Xanthosoma isabellanum Cornejo & Croat, 2021

Cornejo, Xavier & Croat, Tom, 2021, Anthurium gallardoae and Xanthosoma isabellanum (Araceae), two new species from coastal Ecuador, Phytotaxa 505 (1), pp. 107-113 : 111

Xanthosoma isabellanum Cornejo & Croat , sp. nov. ( Fig. 2 )

Xanthosoma isabellanum is a new species similar to Xanthosoma guayaquilense , an allopatric species that is also endemic to coastal Ecuador, but X. isabellanum differs by its blades patent to divergent 0–40°, 0.5 times as long as petiole, anterior lobe broadly acute, the blade glabrous above, and inflorescences with staminate portion 5.0– 6.5 cm long and sterile portion fully covered by staminodia, 2.8–3.5 cm long, instead of leaf blades suberect, 45–80°, 0.3–0.4 times as long as petiole, anterior lobe narrowly acute, the blade shortly white-pilose above, and inflorescences with staminate portion 8–10 cm long and sterile portion fully covered by staminodia, 4–5 cm long of X. guayaquilense . In addition, there are also significant differences on the phenology and biological cycles of both species (see discussion).

Type: — ECUADOR. Guayas: Reserva Ecológica Manglares Churute, base del Cerro Cimalón , ca. 02°25’S, 79°35’W, ca. 50 m, tropical dry to moist forest, Jan 2019 (st), flowered in cultivation in Guayaquil, 02°07’46”S, 79°54’25”W, ca. 6 m, 7 Aug–6 Sep 2020 (fl), X. Cornejo 9336 (holotype GUAY!, mounted material and spirit collection) .

Moderately small tuberous herb to 0.6 m tall; tuber depressed-globose, drying 2–3 cm diam. Bracts narrowly lanceolate, membranous, the outer 1-costate, to 15 × 2 cm, purplish; the inner 2-costate, slightly shorter than the outer bract, greenish-white. Leaves with petioles 30–50 cm long, purplish, drying dark brown, 1 cm diam. near the base, 4–5 mm diam. midway, 3–4 mm diam. near the apex; blades 0–40° patent to divergent, triangular-subhastate, 18–25 cm long, 17–20 cm wide, 0.5 times as long as petiole, broadest across the posterior lobes, drying thin, brownish green above, light grayish green below, the margins sinuate; anterior lobe 13–16 cm long, broadly acute, nearly straight to slightly convex and sinuate on the margins; posterior lobes 7–10 cm long, 3–5 cm wide, subhastate, slightly overlapping at the base, dark green and almost matte above, moderately paler and semiglossy below; upper surface glabrous; midrib strongly raised below, prominent, slightly lighter than the blade; primary lateral veins 2 pairs, raised and concolorous below; basal veins 2 pairs, 1 st pair free to base, 2 nd basioscopic; posterior rib not naked, branching before reaching the tip of the posterior lobe. Inflorescences 1 per axil, erect; peduncle 23–40 × 0.5–0.8 cm, pale green, glossy when fresh; spathe 13–16 cm long, tube green, matte and longitudinally weakly veined without, dark-purple or burgundy to greenish with dark-purple veins within, 3.5–5.0 × 1.7–2.2 cm when fresh, 3.5 × 1.0 cm when dry; blade creamish-white to white on both sides, 7.7–10.0 cm long when fresh, 7–8 cm when dry; spadix 10.3–12.5 cm long, staminate portion 5.0–6.5 × 0.8–1.0 cm and white when fresh, 4–5 × ca. 0.7 cm when dry, sterile portion fully covered by staminodia, 2.8–3.5 cm long, 3–5 mm diam. in the middle, white, the lower part with thickened staminodia 5–9 mm long when fresh, pinkish or sometimes greenish-white; pistillate portion 1.5–2.0 × 0.8–1.0 cm and yellowish to yellow when fresh, 1.5 × ca. 0.7 cm when dry. Infructescences not seen.

Discussion: — Xanthosoma isabellanum is among the smaller species in the genus. This new species is most closely related to Xanthosoma guayaquilense , an allopatric species that is also endemic to coastal Ecuador, but X. isabellanum morphologically differs by the characters written in the diagnosis. In addition, there are also significant differences on the phenology and biological cycles of both species, Xanthosoma isabellanum at least in cultivation (because the phenology has not been observed in a natural habitat) is evergreen during the whole year and can produce inflorescences during the dry and rainy seasons, meanwhile X. guayaquilense in nature and in cultivation produce leaves and inflorescences only for few months, from ending December or January to Apr, that strictly is during the rainy season, being the whole plant fully deciduous, apparently absent, and remaining only the underground tubers during the dry season (Cornejo, pers. obs. in Delannay et al. 2019).

Etymology: —The species is named after my daughter Isabella Cornejo, she aids caring several cultivated native plants at home including X. isabellanum among those.

Habitat and distribution: — Xanthosoma isabellanum is an endemic at ca. 50 m, in a conserved Tropical dry to moist forest life zone at the Reserva Ecológica Manglares Churute, province of Guayas, coastal Ecuador .

Phenology and cultivation: —Flowering during the dry season from August to September, and during the rainy season from December to February. Among native species, Xanthosoma isabellanum is one of the few herbs that can be cultivated as an ornamental under shade in tropical warm cities as Guayaquil. Xanthosoma isabellanum is easy to reproduce by propagules or vegetative seedlings, and has produced inflorescences several times, however, similar to X. guayaquilense , the flowers of X. isabellanum are not pollinated and do not produce fruits, most likely due to the absence of native pollinators in urban areas of Guayaquil. Therefore, efforts for conservation of these endangered species must consider the vegetative propagation and cultivation as ornamental plants.

Conservation status: —The less than 100 individuals found in the original habitat that is thereathened by selective cutting and occasionally fires during the dry season led us to regard Xanthosoma isabellanum as Endangered EN B1 ab(iii) ( IUCN 2017).

Figures

FIGURE 2. Xanthosoma isabellanum.A. Cultivated plant.B. Inflorescence and two leaves.C. Inflorescence at anthesis. D. Longitudinally sectioned inflorescence displaying the purple interior of lower spathe, pistillate flowers, and sterile portion fully covered by staminodia.