Rhynchospora megaplumosa is described as a new species of Rhynchospora, endemic to central Florida, in the section Rhynchospora series Plumosae. It is restricted to sandy openings in scrubby flatwoods in two localized areas of central Florida, in Polk and Manatee counties, where it flowers profusely in areas following burning. Rhynchospora megaplumosa is most closely related to R. pineticola and R. plumosa, but is distinguished by several characters, most conspicuously by its longer (5–7 mm) perianth bristles and golden-brown, narrowly lanceolate, longer spikelets. A key is provided to distinguish it from other species in the series. The habitat and associated species of R. megaplumosa, are also discussed.
In October of 1990, we collected an unusual species of Rhynchospora in Lake Ar- buckle State Forest (now known as Lake Wales Ridge State Forest, Arbuckle Tract) on the eastern edge of the Lake Wales Ridge in Polk County, Florida. This plant clearly belonged to Rhynchospora series Plumosae (C. B. Clarke) Small, a group characterized by plumose floral bristles and consisting of about five species (Channell 1956) centered in the southeastern United States and the Antilles, with a few species extending to Central and South America. Vegetatively, the plant seemed close to Rhynchospora pineticola C. B. Clarke (at that date known by the misapplied name, R. intermedia (Chapm.) Britton as explained in the notes on Rhynchospora series Plumosae, below). However, upon closer examination it was found to differ markedly from R. pineticola, and all other species of series Plumosae in several characters. Subsequent revisits to the collecting locality in 1991 and 1992 failed to relocate any individuals with these characteristics, although R. pineticola was abundant at the site. We were ready to dismiss our collection as an unusual, perhaps teratological, fluke until May of 1993, when at an area of similar habitat a few miles from the original collection a large uniform population of this same entity was discovered. Detailed field notes were made on this population, and a search was made for other species of Rhynchospora and for possible intermediate or intergrading specimens at the site. The results of the field and laboratory examinations indicated a narrow range of character states in this entity, consistent with the previous collection, clearly separated from other members of series Plumosae, and worthy of species' level recognition.
In early 1995 we were made aware by Dr. Richard Wunderlin of a Manatee County collection of an unusual Rhynchospora while annotating Cyperaceae at the USF herbarium. This specimen (S. Cole LM0105) was immediately recognizable as an exact match of our Polk County material of the undescribed species. Subsequent searches for this Rhynchospora in Manatee County by the authors resulted in the discovery of several additional sites, but still restricted to a relatively small area in each of the two known counties. Its exceptionally consistent morphology in two disjunct regions provides further evidence that it represents a distinct, undescribed species.
Taxonomy
Rhynchospora megaplumosa E. Bridges and Orzell, sp. nov., Type: UNITED STATES. Florida. Polk County: Scrubby flatwoods ecotone between scrub and mesic flatwoods, along road #4, 0.2 mi W of main road through Lake Wales Ridge State Forest, Arbuckle Tract, at a point 4.1 mi S of entrance gate at jet Rucks Dairy Rd and 5.0 mi S of jet Lake Arbuckle Rd, ca. 0.8 mi NW of FL 64, ca. 7 air mi NE of Avon Park and 8.5 air mi SE of Frostproof, SWQ, SEQ, Sec. 27, T32S, R29E; Lake Arbuckle 7.5′ Quad., 27°39′45″n, 81°24′13″W, Elev. 79 ft, 15 May 1993, S. L. Orzell and E. L. Bridges 21827 (HOLOTYPE: USF; ISOTYPES: BRCH, BRIT, GA, GH, FLAS, FSU, LSU, MICH, MO, NY, TEX) (Figure 1).
Rhynchosporae pineticola similis sed differt spiculis laete brunneis anguste lanceolatis 8–10 mm longis, setis perianthii quam acheniis multo longioribus 5–7 mm longis excavis ex spicula exsertis ad maturitatem, et acheniis brevioribus 1.5–1.8 mm longis.
Perennial herb, forming small dense clumps from short, stout, knotty, scaly rhizomes. Culms stiff and wiry, 1.5–2.0 mm thick at base, 3–6(-8.5) dm tall. Leaves stiff and wiry, deeply channeled below, becoming involute above, 1–3 mm wide, mostly basal, 1–2(-3) dm long, culm leaves becoming remote and strongly reduced in size upwards. Inflorescence almost always consisting of a single, dense, branched terminal fascicle, at maturity ca. 1.5 cm high and 2.0–2.5 cm wide, very rarely with a smaller lateral fascicle from the same node; bract subtending the inflorescence subulate, 2.0–4.5 cm long, surpassing the inflorescence, with inflorescence branches subtended by progressively reduced subulate bractlets. Spikelets narrowly lanceolate-subulate, light golden-brown, 8–10 mm long, ca. 2 mm wide, mostly 2-fruited; old spikelets persistent in inflorescence for several months and becoming gray with age; outermost spikelet scales empty (sterile), lance-ovate, 2–4 mm long, inner (fertile) spikelet scales narrowly lanceolate, 7–8 mm long, 1-nerved, pale brown to tan with a broad hyaline margin. Perianth bristles 6, 5–7 mm long, plumose on the lower half, the plumose hairs dense and spreading in the lowest 1 mm of the bristle, becoming more ascending and appressed for the next 2–3 mm of the bristle length, and merging into small antrorsely appressed barbs in the upper half of the bristle, the perianth bristles arching outwards from the achene body at maturity, and exserted from the spikelets, giving the spikelets a distinctly bristly appearance. Achene obovoid, nearly spherical above and tapered to the base, scarcely if at all flattened in cross-section and not evidently biconvex, 1.5–1.8 mm long, 1.11.2 mm wide; tubercle conical, the base only half of the width of the achene apex, articulated with the achene at the base, 0.50.7 mm long.
Distribution and habitat: Very localized in frequently burned sandy openings in scrubby flatwoods in two disjunct regions of Polk and Manatee counties, endemic to central Florida. Flowering from as early as March to as late as November, with mature achenes from April until November or later.
Additional specimens examined: UNITED STATES. Florida. Manatee County: Lake Manatee State Recreation Area, NWQ, SEQ, SWQ, Sec. 31, T34S, R20E, Burn Zone lbS, W of Park Office, 30 July 1993, Sam Cole LM0105 (USF); same locality (additional locality data: W of Poley Branch, NE of guard/check station, N of FL 64, ca 2.5 mi W of jet FL 675, ca 14 mi E of Bradenton, Verna 7.5′ Quad., 27°28′44″N, 82°20′45″W, Elev. 66 ft, Soils—Pomello Soils (Arenic Haplaquods)); 4 June 1995, Orzell & Bridges 23685 (USF), N side of FL 64, from 1.0–1.5 mi E of Manatee River bridge, 5.2 mi E of jet Verna- Bethany Rd at Verna Baptist Church, 6.8 mi E of jet Fk. 675, 18.3 mi E of jet 1–75 E of Bradenton, Myakka City 7.5′ Quad., 27°28′00″N, 82°11′24″W, Elev. 90–100 ft, 4 June 1995, Orzell & Bridges 23686 (USF); ca 0.3 mi E of North Fork Manatee River, ca. 2.8 air mi S of Keentown, ca. 4.5 mi SW of jet FL 62 and FL 37, Keentown 7.5′ Quad, 27°31′54″N, 82°08′58″W, Elev. 100 ft, 30 May 1996, Orzell & Bridges 24472 (USF). Polk County: same as type locality, 6 Nov 1993, Orzell & Bridges 22545 (USF); 16 Oct 1994, Orzell & Bridges 23309 (USF): 10 Nov 1995, Orzell & Bridges 24112 (USF); SE of Co Rd 64 at jet with School Bus Rd, 1 mi NE of Highlands Co line on FL 64, ca 7.6 mi NE of Avon Park, Lake Arbuckle 7.5′ Quad., 27°39′20″N, 81°23′36″W, Elev. 8390 ft, 10 Nov 1990, Orzell & Bridges 15823 (FLAS, USF).
Fig. 1.
Rhynchospora megaplumosa (from Orzell & Bridges 21827 (type) and live material from the type population). A. Habit (a scale bar equal to the others in size would be 25 mm long. Scale is 0.5×). B. Inflorescence at achene maturity. C. Spikelet at anthesis. D. Medial spikelet scale. E. Mature achene with perianth bristles. F. Single perianth bristle.
Rhynchospora megaplumosa can be easily distinguished from R. pineticola by its much longer, light golden-brown spikelets (castaneous dark brown in R. pineticola), much longer perianth bristles, and smaller achenes. In addition, the leaves of R. megaplumosa are mostly shorter than those of R. pineticola, usually less than half the length of the flowering culm. Examination of hundreds of individuals in mixed populations of R. megaplumosa, R. pineticola, and R. plumosa Ell. revealed no intermediate forms or any evidence of introgresssion. The following key (revised from Godfrey and Wooten 1979, Gale 1944, and Kukenthal 1949), serves to distinguish all species of this series:
Key to Rhynchospora Series Plumosae
1. Style base bicornute, narrowest at its base and broadened towards the tip; achene obtriangular R. diodon (Nees) Griseb.
1. Style base triangular to deltoid, broadest at the base; achene ovoid, elliptic, to suborbicular in outline 2
2. Spikelets 1 to 5 per culm, remote on 1 to 2 slender branches, the lowermost inflorescence branch strongly divergent 3
2. Spikelets numerous on each culm, congested in corymbose to spiciform fascicles 4
3. Achene body broadly elliptic or ovoid with a constricted neck at the junction of achene and tubercle; tubercle about 0.6 mm high; bristles as long as the achene or longer R. oligantha A. Gray
3. Achene body obovoid with only a groove at junction of achene and conic tubercle; tubercle about 0.4 mm high; bristles less than half the length of the achene R. breviseta (Gale) Channell
4. Inflorescence of a single terminal corymbiform fascicle; spikelets more than 4 mm long; leaves 1–3 mm wide 5
4. Inflorescence an elongate spikelike raceme or a small terminal glomerule; spikelets less than 3 mm long; leaves generally fililform, less than 1 mm wide R. plumosa Ell.
5. Achene body 1.5–1.8 mm long; bristles at maturity arching outward from the achene and exserted from the spikelet scales, 5–7 mm long; spikelets narrowly lanceolate-subulate, 8–10 mm long R. megaplumosa E. Bridges and Orzell
5. Achene body 2.0–2.2 mm long; bristles appressed to the achene body and enclosed within the spikelet scales, 2–3 mm long; spikelets lance-ovoid, ca. 4–6 mm long R. pineticola C. B. Clarke
Notes on Rhynchospora Series Plumosae
The first species described in Rhynchospora series Plumosae (C. B. Clarke) Small was R. plumosa (Elliott 1816). Gray (1835) described two additional species in this series, R. oligantha and R. semiplumosa A. Gray, the latter differing only slightly from R. plumosa and now considered a part of the complex of forms of that species (Gale 1944; Godfrey and Wooten 1979). Chapman (1860) described R. plumosa var. intermedia Chapm., with a description which seems to fit the characters of the robust, spike-like inflorescence form of R. plumosa, in contrast to his description of var. plumosa with the characteristics of the lax, wiry form of R. plumosa with only small glom- erules of spikelets. Britton (1892) elevated Chapman's var. intermedia to species level, and Small (1933) seems to have recognized R. intermedia with the same concept and description as that of Chapman (1860) and Britton (1892). Gale (1944) recognized three species in this series (R. plumosa, R. intermedia, and R. oligantha), and added var. breviseta Gale as a variety of R. oligantha. Gale's concept of R. intermedia, however, is quite different from that of previous authors. Rhynchospora intermedia is described by Gale as having a single terminal corymb and larger achenes than R. plumosa. This concept has subsequently been applied to the Florida scrub and scrubby flatwoods endemic species fitting Gale's concept. The only subsequent published change in the taxonomy of this series was the elevation of R. oligantha var. breviseta to species level (Channell 1956).
In the process of taxonomic and floris- tic work for the Flora of Florida project in 1991, the senior author was made aware of a problem with the application of the name R. intermedia to the species fitting Gale's concept (Robert K. Godfrey, pers. comm.). According to verbal communication from Godfrey, the type material of R. plumosa var. intermedia at NY belongs to the taxon with the spike-like inflorescence and small achenes represented by the type of R. plumosa. Although we have not seen this type, if this is true (as Chapman's (1860) descriptions would imply) it would relegate R. intermedia to synonymy under R. plumosa. Godfrey (pers. comm.) indicated that a valid name does exist for the Florida endemic with the corymbose inflorescence, R. pineticola C. B. Clarke. With the assistance of Richard Wunderlin and Bruce Hansen of USF, we researched this situation and came to the same conclusion. There apparently has been no published documentation of this nomenclatural problem, although the name R. pineticola has begun to be used as the valid name for this species in some works (Kartesz and Meacham 1999). In the following text, we briefly describe our reasoning for accepting R. pineticola rather than R. intermedia. Clarke (1908) described R. pineticola based on the his interpretation of R. intermedia (Chapm.) Britton as a later homonym of R. intermedia Beyr. ex Kunth (Kunth 1837). Rather than simply providing a replacement name, Clarke (1908) provided a new Latin description and several syntypes, thereby clearly establishing R. pineticola as a valid name. However, Kunth listed R. intermedia only based on the annotation of a specimen as this name in Beyrich's herbarium, without a description, and therefore it should not be considered as validly published. Although R. intermedia is therefore not to be rejected as a later homonym, as Clarke (1908) proposed, based on the presumed identity of the type specimen it should be relegated to synonymy under R. plumosa, leaving R. pineticola as the earliest published valid name for the Florida corymbose entity. Other workers apparently have arrived at the same conclusion, although there is no indication if any have seen the critical Chapman type specimen.
The present paper does not address the still unresolved taxonomy of the R. plumosa complex. There are several forms of this species, varying in the length of the plumose portions of the perianth bristles, culm height and stiffness, and inflorescence shape (spike-like vs. small terminal glomerules). Further study may indicate that some of these forms, which may have accounted for the historical confusion of the application of names described above, are deserving of taxonomic recognition. However, R. pineticola and R. megaplumosa are both clearly distinguishable from the R. plumosa complex by numerous consistent characters, as noted in the foregoing key, and can be recognized without regard to the resolution of the taxonomy of the R. plumosa complex.
Phenology, Habitat, and Associated Species
Flowering and fruiting of Rhynchospora megaplumosa is strongly stimulated by fire or other natural or artificial disturbance to the ground cover layer, without which few individuals produce flowers. In addition, the flowering and fruiting phenology of R. megaplumosa seems to be influenced by a combination of growing season temperatures and the timing of rainfall, with rainfall seeming to have the greater effect of the two factors. With ample rainfall following a mild, winter dry season in south-central Florida, initial flowering has been observed as early as late March. Unless there are prolonged rain-free periods March thru May, by mid-May the majority of plants in a population have mature achenes, and plants continue to produce new flowering culms. Production of flowering culms seems to be rather continuous throughout the growing season, until rainfall declines or frost occurs. In years with adequate fall and winter rainfall and no killing frost, R. megaplumosa may flower and fruit all year. However, in the El Niño year of 1998, most plants were in full fruit by mid-May and were becoming senescent, due to the combination of earlier than normal heavy rainfall followed by late spring drought conditions.
The scrubby flatwoods habitat of Rhynchospora megaplumosa is a distinctly Floridian natural community type. It is a well-defined community, that represents the broad transition between the more xeric, upland scrub and the typical poorly drained flatwoods communities of lower topographic positions (Abrahamson and Hartnett 1990; Menges 1999). Scrubby flatwoods are fire-maintained communities with acidic, low-nutrient soils (Ostertag and Menges 1994) and occur where a relatively deep sandy surface soil overlies an impervious spodic layer, resulting in alternating conditions of subsurface saturation and drought, with periodic extreme winter droughts. Soil series of the known Rhynchospora megaplumosa sites include Pomello (Arenic Haplohumods) and Satellite (Aquic Quartzipsamments). Both of these can be thought of as intermediate in depth to water table between the more xeric sandy soils of the upslope scrub and the more poorly drained flatwoods soils downslope.
The habitat of Rhynchospora megaplumosa can be characterized as an open canopy savanna with widely scattered Pinus palustris Mill., P. elliottii Engelm., or P. clausa (Chapm. ex Engelm.) Vasey ex Sarg. There is an open to moderately dense shrub layer of evergreen scrub oaks (Quercus gem- inata Small, Q. minima (Sarg.) Small, and Q. myrtifolia Willd.) and ericaceous shrubs (Befaria racemosa Vent., Lyonia lucida (Lam.) K. Koch, L. fruticosa (Michx.) Torr., and Vaccinium myrsinites Lam.). The shrub layer differs from that of other pine savan- na-flatwoods types in having a higher frequency of evergreen scrub oaks and a sparser herb layer (Abrahamson and Hartnett 1990). There is a moderately dense herbaceous groundcover layer, dominated by Ar- istida beyrichiana Trin. & Rupr., with some patches of open bare sand.
Including all vegetative strata, at least 110 species of vascular plants occur in close association with Rhynchospora megaplumosa at one or more sites (Bridges and Orzell unpublished data). Ninety-five of these 110 species occur with R. megaplumosa at the type locality, for which we have much more comprehensive floristic surveys than for the remaining sites. Among the herbaceous associates of R. megaplumosa are many species which are endemic or nearly endemic to Florida, including Asimina reticulata Shuttlw. ex Chapm., Chapmannia floridana Torr. & A. Gray, Euphorbia polyphylla En- glem. ex Chapm., Gymnopogon chapmani- anus A. Hitchc., Helianthemum nashii Britton, Hieracium megacephalon Nash, Lachn- ocaulon beyrichianum Sporl. ex Korn., Lia- tris tenuifolia Nutt. var. quadriflora Chapm., Palafoxia integrifolia (Nutt.) Torr. & A. Gray, Phoebanthus grandiflorus (Torr. & A. Gray) Blake, Piloblephis rigida (Bartr. ex Benth.) Raf., Polygala rugelii Shuttlew. ex Chapm., and Rhynchospora fernaldii Gale. The large number of endemic species in these habitats is indicative of the floristic and ecological distinctiveness of these peninsular Florida natural communities.
Acknowledgements
Gary A. Reese assisted in searches for additional locations for the species in Lake Wales Ridge State Forest, and in collecting some morphological field data. We thank Robert Godfrey for bringing the problem of Rhynchospora intermedia ,and Richard Wunderlin of USF for bringing the Cole specimen to our attention, providing herbarium access for our study, and for assistance with nomenclatural problems. We thank Wayt Thomas and Ken Cameron of NYBG for their assistance in trying to locate the type material of Rhynchospora plumosa var. intermedia at NYBG. We thank Guy Nesom for providing the Latin diagnosis, and Sandra Barstow for bibliographic assistance. The illustration was expertly prepared by Rebecca Yahr, from both live and dried material. The assistance of Douglas Ripley for providing partial funding for this publication through the U.S. Department of Defense is greatly appreciated.
