Oxalis amorimii 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 : 156-159

Oxalis amorimii Fiaschi sp. nov.

urn:lsid:ipni.org:names:77360846-1

Figs 5–6

Diagnosis

This new species differs from all other species of O. sect. Polymorphae by the presence of leaflets clearly three-nerved, suprabasal actinodromous (terminal blade) or basal actinodromous (lateral blades), characterized by having one basal pair of secondary veins almost as thick as the midrib, extending up to ca ⅔ of the blade length.

Etymology

The name of this species honors the Brazilian botanist and Malpighiaceae expert André M. Amorim, who dedicated a large part of his career to improving our knowledge of the southern Bahia forests. He was the collector of the type of this new species and has devoted himself to cultivate one of the specimens used for the photographic plate presented in Fig. 6 .

Type material

BRAZIL – Bahia • Itanhém, Estrada Itanhém a Batinga, ca 16 km. “Ramal à direita, dando acesso a Faz. Pedra Grande, de Prop. de Etevaldo Rezende da Silva” [right branch, access to Faz. Pedra Grande, owned by Etevaldo Rezende da Silva]; 17°08′17″ S, 40°25′34″ W; 29 Dec. 2004; fl; A.M. Amorim et al. 4614; holotype: CEPEC .

Other material examined

BRAZIL – Bahia • Itanhém, “ ca 16 km da estrada que ruma a oeste de Itanhém, Antiga Fazenda Pedra Grande (Mata do Otevaldo) ” [ca 16 km from the road heading west from Itanhém, Former Fazenda Pedra Grande (Otevaldo's Forest)]; 17°07′58″ S, 40°25′18″ W; 27 Aug. 2022; st.; P. Fiaschi et al. 5457; FLOR .

Description

Unbranched or few-branched, erect subshrubs 20–40 cm tall; young stem with moderate, short, curved hairs, glabrescent towards the base; older stem brownish, terete, slightly striate longitudinally. Leaves pinnate-trifoliolate, distributed along the stem, mostly grouped at stem apex, but not forming a pseudo-whorl, the internodes 1–15 mm long; the petioles 35–80 × 0.4–0.8 mm, canaliculate adaxially, with moderate to abundant, curved to straight hairs, usually verruculose near the base, the base pulvinate, enlarged to ca 1.5 mm diam.; the rachis 9–20 mm long, similar to the petiole; petiolules ca 1 mm long, with abundant, appressed hairs; leaflet blades adaxially glabrescent, with occasional to sparse appressed hairs, especially along the midrib and along the margin; abaxially with abundant, appressed hairs, mostly along the midrib; membranous to chartaceous, adaxially green, abaxially green to slightly purplish. Venation: midrib impressed to canaliculate adaxially, prominent abaxially; clearly three-nerved, suprabasal actinodromous (terminal blade) or basal actinodromous (lateral blades), having one basal pair of secondary veins slightly thinner than the midrib (ca 1 mm vs ca 1.5 mm wide), decurrent, extending up to ca ⅔ of blade length, 3–4 distal secondary pairs thinner than the basal one, and one basal-most intramarginal secondary pair reaching up to ca ½ of the blade length; secondary veins slightly raised abaxially; intercostal tertiary vein fabric visible, irregular-reticulate, exterior tertiary course looped, quaternary vein fabric irregular-reticulate, areolation of good development, freely ending veinlets mostly one-branched. Terminal blade 50–74 × 22–31 mm, ovate to lanceolate or slightly rhombic, the apex acuminate to caudate, the base cuneate to attenuate. Lateral leaflets opposite, the blades 40–49 × 15– 21 mm, ovate to lanceolate, the apex acuminate, the base subsymmetrical to asymmetrical, cuneate to obtuse, sometimes attenuate. Dichasial cymes axillary, shorter than the leaves; the peduncle 42–62 mm long, flattened to adaxially canaliculate, with moderate, short, patent or curved hairs; dichasial branches 2, up to ca 10 mm long, each with the flowers (or scars) densely grouped along the entire length; bracts 1–1.5 mm long, narrowly triangular, abaxially with abundant, appressed hairs; bracteoles up to ca 1 mm long, narrowly triangular, with abundant, appressed hairs. Flower buds ca 7 × 2.5 mm, lanceolate, acuminate. Pedicel 3–7 mm long, articulated at base, leaving a persistent foot up to ca 0.5 mm long; with moderate, ascending to curved hairs. Sepals light green, 5.5–7.5 × 1–1.8 mm, lanceolate, the exposed part with moderate, ascending to appressed hairs, the apex acuminate. Corolla yellow, ca 13.5 mm diam., petals 11.5–13 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 1.5 mm long, glabrous, each with a basal knob, longer filaments ca 4 mm long, non-appendiculate, distally hispidule; pistil: ovary ca 0.5 mm long; styles ca 0.5 mm long, recurved, hispidule; stigmas oblate, facing outwards; gynophore inconspicuous, ca 0.2 mm long; long-styled morph: filaments connate for ca 1 mm of their length; shorter filaments ca 1.5 mm long, glabrous, longer filaments ca 4 mm long, non-appendiculate, distally with occasional, short hairs; pistil: ovary ca 1 mm long; styles ca 4 mm long, erect, hispidule for the entire length; stigmas oblate; carpels uniovulate. Capsules unknown.

Preliminary conservation status assessment

This species is so far known from a single patch of semideciduous forest in a private farmland situated in a very fragmented landscape at the border between the states of Bahia and Minas Gerais, where there are few remaining sites of forested areas. In a recent visit to this area, in August of 2022, we were able to locate less than 20 individuals of the species growing in ʻcabrucaʼ, a system of cocoa cultivation under the canopy of native trees that was traditionally employed in the region, and which is known to provide shelter for the local biodiversity ( Sambuichi & Haridasan 2007; Scroth et al. 2011). Since this species occurs in a single location (area of occupancy of 4 km ²), in an extremely fragmented landscape that suffered from both extent and quality loss, we recommend it to be assessed as Critically Endangered following the IUCN criteria CR B2ab(iii) ( IUCN 2012).

Remarks

This species can be easily distinguished from the remaining species of O. sect. Polymorphae by the presence of three-nerved leaflets, which are unique to this species in the section. From other similar, yellow-flowered species of O. sect. Polymorphae, whose leaves are not congested in a terminal pseudo-whorl, it can also be distinguished from O. decipiens by the leaf terminal blades 50–74 mm long (vs 46–122 mm long), unbranched (vs usually bifid at base) dichasial branches, and flowers with the pedicel 3–7 mm long (vs 1.5–2 mm long), and from O. animarum sp. nov. by the leaf blades abaxial surface with abundant, appressed hairs (vs with moderate, patent to appressed hairs, mixed with shorter and thicker, darker hairs), the peduncles 42–62 mm long (vs 11–30 mm long), and the pedicels with moderate, ascending to curved hairs (vs with abundant, short, patent hairs, mixed with sparse to moderate, longer, glandular hairs).

Distribution and ecology

This species is only known from a small semideciduous forest fragment located in the municipality of Itanhém, close to the border between the states of Bahia and Minas Gerais ( Fig. 5 ).

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. 6. Oxalis amorimii Fiaschi sp. nov.A. Habit.B. Detail of young stem with short, curved hairs. C. Leaf blade adaxial surface. D. Leaf blade abaxial surface. E. Detail of terminal leaflet venation abaxially, showing supra-basal secondary veins (large arrowhead) and distal secondaries (smaller arrowheads). F. Leaf adaxial surface, with detail of lateral leaflets insertion (G). H. Leaf abaxial surface, with detail of lateral leaflets insertion (I). J. Young inflorescence with terminal flower. K. Older inflorescence showing short persistent foot (arrowhead). L. Flower, frontal view. Photos: A, F–I: Carlos Ferreira; B–E, J–L: Pedro Fiaschi.All photos based on cultivated individuals of P. Fiaschi et al. 5457, FLOR, except E, based on A.M. Amorim et al. 4614, holotype, CEPEC.