Oxalis jacobinensis Fiaschi & F.S.Cabral, 2023

Fiaschi, Pedro, Cabral, Fernando Santos & Lima, Duane Fernandes, 2023, A new species of Oxalis sect. Thamnoxys (Oxalidaceae) from the state of Bahia, Brazil, Phytotaxa 606 (2), pp. 147-154 : 148-151

Oxalis jacobinensis Fiaschi & F.S.Cabral , sp. nov. ( Figure 1 )

Type: — BRAZIL. Bahia: Jacobina, Cachoeira Véu de Noiva , 11 o 20’3.9’’S 40 o 30’8.7’’W, 5 November 2022, F.S. Cabral et al. 222 [holotype: FLOR; isotypes (to be distributed): HUEFS, HVASF, K, NY, RB, SPF] .

Diagnosis: —This new species differs from O. monochasiata by the dichasial (vs. monochasial) cymes, the petioles as wide as the rachis (vs. wider than the rachis), the acute to acuminate (vs. obtuse to rounded, sometimes retuse) leaflet apex, and the blade abaxially with abundant adpressed hairs to somewhat tomentose (vs. abaxially with sparse hairs).

Description: — Subshrubs 15–60 cm tall, with an elongated underground xylopodium. Old stem terete, longitudinally striate, densely pilose or glabrous, usually unbranched, the young shoot with moderate to abundant short, curved hairs. Leaves pinnate-trifoliolate, arranged along the stem, but usually crowded to the apex, sometimes almost forming a terminal pseudo-whorl; internodes 1–10 mm long; petioles 27–70 mm long, flattened, adaxially canaliculate, with abundant soft hairs, the base pulvinate, abaxially and laterally with longer strigose hairs; rachis 5–13 mm long, similar to the petiole; petiolules ca. 0.5 mm long, with long strigose hairs; leaflet blades adaxially with moderate adpressed hairs, abaxially with abundant adpressed hairs to somewhat tomentose, usually appearing grayish when fresh; terminal blade 32–68 × 12–34 mm, rhombic-ovate to lanceolate, the apex acute to acuminate, the base cuneate to obtuse; lateral blades 16–50 × 10–29 mm, elliptic or ovate to lanceolate, with the apex acuminate, the base rounded, asymmetric. Venation with midrib adaxially flat, abaxially slightly raised; secondary veins in 5–6 pairs (terminal blade) or 3–5 pairs (lateral blades), slightly raised abaxially, angle of divergence increasing towards the apex; intercostal tertiary veins sometimes visible, irregular-reticulate, exterior tertiary course looped, quaternary veins fabric irregular-reticulate, areolation moderately developed, free ending veinlets mostly one-branched. Dichasial cymes shorter or slightly longer than the leaves; peduncles 50–70 mm long, flattened, moderately villose; branches 2, up to ca. 25 mm long; bracts 2–3 × ca. 0.5 mm long, narrowly triangular, abaxially with moderate to abundant adpressed hairs; pedicels up to ca. 9 mm long (up to ca. 13 mm in fruit), sparsely villose, intermixed with a few shorter glandular hairs, articulated at ca. 1/3 of its length, usually leaving a conspicuous foot of up to ca. 3.5 mm long, terminating in a disc-shaped scar. Sepals 5.5–6.5 × 2.2–2.5 mm, ovate or elliptic, the apex acute to rounded, sometimes mucronate, external ones with moderate adpressed hairs to ca. 0.5 mm long, intermixed with shorter sparse glandular hairs, internal ones glabrous; corolla 18– 23 × ca. 16 mm, dark yellow, with 4–5 orange lines above the throat; short-styled morph: filaments connate for ca. 1.5 mm long; shorter filaments ca. 4.5 mm long, distally hispidule; longer filaments ca. 7 mm long, dorsally appendiculate at ca. 1/3 of its length, hispidule above; pistil: ovary ca. 1.5 mm long; styles ca. 1 mm long, patent, glabrous; stigmas hippocrepiform, papillose; long-styled morph: filaments connate for ca. 1 mm long; shorter filaments ca. 2.5 mm long, glabrous, longer filaments ca. 4.5 mm long, dorsally appendiculate at ca. 2/3 of its length, hispidule above, pistil: ovary ca. 1.2 mm long; styles ca. 5.5 mm long, erect, hispidule for ca. 3 mm long; stigmas hippocrepiform, papillose; gynophore ca. 0.8 mm long. Capsules 8–11 × 5.5–6 mm, longer than the persistent sepals, ovate to elliptic, the carpels narrowing distally, abaxially with moderate stalked glandular hairs, carpels internally hispid, locules two-seeded; seeds ca. 2.8 × 1.4 mm, elliptic, longitudinally crested, with 5-6 horizontal clefts, the apex apiculate, the base rounded. Figure 1 .

Additional specimens examined: — BRAZIL. Bahia: Caem, 11 o 06’21’’S 40 o 24’19.8’’W, 567 m, 15 January 2015, J.M.P. Cordeiro et al. 642 (EAN); idem, beira de estrada, 11 o 06’21’’S, 40 o 24’19.8’’W, 6 November 2022, F.S. Cabral et al. 226 (FLOR); idem, 3 March 2023, P. Fiaschi et al. 5587 (FLOR). Jacobina, Itaitú, Serra do Sincorá, Cachoeira Véu de Noiva , 11 o 19’56.3’’S, 40 o 30’10.3’’W, 631 m, 26 January 2010, A.P. Fontana et al. 6372 (HVASF, SPF). Saúde, trilha para a Cachoeira do Paulista , 11 o 00’38.4’’S, 40 o 26’15.3’’W, 6 November 2022, F.S. Cabral et al. 234 (FLOR); idem, estrada da Cachoeira do Payayás , 10 o 54’5.1’’S, 40 o 25’34.1’’W, 6 November 2022, F.S. Cabral et al. 239 (FLOR) .

Distribution and Ecology: —The new species grows in areas of seasonally dry forests in the Atlantic Forest domain, which extends in the interior of the Bahia state along the northern portion of the Chapada Diamantina region, Brazil ( Fig. 2 ). It was found growing in ravines along roads in the municipality of Caem and along trails in forest fragments near the Itaitu village, in Jacobina, and in the surroundings of Saúde, at approximately 600 m in elevation.

Phenology: — Oxalis jacobinensis has been collected with flowers from November to March, and with fruits from November to January.

Etymology: —The chosen specific epithet honors the municipality of Jacobina, one of the municipalities in northern Bahia where the new species is found, and where the type specimen was collected.

Preliminary conservation assessment: — Oxalis jacobinensis is known from four nearby locations along the northern sector of the Chapada Diamantina, in the surroundings of Jacobina, Caem, and Saúde municipalities. Its known area of occupancy (AOO) is estimated as 16 km 2, and its extent of occurrence (EOO) is ca. 150 km 2. The region where this species is found is partially protected in the Sete Passagens State Park, but the populations that we were able to find during fieldwork are small, having about 20 individuals each. Among the main threats to the known populations of O. jacobinensis we could point the conversion of forests to agricultural lands and mining activities, and the implementation of irresponsible tourism practices ( Araújo et al. 2013). Therefore, this species is here categorized as Endangered (EN) following IUCN (2022) criteria B1, B2a,bi,ii,iii.

Notes: —Despite having the leaves usually densely grouped at stem apex, with rhombic-ovate to lanceolate terminal leaflet blades, and asymmetric lateral leaflet blades, which are characteristic of Oxalis sect. Polymorphae ( Progel 1877: 481) Lourteig (1994: 136) , O. jacobinensis shares with species of O. sect. Thamnoxys the nodding young fruits (vs. erect in O. sect. Polymorphae ) ( Fig. 1I ), and the longitudinally crested seeds with horizontal clefts ( Fig. 1K ) (vs. foveolate seeds with polygonal depressions in sect. Polymorphae ). Moreover, while species from O. sect. Polymorphae have capsules with one-seeded carpels, and usually shorter than the sepals, those of O. jacobinensis are two-seeded and longer than the sepals ( Fig. 1J ).

The placement of O. jacobinensis in O. sect. Thamnoxys is also supported by molecular phylogenetic evidence: in fact, which place it as sister to O. monochasiata Fiaschi (2014: 140) , a species that was originally wrongly described in O. sect. Polymorphae (Fiaschi et al., ined.). These two species share flowers with yellow corolla, short glandular hairs on pedicel, sepals and capsules, whose carpels are two-seeded and distally narrowed. However, in O. monochasiata the inflorescences are monochasial cymes (vs. dichasial cymes in O. jacobinensis ), the petioles are wider than the rachis (vs. of same width in O. jacobinensis ), the leaflet apex is obtuse to rounded, sometimes retuse (vs. acute to acuminate in O. jacobinensis ), and the blade has sparse hairs abaxially (vs. blades abaxially with abundant adpressed hairs to somewhat tomentose in O. jacobinensis ).

This new species can be distinguished from all remaining species of Oxalis sect. Thamnoxys by the presence of an elongated xylopodium, leaves usually grouped in the stem apex, terminal leaflet blades rhombic-ovate to lanceolate, abaxially with abundant adpressed hairs to somewhat tomentose, usually appearing grayish when fresh, dichasial branches up to ca. 2.5 cm long, and pedicels usually articulated at ca. 1/3 of its length, usually leaving a conspicuous foot to ca. 3.5 mm long, which terminates in a disc-shaped scar, large (18–23 mm diam.) yellow corollas, and elliptic capsules with the carpels narrowing distally, and abaxially covered with short stalked glandular hairs.

Among other species of Oxalis that can be found in the same or nearby areas, O. alstonii Lourteig (1978: 291) (O. sect. Polymorphae ) differs from O. jacobinensis by the leaves distributed along the stem (vs. usually grouped in the apex), elliptic to suborbiculate (vs. rhombic-ovate to lanceolate) leaflet blades, and the one-seeded capsules, which are shorter than the calyx (vs. two-seeded and longer than the calyx).

Figures

FIGURE 1. Oxalis jacobinensis Fiaschi & F.S.Cabral.A. Flowering specimen. B. Young stem detail. C. Terminal (right) and lateral (left) leaflet. D. Leaflets insertion on petiole. E. Leaf adaxial surface. F. Leaf abaxial surface. G. Flower, frontal view. H. Detail of inflorescence apex, with young fruit (left) and buds. I. Detail of inflorescence apex, with mature fruit (top) and flower (bottom). J. Mature fruit, lateral view. K. Scanning electron micrograph of the seed, lateral view. Scale bars: a, b, d, g-j = 5 mm; c, e, f = 1 cm; k = 0.5 mm (all photos from a cultivated specimen from the locality where the type was gathered).

FIGURE 2. Geographic distribution map of Oxalis jacobinensis Fiaschi & F.S.Cabral.