136 
Card. Bull. Singapore 69(1) 2017 
Distribution. Known only from the type locality in Sandaun Province, Baiberi. 
Etymology. Named after the late Mr Sten-Ake Svensson (1947 - 2011) of Sweden, 
whose children supported the first author’s work in PNG. 
Habitat and ecology. The single known specimen was growing as an epiphyte 20 
metres up in a very tall tree, nestling inside a fern, Asplenium sp., in a species-rich 
primary forest with limestone karsts. 
Provisional IUCN conservation assessment. Critically Endangered CR B2ab(ii,iii), 
Cl, C2(ai), D (IUCN, 2016). Several botanical expeditions have been conducted in the 
vicinity of the type locality, both by the first author and several other earlier botanists, 
but Hoya stenakei was found only once. The two similar species Hoya archboldiana 
C.Norman and Hoya onychoides P.I.Forst., Tiddle & I.M.Tiddle, on the other hand, 
were encountered several times during the first author’s expeditions in PNG. The type 
locality was to be logged soon after our expedition and it must now be assumed that 
this locality is destroyed. 
Notes. A new species with one of the largest flowers in the entire genus. It belongs 
to the Hoya macgillivrayi group, up until now consisting of only three species, H. 
macgillivrayi F.M.Bailey from Cape York in Queensland, Australia, and two from 
Papua New Guinea, H. archboldiana and H. onychoides . The new taxon is the most 
distinct of these species as their coronas are narrowly star-shaped, when viewed from 
above, and the inside of their corolla lobes are glabrous, whereas Hoya stenakei has 
an almost pentagonal corona and the inside of the corolla lobes is densely pubescent. 
Key to species in the Hoya macgillivrayi group 
(modified from Forster et al., 1995): 
1 a. Inside of corolla lobes pubescent; corona almost pentagonal. H. stenakei 
lb. Inside of corolla lobes glabrous; corona narrowly star-shaped.2 
2a. Corolla campanulate, lobes shorter than the tube and <15 mm long, reflexed. 
. H. archboldiana 
2b. Corolla campanulate-rotate or rotate, lobes as long as or longer than the tube 
and >15 mm long, semi-erect to incurved.3 
3a. Corolla lobes strongly incurved giving a ‘claw-like’ appearance to the lobe, with 
margins strongly reflexed creating a protrusion at the base of sinus between the 
corolla lobes. H. onychoides 
3b. Corolla lobes weakly incurved, with margins slightly reflexed with no protrusion 
formed at the base of the sinus between the corolla lobes. Hoya macgillivrayi 
