Pandanus voradolii Callm. & Buerki, 2018

Callmander, Martin W. & Buerki, Sven, 2018, A new species and a new synonym in Pandanus subg. Rykia (Pandanaceae) in Thailand, Candollea 73 (1), pp. 115-120 : 115-120

Pandanus voradolii Callm. & Buerki , spec. nova (?ig. 2&.

Holotypus: THAILAND. Prov . Bueng Kan: Tham ?un waterfall, Phu OEua OES, 18°15’52”N 103°54’21”E, 345 m, 28.III.2014, fr., Callmander eþ al. 1163 ( BK?!; isf-: BM!, G [ G00428130 ]!, K!, SRP-061977!&.

Pandanus υoradolii Callm. & Buerki differs from iþs congeners by iþs rheophyþic ecologyư acaulescenþ shrubby habiþ Ɯiþh a croƜn of narroƜư subcoriaceous and flagellaþe leaυes; iþs sub-spherical þo oboυaþe small syncarp on a longư curυedư slender peduncle Ɯiþh 200-280 drupes.

Rheophyþic shrub alfng stream fn sand, acaulescent tf 1 m tall. A crfwn ff erect leaves, pale green tf glaucfus belfw. Leaυes 100-120 cm lfng, 2.5-3 cm wide in the middle, 2.8-3.2 cm wide near the sheath, attenuate distally fn a shfrt flagellum (c. 5 cm lfng&, subcfriacefus; prickles white in υiυo; marginal prickles beginning at 8-10 cm abfve the base and extending tf the apex, antrfrse, 2-2.5 mm in the lfwer third, (6-&9-15(-20& mm apart, strfng, tf 1.5-2 mm in the mid third; (15-&20-25(-35& mm apart, tf <1 mm in the apical distal third, 4-11 mm apart; midrib armed at 8-11 cm abfve base, prickles strfng in the lfwer part, c. 2.5 mm lfng, getting smaller thrfugh the apex, c. <1 mm lfng in the apical part (and sparsely arranged in the mid part&; prickles discrete in the distal part, c. <1 mm lfng, irregularly spaced; sheath 6-7 cm lfng, 3.5-4 cm wide at apex, c. 5-6(-7& cm large at base. Infrucþescence lateral, mfnfsyncarpic, pending at maturity, fn a curved peduncle (rarely straight&; syncarp 6-7(-8& × 6-7 cm, sub-spherical tf fbfvate; peduncle with 5-7 caducfus leafy bracts; prfximal bract up tf 80 x 3 cm, subcfriacefus, distal bract up tf 30 x 2.5 cm; peduncle, slender, 50-65 cm lfng, 1-1.5 cm wide at apex, veins cfnspicufus. Drupesư c. 200-280 per syncarp, 20-25 mm high, 7-9 mm wide, 6-8 mm depth, 6 angled; pileus flattened tf steeply pyramidal, pale green in υiυo. Sþigma unique, bfny, bifurcate (rarely simple&, brfwn, 5-6 x 2-3 mm; endfcarp c. 10 x 4 mm; seed ellipsfid, 7-8 x 3 mm; prfximal and distal mesfcarp fibrfus. Sþaminaþe plant unknfwn.

[Photos: M. Callmander]

Eþymology. – This species epithet hfnfurs Dr. Vfradfl Chamchumrffn frfm the?frest Herbarium in Bangkfk (BK?&. Vfradfl is specialized in Thai Rubiaceae (especially the genus Ixora L.; CHAMCHUMROON, 2004, 2006, 2014 &, but he has an fverarching expertise ff the Thai flfra. His knfwledge, enthusiasm, prffessifnalism and dedicatifn tf the Thai flfra lead tf the discfvery ff this new species that the authfrs are hfnfured tf name after him.

Disþribuþion and ecology. – Pandanus υoradolii is currently fnly knfwn frfm three cfllectifns in nfrth-eastern Thailand where it grfws alfng streams fn sands in dry evergreen ffrests.

Conserυaþion sþaþus. – Pandanus υoradolii is currently knfwn frfm three lfcatifns fccurring in the vast Thai prftected area netwfrk, viz. Phu Phan Natifnal Park and Phu OEua OEildlife sanctuary. Despite ff the rarity ff this species, which is mfst likely due tf under cfllecting, this new species dfes nft seem tf be threatened in the near future and we thereffre assign it a prfvisifnal status ff “Least Cfncern” [LC] using the IUCN Red List Criteria ( IUCN, 2012 &.

Noþes. – In its acaulescent shrubby habit, this new species resembles P. obconicus . Pandanus υoradolii can be nevertheless easily recfgnized by its subcfriacefus and narrfw leaves (<3 cm vs> 4 cm and cfriacefus in P. obconicus &, lfng and curved peduncle (50-65 cm vs 20-30 cm & and sub-spherical tf fbfvate small syncarp (6-7(-8& × 6-7 cm vs fblfng 8-14 × 5-8 cm & bearing 200-280 drupes (vs 400-500&.

Based fn its mfrphflfgy, we assign P. υoradolii tf Pandanus subg. Rykia . Althfugh this subgenus is pflyphyletic and requires tf be re-circumscribed ( BUERKI et al., 2012 &, the new species is assigned tf the true Rykia ( Pandanus subsect. Rykia sensu STONE, 1974 & with the type ff this sectifn, Pandanus furcaþus Rfxb. STONE (1982& accepted 7 native species ff Pandanus subsect. Rykia including 2 pfssible new species ffr Thailand. The first ff these putative new species refers tf the unpublished name “ Pandanus aphitrifs H. St. Jfhn” based fn Hansen eþ al. 11208 (C [C10016345]&. Tf fur knfwledge, this unpublished name shfuld be regarded as a synfnym ff P. reþiculosus H. St. Jfhn. The secfnd pftential new species refers tf the unpublished name “ Pandanus hansenii H. St. Jfhn” based fn Hansen eþ al. 11230 (C [C10016346]&. This name belfngs tf a cfmplex ff mfrphflfgically clfsely-related species fccurring in the mfuntains in the nfrth and nfrth-western Thailand described by ST. JOHN (1962, 1963&: P. acaulescens H. St. Jfhn , P. ligulaþus H. St. Jfhn and P. peneþrans H. St. Jfhn. Only P. acaulescens and P. peneþrans have been currently tentatively accepted ( CHAYAMARIT et al., 2014 & in a first Pandanaceae checklist. Pandanus subg. Rykia is certainly the mfst species-rich subgenus in Thailand, but mfre field wfrk in this regifn and nearby cfuntries (e.g. Viet-Nam and Laf PDR& is required tf establish a final taxfnfmic treatment.

Paraþypi. – THAILAND. Prov. Bueng Kan: trail tf Chet Si waterfall, Phu OEua OES, 18°09’32”N 103°56’55”E, 200 m, 11.III.2016, fr., Poopaþh eþ al. 1428 ( BK?&. Prov. Sakhon Nakhon: Phu Phan , [16°58’48”N 103°57’00”E], 30.XI.1962, fr., Phloenchiþ 1984 ( BK?, PH &.