Philodendron rheophyticum Buturi & Temponi, 2015

Philodendron rheophyticum Buturi & Temponi View in CoL , sp. nov. ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 )

Philodendron rheophyticum View in CoL is most similar to Philodendron flumineum Gonçalves (2000: 55) View in CoL , from which it differs by its obscure primary lateral veins, obovate leaf blade, and by the longer length of the spadix (up to 9.5 cm).

Type:— BRAZIL. Paraná: Alto Paraíso, Porto Figueira district, 23°23’5.7” S, 53°47’46.2” W, 04 February 2014, C. V. Buturi et al. 77 (holotype RB!, isotypes KEW!, MBM!, MO!, UNOP!).

Rheophyte. Resin colourless. Stem decumbent, 0.5−1 cm in diameter; internodes 1.2−5 cm long, cylindrical, green to brownish, root

0.8 mm in diameter. Leaf prophyll 6.3−9 × 1.2 cm, whitish. Foliar sheath upright closed, 7−12.5 cm, short ligule projecting, up to 2 mm; petiole 0.3−3.1 × 0.1−0.3 cm, terete to canaliculated adaxially, green; leaf blade 16−31 × 6.7−9.5 cm, obovate to rarely elliptic, apex acuminate, base acute or attenuated, obscure primary lateral veins, discoloured, adaxial face opaque with lateral parallel lines dark green to brownish, chartaceous to sub-coriaceous. Inflorescence: 1 per floral sympodium; peduncle 3−5.5 × 0.3−0.5 cm, spathe 9−12 × 6−7.5 cm, elliptic, median constriction absent, partially closed during anthesis, green to whitish becoming yellow at anthesis, chartaceous; spadix 5−9.5 cm, staminate zone 3−6.2 × 0.5−0.9 cm, basal sterile male zone 0.3−0.8 × 0.9 cm; pistillate zone 1.5−2.7

× 0.7−1.1 cm, stipe of spadix 0.5−0.7 cm. Stamens 1.8−2 × 1.6−1.7 mm, whitish; basal staminodes 2−2.5 × 1.8−2 mm, whitish; gynoecium 2.4−3.6 × 2−2.3 mm, ovary 2.2−3.4 mm, whitish, stigma 0.1−0.2 mm, green to whitish, 3–4 locular, placentation axial, ovules many per locule, ovule 0.2−0.4 mm. Berries not observed.

Phenology:— Flowers in February.

Etymology:— The specific epithet is a reference to the rheophytic habit of the plant, which is very rare in Philodendron , being described only in two species so far: P. flumineum and P. carajasense .

Distribution and habitat:— Philodendron rheophyticum occurs along the Paraná River in the Ilha Grande National Park, Alto Paraíso city, Paraná State, Brazil, located in a remnant of the Seasonal Alluvial Semideciduous Forest ( Roderjan et al. 2002).

Conservation:— Philodendron rheophyticum is endemic to Ilha Grande National Park and grows at the riverside of Paraná River. Although with a dense population, it was observed only in a portion of the river. This park belongs to the Paraná River Biodiversity Corridor and both suffer human interference by the presence of a hydroelectric dam. The discovery of this endemic new plant highlights the importance of conserving the fragile remnants of the Atlantic Forest.

Paratypes:— Brazil. Paraná: Alto Paraíso, Ilha Grande National Park, 09 March 2013, C. V. Buturi et al. 06 (UNOP!).