Mcvaughia piauhiensis R.F.Almeida & Guesdon, 2019

Almeida, Rafael F., Guesdon, Isabel R., Pace, Marcelo R. & Meira, Renata M. S., 2019, Taxonomic revision of Mcvaughia W. R. Anderson (Malpighiaceae): notes on vegetative and reproductive anatomy and the description of a new species, PhytoKeys 117, pp. 45-72 : 45

2. Mcvaughia piauhiensis R.F.Almeida & Guesdon sp. nov. Figs 7 , 8 , 11

Diagnosis.

Mcvaughia piauhiensis differs from M. sergipana Amorim & R.F.Almeida due to its leaf blades abaxially lanate-velutinous (versus sericeous), margins plain (versus revolute), conspicuous and stalked glands only near base and apex (versus throughout the leaf blade), cincinni 3-7-flowered (versus 2-flowered), margins of posterior petal glandular at base only (versus entirely glandular), and staminode opposite the posterior petal with slender filament (versus with stout filament). It also differs from M. bahiana W.R.Anderson due to its subshrub habit (versus shrub habit), leaf blades lanate-velutinous (versus tomentose), flowers 1.5-2 cm diam. (versus 1-1.2 cm diam.), staminode opposite the posterior petal as long as fertile stamens (versus shorter than fertile stamens), and the apex of styles uncinate (versus truncate).

Type.

BRAZIL. Piauí: Guaribas, Parque Nacional da Serra das Confusões, Barreiro, fl., 28 Mar 2007, R. Barros 2922 (holotype: HUEFS barcode HUEFS135774!; isotype: CEPEC!, TEPB!).

Description.

Subshrubs ca. 50 cm tall. Branches densely lanate-velutinous, glabrescent at age. Stipules 4-4.5 mm long, adaxially glabrous, abaxially densely lanate-velutinous. Leaves opposite; leaf blades 6-11 × 3-6 cm, chartaceous to subcoriaceous, elliptic to obovate, base cuneate, margins plain, entire, apex acute to apiculate, adaxial side light green in sicco, initially lanate-velutinous to glabrescent, abaxial side dark green in sicco, initially lanate-velutinous to glabrescent, except from midvein at base, a pair of conspicuous glands at base abaxially, on each side of the midrib, a few inconspicuous glands scattered on the blade, with 2 conspicuous glands near apex; petiole 0.8-1 cm long, canaliculate, densely lanate-velutinous, eglandular. Thyrsi of 5-8-flowered cincinni; rachis 6.5-7 cm long, smooth, densely tomentose-velutinous, with rusty hairs; lateral cincinni 14-15, alternate; bracts 1.5-2.5 mm long, triangular, appressed to the peduncle, eglandular, tomentose-velutinous; peduncle 3-4 mm long, tomentose-velutinous; bracteoles 1.5-2 mm long, triangular, subopposite, appressed to the peduncle, tomentose-velutinous, one of each pair bearing a conspicuous gland at base, 1.3-1.8 mm long. Flowers 1.5-2 cm diam. at anthesis, floral buds 3-3.5 mm long, pedicel 2-3 mm long, tomentose-velutinous. Sepals 2-2.5 × 1-1.3 cm, straight, keeled, covering most of the androecium, apex rounded, margin short ciliate, adaxial side glabrous, abaxial side tomentose, glabrescent near the margin; 10-glandular, glands 1-1.2 × 0.7-0.8 mm, yellow, elliptic. Petals yellow, soon deciduous; anterior lateral petals orbicular, cucullate, nested inside one another, limb 2.9-3.2 × 4-4.3 mm, margin erose, eglandular, claws 1-1.2 × 0.2-0.25 mm, glabrous; posterior lateral petals obovate, spreading, limb 4-5 × 4-4.5 mm, margin erose, eglandular, claws 1.5-2 × 0.3-0.35 mm, glabrous; posterior petal obovate to orbicular, erect, limb 5-5.5 × 5-5.5 mm, margin erose, 2-3 pairs of reniform glands at the base of limb, proximal pair larger, claws 2.5-3 × 0.6-0.8 mm, adaxially pubescent. Stamens free at base, filaments 2-3 × 0.2-0.4 mm, cylindrical, thicker at base; connective inconspicuous, glabrous; anthers 0.3-0.45 × 0.4-0.45 mm; staminodes opposite the posterior-lateral sepals covered by sepals, filaments ca. 1 mm long, long-triangular, anthers ca. 0.2 mm long, oblong, locules lacking; staminode opposite the posterior petal not covered by sepals, exserted, diverging from styles, filament 2-2.1 × 0.2-0.4 mm long, anther 0.25-0.3 mm long, oblong, locules reduced. Ovary ca. 1 × 1 mm, ovoid, densely tomentose; styles 3, erect, ca. 3 × 0.5 mm, cylindrical, parallel, tomentose at base, uncinate at apex, anterior style slightly smaller than posterior ones; stigma lateral, circular. Drupes (immature) 5-6 × 2-3 mm, cylindrical, slightly twisted, apex with persistent styles, rusty tomentose, with two chambers, proximal chamber containing the seed, distal chamber containing an oily substance; seed (immature) globose, smooth. Embryo not seen.

Distribution, habitat, and phenology.

Mcvaughia piauhiensis is known only from sandy caatingas (seasonally dry forests) within Serra das Confusões National Park in state of Piauí, Brazil (Fig. 11 ). Flowering in March.

Conservation status.

Mcvaughia piauhiensis is known only from a single population within the limits of the Serra das Confusões National Park in state of Piauí, Brazil. Until additional fieldwork can be done in seasonally dry forests from Piauí, this species is best categorized as data deficient (DD).

Etymology.

The epithet refers to the distribution of M. piauhiensis , which is restricted to the state of Piauí, Brazil.

Anatomical notes.

This new species resembles M. bahiana in several aspects. The distribution pattern of leaf glands is quite similar, with both showing only one pair of conspicuous glands at base and a few conspicuous glands scattered over the blade (Fig. 3B ). The basilaminar and laminar glands correspond to short-stalked glands (Fig. 3E, J ). The sinuous outline of the anticlinal epidermal cell walls recorded on the abaxial leaf surface in M. bahiana (Fig. 3Q ) was also observed in M. piauhiensis . On both surfaces of M. piauhiensis , the malpighiaceous hairs are less frequent (Fig. 3M ), when compared with M. bahiana and M. sergipana , but the indumentum is clearly lanuginose-velutinous in young leaves. The distribution pattern of glands on the posterior petal is the same observed in M. bahiana , as ca. 5 short-stalked glands on the proximal portion of the petal limb margin (Fig. 4Q ). Although no recent field observations have been recorded, we believe that the color of the glands and the color of the flower are the same observed in M. bahiana .

Figures

Figure 3. Leaf morphoanatomy of Mcvaughia species. A patterns of leaf glands distribution on the abaxial leaf surface of M. bahiana B patterns of leaf glands distribution on the abaxial leaf surface of M. piauhiensis C patterns of leaf glands distribution on the abaxial leaf surface of M. sergipana D transverse section of leaf base showing the basilaminar pair of stalked glands (white arrows) E basilaminar leaf gland with a stalk (black arrow) in M. piauhiensis F basilaminar gland in M. sergipana showing a sessile position (SE = anatomical arrangement with secretory epidermis, SP = vascularized secretory parenchyma) G-H laminar glands on the apex of cleared leaves of M. sergipana and M. bahiana respectively, note the apical tooth (G) I sessile laminar glands in M. sergipana J stalked laminar gland in M. piauhiensis K-L transverse sections of the leaf blade; mesophyll with uniserial palisade-like parenchyma and spongy parenchyma composed by several or few layers in M. sergipana and M. bahiana, respectively; note the idioblast with druse crystals at the mesophyll (white arrow) and the stomata distribution at the abaxial leaf surface (black arrow) M-N adaxial epidermis surface of M. piauhiensis and M. sergipana, showing scars of malpighiaceous trichomes O abaxial epidermis surface of trichomes abundance in M. bahiana P-Q outline of the anticlinal epidermal cell walls: straight in M. sergipana (P) and sinuous in M. bahiana (Q). Laminar scale bars: 1 cm (A-C), 100 μm (D, F-K, N-O), 150 μm (E), 50 μm (L-M, P-Q).

Figure 4. Reproductive morphoanatomy of Mcvaughia species. A inflorescence during development, showing a bracteole gland (BG) and Sepal glands (SG) B ten sepal glands encircling the calyx C Petal glands (PG) along the margin of posterior petal D-F transverse section of bracteole glands in M. sergipana, M. bahiana and M. piauhiensis, respectively G anatomical arrangement of bracteole gland, with a palisade-like secretory epidermis (SE) and secretory parenchyma (SP) H-I transverse section of floral bud and anthesis flower in Mcvaughia bahiana and M. sergipana; calyx gland pair displaced at the anterior sepal J calyx gland structure, showing a secretory epidermis (SE) and vascularized secretory parenchyma (SP) K-L petal glands on the margin of petals in M. sergipana and M. bahiana respectively M-N detail of the petal glands at the apex of the petal limb in M. sergipana, cleared and in SEM image O-Q petal glands positioned at the base, M. bahiana on SEM image, M. bahiana and M. piauhiensis cleared R-T conspicuous and stalked petal glands at the base of M. sergipana, in SEM image, cleared and longitudinal section. Scale bars: 200 μm (D), 150 μm (E-F), 50 μm (G), 500 μm (H-I), 100 μm (J, P-S), 300 μm (L-M), 200 μm (N, T).

Figure 7. Mcvaughia piauhiensis. A seasonally dry forests from Serra das Confusoes, Piaui, Brazil B abaxial surface of a leaf C detail of epipetiolar stipules D inflorescence E rehydrated flower showing the stamens (white arrows = reduced stamens) and styles. A by S. E. Martins B-E by R. F. Almeida.

Figure 8. Photograph of the holotype of Mcvaughia piauhiensis.

Figure 11. Distribution map of Mcvaughia: triangle - M. bahiana, circle - M. piauhiensis, and square - M. sergipana. Solid blue line in the center represents the Sao Francisco River today. Dotted blue line represents the past course of Sao Francisco River. Blue circle represents the Sao Francisco paleo lake. Light green - Atlantic Forest domain, dark green - Amazon Forest domain, orange - Cerrado domain, and yellow - Caatinga domain. AL - state of Alagoas, BA - state of Bahia, CE - state of Ceara, MA - state of Maranhao, PB - state of Paraiba, PE - state of Pernambuco, PI - state of Piaui, RN - state of Rio Grande do Norte, and SE - state of Sergipe.