Viola viarum Pollard
Common names:
Limestone Riverbank Violet, Wayside Violet
Synonyms:
Viola viarum Pollard, in Britton, Man. fl. n. states, ed. 1: 635. 1901. TYPE: USA, Missouri: St. Louis, along railroads in dry soil, 15 Jul 1899, J. B. S. Norton 32 (LECTOTYPE (designated by Ballard et al. 2020. Journal of the Botanical Research Institute of Texas 14(2): 227-228): PH (PH00029301, internet image!); ISOLECTOTYPES: MO, NDG (NDG33192, internet image!), NEB (NEB-V-0000594, internet image!), OS (OS0000376, internet image!), RM (RM0004526, internet image!), RM (RM0004527, internet image!), and RSA (RSA0006465, internet image!).
Description:
Acaulescent rosulate perennials from thick rhizome, ≤ 30 cm tall; foliage and peduncles green, lower surface of leaf blades sometimes slightly paler than upper, plant glabrous throughout; stipules free, irregularly glandular-fimbriate; heterophyllous, leaves erect or ascending, largest leaf blades longer than broad to as broad as long, moderately to deeply pedately divided into (3)5–7(9) lobes, undivided terminal primary division distinctly broader than any lobes present on the lateral primary divisions and not distinctly narrowed at its base, the lateral lobes (if present) less than 1/2 the length of the terminal primary division, ≤ 90 × 85 mm, outline during chasmogamous flower ovate-triangular to narrowly ovate, in fruit commonly becoming broadly ovate or deltate-triangular, base truncate to shallowly cordate, margins subentire or low-serrate (rarely pronouncedly serrate), eciliate, apex acute to obtuse; chasmogamous peduncle held just above the leaves; chasmogamous flower ≤ 22 mm; calyx glabrous, eciliate; lowest sepals linear-lanceolate to lanceolate, acuminate; auricles somewhat prominent, quadrate and erose, weakly elongating to 2(3) mm in fruit; corolla blue to purple, throat white; spur short-globose; lateral petals densely bearded with slightly clavate hairs, spurred petal sparsely bearded; chasmogamous capsule green; cleistogamous flowers produced after chasmogamous, peduncle ascending to erect, equalling or surpassing shorter petioles; cleistogamous capsule 7–14 mm, green drying tan with fine red or purple spots, glabrous; seeds 1.5–2.1 × 1.0–1.4 mm, medium to medium-dark brown with scattered small dark spots.
Similar species:
Viola edulis?, Viola egglestonii
Ecology:
Moist to wet limestone gravel and bedrock of riverbanks and streamsides, bluffs, bottomland prairies, persistent along roadsides, lawns and other disturbed areas formerly in natural habitat.
Distribution:
Missouri River and Ozarks regions in central and lower Midwest, w. IL to se. SD, south to MO, nw. LA and e. OK.
Rarity:
State listed in IL [records require confirmation].
Phenology:
Chasmogamous flower April–May, chasmogamous fruit May–June, cleistogamous fruit July–September.
Affinities:
This species belongs to the Acaulescent Blue Violet lineage, sect. Nosphinium W.Becker, subsect. Boreali-Americanae (W.Becker) Gil-ad, in the Viarum species group.
Hybrids:
Hybridizes with V. cucullata (Brainerd 1924) and V. missouriensis (Russell 1965, Harvey Ballard 2013). Hybrids exhibit intermediate or recombinant characteristics in traits of foliage, chasmogamous flower, cleistogamous fruit and seeds (when these do not abort). Information on reproduction is unavailable.
Comments:
Pollard mentioned in his protologue "Type collected by J. B. S. Norton at Valley Park, Mo., July 15, 1899." He cited one collection but did not designate a particular specimen as holotype and did not reference a herbarium. Stafleu and Cowan (1983) noted that Pollard’s herbarium and types are at US, with duplicates at several other herbaria. They also stated that Norton’s herbarium and types from that time period are at MO. The JSTOR Global Plants database has images of several specimens with the same label information, all bearing a label inaccurately naming them as paratypes (they are syntypes). The US03017761 sheet has the date "Apr. 29 ’99," disqualifying it as a syntype. The PH00029301 sheet, chosen by Ballard et al. (2020) matches the protologue in all details and is representative of the species in cleistogamous fruit, and it was designated as the lectotype.
Brainerd (1921b), Brainerd Baird (1942), Fernald (1950), Alexander (1963), Swink and Wilhelm (1979), and Ballard (2013) accepted this as a distinct species. Russell (1965) presented it among other accepted species but described a situation in his yard where divided-leaved plants appeared to "intergrade" into locally occurring V. missouriensis, and he postulated that the present taxon might be a mere genetic variant. Gleason and Cronquist (1991), McKinney (1992), McKinney and Russell (2002), and Little and McKinney (2015) synonymized it in a very broadly delimited V. palmata. Gil-ad (1995, 1997, 1998) studied seeds from Brainerd 176, and Brainerd s.n., 7 Oct 1906 (VT) from Eagle Rock, Missouri, and from a hybrid swarm he interpreted as involving V. viarum from Gil-ad 415, 416, and 417 in Pettis Co., Missouri. Gil-ad found no unique micromorphological structures but noted structures were shallow and could not be interpreted accurately. He found similarities of seed micromorphological features with V. affinis, V. missouriensis, V. nephrophylla, V. pedatifida, and V. triloba. Correlating macromorphological traits with micromorphological features suggested to him a hybrid origin of V. viarum involving V. missouriensis and V. nephrophylla with a taxon possessing lobed or divided leaf blades, such as V. pedatifida or V. triloba. He excluded V. viarum as a species. The several living populations I have examined in western and southern Missouri, when putative local hybrids were excluded, were fully fertile via chasmogamous and cleistogamous reproduction and highly uniform in their morphological characteristics. Gil-ad's proposal of a hybrid origin notwithstanding, the taxon as narrowly circumscribed here possesses a distinct suite of macromorphological features, a modally unique habit, and reproduction indicative of a separate evolutionary species. It is distinct in its strictly glabrous foliage and peduncles, largest leaf blades longer than broad to as broad as long, deeply pedately divided into (3)5–7 lobes with the undivided terminal primary division distinctly broader than the lobes on the divided lateral primary divisions, the lateral lobes less than (rarely scarcely more than) 1/2 the length of the midrib, eciliate calyx, slender acuminate sepals, sparsely bearded spurred petal, slightly to moderately elongating auricles in fruit, finely spotted cleistogamous capsule on an ascending to erect peduncle, and brown seeds with scattered small dark spots. Its riverbank limestone habitat is also distinctive. The taxon is accepted here as a distinct species under the Unified Species Concept.
I have found that populations of typical, extreme V. viarum with deeply pedately dissected leaf blades during later chasmogamous flower and early to mid-cleistogamous fruit are invariably accompanied by plants with much less deeply divided leaf blades and other macromorphological features, suggesting hybridization with V. missouriensis and other locally occurring species with uncut leaf blades. The type of Viola viarum f. pilifera E.J.Palmer & Steyerm. represents a later-generation hybrid involving the present species and Viola sororia. Russell's example of so-called "intergradation" with V. missouriensis probably represented a hybrid swarm. The illustration he chose for this taxon is not typical of the deeply biternate-leaved extreme of V. viarum and is likely a hybrid individual. Hybrids involving V. palmata var. palmata or V. pedatifida with V. affinis or V. missouriensis casually resemble the present species in certain features and may also have been misidentified as such. These putative hybrids commonly end up on herbarium specimens as inadvertent mixed collections or comprise the entire sheet, and some have passed unnoticed by Brainerd and others, who accepted such specimens as normal components of variation in the present species. Herbarium collections attributed to this species (including Swink and Wilhelm's dubious records) should be reexamined to exclude hybrids, in order to more narrowly circumscribe the taxon and gain a more accurate understanding of its geographic distribution. The present species is similar to V. egglestonii in its preference for limestone but it occupies consistently moister microsites, in cobble or crevices of bedrock along streams and rivers, occasionally on the higher ground of riverside bluffs (where it must compete with more mesic-loving hybrids and other species). The infrequently applied common name "Plains Violet" is a misnomer, since the species extends only a modest distance westward into the Great Plains region along its preferred river- and streamside habitat. A cumbersome but descriptive new common name, "Limestone Riverbank Violet", is proposed here (better names are encouraged!). Specimens previously referred to this from limestone canyons of the Guadalupe Mountains of New Mexico and Texas have been described as a distinct southwestern species, V. calcicola R. A. McCauley & H. E. Ballard, also belonging to the Viarum species group (McCauley and Ballard 2013).
Literature Cited:
Alexander, E. J. 1963. Violaceae. In Gleason, H. A., The new Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. Hafner Publishing Co., Inc., New York, NY. 552-567.
Ballard Jr., H. E. 2013. Violaceae. In Yatskievych, G., Flora of Missouri. Missouri Botanical Garden Press, St. Louis, MO. 1218-1243.
Brainerd, E. 1921b. Violets of North America. Vermont Agricultural Experiment Station Bulletin 224: 1-172.
Brainerd, E. 1924. The natural violet hybrids of North America. Vermont Agricultural Experiment Station Bulletin 239.
Brainerd Baird, V. 1942. Wild violets of North America. University of California Press, Berkeley, CA.
Fernald, M. L. 1950. Violaceae. In Gray's Manual of Botany, 8th ed. American Book Company, New York, NY. 1022-1042.
Gil-ad, N. L. 1995. Systematics and evolution of Viola L. subsection Boreali-Americanae (W. Becker) Brizicky. Ph.D. dissertation. University of Michigan, Ann Arbor, MI.
Gil-ad, N. L. 1997. Systematics of Viola subsection Boreali-Americanae. Boissiera 53: 1-130.
Gil-ad, N. L. 1998. The micromorphologies of seed coats and petal trichomes of the taxa of Viola subsect. Boreali-Americanae (Violaceae) and their utility in discerning orthospecies from hybrids. Brittonia 50: 91-121.
Gleason, H. A., and A. Cronquist. 1991. Violaceae. In Manual of vascular plants of northeastern United States and adjacent Canada, 2nd ed. New York Botanical Garden, Bronx, NY. 157-163.
Little, R. J., and L. E. McKinney. 2015. Violaceae. In Flora of North America: Cucurbitaceae to Droseraceae, 106. Oxford University Press, New York, NY.
McCauley, R. A., and H. E. Ballard Jr. 2013. Viola calcicola (Violaceae), a new endemic violet from the Guadalupe Mountains of New Mexico and Texas. Journal of the Botanical Research Institute of Texas 7: 9-20.
McKinney, L. E. 1992. A taxonomic revision of the acaulescent blue violets (Viola) of North America. Sida, Botanical Miscellany 7: 1-60.
McKinney, L. E., and N. H. Russell. 2002. Violaceae of the southeastern United States. Castanea 67: 369-379.
Russell, N. H. 1965. Violets (Viola) of the central and eastern United States: An introductory survey. Sida 2: 1-113.
Swink, F., and G. Wilhelm. 1979. Violaceae. In Plants of the Chicago region, 2nd ed. revised and expanded. Morton Arboretum, Lisle, IL. 384, 801-810.
Chasmogamous flowering habit from herbarium specimen: MO, Taney Co., Frequent on rock soil along Shoal Creek ca. 1/2 mile east of Protem, Sect. 5, T21N, R17W, 8 Apr 1961, P. L. Redfearn, Jr. 8009 (FSU000116649)
Cleistogamous fruiting habit from herbarium specimen: MO, St. Clair Co., In lime gravel on East banks of Osage River, 3-1/2 mi. north of Iconium at Wagon Ford, 7 Aug 1937, J. A. Steyermark 24389 (MUHW034566)
Chasmogamous flowering habit from herbarium specimen: MO, Daviess Co., west-facing limestone wood slopes and outcrops along South Big Creek of Grand River, T 59 N, R 28 W, SW 1/4 sect. 4, 5 mi. northeast of Altamont, Alluvium of stream bed between limestone ledges and sandy bars, 24 May 1957, J. A. Steyermark 84780 (MISS0046359)
Leaves during cleistogamous fruit from herbarium specimen: MO, St. Clair Co., In lime gravel on East banks of Osage River, 3-1/2 mi. north of Iconium at Wagon Ford, 7 Aug 1937, J. A. Steyermark 24389 (TENN-V-0153490)
Leaves during cleistogamous fruit from herbarium specimen: MO, St. Louis, along railroads in dry soil, 15 Jul 1899, J. B. S. Norton 32 (NEB-V-0000594, syntype of Viola viarum)
Seeds from herbarium specimen: MO, Eagle Rock, donor B. F. Bush, 10 Jun 1910, Ex horto E. Brainerd 176 (NY)
Map by the Biota of North America Program