Drosera magnifica Rivadavia & Gonella

Paulo Minatel Gonella, Fernando Rivadavia & Andreas Fleischmann, 2015, Drosera magnifica (Droseraceae): the largest New World sundew, discovered on Facebook, Phytotaxa 220 (3), pp. 257-267 : 258-264

Drosera magnifica Rivadavia & Gonella , sp. nov. ( Figs. 1–4 )

Type: — BRAZIL. Minas Gerais: Conselheiro Pena, Pico do Padre Ângelo, 1530 m, 28 November 2013, Gonella & Rivadavia 645 (holotype SPF!, isotypes BHCB!, MO!, P!, RB!, SPF!).

Diagnosis: — Drosera magnifica differs from D. graminifolia and D. spiralis by the long prostrate or ascending stems up to 123.5 cm long; by the higher number of active leaves per rosette, which are sessile and broader linear-lanceolate in shape, 100–240 × 3–8 mm, with circinate-involute vernation (lateral margins of lamina involute in bud), entirely lacking glandular trichomes, with a raised midrib on the adaxial surface extending from base to ⅓–½ of the leaf length, the adaxial surface with a short, triangular to narrowly triangular tentacle-free zone at the base that is eglandularpilose, and the mature leaves with revolute margins; by multiple-branched inflorescences (branched scorpioid cymes), covered with stalked glandular trichomes 0.1–0.4(–0.5) mm long; and by the larger fusiform seeds 1–1.2 mm long.

Description: — Perennial rosetted herbs, caulescent; stem well-developed, up to 123.5 cm long, prostrate or ascending (supported by surrounding vegetation), often apically branching once and with basal sprouts, covered by the persistent dead leaves (70–100 mm between inflorescences from different years). Roots succulent, black, sparsely branched, densely covered by root hairs. Indumentum consisting of white (drying gold colored) eglandular trichomes up to 4 mm long, occurring on the base of the adaxial leaf surface, whole abaxial leaf surface, scape, bracts, pedicels and sepals; stalked glandular capitate trichomes 0.1–0.4(–0.5) mm long on scapes, bracts, pedicels and sepals; minute sessile glands ca. 0.03 mm in diameter on both leaf surfaces, scapes, bracts, pedicels and sepals. Leaves 100–240 × 3–8 mm, active leaves 7–18 per rosette, linear-lanceolate, apex acute, vernation circinate-involute (regular or irregular), lamina of mature leaves with revolute margins, green in color, erect to semi-erect, with a raised midrib on adaxial surface extending from base to approximately ⅓–½ of length (less conspicuous in dried specimens), leaves becoming reflexed and drying curled when old; petioles absent in mature plants (leaves sessile), but often distinct in juvenile plantlets; lamina comprising the entire leaf length, with the abaxial surface densely eglandular-pubescent, especially towards the margins, and covered with numerous sessile glands, while the adaxial surface is covered with numerous sessile glands and red, carnivorous, capitate tentacles with radial symmetric gland heads, except for a triangular to narrowly-triangular tentacle-free zone of 7–45 × 2–7 mm at the base, which is densely to sparsely eglandular-pilose, but glabrous at the very base; stipules 8–15 mm long, 3.5–9.0 mm wide at the base, triangular, membranaceous, translucent bronze-gold in color (sometimes whitish to reddish), apex acute and fimbriate. Scapes 1 per plant (in plants with forked stems, one scape per rosette), terete, hollow, base erect and 2–5 mm in diameter, 165–350 mm in total length (including floriferous part; the peduncle 120–225 mm long), densely pilose, covered with glandular and eglandular trichomes, the indumentum becoming denser towards the apex; inflorescence in a multiple-branched scorpioid cyme, with (2–)6–10(–14) branches, green to reddish-green in color, bearing 17–190 flowers, often with 1–4 larger bracts not supporting a flower at the base of the rachis (“sterile bracts”), 7–12 mm long, linear; floral bracts caducous, 4–6 mm long, linear-lanceolate to ovate, usually absent, densely glandular and eglandular-pilose on the abaxial surface; pedicels 2.5–7.0 mm long, inserted 2–7 mm apart from each other, densely glandular and eglandularpilose; sepals 5, pinkish-red when in bud and during anthesis, greenish when in fruit, 4.5–8.0 mm long, 2.2–3.0 mm wide, oblong-obovate to ovate, united at basal 1/4–1/5 of length, densely glandular-pilose and sparsely eglandularpilose, apex rounded to broadly acute; petals 5, 8– 10 mm long, 6–8 mm wide, obovate, light pink; stamens 5, ca. 3.5 mm long, filaments white, anthers 1.5–1.8 mm long, bithecate, yellow; ovary 1.2–1.5 mm in diameter at anthesis, 3- carpellate, globose, rounded in outline, green; styles 3, forked at the base, 4.0– 4.8 mm long including stigmas, stigmas simple or bilobed, pinkish-white in color; fruit a dry capsule, 1.5–2.5 mm long, globose, 3-valvate. Seeds fusiform, 1.0–1.2 × 0.2–0.3 mm, testa reticulate, dark brown.

Etymology: —The epithet “ magnifica ” refers to the magnificent appearance of this new species, which has remained undiscovered until so recently, even though it is one of the three most robust species of the genus and largest sundew in the New World.

Distribution and habitat:— Drosera magnifica is a microendemic species, so far only known to occur on the summit of the Pico do Padre Ângelo, in the municipality of Conselheiro Pena, eastern Minas Gerais state, Brazil ( Figs. 1 , 3A ). The new species occurs on sandstone outcrops among herbaceous and shrubby vegetation in a vegetation type intermediate between campos rupestres (“rocky fields”) and campos de altitude (“highland fields”), in a narrowly defined habitat at elevations around 1500–1530 m ( Fig. 3 ). Plants grew mostly in soil composed of a very loose layer of organic matter mixed with sand over sandstone, or more rarely in cracks of bare sandstone.

On the Pico do Padre Ângelo, D. magnifica was observed to occur mostly at a single site on the south slope of the summit, with thousands of plants concentrated in an area of about 50 × 50 m ( Fig. 3 B). This slope is approximately at a 45-degree angle and receives significant moisture in the form of condensation from uplift winds. Two smaller subpopulations were seen on gentle slopes on the north side of the summit, distant ca. 200 m and 300 m from the main population, and bearing around 10 and 100 individuals, respectively.

Typical members of the altitude vegetation growing together with D. magnifica are: the subshrub Baccharis platypoda Candolle (1836: 409) (Asteraceae) , the bromeliad Vriesea sanctaparecidae Leme (2013: 45) (Bromeliaceae) , as well as other species belonging to Asteraceae , Bromeliaceae , Melastomataceae , Orchidaceae , Rubiaceae , mosses and lichens ( Fig. 3 ). Although a few pockets of Sphagnum Linnaeus (1753b: 1106) moss were observed in the area, D. magnifica was not found growing with it, but only next to it.

Because of their proximity and similar elevation, the Pico da Aliança (ca. 1440 m, 10 km to the southwest) and Pico do Pinh"o (ca. 1430 m, 5 km to the north) were also explored, but these were found to be comparatively drier and no D. magnifica populations were located. The only other peak in the vicinity likely to harbor D. magnifica is the Pico do Sossego (ca. 1550 m, 7 km to the north), which is still unexplored botanically.

Phenology: —The available data indicates that the flowering period of D. magnifica is comprised between late dry season and early wet season (from October to December), with only a single inflorescence produced per mature rosette. No plants were seen in flower in May or July, when only dry old scapes were observed.

Conservation Status: —Critically Endangered: CR B1ab(iii) + B2ab(iii). Drosera magnifica is a microendemic species, currently known to occur on a single mountain summit where it is locally abundant, but restricted to a fragile and isolated habitat.

Habitat degradation was observed along most of the summit trail, caused by coffee and eucalypt plantations ( Fig. 3A ), cattle ranching, and invasive species of grasses, such as “capim gordura” [ Melinis minutiflora Palisot de Beauvois (1812: 54) ], Brachiaria ( Trinius 1826: 39) Grisebach (1853: 469) (Poaceae) , and the fern Pteridium arachnoideum ( Kaulfuss 1824: 190) Maxon (1924: 89) (Dennstaedtiaceae) . Because of its highly restricted occurrence as well as the observed and projected decline of habitat quality, D. magnifica is here listed as Critically Endangered (CR) according to the criteria of IUCN (2012).

The Pico do Padre Ângelo and surrounding mountains (including the Serra do Pinh"o and Pico da Aliança) should be a priority aim for conservation, as they contain some of the very last remaining areas of eastern Minas Gerais that are not completely degraded, and which harbor a unique and still very poorly-known biodiversity. The surrounding lowlands have been heavily deforested over the past century and only small patches of rainforest remain between cattle ranches and family farms. The species-rich and fragile campos rupestres found on these highlands harbor narrowly endemic taxa, such as the recently described bromeliads Alcantarea nana Leme (2014: 72) , A. occulta Leme (2013: 10) and Vriesea sanctaparecidae ( Leme & Kollmann 2013, Leme et al. 2014), as well as the orchid Cattleya alvarenguensis ( Campacci 2014: 382) Berg (2014: 84) , among several other still undescribed species (pers. obs.).

Ecological notes: —All observed specimens of D. magnifica show a well-developed stem ( Fig. 2 A), usually prostrate, but often erect and supported by surrounding shrubby vegetation, reaching 30–40 cm above the soil surface ( Fig. 3 C–F). Stems were frequently observed to branch once (rarely more), and new growing tips were frequently seen sprouting from the stem bases ( Fig. 3 F). In some cases, young plantlets were also observed emerging from roots. Not a single seedling was found during either of our visits, which is surprising considering the numerous flowers and the large quantity of seed produced by D. magnifica .

Large numbers of insects (mostly from Hymenoptera: Terebrantia, as well as small Coleoptera, Diptera, and Lepidoptera) were observed stuck on the leaves of D. magnifica in November and May, but not as many in July. Nutrition obtained from the abundant prey may be an important factor in sustaining the surprising robustness of this new species as well as the fast growth rate (see below), since it grows in very scarce and structured soil over sandstone.

Acephalous dipteran larvae were observed on many specimens of D. magnifica , hidden among the young leaves, as were also their pupae on the abaxial leaf surfaces. Similar dipteran larvae have previously also been observed by F.R. to live on the leaves of the related D. spiralis (pictured as living on “ D. graminifolia ” in McPherson 2010 ).

Additional specimens examined

Drosera magnifica

(paratypes) — BRAZIL. Minas Gerais: Conselheiro Pena, Pico do Padre Ângelo, 1530 m, 0 8 July 2014, Gonella et al. 675 ( SPF, M).

Figures

FIGURE 1. Distribution area of D. magnifica (star), D. graminifolia (triangles) and D. spiralis (circles).

FIGURE 2. Drosera magnifica (based on the holotype). A) habitus, showing an erect inflorescence at anthesis as well as two prostrate dead ones, the older entangled by the remains of dead leaves. B) leaf base, adaxial surface. C) leaf base, abaxial surface. D) stipule. E) immature leaf, with regular circinate-involute vernation. F) apex of an inflorescence branch, with a spent flower and a flower bud, the arrow indicating a detail of the indumentum on the pedicel and calyx, composed by eglandular trichomes, long-stalked glandular trichomes and sessile glands. G) flower. H) gynoecium. I) seed (drawing by Rogério Lupo).

FIGURE 3. A) View of the Pico do Padre Ângelo, eastern Minas Gerais state, Brazil, with coffee and eucalypt plantations visible near the base. B) high-montane habitat of D. magnifica, among rocks and shrubs, with the Pico da Aliança in the background. C − D) numerous flowering individuals with stems prostrate or ascending; the large specimen on the right side of figure D is the holotype. E) specimen with ascending stem supported by surrounding vegetation. F) group of individuals with long stems, first prostrate then ascending, covered by remains of dead leaves, with smaller rosettes sprouting from the stem bases (bottom right). (A, C – F by P. M. Gonella; B by F. Rivadavia).

FIGURE 4. Drosera magnifica. A − B) detail of the center of the rosette, showing the numerous young leaves with both regular and irregular circinate-involute vernation and densely eglandular-pilose abaxially C) adaxial surface of a leaf base, with a narrowly triangular tentacle free zone and a prominent midrib; notice the large bronze-gold stipules. D) detail of the multiple-branched scorpioid cyme. E) flower, flower buds and spent flowers. (A – C, E by P. M. Gonella; D by F. Rivadavia).