Oxalis sect. Polymorphae (Progel) Lourteig

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 : 179-181

Identification key to species of Oxalis sect. Polymorphae

(species with * are here segregated from O. polymopha s. lat. but should be excluded from the section)

1. Leaves arranged along the stem ( Fig. 7A ), sometimes more densely so at stem apex, but not forming a single terminal pseudo-whorl ......................................................................................................... 2

– Leaves densely grouped at stem apex, forming a single terminal pseudo-whorl ( Fig. 14S, Y ) or multiple pseudo-whorls .................................................................................................................. 10

2. Pedicel and sepals with glandular hairs ( Fig. 7H ); sometimes rare and diminute ............................ 3

– Pedicel and sepals without glandular hairs ....................................................................................... 5

3. Leaflet blades with obtuse, rounded or slightly retuse apex ................................ O. alstonii Lourteig

– Leaflet blades with acute, acuminate or caudate apex ...................................................................... 4

4. Inflorescences longer than the petiole of adjacent leaves, dichasial branches> 5 mm long, with flowers arranged distally to a long sterile portion; leaflet blades glabrous, with occasional marginal hairs .. .................................................................................... O. pardoensis (Lourteig) T.S.Costa & Fiaschi

– Inflorescences shorter than the petiole of adjacent leaves, dichasial branches 1.5–4 mm long, with flowers densely grouped along the entire length; leaflet blades glabrescent adaxially, with moderate, patent to appressed hairs abaxially ..................................................... O. animarum Fiaschi sp. nov.

5. Inflorescences mostly cauliflorous ( Fig. 10F ), not observable in young plants with poorly developed stem ................................................................................................................................................... 6

– Inflorescences mostly axillary ( Fig. 6A ), but sometimes with a few cauliflorous ones ................... 7

6. Fruits with carpels distally prolonged ca 2 mm long, slightly longer than the sepals ( Fig. 8L ); leaf blades pubescent; flowers with yellow petals ( Fig. 8K ); inflorescences usually with bifid dichasial branches ( Fig. 8I ) ................................................................................................. O. decipiens Progel

– Fruits with carpels not prolonged ( Fig. 10K–L ) or distally prolonged up to ca 0.5 mm of their length, shorter than the sepals; leaf blades glabrous; flowers with white petals ( Fig. 10J ); inflorescences with entire dichasial branches ( Fig. 10H ) .......................................................... O. idimae Fiaschi sp. nov.

7. Leaflet blades with obtuse, rounded or slightly retuse apex ................................ O. alstonii Lourteig

– Leaflet blades with acute, acuminate or caudate apex ...................................................................... 8

8. Flowers with white to pinkish corolla lobes ...................................... O. polymorpha Mart. ex Zucc.

– Flowers with yellow corolla lobes .................................................................................................... 9

9. Trinerved leaflets ( Fig. 6E ); leaflet blades abaxially with abundant, appressed hairs; inflorescence dichasial branches with flowers congested from the base ( Fig. 6K ) ..... O. amorimii Fiaschi sp. nov.

– Pinnately-nerved leaflets ( Fig. 1C ); leaflet blades abaxially glabrous, with occasional hairs along the margin; inflorescence dichasial branches with flowers not congested or, if congested, after a sterile portion ( Fig. 1A ) ........................................................ O. pardoensis (Lourteig) T.S.Costa & Fiaschi

10. Flower and fruit pedicel glabrous, sometimes with sparse, appressed hairs in bud ........................11

– Flower and fruit pedicel with sparse to very abundant, appressed, curved or patent hairs ............ 14

11. Petioles with intermixed unicelular and pluricelular hairs; mature inflorescences with short dichasial branches (0.5–3 mm long) and flowers (or persistent floral bracts) distributed along the entire length ........................................................................... O. cipoensis T.S.Costa, Sakuragui & Fiaschi

– Petioles glabrous or only with unicelular hairs; mature inflorescences usually with elongated dichasial branches (3.5–17 mm long) and flowers (or persistent floral bracts) distally congested ............... 12

12. Terminal leaflet blade 8–10.5 × ca 2 mm, narrowly elliptic to narrowly oblong or slightly oblanceolate; young stem glabrous; floral bracts glabrous; flowers with yellow corolla lobes ................................ ......................................................................................................................... O. artemioides Fiaschi

– Terminal leaflet blade 10–66 × 5–38 mm, ovate to lanceolate or elliptic to narrowly elliptic; young stem with moderate to very abundant, appressed or curved hairs; floral bracts with sparse, appressed hairs; flowers with white corolla lobes ........................................................................................... 13

13. Leaves grouped in a single, terminal pseudo-whorl; habit unbranched, 10–40 cm tall; terminal leaflet blade 20–66 × 17–38 mm, the base obtuse to rounded or slightly cordate ... O. colatinensis Fiaschi

– Leaves grouped in multiple pseudo-whorls; habit branched, (20–) 50–200 cm tall; terminal leaflet blade 10–20(–30) × 5–13 mm, the base cuneate to obtuse ................................... O. blackii Lourteig

14. Young stem with abundant to very abundant, appressed-retrorse hairs ..... O. umbraticola A.St.-Hil.

– Young stem with sparse to very abundant, appressed, curved or patent hairs, sometimes intermixed with glandular, pluricellular hairs, or glabrescent .......................................................................... 15

15. Peduncle and/or pedicels with intermixed unicelular and glandular-pluricelular hairs, or only with glandular hairs ................................................................................................................................ 16

– Peduncle and pedicels usually only with unicelular hairs, sometimes with few intermixed glandular hairs ................................................................................................................................................. 17

16. Lateral leaflets with symmetric to slightly asymmetric blades, similar to the terminal leaflet blade; petiole longer than the terminal leaflet blade ................................................... O. kollmannii Fiaschi

– Lateral leaflets with strongly asymmetric blades, diferente from the terminal leaflet blade; petiole usually shorter than the terminal leaflet blade ...................................................... O. neuwiedii Zucc.

17. Leaflet blades glabrous or glabrescent on both surfaces ................................................................ 18

– Leaflet blades with sparse to abundant hairs abaxially, glabrescent or with sparse hairs adaxially ... ......................................................................................................................................................... 20

18. Petioles as long as or longer than terminal leaflet blade; leaflet blades with obtuse, rounded or slightly retuse apex; corolla ≤ 10 mm wide ...................................................................... O. alstonii Lourteig

– Petioles usually shorter than terminal leaflet blade; leaflet blades with acute to acuminate apex; corolla ≥ 15 mm wide .................................................................................................................................. 19

19. Terminal leaflet blade ≥2 × longer than the lateral blades ( Fig. 11B ), with 5 –7 pairs of secondary veins; blade margins plane, ciliate. Pedicels with abundant, short, retrorse hairs; peduncles 9–50 mm long ..................................................................................................... O. itatingae Fiaschi sp. nov. *

– Terminal leaflet blade up to ca 1.5 × longer than the lateral blades ( Fig. 13C, D ), with 9–12 pairs of secondary veins; blade margin plane to revolute, with the occasional hairs usually hiding under the margin. Pedicels with sparse to moderate, curved to appressed, antrorse hairs; peduncles 82–110 mm long .................................................................... O. tijucana (Lourteig) Fiaschi comb. et stat. nov. *

20. Terminal leaflet apex acute or acuminate; lateral leaflets strongly asymmetric ............................. 21

– Terminal leaflet apex obtuse or rounded, sometimes acute; lateral leaflets symmetric or slightly asymmetric ....................................................................................................................... O. puberula

21. Flowers with white to pinkish corolla lobes; leaflet blades adaxial surface usually glabrescent ....... ............................................................................................................ O. polymorpha Mart. ex Zucc.

– Flowers with yellow corolla lobes; leaflet blades adaxial surface with moderate, appressed hairs ... ........................................................................................................................... O. roselata A.St.-Hil.

Figures

Fig. 7. Oxalis animarum Fiaschi sp. nov. A. Habit. B. Detail of young stem with short, curved hairs (note very short young inflorescence). C. Detail of leaflet blades insertion. D. Terminal leaflet abaxial surface. E–F. Lateral leaflets abaxial surface. G. Inflorescence with old flower (left) and young buds (right). H. Inflorescence detail showing flowers with glandular pedicel and sepals. I. Flower, frontal view. J. Fruit, lateral view. K. Seed, lateral view. Photos: A–F: Jhonathan Radavelli; G–J: Pedro Fiaschi; K: Gabriela Rhoden. A–F based on F.S. Cabral et al. 275, FLOR; G–J based on P. Fiaschi et al. 5620, FLOR; K based on M.L.L. Martins & R. Alves 2455, FLOR, HURB.

Fig. 14 (on next page). Comparative figure among segregated, yellow-flowered species of the former Oxalis polymorpha Mart. ex Zucc. s. lat. (following Lourteig 1994 and Fiaschi 2014); A, G, M, S, Y = Stem apical portion; B, H, N, T, Z = Terminal leaflet; C, I, O, U, Aʼ = Lateral leaflet; D, J, P, V, Bʼ = Inflorescenca detail; E, K, Q, W, Cʼ = Flower, frontal view; F, L, R, X, Dʼ = Fruit, lateral view (unknown in O. amorimii, F). A–F. Oxalis amorimii Fiaschi sp. nov. G–L. Oxalis animarum Fiaschi sp. nov. M–R. Oxalis decipiens Progel. S–X. Oxalis itatingae Fiaschi sp. nov. Y–Dʼ. Oxalis tijucana (Lourteig) Fiaschi. Scale bars: A, G, M, S, Y = 2 mm; B–C, H–I, N–O, T–U, Z–Aʼ = 1 cm; D, J, P, V, Bʼ = 5 mm; E, K, Q, W, Cʼ = 2 mm; L, R, X, Dʼ = 1 mm.

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.

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.

Fig. 8. Oxalis decipiens Progel. A–B. Habit (note cauliflorous and axillary inflorescences in B). C. Detail of young stem. D. Terminal leaflet, abaxial view. E. Lateral leaflet, abaxial view. F. Detail of leaflet blades insertion, abaxial surface. G–H. Detail of young inflorescences with flower buds. I. Older inflorescence with bifid dichasial branches. J. Inflorescence detail with flower and young buds. K. Flower, frontal view. L–M. Fruits, lateral view (note carpels prolonged for ca 2 mm of their length). N. Seed, lateral view (the central dark spot is likely due to incomplete SEM coating). Photos: A–M: Pedro Fiaschi; N: Gabriela Rhoden; A, C, G, N based on E. Richetti et al. 64, FLOR; B, L based on P. Fiaschi & J.L. Costa Lima 4656, FLOR; D–F, H–K, M based on J.C. Vasques et al. 57, FLOR, HUEFS, RB, SPF.

Fig. 1 (on next page). Lectotype of Oxalis polymorpha Mart. ex Zucc. (Martius s.n.; M-0172333), showing a few morphological features.A. Dichasial branches with the flowers distally grouped. B. Young stem with very abundant, patent hairs (B1) and first flower with the pedicel articulated in the mid-portion (B2). C. Leaf blade venation conspicuous abaxially. D. Leaves distributed along the stem. E. Young fruit with the carpels only slightly prolonged apically. Modified from a high-resolution image provided by the Botanische Staatssammlung München.

Fig. 11. Oxalis itatingae Fiaschi sp. nov. A. Habit. B. Leaf adaxial surface. C. Leaf abaxial surface (one lateral leaflet removed). D. Detail of leaflet ciliate margin. E. Habit (under cultivation).F. Detail of leaflet blades insertion, adaxial surface. G. Detail of leaflet blades insertion, abaxial surface H. Inflorescence with flower buds. I. Inflorescence with closing flower and young buds. J. Detail of hairs on the pedicel. K. Mature fruit, lateral view. L. Fruit after seeds ejected, lateral view. M. Seed, lateral view. Photos: A: Pablo Feliz; B-L: Pedro Fiaschi; M: Gabriela Rhoden. A based on P. Feliz 372, RB; B–C, E, H–M based on P. Fiaschi et al. 4472, holotype, FLOR; D, F–G based on J.C. Vasques et al. 86, FLOR.

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.