Persicaria humboldtiana Funez & Hassemer 2021, sp. nov.
Creators: name: Funez, Luís A.
name: Hassemer, Gustavo
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Caryophyllales
Polygonaceae
Persicaria
Persicaria humboldtiana

description: Persicaria humboldtiana Funez & Hassemer, sp. nov.   
 Type: — BRAZIL. Santa Catarina: Corupá: RPPN Emílio Fiorentino Battistella, 12 January 2020, L. A. Funez 9599 (holotype FURB! [Figure 1]).   
 Diagnosis: —Differs from Persicaria minor (Huds.) Opiz by petiolate broad-lanceolate leaves and tepals up to 1.1 mm long, with marked venation.   
 Description (Figure 1): —Herbs perennial. Stems 15–40 cm long, erect to ascending, usually branched near the base, rooting at basal nodes, glabrous, 0.7–1.8 mm diam., internodes 20–35 mm long. Ochrea brownish hyaline, cylindric, 4–8 mm long, membranaceous, base inflated, margins truncate, with bristles 2–3 mm long, surface scarcely strigose, trichomes ca. 1 mm long, eglandular; petiole 3–6 mm long, adnate to the lower half of ochrea, antrosely pubescent; blade, broadly lanceolate, 3.3–6.5 × 1.2–2.3 cm, base long-attenuate, apex acute to acuminate, margins antrorsely appressed-pubescent, adaxial and abaxial surface appressed-pubescent along midvein and glabrous on lamina. Inflorescences terminal, or also axillary, erect to apically curved, uninterrupted, 3.2–5.6 × 0.3 cm, pedunculated, peduncle to 1.4 cm long, glabrous; ochreolae 1.0–1.8 × 0.3–0.5 mm, glabrous, margins ciliate with 1–4 bristles 0.1–1.0 mm long. Pedicels ascending, ca. 0.5 mm long. Flowers bisexual, 2–3 per ochreate fascicle, homostylous; perianth white, not glandular-punctate, membranaceous with conspicuous venation; tepals 5, connate 1/3–1/4 of their length, obovate, 0.8–1.1 × 0.3–0.6 mm, margins entire, apex obtuse to rounded; stamens 6, included, filaments 0.6–0.7 mm long, adnate to petals at base; anthers white, elliptic to ovate, ca. 0.1 mm long; styles 2, ca. 0.5 mm long, included, connate 1/3 of its length, stigma capitate. Ovary conic, 0.6 × 0.4 mm. Fructiferous perianth greenish, 1.7–2.0 × 1.0– 1.1 mm. Achenes dark brownish, trigonous, 1.8–1.9 × 0.9–1.0 mm, with an apical portion 0.2–0.3 mm long, shiny, smooth.   
 Etymology: —The specific epithet is a tribute to the German explorer, geographer and naturalist Friedrich Wilhelm Heinrich Alexander von Humboldt (1769–1859), who was originally honoured by the name Hansa Humboldt, the original name of Corupá, the Brazilian municipality where the new species, according to the best of evidence, is restricted to. The village of Hansa Humboldt was founded by German immigrants in 1897, and had its original name forcibly changed to Corupá in 1944 as part of Getúlio Vargas’ policy of persecution of the German-speaking population in Brazil.   
 Phenology: —Confirmed flowering and fruiting: January. This species was seen alive during the late autumn and winter, but not fertile. Thus, it is probably that species blooms along the summer and parts of spring and autumn, as most of the Brazilian species.   
 Distribution: —The new species is only known from the type locality, in Salto Grande waterfall, in the Emílio Fiorentino Battistella Natural Heritage Particular Reserve, in Corupá municipality, northern Santa Catarina, southern Brazil (Figure 2).   
 Habitat: — Persicaria humboldtiana inhabits humid rocks along the riverbanks, at permanently humid spots due to constant splashing, and is susceptible (and seemingly resistant) to occasional flooding. The new species occurs in the same locality and environment as the narrowly endemics Plantago humboldtiana Hassemer in Hassemer & Rønsted (2016: 4–9) and Ludwigia humboldtiana Funez et al. (2020: 80–87), what demonstrates the high importance of this habitat for biodiversity conservation.   
 Conservation status: — Persicaria humboldtiana is here assessed as Critically endangered CR according to the criterion B2a,b(iii) of IUCN (2019). The area of occupancy (AOO) of less than 2 km ², with only one population known. This population is located within an environmentally protected area (Emílio Fiorentino Battistella Natural Heritage Particular Reserve); nevertheless, the species unfortunately cannot be considered satisfactorily safe, because of the ongoing trend of reduction of environment protection areas in the region, due to the pressure caused by the agricultural advance in Santa Catarina state (Hassemer et al. 2015) and in Brazil as a whole, leading to the conversion of natural environments in agricultural and silvicutural lands.   
 Notes: —This species is most similar to Persicaria minor, a cosmopolitan species common in Eurasia and North America, with only one record in South America, in Argentina (Cialdella 1989). Despite the similarities due the small size of the vegetative and reproductive characters of both species, P. humboldtiana is easily differentiated due its petiolate, broadly lanceolate leaves (vs. sessile, linear lanceolate leaves in P. minor). Another very useful characteristic to distinguish these species is the size of the tepals, much smaller in P. humboldtiana, 0.8–1.1 mm long, with prominent veins (vs. 2.5–3.0 mm long, with inconspicuous venation in P. minor) (see Table 1).   
 Other species similar to Persicaria humboldtiana are P. hydropiperoides (Michaux 1803a: 239) Small (1903: 378–379, 1330), P. maculosa Gray (1821: 269) and P. setacea (Baldwin in Elliott [1817: 455]) Small (1903: 379, 1330), but the size of the tepals are conspicuously bigger than in P. humboldtiana; all these species has flowers with tepals longer than 2.5 mm long and sessile leaves, whereas P. humboldtiana tepals are 0.8–1.1 mm long and its leaves are petiolate.
description: Published as part of Funez, Luís A. & Hassemer, Gustavo, 2021, Novelties in Persicaria (Polygonaceae): description of a narrowly endemic new species from southern Brazil, and typification of the name Polygonum minus, pp. 60-70 in Phytotaxa 490 (1) on pages 61-64, DOI: 10.11646/phytotaxa.490.1.5, http://zenodo.org/record/5753697