Trillium georgianum S.B. Farmer, 2017
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publication ID |
https://doi.org/ 10.11646/phytotaxa.296.3.8 |
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persistent identifier |
https://treatment.plazi.org/id/03918793-727A-6844-B3B8-FA4F19E50212 |
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treatment provided by |
Felipe |
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scientific name |
Trillium georgianum S.B. Farmer |
| status |
sp. nov. |
Trillium georgianum S.B. Farmer View in CoL sp. nov. ( Fig. 1–2 View FIGURE 1 View FIGURE 2 )
Similar to Trillium texanum in the presence of stomata on the upper leaf surfaces, high proportion of sterile leaves, and a thin branching rhizome; but differing from T. texanum and all other members of the Trillium pusillum Complex in the long narrow leaves.
Type:— USA. Georgia: Whitfield County, Floden, Schilling , and Lampley 2884, 17 March 2016 (Holotype, TENN!; isotypes, BRIT!, GA!, MO!, NCU!, US!).
Perennial from long, thin rhizomes, 98–116(–137) mm tall. Stems single, with either a single leaf or with a single whorl of 3 bracts, 6-angled near bracts. Bracts (Leaves) 35–48.5 (–56) mm × 7–10(–11) mm, 3.9–5.9(–6) times longer than wide, numerous stomata evenly distributed in upper surface, blade dark green with maroon undertones especially when young, not mottled, 3 primary veins, linear to linear-lanceolate. Pedicel 13–24(–29) mm. Flower above leaves, ascending to erect; sepals 15–17(–19) mm × 5–7 mm, 2.4–3(–3.8) times longer than wide, conspicuous, spreading to same plane as petals, dark green with maroon undertones when young; petals 15–19 mm × 5–9 mm, 1.7–2.7(–3.2) times longer than wide, of short duration, spreading-ascending, exposing stamens and ovary, weakly recurved in distal half, white, aging to deep rosy pink, veins not engraved but major petal veins clearly visible, thin-textured, widest above base, margins strongly undulate, quite variable in petal width and degree of undulation between individuals and populations; stamens 7–8(–8.2) mm, erect-spreading; filaments 3–3.5(–4) mm, shorter than anthers, greenishwhite, slender; anthers 4–4.5(–5.2) mm, ± straight, yellow, thicker than filaments, dehiscence introrse; connectives not extended beyond anther sacs, pinkish-purple; ovary 2.7–3.5 mm tall, conspicuous, green, ovoid, obscurely 6-angled; style 1.5–3(–3.7) mm, green; stigmas 3, 1.5–2.2 mm, confluent with style, green, long-spreading, uniformly thin and threadlike. Fruits white or pale greenish, ovate. Flowering: late March to early April.
Additional specimens examined (paratypes):— USA, Georgia, Whitfield Co., 5 April 2002, Farmer s.n. ( TENN!) ; ibidem, 26 March 1996, Allison and Dickman 9096 ( GA!) ; ibidem, 21 March 1996, Dickman s.n. ( GA!) .
Etymology:—The species is named for the state of Georgia which is the location of the only known site for it. As a common name we suggest Georgia Dwarf Trillium .
Habitat and distribution:—The single known locality for Trillium georgianum ( Fig. 2 View FIGURE 2 ) is a perched calcareous flatwoods (200–225 m elevation) with the following herbaceous associates: Arisaema pusillum (Peck) Nash , Claytonia virginica L. var. acutiflora DC. , Galium tinctorium L. var. tinctorium , Gratiola floridana Nutt. , Lilium michiganense Farw. , Luzula acuminata Raf. var. carolinae (S.Watson) Fernald , Mitchella repens L., Platanthera flava (L.) Lindl. var. flava , Ranunculus hispidus Michx. , and Ranunculus pusillus Poir. Plants of T. georgianum are clustered upon and around the edges of mounded islets inhabited also by abundant mosses (especially American tree-moss, Climacium americanum Brid. and Sphagnum sp. ). These microhabitats are scattered among seasonally wet, shallow depressions. The exposed soils shrink and swell and by summer usually appear parched and cracked. Nearby, at slightly lower elevations, small streams meander lined with plants more typical of streamside banks, seepage swamps, and floodplains. These other wetland habitats and adjacent streambanks harbor other species, such as Lobelia cardinalis L., Primula meadia (L.) A.R.Mast & Reveal, Rudbeckia laciniata L., Samolus parviflorus Raf. , Trillium lancifolium Raf. , and Xanthorhiza simplicissima Marshall , but the Trillium georgianum habitat is not a floodplain. Unlike most trilliums, Trillium georgianum proliferates by rhizome branching and typically forms tight clusters of vegetative clones with a few flowering stems intermixed. Plants occur under a dense canopy that includes an overstory of Acer rubrum L., Fraxinus pennsylvanica Marshall , Nyssa sylvatica Marshall , Quercus michauxii Nutt. , Quercus nigra L., Quercus phellos L., and Quercus shumardii Buckley. The understory is variable from open to closed and in addition to saplings from canopy trees, has the following dominants: Cercis canadensis L., Cornus florida L., Crataegus marshallii Eggl. , Ilex decidua Walter , and tangles of Smilax laurifolia L. Plants of Trillium georgianum were first observed in March 1995 by a consultant, Brian Dickman, who was looking for wetland mitigation sites. The area was being developed as an industrial complex despite the nature of the seasonally wet, shrink and swell clayey soils. By April 1996, state botanists verified the specimens as Dwarf Trillium , Trillium pusillum . Portions of the flatwoods had already been ditched; large tracts were being clearcut and leveled, some were being filled with soil from nearby uplands. The flatwoods occupied by T. georgianum continues to be degraded in bits and pieces, but some protection efforts are underway. The Tennessee Valley Authority and Dalton Utilities, a unit of the Whitfield County government, both hold tracts harboring T. georgianum that, hopefully, will remain perpetually intact. Formal agreements with various governmental agencies must be negotiated to protect permanently the type locality. In addition, the Georgia Plant Conservation Alliance, including various botanical gardens, maintains cultivated stock used to establish additional flatwoods populations on permanently protected lands. Nevertheless, T. georgianum occurs only in scattered subpopulations within this single flatwoods habitat despite attempts to locate additional plants in the watershed. Truly, this taxon of the Trillium pusillum Complex remains highly threatened and may deserve listing under provisions of the federal U.S. Endangered Species Act. Trillium georgianum must be considered a rare species. It is currently known from only a single extended site along the drainage of Swamp Creek, a tributary of the Conasauga River ( Fig. 2 View FIGURE 2 ). The population numbers in the hundreds of individuals, but the location near or in an industrial park means that they are potentially threatened by development. Part of the site where T. georgianum occurs was, in fact, slated for development and a subsequent rescue operation removed many plants and significantly decreased the population. Based on its rarity, it is recommended that it be considered for state and even federal government protection.
Taxonomic relationships:— Jacobs & Jacobs (1997) recognized this taxon as being distinct and informally proposed the name Trillium pusillum var. georgianum for it. Information including images and illustrations of the species (listed as T. pusillum ) are provided by Chafin (2007). It is the only member of the Trillium pusillum Complex that occurs in Georgia. Trillium georgianum shares the rare trait of adaxial stomatal openings on the leaves with T. texanum ( Buckley 1860: 443) . These give the leaves a farinose, granular, or mealy appearance. The two species are also characterized by producing both single-leaved and three-leaved stems from a single rhizome ( Fig. 1A View FIGURE 1 ), a trait that may be restricted within Trillium to these two species; thus single-leaved individuals are common and conspicuous in populations of them. In other species of Trillium , single-leaved stems are produced only in young, immature plants. In addition, the leaves of T. georgianum are lanceolate and very narrow (3.9–5.9 times longer than wide), much more so than any of the other species in the Trillium pusillum group. The combination of these three characters makes this an easily identifiable species. The most similar species of the Trillium pusillum group is T. texanum , and the two species can be differentiated by leaf shape, which is ovate to lance-ovate and less than 3.9 times as long as wide in T. texanum ; by the horizontal or slightly declining leaf position in T. georgianum , compared to ascending in T. texanum ; by petal shape, which in T. georgianum is broadly ovate and 1.7–2.7 times as long as wide, compared to narrowly ovate and 2.8–3.8 times as long as wide in T. texanum . In addition, although plants of both species are found in wet areas, those of T. texanum are typically found on elevated areas around the bases of trees, whereas plants of T. georgianum are not associated with tree hummocks. The blooming period of T. texanum , late February to early March, is earlier than that of T. georgianum . The two species are widely separated geographically, with the nearest occurrence of T. texanum (Miller Co., AR) over 800 km to the west of the locality for Trillium georgianum .
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