Euphorbia hammeri K.A. Bradley & Sadle, 2021

Weakley, Alan S., Poindexter, Derick B., Medford, Hannah C., Franck, Alan R., Bradley, Keith A., Sadle, Jimi & Kelley, John Michael, 2021, Studies In The Vascular Flora Of The Southeastern United States. Vii, Journal of the Botanical Research Institute of Texas 15 (1), pp. 23-56 : 33-39

Euphorbia hammeri K.A. Bradley & Sadle , sp. nov. ( Figs. 6 , 7 , 8 ). TYPE: U.S. A. FLORIDA. Monroe Co.:Big Cypress National Preserve. Around bases of cypress trees in a pine-cypress area, 24 May 1978, D. & S. Black 203 (HOLOTYPE: FNPS!, Fig. 6 ; ISOTYPE: FTG!).

Diagnosis.— Differing from E. porteriana and E. ogdenii by its narrowly lanceolate to narrowly elliptic (vs. ovate to narrowly elliptic) leaves that are generally3–6 (vs.1.0–2.5) times as long as wide,with 1 vein (vs.1–3 veins), widely spaced on the stem (vs.narrowly spaced),red to deep red pigmentation throughout the plant except for deep green adaxial leaf surfaces (vs. green to pink);slender elongated peduncles (vs. stout, short); and by large (vs.small), deep purple to purplish black (vs. green to pink) glands, with radially narrow (vs.wide) appendages that border the gland.

Description.— Herbs, perennial, with thickened taproot, 5 mm diam. Stems erect to ascending, sometimes slightly woody at base, reddish to red throughout, not mat-forming, 15–60 cm, glabrous. Leaves opposite, generally held perpendicular to stem, widely spaced on stem, 2–4 cm apart; stipules usually distinct, occasionally connate basally, triangular, entire or 2–3 parted, 0.4–0.6 mm, glabrous, petiole 0.5–2.0 mm, glabrous; blades sometimes slightly falcate, narrowly elliptic or linear-elliptic, 4.9–12.5 × 1.1–2.5 mm, (2.2–)3–6(–8.25) times longer than wide, base asymmetric, rounded, margins entire, apex acute, sometimes mucronate, abaxially purple or red, adaxially green, glabrous; 1-veined from base, vein light to deep red.Cyathia solitary at distal nodes; peduncle slender, usually longer than cyathial cup, 1.0– 1.5 mm. Involucres turbinate to campanulate, 0.7–1 × 0.8–1 mm, usually glabrous, rarely very sparsely short pubescent; glands 4, dark red to purplish black, slightly concave, narrowly elliptic-oblong, 0.5–0.9 × 1.0– 1.6 mm; appendages dark red, bordering and with radial dimension less than that of the gland, (0–)0.1–0.4 × 1.2–1.5 mm, distal margin entire or slightly crenulate. Staminate flowers 8–14, anthers orange. Pistillate flowers: ovary glabrous, subtended by triangular calyxlike structure; styles 0.5–0.6 mm, bifid 1/2–2/3 length. Capsules deep red, broadly ovoid, 1–1.5 × 1.7–2.1 mm, glabrous; columella 1–1.4 mm. Seeds reddish brown, ovoid, 4-angled in cross section, 0.7–1 × 0.6–0.7 mm, smooth or obscurely wrinkled.

Additional specimens examined. FLORIDA. Monroe Co.: found in pineland S of Pace’s Dike which burned 3 months ago, T55S,R33E,Sec. 35, 4 Apr 1979, Rochefort 100 (FNPS);Big Cypress National Preserve, Lostman’s Pines area, located approx. 6.12 km S of Loop Road (CR94), 17.34 km W of the Miami-Dade county line,S of Charlie Jumper Hammock, common in wet pine rockland, 8Sep 2002, Woodmansee & Sadle 958 (FNPS); Big Cypress National Preserve, S of Loop Road, in pine flatwoods, 8 Nov 2002, Bradley 2441 (FNPS); Big Cypress National Preserve, in Pinus-Sabal savanna with some exposed limestone S of Loop Road, 23 Oct 2004, Sadle & Hodges 242 (FNPS). Miami-Dade Co.: Everglades National Park, in pine rockland with Cladium jamaicensis , Schizachyrium rhizomatum , Serenoa repens , Sabal palmetto , Muhlenbergia capillaris , Chamaesyce conferta , Morinda royoc , Chiococca parvifolia , and Cassytha filiformis , 2 May 2017, Sadle 744 (FNPS); Everglades National Park, in marl prairie/pine rockland ecotone and adjacent marl prairie, southern edge of Pine Block B, plants erect, stems, cyathia and capsules red,leaves green, ca. 1,000 individuals, 30 May 2017, Sadle748 (FNPS).

Euphorbia hammeri occurs in open understory, fire-dependent, and seasonally flooded habitats dominated by Pinus densa (Little & K.W. Dorman) Silba in the southern tip of the Florida peninsula. It is known from two geographically isolated areas, both located entirely within lands managed by the National Park Service and separated from one another by the Shark River drainage of the southern Everglades . Lostman’s Pines is a loosely defined region south of Florida State Road 94 (Loop Road) in southern Big Cypress National Preserve. The area is characterized by thin marl and sand soils overlaying limestone bedrock. Subtle topographic changes and associated hydrologic conditions result in island-like formations of pine forest intermixed with graminoid prairies, Taxodium ascendens Brongn. forests and savannas and rockland hammocks dominated by temperate and tropical hardwood trees. In this area, E. hammeri occurs in association with mesic to moist P. densa savannas with some exposed limestone outcrops. Long Pine Key in Everglades National Park is located at the southwestern end of the Miami Rock Ridge. This region includes a series of elevated Miami Oolite limestone formations overlain with thin marl soils that support pine rockland and rockland hammock habitats bisected by marl prairies that occur in lower elevation, north-to-south drainages. Within Long Pine Key, E. hammeri occurs in a small area of pine rockland and associated marl prairie. The occurrence is immediately north of a previously farmed area where both habitat types are no longer present. The distribution of E. hammeri is similar to that of two other southern Florida endemic plants, Digitaria pauciflora Hitch. ( Poaceae ), and Sideroxylon reclinatum Michx. ssp. austrofloridense (Whetstone) Kartesz & Gandhi ( Sapotaceae ). Both species are also restricted to pineland and marl prairie habitats in Long Pine Key and southern Big Cypress National Preserve.

Euphorbia hammeri is locally frequent but has a very limited known range, which makes it disproportionately vulnerable to ecological changes, so it should be considered a species of conservation concern. We recommend for it a conservation rank of G2 “Imperiled” ( NatureServe 2020). Fortunately, the entire distribution of E. hammeri is located within lands managed by the National Park Service and is largely protected from development and land-use changes. Localized impacts to plants and suitable habitat from administrative and recreational off-road vehicle use are also likely affecting the occurrence in the Lostman’s Pines region of Big Cypress National Preserve. Potential range-wide threats to the species include non-native plant infestations, failure to maintain natural fire patterns, and sea level rise. Both park service units have long-standing and active fire management and exotic plant control programs, which currently minimizes these threats. Additionally, changes in hydrologic conditions associated with landscape-scale restoration projects and sea level rise have the potential to alter hydroperiods in areas where E. hammeri occurs, which may represent a significant threat to the long-term survival of the species.

We find that Chamaesyce scoparia plants in the Florida Keys differ sufficiently from related taxa to be recognized at species rank, following Small’s original concept, circumscription, and rank (Small 1913, 1933). This species is geographically isolated from E. hammeri and E. porteriana and readily distinguished from them by several characters. Leaf shape is most similar to E. hammeri but C. scoparia leaves are consistently both shorter and with lower length-to-width ratios. Plants are green to often suffused with light pink but lack the deep red coloration of E. hammeri . The glands are much smaller than those of E. hammeri and have usually flabellate appendages that are wider than the glands in the radial dimension. Chamaesyce scoparia is readily distinguished from E. porteriana ( Figs. 9 , 10 ) by its narrowly elliptic to narrowly ovate leaves, rounded instead of cordate leaf bases, and smaller glands ( Table 2). The species is widespread in the upper and lower Florida Keys from at least Plantation Key to Key West. It is always associated with either Miami Oolite or Key Largo Limestone and can be found in pine rockland, coastal rock barrens, and canopy gaps or edges of rockland hammocks. The species is rare and should be considered globally imperiled.

After being named at species rank, Chamaesyce scoparia has been treated at varietal rank as C. porteriana Small var. scoparia (Small) D.G. Burch and as E. porteriana (Small) Oudejans var. scoparia (Small) Oudejans. In order to treat this taxon at the appropriate species rank in Euphorbia , however, a new name is required because a new combination at species rank based on the epithet ‘ scoparia’ is blocked by an earlier homonym, Euphorbia scoparia N.E. Br. 1911 , a plant of Africa. We name it after the late John C. Ogden (1938–2012), ornithologist, Everglades restoration scientist, our friend, and next-door neighbor and close friend of Roger L. Hammer.

Figures

FIG. 6. Euphorbia hammeri. Holotype,Black & Black 203,FNPS.

FIG. 7.Euphorbia hammeri. Miami-Dade County,Everglades National Park (photo by Roger L. Hammer).

FIG. 8. Euphorbia hammeri. Monroe County,Big Cypress National Preserve (photo by Keith A.Bradley).

FIG. 9. Euphorbia porteriana. Holotype,Garbers.n., NY.

FIG. 10.Euphorbia porteriana. Miami-Dade County,Everglades National Park (photo by Roger L.Hammer).