Oxalis idimae Fiaschi, 2025

Fiaschi, Pedro, Cabral, Fernando Santos, Caballero, Leonardo Ronald Gaspar & Lima, Duane Fernandes, 2025, Updating the taxonomy of polymorphic plant taxa: six Atlantic Forest species segregated from the widely circumscribed Oxalis polymorpha Mart. ex Zucc. (Oxalidales, Oxalidaceae), European Journal of Taxonomy 989, pp. 144-188 : 167-170

Oxalis idimae Fiaschi sp. nov.

urn:lsid:ipni.org:names:77360848-1

Figs 5 , 10

Diagnosis

Oxalis idimae sp. nov. differs from O. decipiens by the glabrescent young stem (vs with abundant to very abundant, curved hairs), leaf blades abaxially glabrous (vs with abundant, appressed hairs), sometimes with occasional hairs on the margin (vs with abundant hairs), venation with the midrib impressed (vs canaliculate) adaxially, conspicuous secondary veins (vs slightly visible or inconspicuous), and areolation of good (vs moderate) development, inflorescences with (1–)2 single branches (vs with (1–)2(–3) usually bifid branches), flowers with white (vs yellow) flowers, and broadly ovoid (vs pyriform) capsules with the carpels lacking apical prolongations or prolonged to only ca 0.5 mm of their length (vs with the carpels prolonged for ca 2 mm of their length).

Etymology

This new species honors the plant collector and amateur botanist Idimá Gonçalves Costa, who has recently discovered several new species of plants in the forest of northern Rio de Janeiro state, such as Anthurium idimae Theófilo & Nadruz ( Valadares & Coelho 2017) , Besleria aurea I.G.Costa & G.E.Ferreira ( Ferreira et al. 2016) , Conchocarpus hendrixii Groppo, I.G.Costa & Bruniera ( Groppo et al. 2019) , Eugenia asema I.G.Costa & M.C.Souza ( Sobral et al. 2017) , and Hippeastrum idimae Dutilh & R.S.Oliveira ( Oliveira et al. 2017) .

Type material

BRAZIL – Rio de Janeiro • Cardoso Moreira , localidade de Vinhático; 21°31′8.86″ S, 41°37′18.01″ W; 238 m a.s.l.; 6 Mar. 2017; I.G. Costa 879; holotype: FLOR [ FLOR 66532 ]; isotypes: HUEFS, RB, SPF .

Other material examined

BRAZIL – Rio de Janeiro • Cardoso Moreira , “ 3 km após ponte via BR 356 sentido Campos dos Goytacazes, entrada à direita” [3 km after bridge, on road BR 356 to Campos dos Goytacazes, entrance to the right]; 21°30′58″ S, 41°36′27″ W; 27 Jan. 2018; fl, fr; E. Richetti et al. 70; FLOR • Cardoso Moreira ; 5 Mar. 2024; J.C. Vasques et al. 78; FLOR, RB, SPF • Italva , “localidade de Quimbira, em escarpa de afloramento rochoso no interior da mata” [locality of Quimbira, on a rocky outcrop escarpment inside the forest]; 21°27′23″ S, 41°35′47′′ W; 150 m a.s.l.; 11 Apr. 2014; fl; I.G. Costa 400; RB, SPF • Italva, Quimbira ; 21°27′25″ S, 41°35′43.7″ W; 51 m a.s.l.; 18 Feb. 2017; fl; T.S. Costa et al. 123; FLOR • Italva ; 5 Mar. 2024; J.C. Vasques et al. 81; FLOR, HUEFS, RB • Italva, Pão de Ló ; 21°27′29″ S, 41°36′25″ W; 13 Dec. 2015; J. Rossini & I.G. Costa 835; R .

Description

Unbranched or few-branched, erect subshrubs, 60–120 cm tall; young stem glabrescent, with occasional to sparse, curved to appressed hairs; older stem ochreous, terete, slightly striate longitudinally. Leaves pinnate-trifoliolate, arranged along the stem, densely grouped at stem apex, sometimes forming multiple pseudo-whorls, the internodes 5–40 mm long; the petioles 31–110 × 0.5–0.8 mm, slightly canaliculate adaxially, with occasional, appressed hairs, more densely in the proximal region, the base pulvinate, enlarged to ca 1.2 mm diam.; the rachis 10–28 mm long, similar to the petiole; petiolules ca 1 mm long, with sparse, appressed hairs; leaflet blades adaxially glabrous, abaxially glabrous, the margin sometimes with occasional hairs in the proximal part; membranous, adaxially green, abaxially lighter green. Venation: midrib impressed adaxially, impressed to slightly raised abaxially; secondary veins 5–8 pairs, conspicuous, impressed on both surfaces, sometimes very slightly raised abaxially, angle of divergence inconsistent; intercostal tertiary veins irregular-reticulate, exterior tertiary course looped, quaternary veins fabric irregular-reticulate, areolation of good development, free ending veinlets unbranched or with one branch. Terminal blade 54–110 × 24–48 mm, ovate to lanceolate, the apex acuminate, the base obtuse. Lateral leaflets opposite, the blades 31–73 × 15–33 mm, ovate to lanceolate, the apex acuminate, the base subsymmetrical to asymmetrical, rounded to almost truncate. Dichasial cymes cauliflorous, shorter than the leaves; the peduncle 6–65 mm long, slightly flattened laterally, with moderate, curved or appressed hairs; dichasial branches (1–)2, 0.5–8 mm long, each with the flowers (or scars) densely grouped along the entire length or with the proximal part elongated, and the scars far from the terminal flower; bracts 0.7–1.5 mm long, lanceolate to linear, abaxially with moderate to abundant, appressed hairs; bracteoles ca 0.5 mm long, triangular-ovate, with moderate, appressed hairs. Flower buds 4–4.5 × ca 1.5 mm, lanceolate, acuminate. Pedicel 3–6 mm long, articulated at base, leaving a persistent foot up to ca 0.5 mm long; with moderate to abundant, appressed hairs. Sepals greenish, ca 6 × 1.7–1.8 mm, lanceolate, the exposed part with sparse to moderate, appressed hairs, the apex acuminate. Corolla white, ca 10 mm diam., petals ca 10 mm long, each with two orange maculae above the throat; short-styled morph: filaments connate for ca 0.5 mm of their length; shorter filaments ca 3.5 mm long, glabrous, each with a basal knob, longer filaments ca 5 mm long, non-appendiculate, hispidule; pistil: ovary ca 0.7 mm long; styles ca 0.7 mm long, proximally hispidule; stigmas oblate; gynophore ca 0.5 mm long; long-styled morph: filaments connate for ca 0.5 mm of their length; shorter filaments ca 1.2 mm long, glabrous, each with a basal knob, longer filaments ca 3.5 mm long, non-appendiculate, hispidule in the distal ⅓; pistil: ovary ca 0.8 mm long; styles ca 3 mm long, erect, hispidule along the entire length; stigmas oblate; gynophore ca 0.3 mm long. Capsules ca 4.5 × 4.5 mm, broadly ovoid, glabrous, slightly shorter than the calyx lobes, the apex not prolonged or prolonged to ca 0.5 mm long; locules one-seeded, internally glabrous; seeds ca 2 × 1.2 mm, semi-obloid, with a honeycombed-foveolate surface.

Preliminary conservation status assessment

This species is only known from a few seasonally dry forest fragments in the northern part of Rio de Janeiro state, which has historically suffered from a steady conversion of forests in cultivated areas for agricultural activities or pastures for cattle farming. The species is not known from any protected area, and the only fragments where it occurs are privately-owned; thus, it may be suffering from both extent and quality loss. With an EOO of only 8.6 km ², it is suggested that this species should be considered as Critically Endangered following the IUCN criteria CR B1ab(iii) ( IUCN 2012).

Remarks

Costa et al. (2019) had access to one specimen of O. idimae sp. nov. (I.G. Costa 400, RB), but they decided to treat it under O. polymorpha subsp. polymorpha , which was distinguished from O. polymorpha subsp. tijucana by the leaves spacely distributed along the stem (vs grouped in a pseudo-whorl at stem apex).

Oxalis idimae sp. nov. can be distinguished from all other species that are here segregated from O. polymorpha by the following combination of character states: glabrescent young stem, glabrous leaf blades (the margin sometimes with occasional hairs), inflorescences mostly cauliflorous, with white flowers, and capsules with the carpels without apical prolongation or prolonged to only ca 0.5 mm long. Moreover, it can be distinguished from O. decipiens , which also sometimes bears cauliflorous inflorescences, by several additional features (see Table 3).

Distribution and ecology

This species is presumably endemic to the northern part of Rio de Janeiro state, where it is known only from seasonally dry forests.

Figures

Fig. 5. Geographic distribution map of Oxalis polymorpha Mart. ex Zucc. (the single record in the Caatinga domain represents the type) and some of the segregated species recognized here, all of which are endemic to the Brazilian Atlantic Forest domain.

Fig. 10. Oxalis idimae Fiaschi sp. nov. A. Habit. B. Leaf, adaxial surface. C. Terminal leaflet detail, adaxial surface. D. Lateral leaflet, adaxial surface. E. Detail of leaflet blades insertion, adaxial surface. F. Stem with cauliflorous inflorescences bearing flowers and buds. G. Detail of young inflorescence with buds. H. Older inflorescence detail, showing densely grouped flowers (scars) along the entire length. I. Developing fruit in lateral view. J. Flower, frontal view. K. Young inflorescence with buds, flower (lateral view) and fruits. L. Fruit, lateral view. M. Seed, lateral view. Photos: A–L: Pedro Fiaschi; M: Gabriela Rhoden. A, J based on J.C. Vasques et al. 81, FLOR, HUEFS, RB; B–G based on J.C. Vasques et al. 78, FLOR, RB, SPF; H–I, K–L based on T.S. Costa et al. 123, FLOR; M based on E. Richetti et al. 70, FLOR.