A NEW SPECIES OF AERIDES (AERIDINAE: ORCHIDACEAE) FROM SULAWESI, INDONESIA

A new species of Aerides from Sulawesi Island, Indonesia, is described and illustrated. This new species is placed in Aerides sect. Falcata and is, so far, the only member of this section recorded from Indonesia. The species is endemic to the northern part of Sulawesi Island.


Introduction
The genus Aerides Lour.(Orchidaceae) is a small genus of 31 species distributed from India, China, to the Philippines, Sulawesi and Papua New Guinea (Christenson, 1984;POWO, 2023).In the past five years, several new species have been discovered and described, including Aerides agasthiyamalaiana Karupp.& P.S.S.Rich.from India, A. phongthuyii Aver.& V.C.Nguyen from Vietnam, A. cootesii Cabactulan et al. and A. turma M.Leon et al. from the Philippines.It is presumed that several new species still await discovery.
Indonesia is known to be one of the most important orchid diversity hotspots in the world and a centre of diversity for many orchid genera, including Aerides (Metusala, 2017;Metusala & Supriatna, 2017;Metusala, 2019aMetusala, , 2019b;;Metusala & O'Byrne, 2020;Metusala et al., 2021).Currently, five Aerides species are recorded from Indonesia and are distributed from Sumatra in the west to Sulawesi in the east of the archipelago (POWO, 2023).Aerides odorata Lour. is the most widespread species and is recorded from Sumatra, Java and Kalimantan (Indonesian Borneo).There are two species from the Lesser Sunda Islands (Aerides odorata and A. timorana Miq.) and four from Sulawesi (A. huttonii (Hook.f.) J.H.Veitch, A. inflexa Teijsm.& Binn., A. odorata and A. thibautiana Rchb.f.), of which all but A. odorata are endemic to that island.Based on POWO (2023), there are no records of the genus from Maluku or Indonesian New Guinea.
The Philippines are particularly rich in Aerides, having 12 species, 11 of which are endemic to the country.As one of the nearest islands to the Philippines, Sulawesi is also known to be particularly rich in the genus compared with other Indonesian islands.During a botanical expedition undertaken by staff from Purwodadi Botanic Garden in 2000, unidentified specimens of Aerides were collected from the northern part of Sulawesi.After many years of cultivation, only a single mature individual has survived, but it flowered for the 2 A new species of Aerides first time in the garden in 2012, allowing it to be recognised as a species of Aerides new to science.This new species is described here.
Distribution.Indonesia, Sulawesi Island, Gorontalo Province.Exact locality withheld to protect population from illegal orchid collectors.
Habitat and ecology.Growing as an epiphytic under the shade of old trees in semi-open hilly area.Flowering so far recorded only between April and May (ex situ in Purwodadi Botanic Garden, East Java, 300 m).This species has a narrow leaf shape with a thick waxy cuticle layer on the leaf adaxial surface, which in tropical epiphytic orchids is usually related to adaptation to low humidity, hot temperature, relatively high light-intensity environments, and long drought period (Al Farishy et al., 2017;Metusala et al., 2017;Metusala, 2019a;Ishmah et al., 2021;Suffan et al., 2021;Metusala & Al Farishy, 2022).
Etymology.The specific epithet honours the late Peter O'Byrne, a Southeast Asian orchid specialist who kindly taught the author during his early career as an Indonesian taxonomist.
Proposed IUCN conservation category.Aerides obyrneana is so far known only from a single locality in Gorontalo province.The bright attractive colour and very unusual lip shape compared with that of other Indonesian Aerides make this species vulnerable to over-collection by commercial collectors and orchid enthusiasts.Intensive collection to meet the high demand from collectors often has a great negative impact on the sustainability of orchid population in their habitat (Metusala, 2017).The quality of natural habitat is also declining, due to conversion of forest to plantations.The species is thus provisionally assessed as Critically Endangered B2ab (i,ii,iii,v) until more data on its current population become available.
Notes.From the large lip mid-lobe compared with its side lobe, and its mid-lobe being perpendicular to the side lobes, Aerides obyrneana is most similar to species in Aerides sect.Falcata, a section mostly found in mainland Southeast Asia (Averyanov et al., 2019;Motes et al., 2020).A new species of this group, Aerides upcmae, published in 2020 from Mindanao Island in the Philippines (Motes et al., 2020), extended the distribution of the section east.The discovery of Aerides obyrneana in the northern part of Sulawesi Island extends sect.Falcata south, and it is the only member of this section in Indonesia.It is clear that Aerides obyrneana and A. upcmae show intermediate characters between sect.Falcata and sect.Aerides, especially in their spur shape.These sections may ultimately be merged, or a new section may be created to accommodate both species; however, until a more detailed study of the sectional classification in the genus is carried out, Aerides obyrneana is placed in sect.Falcata.Aerides obyrneana is morphologically similar to A. upcmae and A. houlletiana (Table ).The flowers of Aerides obyrneana are similar to those of A. houlletiana but differ in having a broadly flabellate lip mid-lobe, unequally oblong lip side lobes that are broader towards the truncate apex with erose apical margins, a low median keel that extends from spur aperture to centre of the lip mid-lobe, a curved spur, and a prominent bilobed callus that is raised on the front wall under the spur aperture.By contrast, Aerides houlletiana has a subrectangular to broadly ovate lip mid-lobe, unequally elliptic lip side lobes with obtuse to rounded apex and entire apical margins, two distant longitudinal keels that converge in the base area of the lip mid-lobe, and a straight spur, and is without a prominent callus on the front wall under the spur aperture (Figure 3).