Oxalis tijucana (Lourteig) 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 : 173-179

Oxalis tijucana (Lourteig) Fiaschi comb. et stat. nov.

urn:lsid:ipni.org:names:77360850-1

Figs 12–13

Type material

BRAZIL – Rio de Janeiro • Rio de Janeiro, Parque Nacional da Tijuca, Serra dos Pretos Forros, Represa dos Ciganos ; 200–300 m a.s.l.; 30 Sep. 1977; fl, fr; G. Martinelli et al. 3196; holotype: P [ P02440300 ]; isotypes: RB [ RB00271307 , RB00585541 ], SPF [ SPF00197792 ] .

Other material examined

BRAZIL – Rio de Janeiro • Rio de Janeiro, Cascadura, Serra da Bica ; Nov. 1897; fl; E. Ule 4537; R • Rio de Janeiro, Serra da Bica, “par Ribeiro” ; 21 Feb. 1883; A.F.M. Glaziou 13648a; P • Rio de Janeiro, Jacarepaguá, Curicica, FioCruz, “caminho da cachoeira” [waterfall path]; 22°56′37.17″ S, 43°24′51.72″ W; 13 Apr. 2015; fl; J.P. Costa s.n.; HUEFS [ 217077 ], RBR [ 37031 ] • same data as for preceding; 7 Mar. 2024; fl, fr; J.C. Vasques et al. 85; BAL, FLOR, RB, RBR, SPF .

Description

Unbranched, erect subshrubs, 25–30 cm tall, with the stem sometimes spreading under the leaf litter; young stem glabrescent, with sparse, appressed hairs; older stem brownish, terete, longitudinally striate. Leaves pinnate-trifoliolate, densely grouped at stem apex, appearing arranged in a terminal pseudo-whorl, but sometimes with a few leaves inserted below, the internodes 1–25 mm long; the petioles 49–105 × 0.5– 1 mm, canaliculate and with abundant, curved hairs, along the margin adaxially, abaxially glabrous or with occasional hairs, the base pulvinate, enlarged to ca 2.5 mm diam., articulated at 1–2 mm of its length; the rachis 6–15 mm long, similar to the petiole; petiolules thick, 1–1.5 mm long, adaxially with hairs slightly larger and thicker than the petiole ones; leaflet blades adaxially glabrous; abaxially glabrous or with occasional hairs along the midrib and sparse hairs usually hiding under the revolute margin; membranous to chartaceous, abaxially lighter colored than adaxially. Venation: midrib canaliculate adaxially, at least in the proximal part, raised abaxially; secondary veins 8–12 pairs, conspicuous, impressed on both surfaces, angle of divergence increasing towards the apex; intercostal tertiary veins irregular-reticulate, exterior tertiary course looped, quaternary veins fabric irregular-reticulate, areolation moderately developed, free ending veinlets mostly with one branch. Terminal blade 100–160 × 29–48 mm, narrowly elliptic to lanceolate, the base attenuate to cuneate, the margin plane to revolute, the apex acute to acuminate. Lateral leaflets opposite, the blades 90–140 × 24–36 mm, lanceolate, the base asymmetrical to strongly asymmetrical, cuneate to obtuse, the apex acute to acuminate. Dichasial cymes axillary, shorter than the leaves; the peduncle 82–110 mm long, laterally flattened, with occasional to sparse, curved hairs; dichasial branches 2, up to ca 22 mm long, each with the flowers (or scars) densely grouped along the entire length; bracts ca 1 mm long, triangular, abaxially with abundant, appressed hairs; bracteoles ca 0.8 mm long, triangular, with abundant, appressed hairs. Flower buds ca 6.5 × 2.5 mm, lanceolate-acuminate. Pedicel 4.5–7 mm long, articulated at base, leaving a persistent, subsessile foot; with sparse to moderate, curved to appressed, antrorse hairs. Sepals light green, 7–10.5 × 1.5–2.4 mm, lanceolate to narrowly oblong, symmetric to slightly asymmetric, the apex acuminate to obtuse, sometimes mucronate, the exposed part with moderate, curved or straight hairs, sometimes with hairs ca 1 mm long. Corolla yellow, ca 18 mm diam., petals ca 13 mm long, each with two orange maculae above the throat; short-styled morph: filaments connate for ca 2 mm of their length; shorter filaments ca 5 mm long, glabrous; longer filaments ca 7 mm long, non-appendiculate, distally hispidule; pistil: ovary ca 1.2 mm long; styles ca 1.5 mm long, erect, glabrous; stigmas oblate; gynophore ca 1.5 mm long; long-styled morph: filaments connate for ca 1.5 mm of their length; shorter filaments ca 2.7 mm long, glabrous, longer filaments ca 4.5 mm long, non-appendiculate or very slightly appendiculate at ca 2 mm long, distally hispidule; pistil: ovary ca 1.2 mm long; styles ca 4 mm long, erect, hispidule for the entire length; stigmas oblate; gynophore ca 1.2 mm long; carpels uniovulate. Capsules ca 6 × 5.5 mm, obloid to broadly depressed ovoid or pyriform, glabrous, as long or slightly longer than the calyx lobes when fully developed, the apex prolonged for 1.5–2 mm of its length; locules one-seeded, internally glabrous; seeds 3.2–3.5 × 2–2.2 mm, semi-broadly ovoid, with a honeycombed-foveolate surface.

Preliminary conservation status assessment

Oxalis tijucana is restricted to preserved forests in the western part of Rio de Janeiro municipality, where it occurs in more urbanized areas than O. itatingae sp. nov. ( Fig. 12 ); moreover, its EOO = 23 km 2 and AOO = 12 km 2 are much smaller than those of the latter species. It is very likely that this species no longer occurs in Serra da Bica, a locality where it was only collected in the late 19 th century, and which is now an area dominated by criminal groups and only partially covered by degraded forests. The indication that O. tijucana has been suffering a continuous decline of habitat quality and extent suggests that it should be categorized as Critically Endangered following IUCN criteria CR B2ab(iii) ( IUCN 2012).

Remarks

This taxon was originally proposed as Oxalis polymorpha subsp. tijucana by Lourteig (1994) based on the presence of glabrous leaflets and canaliculate petioles, with the margin densely hirsute-ciliate. Other than these features, the species also differs from O. polymorpha by the leaves densely grouped at stem apex, forming a single terminal pseudo-whorl (vs leaves arranged along the stem), the pedicels with abundant, short, retrorse hairs (vs abundant, appressed to curved, antrorse hairs), and the obloid fruits with the carpels prolonged for ca 1 mm long (vs very broadly ovoid to broadly depressed ovoid fruits with the carpels prolonged for ca 0.5 mm long) (see Table 3 ).

Molecular phylogenetic evidence now available ( Fig. 3 ) points to a sister-group relationship between a clade formed by O. inopinata plus O. itatingae sp. nov. and a larger clade that includes all remaining species of O. sect. Holophyllum . Due to its morphological similarity to O. itatingae , O. tijucana very likely also belongs to this first, smaller clade. Thus, its placement under O. polymorpha (and in O. sect. Polymorphae, Fig. 3 ) would not be supported, even though O. tijucana (and O. itatingae ) have three-foliolate leaves, while O. inopinata and the remaining species of O. sect. Holophyllum are unifoliolate (Fiaschi et al. 2024). Among the morphological features that may support the placement of these two, three-foliolate species ( O. tijucana and O. itatingae ), together with O. inopinata (see fig. 11 in Fiaschi et al. 2024) are the canaliculate petioles with ciliate margin, the glabrous leaflet blades with conspicuously ciliate margins, and the inflorescences with dichasial branches bearing densely grouped bracteoles along the entire length ( Fig. 13K ).

Distribution and ecology

This species is restricted to rainforests in the surroundings of Rio de Janeiro city, especially in Cascadura, Curicica and Jacarepaguá neighborhoods, where it is commonly found in shady environments of preserved forests.

Figures

Fig. 12. Geographic distribution of Oxalis itatingae Fiaschi sp. nov. and O. tijucana (Lourteig) Fiaschi comb. et stat. nov. Inset shows southeastern Brazilian states.

Fig. 13. Oxalis tijucana (Lourteig) Fiaschi comb. et stat. nov. A. Branch with inflorescence. B. Detail of the petioles swollen at base (pulvinae). C. Terminal leaflet adaxial surface. D. Lateral leaflet adaxial surface. E. Lateral leaflet abaxial surface. F. Detail of leaflet blades insertion, adaxial view. G. Detail of leaflet blades insertion, abaxial view. H. Flower, frontal view. I. Inflorescence with open flower. J. Inflorescence with old flowers. K. Older inflorescence with elongated dichasial branches. L. Fruit, lateral view. M. Distal part of dichasial branch with mature fruit. Photos: Pedro Fiaschi, all based on J.C. Vasques et al. 85.

Fig. 3. Phylogenetic relationships among samples of Oxalis polymorpha Mart. ex Zucc. s. lat. (boldface terminals) based on combined ITS and plastid data. Branch support values are indicated above (maximum likelihood bootstrap, BS) and below (Bayesian inference posterior probabilities, PP) branches. The inset (upper left corner) shows the same topology with branch lengths. The orange gradients indicate species previously assigned to O. sect.Polymorphae (Progel) Lourteig (see text for details on O. itatingae Fiaschi sp. nov. and O. monochasiata Fiaschi). The illustrations on the right side represent (out of scale) the morphological variation of O. cf. polymorpha and five of six segregated species (O. amorimii Fiaschi sp. nov., O. animarum Fiaschi sp. nov., O. decipiens Progel, O. idimae Fiaschi sp. nov., and O. itatingae).