Pandanusgrayorum Callm., Buerki & Gallaher, 2021
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publication ID |
https://doi.org/ 10.1071/SB20033 |
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DOI |
https://doi.org/10.5281/zenodo.5643376 |
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persistent identifier |
https://treatment.plazi.org/id/03CA87CD-1438-3C52-1D42-7D62FBEAFC68 |
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treatment provided by |
Diego |
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scientific name |
Pandanusgrayorum Callm., Buerki & Gallaher |
| status |
sp. nov. |
Pandanusgrayorum Callm., Buerki & Gallaher View in CoL , sp. nov. ( Fig. 1 View Fig .)
Type: AUSTRALIA. Queensland: Cook District, Jubilee Road, off Flying Fish Point Road, Innisfail , 17 ° 290460 S, 146 ° 020260 E, 8 m, 4.x.2018, fr., B. Gray 9976 (holo: G 00446800 ! [3 sheets + carpological specimen]; iso: BISH!, BRI, CANB, CNS 148706! [3 sheets + carpological specimen]) .
Pandanus sp. (Russell River) in W.E.Cooper & W.T.Cooper, Fruits Austral. Trop. Rainforest 390 (2004).
Diagnosis
Pandanus grayorum is distinguished from P. gemmifer in having larger crown leaves (210 – 280 × 7 – 8 cm v. 170 – 230 × 5 – 6 cm in P. gemmifer ) and syncarps (35 – 40 × 18 – 22 cm v. 23 – 25 × 10 – 18 cm); apex of phalanges flat or slightly domed at apex, divided by apical sinuses ~ 0.5 cm deep into small, often truncate pyramids as many as there are carpels (v. rounded to the stigmatic cluster, 12 – 15 mm wide with narrow apical central sinuses restricted to the central cluster); stigma on apex or on the edge of the slightly truncate apical face of each pyramid (v. on proximal face of the central apex cluster).
Description
Tree up to 9 m tall, stem with conical nodules, prop roots at base up to 50 cm high, upper branches (and sometimes stem) producing axillary sprouts (plantlets). Leaves 210 – 280 cm long, 7 – 8 cm wide in the middle, ~ 9 cm wide near the sheath, gradually attenuate in the upper part, coriaceous; longitudinal veins visible on both surfaces; marginal prickles beginning at 7 – 9 cm above the base and extending to the apex, antrorse, 5.5(– 6) mm in the lower third, 5(– 10) mm apart, to 2 – 5 mm long in the mid-third; 3 – 5 mm apart, up to ~ 1 mm long in the distal third, 2 – 3 mm apart; midrib armed in the upper 1/4, prickles 4 – 5 mm long), irregularly disposed (3 – 10 mm) in the middle, then regularly disposed, spaced (2 – 5 mm) as long as on the marginal in the distal 1/3; sheath 5 – 9 cm long, ~ 9 cm wide at apex, ~ 10 – 11 cm wide at base. Infrutescence terminal, a solitary syncarp on a curved peduncle; syncarp 35 – 40 × 18 – 22 cm, oblong to obovate, bright red at maturity; peduncle ~ 60 – 70 cm long, 2 cm wide at apex, trigonous, veins visible, first bract borne just above the base of syncarp, 8 bract scars along peduncle and the remaining bracts crowded at the base of the syncarp. Phalanges, 60 – 80 per syncarp, 6 – 8(– 9) cm high, 4 – 5(– 6) cm wide, 2.5 – 3.5 cm thick, 4 – 6 angled; carpels (8 –) 12 – 18(– 20), incompletely united, free in the upper ~1/3 – 1/2, tapering to the base; pileus flat or slightly domed at the apex, divided by apical sinuses ~ 0.5 cm deep into small, often truncate pyramidsasmanyastherearecarpels. Stigma 1 percarpel,oblique to vertical, generally reniform, sometimes deltoid on apex or on the edge of the slightly truncate apical face of each pyramid; endocarpbony, inlower 2/3, marginsup to 5 mm wide, 1.2 – 2.5 cm long in the centre, 1 – 2 cm wide; seed locule oblong, 1.5 – 2.5 × 0.5 – 1 cm, superior and inferior mesocarp thick and fibrous. Staminate inflorescence terminal, pendent, creamy white, up to 76 cm long, a three-sided raceme of spikes; peduncle fleshy, flaccid and soon disintegrating; lowest floral bract 67 × 4.8 cm, margins finely toothed, apex long-subulate, median bract 31 × 4.2 cm, with fine marginal prickles, basal floral bracts extending longer than distal floral bracts; spikes dense, cylindric, 6 – 10 × 2.5 – 4 cm, with manystaminate flowers; each spike of a fleshy central axis with stemonophore 10 – 13 mm longeach bearing 20 – 26 stamens; stamens with filament 1 – 2 mm long, anthers 2.5 – 4.5 × 0.8 – 1.2 mm, including an apiculus 0.3 – 0.5 mm. ( Fig. 1 View Fig .)
Distribution
This species is known from the Wet Tropics of north-eastern Queensland on and near the banks of the lower reaches of the Mulgrave, Russell, Alice, Johnstone and Moresby rivers and associated subcoastal flood plains ( Fig. 2 View Fig ). Plants identified as P. grayorum have been observed in the Ella Bay, Moresby Range and Russell River National Parks and Etty Bay Conservation Reserve but most of the distribution occurs in fragmented remnants among agricultural land, suggesting its previous distribution may have been wider. It occurs in sympatry with P. solms-laubachii , but is parapatric with P. gemmifer , which occurs in the mid-upper reaches of the adjacent Barron, Tully and Herbert River systems to the north and south, on the Atherton Tableland, and on the McIlwraith Range on Cape York Peninsula.
Habitat and ecology
Pandanus grayorum occurs in lowland rainforest, specifically simple to complex mesophyll vine forest, riparian gallery forest and rainforest margins with mangrove estuaries or Melaleuca- dominated woodlands. It occurs near large river banks and associated small creeks, moist gullies and tidal estuaries near sea level. Reproduction is both via seed and from vegetative propagules, which form a localised colony of trees. The vegetative propagules float and can be dispersed in fresh and tidal waters. They are covered in sharp curved hooks and are potentially zoochorous. Pandanus grayorum can occur as a subcanopy, canopy or in open areas as an emergent tree.
Phenology
Flowering occurs in October to January, with fruit developing over 1 year to ripen the following October through December. Field observations suggest that there are locally male- or female-biased stands, with an overall female bias across the whole population. Vegetative propagules are produced all-year round.
Conservation status
Pandanus grayorum is known from few collections from several populations along rivers banks and small creeks. On the basis of collection and observation records, it has an extent of occurrence (EOO) of 231 km 2 and an area of occupancy (AOO) of 28 km 2. Most records are from localities outside national parks. No threats were observed at the known localities; however, adjacent areas are road reserves and agricultural landscapes where disturbance and clearing has occurred and may continue into the future, so it is conceivable that populations may be damaged by future activities. A preliminary assessment suggests the IUCN rating of Vulnerable [VU B1ab(iii, iv)+B2ab(iii, iv)], using the IUCN Red List Categories and Criteria (International Union for Conservation of Nature 2012).
Etymology
This new species is named in honour of Joy and Bruce Gray. Bruce was formerly a technical officer with CSIRO in Atherton and has collected extensively in remote areas of northern Queensland. Over his career, Bruce has made a significant contribution to the knowledge of the northern Queensland flora through his herbarium collections, discovered many new species, and made the type collections of 114 species, in addition to the one described here. Joy and Bruce welcomed the first author with a wonderful hospitality in Atherton in 2017 and Joy’ s support of Bruce has in effect enabled so many of Bruce’ s endeavours, including an epic trip to the tip of Cape York Peninsula in 2017. The first author finally dedicates this new Pandanus species for Bruce’ s 80th birthday.
Notes
Vegetative propagation in the genus Pandanus has been recorded in Australia and Madagascar: ‘small branchlets develop near (the) apex of branches, then drop off; these act as vegetative propagules’ ( Stone 1970, p. 127). This vivipary is known in three species in Madagascar ( Guillaumet 1972), but it remains rare. The active vegetative propagation in P. grayorum and P. gemmifer is so vigorous on aerial branches that they can easily be identified in the field.
Pandanus grayorum occurs in close parapatry with P. gemmifer ( Fig. 2 View Fig , 3), with P. grayorum occurring on the lower reaches of the Mulgrave, Russell, Alice, Johnstone and Moresby river systems, whereas P. gemmifer occurs on the Barron River system to the north and the Tully and Herbert river systems and nearby drainages to the south ( Fig. 2 View Fig ). The two species are distinguished by the dimensions of their leaves and syncarps and the morphology of their phalanges ( Table 1 View Table 1 ).
Pandanus grayorum occurs in close sympatry with P. solmslaubachii ( Fig. 4 View Fig ) and shares a somewhat similar tree architecture. Pandanusgrayorum is readily identified by the presence of axillary buds developing into plantlets, which are absent in P. solms-laubachii . Pandanus grayorum also lacks the dense ascending rootlets present in P. solms-laubachii . The two species aredistinguished by thedimensions of their leaves, shape of syncarps and the morphology of their phalanges ( Table 1 View Table 1 , Fig. 1 View Fig , 4 View Fig ). The leaf form of P. grayorum is more arcuate and the leaves are glossy, whereas in P. solms-laubachii the leaves are more straight and folded and are moderately glaucous.
The genetic and morphological similarities among P. gemmifer , P. grayorum and P. solms-laubachii suggest that hybrid speciation may have played a role in the diversification of these species ( Gallaher et al. 2015). Pandanus grayorum is the second taxon to be described that shares characteristics of both Pandanus section Austrokeura and Australibrassia (however, these sections were not retrieved as monophyletic groups in the molecular phylogeny, which might suggest that these characters evolved independently in this group; Buerki et al. 2012; Gallaher et al. 2015). Both phylogenomic and population genetic studies, coupled with field observations, are recommended to clarify species delimitations within this challenging group of Pandanaceae .
Additional specimen examined
Australia. Queensland: Harveys Creek, swamp forest , 17 °15035.0000 S, 145 °55014.0000 E, 23.IX.1971, S.T. Blake 23631 ( BRI, CANB) ; Bellenden Kerlanding, Russell River NP, 17 °1602200 S, 145 °5605100 E, 5 m,fr., A.Field & F. Zich 5015 ( BRI, CNS, G) ; Polly Creek, Garadunga, in road reserve near junction of Polly Creek road and Jubilee Road , 17 °2900200 S, 146 °0200100 E, 12 m, fr., A. Field & F. Zich 5017 ( BRI, CNS, G) ; Nind’ s Creek, Coquette Point, in road reserve of Coquette Point road abutting Moresby Range NP , 17 ° 3200200 S, 146 °0304200 E, 1 – 2 m, fr., A. Field & F. Zich 5018 ( BRI, CNS, G) ; Moresby River tributary, in road reserve of Bruce Highway between Danesi Road and Croatto Road , 17 °3605400 S, 146 °0105000 E, 9 m, staminate fl., A. Field & F. Zich 5019 ( BRI, CNS, G) ; Etty Bay , 17 ° 330 S, 146 °050 E, 7.XII.2011, fr., T. Gallaher 337 ( BISH, HAW) ; Russell River, below Russell River boat camp , 17 °1602100 S, 145 ° 5605400 E, 7 m, 13. XII.2017, fr., B. Gray 9955 ( BRI, CNS, G) ; Russell River NP, Russell River road , 17 ° 1602800 S, 145 °5605000 E, 3 m, 29.X.2003, fr., B. Gray 8831 ( BRI, CANB, CNS) .
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