Portulaca ferricola J.R.Ferraz & Hassemer

Ferraz, José Roberto, Rossetto, Elson Felipe Sandoli, Ribeiro, José Eduardo L. S. & Hassemer, Gustavo, 2022, Taxonomic notes Portulaca (Portulacaceae) in South America I: the taxonomic status of P. mucronulata var. microphylla, Phytotaxa 560 (1), pp. 71-81 : 72-80

Portulaca ferricola J.R.Ferraz & Hassemer , nom. et stat. nov.

≡ Portulaca mucronulata var. microphylla Legrand (1949: 355) non Richard (1845: 620) (Art. 6.11 of the ICN).

Type: — BRAZIL. Mato Grosso do Sul: Corumbá, March 1906, Etchichury 85 (holotype SI 003157!) .

Diagnosis:— Portulaca ferricola can be morphologically distinguished from the other Portulaca species by the combination of the following characters:slightly swollen roots,decumbent branches and stem covered with an exfoliating bark, lanceolate or ovate-lanceolate leaves, abundant leaf axillary hairs stiff and a hemispheric operculum.

Description ( Figs. 1 , 2 , and 4): — Perennial succulent herb, up to 6 cm high; roots slightly swollen, covered with an exfoliating brown bark. Stem branched, covered with an exfoliating brown bark; primary branches 4‒12 cm long, decumbent, covered with an exfoliating bark, green in young living specimens, brownish in old living specimens, pale yellow or brownish in herbarium material; secondary branches usually with internodes very short, which gives the branch the appearance of a fascicle. Leaves alternate, subopposite at the apex, simple, fleshy, green in a wet environment, reddish in a dry environment; petiole 0.4‒0.6 mm long, green lighter than the blade; blades 3.5‒8.5 × 1.0‒ 2.5 mm, terete, lanceolate or ovate-lanceolate, adaxially and abaxially glabrous; base slightly rounded; apex acute, reddish; margins entire; leaf axillary hairs abundant (denser at the apex), up to 2 cm long, stiff, white in living specimens, yellow or brownish in herbarium material. Inflorescence a terminal head, 2‒4-flowered, subtended by an involucre of 6‒15 leaves. Flowers sessile; sepals 2, unequal, connate at the base, 5.2‒7.8 × 4.0‒ 6.5 mm, ovate, apex acuminate, margins scarious; petals 5, magenta, sometimes vinaceous, with a reddish spot in the adaxial surface at the base, 1.5‒2.2 × 0.8‒1.6 cm, obovate, apex obcordate, emarginate; stamens 50‒80, filaments connate at the base and forming a ring ca. 0.8‒1 mm long, filaments 2.0‒4.5(‒5.0) mm long, unequal, magenta, glabrous; anthers ca. 1 mm long, dark yellow, pollen released through longitudinal slits; ovary sub-globose; style 7.5‒8 mm long, very thickened near the stigmatic branches, magenta, glabrous; stigma magenta, 5‒10-lobed, 1.5‒2.2 mm long, linear, 3-nerved, the stigmatic surfaces covered with small hairs. Fruit a circumscissile capsule, sessile or pedicelate, pedicel 0.2‒0.4 mm long, capsule 4.0‒ 6.5 mm long, dehiscence line ca. at the lower third; operculum hemispheric, green, shiny, apiculate; fruit base sometimes reduced. Seeds ca. 30 per capsule, 0.52‒0.85 mm, subreniform, black, ornate, constriction zone present, individual cells elongated, anticlinal walls undulate with T-, U-, and V-type patterns, sometimes bifurcating, periclinal walls convex, the cells toward the peripheral face of the seed par-domed.

Etymology:— The specific epithet “ ferricola ” is derived from the Latin ferreus (iron) and - icola (dweller), referring to the ironstone outcrops and shallow ferruginous soils, habitats in which the species is found.

Phenology:— Flowering and fruiting times from December to June.

Geographic distribution and habitat:— Portulaca ferricola was collected in two municipalities (Corumbá and Ladário) in western Mato Grosso do Sul State, Brazil, and in one province (Germán Busch) in Santa Cruz Department, eastern Bolivia ( Fig. 3 ). This species is endemic to ironstone grasslands (canga vegetation), growing in ironstone outcrops and shallow soils at an elevation of 100–280 m a.s.l. This canga vegetation is surrounding by savannas and Seasonal Decidual Forest and occur along the foot of the plateau hills, presenting an impermeable substrate and with little presence of sediments ( Takahasi & Meirelles 2014, Villarroel et al. 2017). The associated plants includes edaphic endemic species, such as Gomphrena centrota Holzhammer (1955: 188) , Discocactus ferricola Buining & Brederoo (1975: 2) , and Deuterocohnia meziana Kuntze ex Mez (1896: 465) ( Lima et al. 2019).

Conservation status:— Endangered (EN – B1ab[i, ii, iii]+2ab[i, ii, iii]). There are only five known populations of Portulaca ferricola occupying an AOO (Area of Occupancy) of 20 km 2 and EOO (Extent of Occurrence) of 294.066 km 2. The major threats to this species include habitat degradation, trampling from cattle and direct competition by invasive non-native plant species from adjacent pastures, such as the grass Megathyrsus maximus ( Jacquin 1781: 2) Simon & Jacobs (2003: 572) .

Nomenclatural notes:— Elevation of Portulaca mucronulata var. microphylla to species rank was not possible by means of a new combination, because of the existence of the earlier and validly published name P. microphylla Richard (1845: 620) . Therefore, P. ferricola , a new name, is proposed, in accordance with Art. 6.11 of the ICN.

Taxonomic notes:— The abundant stiff leaf axillary hairs are an unusual feature in Portulaca species that give herbarium specimens a caterpillar-like appearance ( Legrand 1962). In addition to P. ferricola , only three other South American species have very conspicuous stiff trichomes: P. cardenasiana , P. eruca , and P. mucronulata var. mucronulata .

Portulaca cardenasiana (dry Chaco vegetation from Bolivia and Paraguay) shares with P. ferricola the ovatelanceolate leaves and branches and roots with exfoliating bark. However, P. ferricola can be distinguished from P. cardenasiana by the smaller branches (4‒12 cm vs. 15‒20 cm), stem habit (decumbent vs. decumbent to erect), apices of branches not widened and with a series of 6‒15 leaves (vs. widened and with more than 20 leaves organized in several series), and operculum shape (hemispheric vs. campanulate to subconical) ( Table 1 ). Furthermore, P. cardenasiana can be easily recognized in herbaria by its short fascicles of leaves overlapped by brown trichomes, which persist after the leaf-fall ( Fig. 5 ).

Portulaca ferricola also has reproductive characters similar to P. eruca (endemic species from Argentina and Paraguay; Fig. 6 ) and P. mucronulata var. mucronulata (mountain range in central Argentina; Fig. 7 ). P. ferricola differs from P. eruca by the stem ramification and habit (branched and decumbent vs. simple to few branched and decumbent to erect), roots (slightly swollen vs. tuberous), and leaf shape (lanceolate or ovate-lanceolate vs. subulate) ( Table 1 ). On the other hand, P. ferricola can be distinguished from P. mucronulata var. mucronulata by the leaf shape (lanceolate or ovate-lanceolate vs. linear), longer petals (1.5‒2.2 cm vs. 0.8‒1.0 cm), and the presence of an exfoliating bark in the branches, stem and roots (vs. absent) ( Table 1 ).

Additional specimens examined:— BOLIVIA. Santa Cruz: Germán Busch, Serranias del Mutún , 14 March 2008, Villarroel et al. 2069 ( MO2136220 , USZ) . BRAZIL. Rodovia BR-262, Serra do Urucum , 14 April 1972, Hatschbach 29490 ( MBM021046 ) ; Mato Grosso do Sul: Corumbá, Fazenda Banda Alta , 9 June 1994, Hatschbach et al. 60832 ( MBM245674 ) ; ibidem ( US 01344988); ibidem Hatschbach et al. 60832B ( MBM245672 ) ; Fazenda Monjolinho, Takahasi 824 ( COR00030468 ) ; ibidem ( FUEL056657 ) ; Fazenda Monjolinho, 14 December 2006, Takahasi et al. 1169 ( COR00030445 ) ; ibidem ( FUEL056655 ) ; Fazenda Figueira , 13 March 2006, Takahasi et al. 970 ( COR) ; ibidem ( FUEL056656 ) ; Fazenda Banda Alta , 17 January 2007, Takahasi et al. 1193 ( COR00007789 ) ; ibidem ( FUEL056650 ) .

Figures

FIGURE 1. Portulaca ferricola. A. Overview of the habitat. B. Aspect of the individual in wet period. C. Aspect of the individual in dry period.D. Flower. E. Detail of stem and branches covered with an exfoliating brown bark. F. Fruit. G. Seeds (Takahasi et al. 1193, FUEL), blue circle highlighting the cells toward the peripheral face of the seed par-domed and red circle highlighting the anticlinal walls undulate with U- and V-type patterns [photos by A. Takahasi (A–D) and by J.R. Ferraz (E–G)].

FIGURE 2. Holotype of Portulaca ferricola (Etchichury 85, SI003157!).

FIGURE 3. Distribution map of Portulaca ferricola and closely related taxa.

FIGURE 5. Isotype of Portulaca cardenasiana (Cárdenas 2740, F0067856!).

FIGURE 6. Portulaca eruca with evident tuberous root (Hunziker 12578, CORD!).

FIGURE 7. Paratype of Portulaca mucronulata var. mucronulata (Peirano 9482, LIL000440!).