A New Southern Hemisphere Species of Potentilla (Rosaceae)

Abstract

Potentilla A. Castagnaro & M. Arias, sp. nov., from Tucumin, Argentina, is described and illustrated. Potentilla was originally determined as P. norvegica. The latter and PR anserina were the only two species of this large genus primarily of the Northern Hemisphere cited from Argentina. Potentilla is distinguished from P norvegica by morphological-reproductive (flowers and achenes), anatomical (stomata), and genetic (chromosome number) characters. The genus Potentilla belongs to the family Rosaceae and includes approximately 500 species of annual and perennial herbs and shrubs (Davidson, 1995), most of them from the Northern Hemisphere (Acharya-Goswami & Matfield, 1975). Potentilla norvegica was characterized by Linnaeus (1753) as a Scandinavian species. In 1900 Lillo found morphologically similar specimens in Tucum~n (Argentina), which he identified it as P. norvegica. Later, Zardini (1973) cited this species from C6rdoba and La Rioja, and Novara (1993) observed similar specimens in the Valle de Lerma, province of Salta, Argentina (Fig. 1). However, studies carried out by our group with recently collected material, comparison with materials from different herbaria, and an exhaustive literature search revealed that all specimens found in Argentina that were erroneously called P norvegica belong to a new species designated here as P (Fig. 2); this new species does not resemble any other European or North American species (Focke, 1888; Wolf, 1908; Rothmaler, 1959; Kalkman, 1968; Werner & Soule, 1976; Fitter et al., 1986; Ikeda & Ohba, 1993). Furthermore, the true P. norvegica does not occur in Argentina or at least has not yet been reported from there. The main morphological-reproductive, anatomical, and genetic differences observed between P. and the European P norvegica are shown in Table 1. Despite the fact that this plant was originally classified as P. norvegica because of its broad similarities to the European species, we have considered it to be novel not only for its diploid status, but also because morphological and anatomical analyses (Ikeda & Ohba, 1993; Leht, 1991) showed relevant taxonomic characters that clearly discriminate P. from P n rvegica. The name tucumanensis refers to the geographical region that in the colonial period was called Regi6n del Tucumin. Potentilla A. Castagnaro & M. Arias, sp. nov. TYPE: Argentina. Tucumin: Dpto. Trancas, Loc. Potrero, 1500-1600 m, sunny disturbed areas, 12 Sep. 1996, D. Kirschbaum 11 (holotype, LIL 602866). Figure 2. Herba annua erecta 10-30 cm alta. Folia trifoliolata pubescentia, basalia petiolis longis apicaliaque petiolis brevibus insidentia; foliolo terminali 6-20 mm longo, 515 mm lato, elliptico, profunde bidentato; venatione brochidodroma; estipulis bipartitis. Inflorescentia ex flore solitario constans; bracteolis calyculi elliptico-lanceolatis, apice attenuatis, pubescentibus, venatione reticulata. Flos 3-6 mm longus, 4-9 mm latus; sepalis triangularibus; petalis flavis, lanceolato-spathulatis, glabris, venatione dichotoma, 1.8-2.5 mm longis, 0.7-1.5 mm latis; staminibus 15 tricyclis aequalibus, filamentis filiformibus curvatis, antheris subglobosis. Achenia ochracea, reniformia; tegumento laevi, rare alato; stylo in fructu persistente, membranaceo; stigmate bilobo, incurvato. Numerus chromosomatum: 2n = 2x = 14. Annual herb, erect, 10-30 cm high; root unbranched, vertical. Leaves 3-foliolate, pubescent with glandular and unicellular trichomes on both sides of epidermal leaves; terminal leaflet 6-20 x 5-15 mm, elliptic, deeply bidentate; basal leaves with long petioles (30-70 mm) and apical leaves with short petioles (1-30 mm); stipules bipartite; venation brochidodromous. Flower solitary, 3-6 x 4-9 mm; peduncle 5-15 mm long; epicalyx bracteoles elliptic-lanceolate with attenuate apex, 2.53.5 x 0.8-1.0 mm, pubescent with reticulated veins. Sepals triangular, veins reticulated, pubesNovoN 8: 333-336. 1998. This content downloaded from 40.77.167.24 on Mon, 19 Sep 2016 06:13:48 UTC All use subject to http://about.jstor.org/terms