Vicia has 12 species in Mexico; 4 of the 12 are introduced. Two new names are proposed: Vicia mullerana B.L. Turner, nom. & stat. nov., (based on V. americana subsp. mexicana C.R. Gunn, non V. mexicana Hemsl.), and V. ludoviciana var. occidentalis (Shinners) B.L. Turner, based on V. occidentalis Shinners, comb. nov. Vicia pulchella Kunth subsp. mexicana (Hemsley) C.R. Gunn is better treated as V. sessei G. Don, the earliest name at the specific level. A key to the taxa is provided along with comments upon species relationships, and maps showing distributions.
Vicia, with about 140 species, is widely distributed in temperate regions of both hemispheres (Kupicha, 1982). Some of the species are important silage, pasture, and green-manure legumes. Introduced species such as V. faba, V. hirsuta, V. villosa, and V. sativa are grown as winter annuals in Mexico, but are rarely collected. Gunn (1979) provided an exceptional treatment of the Mexican taxa, nearly all of which were illustrated by full-page line sketches. As treated by Gunn, eight species are native to Mexico and four are introduced. I largely follow Gunn's treatment, but a few of his subspecies have been elevated to specific rank, or else treated as varieties.
Key to the Species of Vicia in Mexico (largely adapted from Gunn, 1979)
1. Stipules bearing dark splotches(2)
1. Stipules lacking dark splotches(3)
2. Tendrils absent; plants erect, black after drying2. V. faba
2. Tendrils present; plants vine-like, green after drying10. V. sativa
3. Style glabrous or glabrate; corollas 3–5 mm long4. V. hirsuta
3. Style hairy; corollas mostly 6 mm long or more(4)
4. Hairs on style not all similar and circling the shaft(5)
4. Hairs on style all similar and circling the shaft(8)
5. Stylar hairs medial; racemes 1–2-flowered6. V. leucophaea
5. Stylar hairs apical; racemes 2–4-flowered(6)
6. Annuals; racemes 1–5 flowered7. V. ludoviciana
6. Perennials; racemes 2–26 flowered(7)
7. Corolla 6–10 mm long9. V. pulchella
7. Corolla 11–18 mm long11. V. sessei
8. Banner 10 mm long or less(9)
8(4). Banner 11 mm long or more(10)
9. Style branches not tufted apically, hairs relatively short; not Baja California3. V. hassei
9. Style branches tufted apically, hairs relatively long; Baja California5. V. humilis
10(8). Calyx gibbous at base; racemes mostly 10–14-flowered12. V. villosa
10. Calyx not basally gibbous; racemes mostly 3–10-flowered(11)
11. Calyx tube 4–6 mm1. V. americana
11. Calyx tube 2–3 mm long8. V. mullerana
1. Vicia americana Muhl. ex Willd., Sp. Pl. 3: 1096. 1802. Fig. 1.
As treated by Gunn (1979), Vicia americana is highly variable and largely confined to the USA. He recognized within its fabric populations from north-central Mexico that he called V. a. subsp. mexicana C.R. Gunn, typified by plants collected from near Monterrey, Nuevo Leon, Mexico and known by other populations from that general area (Fig. 1).
Gunn distinguished Vicia americana subsp. mexicana from V. a. subsp. americana by characters of the calyx, the teeth unequal in the latter, more or less equal in the former. A better calyx character is size, as emphasized in the above key; V. m. subsp. mexicana also possesses fewer flowers per raceme and smaller flowers and appears to possess a syndrome of characteristics that appear confined to north-central Mexico. For V. a. subsp. americana, Gunn noted that “In Texas, V. a. subsp. americana occurs no further south than the Panhandle” and added that populations of V. a. subsp. americana (said to be typified by Oaxacan material but I have never seen a specimen collected from Oaxaca) are to be found in central Mexico, these thought to be relics “of what once was a larger population in Mexico.” I agree with this assertion, but believe that his V. a. subsp. mexicana, which is known from north-central Mexico, evolved independently and is worthy of specific status, possessing a combination of singular characteristics and restricted geography and showing little evidence of intergradation with V. a. subsp. americana. The newly discerned entity is described below as V. mullerana.
2. Vicia faba L., Sp. Pl. 737. 1753. Fig. 2.
Relatively few collections of Vicia faba, a widely cultivated species, have been made in Mexico. Gunn provided an excellent account of the species. Most of the dots on my Fig. 2 are taken from specimens cited (but not mapped) by him.
3. Vicia hassei S. Wats., Proc. Amer. Acad. Arts 25: 129. 1890. Fig. 1.
This species is known from Mexico only by collections from northern Baja California and off-shore islands. It superficially resembles V. ludoviciana but is readily distinguished by its stylar hairs that are of unequal lengths rather that of equal lengths (Lassetter 1975, Gunn 1979).
In Gunn's key to species, in which Vicia hassei is separated from V. humilis (key couplet 9, there appears to be an error of repetition as regards style and calyx characters, an unusual slip for Mr. Gunn, his work mostly error free.
4. Vicia hirsuta (L.) Gray, Nat. Arr. Brit. Pl. 2: 614. 1821. Fig. 2.
This cultivated species is identified by its peculiar stylar hairs (only a few scattered cilia at the apex) and relatively small, hairy pods. Gunn cites three collections from Mexico, mapping only one of these; the sole square on my Fig. 2 is that of a Hinton collection from Temascaltepec, Mexico State.
5. Vicia humilis Kunth, Nov. Gen. Sp. Pl. 6: 498. 1824. Fig. 3.
As noted by Gunn, this is a commonly encountered native species of Mexico as shown in Fig. 3. Note my comments under Vicia hassei re keying errors.
6. Vicia leucophaea Greene, Bot. Gaz. 6: 217. 1881. Fig. 3.
This relatively rare species is known by collections from northwestern Mexico and adjacent USA. It is identified by its unique stylar pubescence and inflorescences with 1–2 flowers.
7. Vicia ludoviciana Nutt. ex Torrey & A. Gray, Fl. N. Amer. 1: 271. 1838. Fig. 2.
Isely (1998) provided an overview of variation in Vicia ludoviciana, recognizing two broadly delimited regional taxa, both occurring in Texas, only one extending into Mexico.
The type of this relatively widespread variable species was, according to the description of the species, collected by Leavenworth from “grassy places on the Red River in Texas” in the early 1800s. Shinners (1948) provided an excellent overview of the complex, noting that it is seemingly composed of an eastern assemblage of populations, which he referred to as Vicia ludoviciana var. ludoviciana (I include in this V. l. var. laxiflora Shinners and V. l. var. texana [Torrey & A. Gray] Shinners, both typified by plants from eastern Texas), and western assemblage of populations, which he referred to as V. leavenworthii var. occidentalis Shinners. The distribution in Texas of these two regional complexes, which I recognize as intergrading in Texas, but not in Mexico, is shown in Fig. 2 (taken from Turner et al. 2003).
Broich (2007) took up the name Vicia ludoviciana var. leavenworthii (type from Arkansas) for the western assemblage. In my opinion it is better named Vicia ludoviciana var. occidentalis (Shinners) B.L. Turner, comb. nov. based upon Vicia leavenworthii var. occidentalis Shinners, Field & Lab. 16: 22. 1948 (holotype: Muller s. n., Chisos Mts, 29 Jul 1932, SMU; isotypes MO, NY).
Gunn (1979) treated the two regional groupings as subspecies, with the Mexican material as part of his Vicia ludoviciana subsp. ludoviciana (T. & G.) Lassetter & Gunn (Lasseter 1984, cf. Turner and Nesom 2000 for additional discussion). Mexican material of this taxon is more appropriately labeled Vicia ludoviciana var. occidentalis (see above). The following key gives the major differences between the varieties.
Key to the varieties of Vicia ludoviciana
Leaflets of mid-stem leaves 1–3 mm wide, length 5–10 times width; racemes usually shorter than subtending leaves, mostly 1–3(4)-flowered; central and western USAvar. occidentalis
Leaflets of mid-stem leaves (2)-3–5 mm wide, length 4–6 times width; racemes mostly longer than subtending leaves, 4 or more flowered; eastern USAvar. ludoviciana
8. Vicia mullerana B.L. Turner, nom. & stat. nov. Fig. 4.
Based on Vicia americana Muhl. Ex Willd. subsp. mexicana C.R. Gunn, USDA Tech. Bull. 1601: 25. 1979, non Vicia mexicana Hemsl. Type: Mexico. Nuevo Leon, Puerta, Jul 1933, C.H. Muller and M.T. Muller 510 (Holotype: MEXU; Isotypes: F, TEX).
Perennial herbs, 10–60 cm high. Stems glabrous. Leaves (tendrils excluded) 2–6 cm long; leaflets (2-)4–9, linear-lanceolate to ovate, entire, mostly 15–30 mm long, 2–8 mm wide. Stipules lanceolate to irregularly deltate, 3–5 mm long, lacking dark splotches. Peduncles 2–6 cm long, 1–4-flowered. Pedicels ca. 2 mm long. Corollas 8–10 mm long, the banners 6–9 mm long. Calyces sparsely hairy, 4–6 mm long, not gibbous; tubes 2–3 mm long; lobes 1–3 mm long. Style apex tufted, length of lower hairs 2–3 times the upper. Legumes glabrous, 25–30 mm long, 6–7 mm wide.
Vicia mullerana consistently differs from V. americana in having fewer, smaller flowers with smaller calyces. It is discussed in more detail under V. americana, above. According to label data, the plants occur in pine-oak forests, from 1400 to ca. 3000 m; flowering: Apr-Aug.
Vicia mullerana is named for Prof. Cornelius Herman (Neil) Muller and his wife, M.T. Muller (nee M. E. Taylor) who collected the type material.
9. Vicia pulchella Kunth, Nov. Gen. Sp. Pl. 6: 499. 1824. Fig. 5.
According to Gunn (1979), Vicia pulchella is the most common and widespread native Mexican vetch, and it is one of two vetches endemic to Central America. He recognized within this complex two sympatric infraspecific taxa, Vicia pulchella subsp. pulchella and V. p. subsp. mexicana [ = M. sessei], these largely delimited by corolla length. Gunn stated, “Of the approximately 250 specimens of the subspecies pulchella and mexicana collected in Mexico and Guatemala, only three have an intermediate flower length.” I agree with Gunn's assessment. I, too, found no evidence of intergradation between the two taxa, at least among the sheets from Mexico that I examined at LL-TEX.
Because Vicia pulchella and V. sessei are sympatric, showing little evidence to form natural hybrids, they appear worthy of specific rank, as treated herein.
10. Vicia sativa L., Sp. Pl. 736. 1753. Fig. 4.
This is a widespread, cultivated species, native to Europe, having a long list of synonyms. It is reportedly represented by five or more infraspecific taxa, as well noted by Gunn (1979), who provided a key to at least six of the described subspecies. In Mexico, I have treated the complex as a single species without infraspecific taxa, as indicated in Fig. 4.
11. Vicia sessei G. Don, Gen. Hist. 2: 318. 1832. Fig. 6.
Vicia mexicana Hemsl.
Vicia pulchella subsp. mexicana (Hemsl.) C.R. Gunn
Reasons for the treatment of this taxon at specific rank are given under Vicia pulchella above. The correct name at the specific level is Vicia sessei G. Don, typified by Sesse & Mocino 3636, from Mexico.
12. Vicia villosa Roth, Tent. Fl. Germ. 2: 182. 1793. Fig. 1.
This is a cultivated species, native to Europe and widely distributed elsewhere. Gunn (1979) was only familiar with collections from Guatemala; more recent collections (LL-TEX) have been obtained from Mexico in or near cultivated fields in southern Coahuila and adjacent Nuevo Leon.
I am grateful to my editorial assistant, Jana Kos, for reading the manuscript and helpful suggestions. John Strother provided many editorial and content suggestions that greatly improved the paper. Guy Nesom provided conversational input re typification of Vicia mexicana. My colleagues, Tom Wendt and Bob Harms provided computer assistance. Distribution maps are based on specimens housed at LL-TEX, and those cited by Gunn (1979). MA, at my request, provided a photograph of the holotype of V. sessei, for which I am grateful. Marianna Grenadier produced the final versions of the maps.