa Schltdl., Dalea ehrenbergii Schltdl., Dalea seemanni S.Watson, Parosela seemanni (S.Watson) Rose, Parosela tuberculina Rydb., Dalea tuberculina (Rydb.) F.J.Herm., Parosela longeracemosa Brandegee
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Description
Species Description - Fruticose when adult, becoming commonly a rounded many-stemmed bush 5-12 dm tall, but in barren or exposed sites sometimes diffuse or prostrate, in shade or in competing brush becoming a shrub with few slender crooked trunks irregularly branching distally, up to 2, exceptionally subarborescent and up to 3.5 m tall; leaves (0.7) 1-2.5 (3) cm long; leaflets (2) 3-6 rarely 4-9 pairs, 2-7 (8) mm long, varying from thinly pilosulous to glabrous above, green, greenish, or ashen; spikes usually elongating and loose from early anthesis, the flowers (pressed) either contiguous or separated by spaces over twice the width of a calyx, without petals or androecia 6-9 mm diam, the villosulous axis becoming (1) 1.5-23 cm long; bracts 1.5-3 (4) mm long; calyx (3.2) 3.4-5.2 mm, the loosely villous-pilosulous, subappressed-silky, rarely almost (quite) glabrous tube (2.1) 2.3-3.2 mm, the dorsal tooth 1-1.9 (2.2) mm long; epistemonous petals usually bright rose-purple, sometimes violet or vivid blue, sometimes pale rose-purple, the keel-blades 4.6-7 mm long; n = 14 (Spellenberg, 1973); 2n = 7 II, 28 (Mosquin). — Collections: 154 (xvii).
Distribution and Ecology - Stony hillsides, bouldery draws and dry washes, benches in barrancas, sometimes on rock-ledges, commonly in open places but s.-ward and on the Gulf slope entering thin oak woodland or drought-deciduous brush and thorn-scrub, sometimes colonial in hedges and at edge of fields, (500) 600-2700 m (mostly 2000-9000 ft), widespread, common, and often locally abundant from the margins of the Chihuahuan Desert in centr. Chihuahua and w.-centr. Coahuila s. over the Meseta Central to the middle Neovolcanic ranges from the basin of Lago Chapala, Jalisco e. to the w. foothills of Cofre de Perote and Orizaba in Puebla and adjoining Veracruz, extending s. to the edge of the Balsas Depression in Morelos, s.-e. Mexico and adjoining Michoacan, and s. from Puebla interruptedly through the upper Papaloapan drainage and foothills of Mixteca Alta into centr. Oaxaca; apparently disjunct on summit of Sierra de Tamaulipas, Tamaulipas; in centr. Coahuila and along n. Sierra Madre in Nuevo Leon intergrading with var. argyrea, in s. Puebla and Oaxaca with vars. canescens and naviculifolia. — Flowering June to January, most abundantly and dependably from August to November.
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Discussion
(Plate XCIX)
The var. bicolor is the commonest purple-flowered shrubby dalea of the Mexican Plateau, characterized by the combination of warty stems, relatively few (usually only 3-6) pairs of leaflets, and narrow spikes of short-toothed calyces subtended by long-persistent bracts. The variety is composed of a mosaic of local races that differ in amount and orientation of pubescence, in density and length of spikes, in exact number (and to some degree shape) of leaflets, and in color of the epistemonous petals, which vary from pale rose-purple through vivid phlox-purple to violet or (less often) cobalt blue. To the field observer, however, these variable features are quite overshadowed by the extraordinary plasticity of habit and stature. On the Central Plateau north of the Bajio, the average adult plant of var. bicolor forms a rounded, more or less erect, many-stemmed bush up to about a meter tall, but the potential stature is not achieved in exposed places; on the other hand even in desert Coahuila plants twice that height are found in sheltered hollows of canyon washes. In the more benign climate of the Neovolcanic mountains a stature of two meters is normal, the plants there forming thin erect shrubs consisting of a few crooked leafless trunks bearing aloft a bushy head. In eastern San Luis Potosi, where var. bicolor descends into the edge of the relatively moist oak woods of the Gulf slope, it is possible to stand in the shadow of arborescent specimens and reach or even jump for the lowest flowers. By contrast on the thin pumice soils at the foot of Cofre de Perote and Orizaba in eastern Puebla and adjoining Veracruz var. bicolor is represented by a lowly depressed or humifuse ecotype, described long ago as D. thymoid.es Schlechtd., of which the most vigorous individual rises no more than one or two decimeters from the ground.
Field experience suggests that the extent to which habital differences are inherited and imposed on the individual by environment varies from one population to another. Possibly, therefore, within comprehensive var. bicolor there may lie concealed by random variation elsewhere in the complex some genetically stabilized entities. But when a summit branchlet taken from a tall shrub in Michoacan is (in the herbarium) indistinguishable from the whole stem, cut at the root, of some northern xerophytic bushlet, taxonomic discrimination founders. The discovery by Mosquin of tetraploid var. bicolor in Aguas Calientes and Zacatecas indicates genetic ferment within the species, but unfortunately it seems impossible to distinguish by means of exterior morphology between known diploid and known tetraploid specimens.
Notable variations other than those involving habit and stature and largely independent of either are expressed in length of spike, leaflet number, and pubescence of the calyx. The extreme conditions of the spike are on one hand a subcapitate to shortly oblong cluster of 7-20 flowers with calyces subcontiguous, on the other a series of 50 or more flowers strung out, distant each from the next by its own wideth or more, along a flexuous axis up to two decimeters long. In the arid climate of the Central Plateau the leaflets are commonly 3-6 pairs in primary cauline leaves, but these rise (inconsistently) to 5-9 pairs in Michoacan and southeast Mexico. In the barrancas high on the Gulf slope in Hidalgo, and sporadically elsewhere, the calyces become densely villous with longer hairs, the minor variant recognized by Rydberg (1920, p. 88) as Parosela seemanni.
Along the eastern edge of its range var. bicolor passes successively into the next three varieties, only the last of which is at all strongly characterized. The dominant race in western Coahuila and adjoining central Chihuahua is at once densely and loosely pubescent with ordinarily short spikes (as in var. argyrea) but villosulous calyces. A prostrate or diffuse variant of this more commonly bushy and erect variant, similar to the diffuse states already noted from further south, was annotated by I. M. Johnston (see especially Stewart 52,515 etc., GH) as a species nova, but lacks convincing differential characters.
The var. bicolor is sympatric over parts of its range with several more or less closely related species and seems to give rise occasionally to fertile hybrids. Near Zimapan, Hidalgo, colonies of D. dorycnioides, there extremely abundant on arid limestone, interfinger along water-courses through the hills with thin stands of D. bicolor, and seemingly intermediate individuals are found between them (Ripley & Barneby 13,618, NY). In municipio Jacala, Hidalgo, a plant combining the growth-habit and narrow panicle of spikes characteristic of D. tomentosa with the relatively large bicolored flower of D. bicolor (Moore 5030, BM, GH, MEXU, UC) suggests another interspecific cross.
On the headwaters of Rio Conchos in southern Chihuahua a form of var. bicolor is recorded as furnishing "significant animal food" (Pennington 349, TEX) with a vernacular name carnero.
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Objects
Representative: Tamaulipas: Martinez & Borja F-1916 (TEX). Chihuahua: Pringle 301 (BR, F, GH, NY, US); Ripley & Barneby 13,914 (NY). Coahuila: Palmer 162 (C, F, NY, UC, US); Pringle 2400 (BR, F, M, NY, UC, US, W, Z); Ripley & Barneby 13,275 (CAS, MEXU, NY, US). Nuevo Leon: M. Taylor 229 (F, UC, TEX); Lucas 103 (F); Ripley & Barneby 13,295 (NY). Durango: Palmer 516 (F, GH, NY, UC, US); Gentry 6885 (NY), 6895 (ARIZ); Mosquin 6887 (NY, diploid). Zacatecas: Pringle 1755 (BR, F, M, SD, UC, W); Gentry 6890 (NY); Mosquin 6855, 6856, 6857 (flowers pink, white, purple respectively, all tetraploid, NY). Aguas Calientes: Hartweg 64 (K, NY, W); Mosquin 6858 (NY, tetraploid). San Luis Potosi: Ripley & Barneby 13,770 (CAS, NY), 14,761 (CAS, MEXU, NY, US); Parry & Palmer 156, 158 (BR, F, NY). Guanajuato: Kenoyer 1780 (GH); Sohns 495 (UC). Queretaro: Rose, Painter & Rose 9512, 11,162 (NY, US). Hidalgo: Matuda 4397 (NY), 19,625 (US); Gilly 69 (F, NY); Ripley & Barneby 13,630 (CAS, NY). Jalisco: Shreve. 9295 (ARIZ, UC). MichoacAn: Ripley & Barneby 13,402 (CAS, MEXU, NY), 13,436 (CAS, MEXU, NY), 14,804 (CAS, NY); Hinton 13,397 (F, NY, US); Arsene 5825 (F, GH, L, NY). Mexico: Pringle 9742 (F, NY, L, Z); Hinton 2327 (GH, NY, UC, US); Ripley & Barneby 14,354 (CAS, NY, US). Distrito Federal: Bilimek 124 (BR, C, NY, UC); Orcutt 4353 (F, GH). Morelos: Paray 1294 (ENCB). Puebla: Balls 5529 (GH, K, UC, US); Pittier 409 (US). Veracruz: typus of D. thy mi folia. Oaxaca: E. W. Nelson 1646 (NY); Seler 1522 (US); Ripley & Barneby 13,671 (NY), 14,670 (CAS, MEXU, NY, UC, US).
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Distribution
Tamaulipas Mexico North America| Chihuahua Mexico North America| Coahuila Mexico North America| Nuevo León Mexico North America| Durango Mexico North America| Zacatecas Mexico North America| San Luis Potosí Mexico North America| Guanajuato Mexico North America| Querétaro Mexico North America| Hidalgo Mexico North America| Jalisco Mexico North America| Michoacán Mexico North America| México Mexico North America| Distrito Federal Mexico North America| Morelos Mexico North America| Puebla Mexico North America| Veracruz Mexico North America| Oaxaca Mexico North America| Mexico North America|