Tuesday, April 7, 2020

[Botany • 2020] Hoya sulawesiana & H. surisana • Two New Species of Hoya (Apocynaceae, Asclepiadoideae) from Sulawesi, Indonesia

Hoya sulawesiana S.Rahayu & Rodda

in Rodda & Sri Rahayu, 2020. 
 Taiwania. 65(2)taiwania.ntu.edu.tw

We document the discovery of two new species of Hoya from Sulawesi, Indonesia, Hoya sulawesiana S.Rahayu & Rodda and Hoya surisana Rodda & S.Rahayu. Hoya sulawesiana is similar to Hoya isabelchanae Rodda & Simonsson in flower morphology because both species have very pubescent globose corolla but they can be separated based on leaf morphology and corolla indumentum type. Hoya surisana is very unusual because its flowers display a combination of large calyx lobes, a white, pubescent, campanulate corolla, and dark purple corona lobes so far not observed in any other species of the genus.

Keyword: Acanthostemma, Celebes, Cystidianthus, Hoya, Makalangkan Mountain, Mamuju, Marsdenieae

Fig. 1. Hoya sulawesiana S.Rahayu & Rodda.
 A, inflorescence; B, inflorescence, side view; C, flower, top view; D, flower, side view; E, corona, side view; F, corona, from underneath; G, leaves: right, from above; left, from underneath; H, pollinarium.
photos, A-G by Surisa Somadee; H by Michele Rodda.

Hoya sulawesiana S.Rahayu & Rodda, sp. nov. 

Similar to Hoya isabelchanae Rodda & Simonsson in inflorescence, corolla and corona morphology, but differing in lamina shape (orbicular-ovate (to elliptic), convex, to 7 cm long in H. isabelchanae vs. lanceolate or elliptic in H. sulawesiana 7–30 cm long), and in type of corolla inner surface pubescence (hairs straight and pointing outwards in H. isabelchanae vs. recurved towards the corona in H. sulawesiana).  

Distribution. Only known from South Sulawesi in Towuti and West Sulawesi in Mamuju at low elevation (100–300 m). 

Etymology. Hoya sulawesiana is named after the island of Sulawesi, where it is endemic.

Fig. 2. Hoya surisana Rodda & S.Rahayu.
 A, inflorescence; B, buds, almost ready to open; C, inflorescence back view, showing the large calices; D, leaves: right, from underneath; middle, from above; left, from above and immature;
photos, A-C by Surisa Somadee; D by Michele Rodda.

Fig. 3. Hoya surisana Rodda & S.Rahayu.
A, flower; B, flower, side view; C, calyx; D, E, corona, side view; F, corona, from underneath; G, follicle showing seeds within; H, pollinarium.
 photos, A-G by Surisa Somadee; H by Michele Rodda.

Hoya surisana Rodda & S.Rahayu, sp. nov.
 Similar to that of Hoya mappigera in corolla and corona shape and colour, but differing in number of flowers, size and shape of the calyx and corolla and in corolla pubescence. 

Distribution. only known from West Sulawesi, Makalangkan mountain, at about 500 m elev. 

Etymology. Hoya surisana is named after Surisa Somadee, Thai Hoya expert and grower.  

Michele Rodda and Sri Rahayu. 2020. Two New Species of Hoya (Apocynaceae, Asclepiadoideae) from Sulawesi, Indonesia. Taiwania. 65(2); 209-215.  taiwania.ntu.edu.tw/abstract.php?type=abstract&id=1675