Hanguana deflexa Hrones & Dancak, 2021

Hrones, Michal, Leong-Skornickova, Jana, Niissalo, Matti A. & Dancak, Martin, 2021, Hanguana deflexa (Hanguanaceae), a new forest species from Sarawak, Borneo, PhytoKeys 181, pp. 9-19 : 9

Hanguana deflexa Hrones & Dancak sp. nov.

Figures 1 , 2

Diagnosis.

Similar to Hanguana loi Mohd Fahmi, Sofiman Othman & P.C.Boyce but differs in flat leaf blade (vs corrugated), pseudopetioles 0.8-2.1 cm wide (vs to 0.6 cm wide), rachis of infructescence up to 10 cm long (vs ca 58 cm long), ripe fruit ca 1 cm in diam. (vs ca 0.5 cm in diam.), and unbranched partial infructescences (vs branched).

Type.

Malaysia, Sarawak, Lawas district , Long Tuyo village, on slopes in primary rainforest above left bank of Tuyo river, ca 2.3 km ESE of village, 4°27.75833'N, 115°29.86000'E, ca 610 m a.s.l., 22 Jan 2020; M. Hroneš & M. Dančák 422020 (holotype SAR, isotype OL) .

Description.

Herbaceous, dioecious mesophyte to ca 1.5 m tall. Stem terete, to 2.5 cm in diam., basally semi-ascending to erect, fully covered by leaf sheaths when young, with age becoming leafless and covered by fibrous remnants of leaf sheaths, terminally with crown of up to 10 leaves; stolons absent. Leaves 70-110 cm long, spreading then arching, bases imbricate with hyaline margins (young leaves), turning brown and erose-marcescent with age; pseudopetiole 13-70 cm long, 0.8-2.1 cm wide, accounting for 1/3-1/2 of entire leaf length, roundly channelled with sharp margins, basally greyish-white floccose; leaf blade 40-70 × 8-20 cm, narrowly elliptic to elliptic, base attenuate, tip long narrowly attenuate with apicule to 5 mm, leathery, flat, adaxially mid to dark green (in close-up with darker green blotches and transverse veins resulting in checker-like variegation), greyish-white floccose when young, falling off in older leaves, abaxially light green, prominently floccose in young leaves, falling off with age; midrib weakly impressed, pale green adaxially, round-raised, lighter green, almost glabrous and shiny abaxially. Male inflorescences not seen, female inflorescence not seen. Infructescence deflexed, procumbent to suberect, comprising of up to 5 partial, whorled, alternate-secund, spiciform infructescences ascending at 70°-80° angle, plus a terminal spike; peduncle and rachis together up to 35 cm tall, pale green when fresh, densely pale brown-grey flocculose, visible portion of peduncle up to 25 cm long; sterile bract one per peduncle, foliaceous, persistent, narrowly ovate to narrowly elliptic with a basal claw, up to ca 14-24 (incl. 2 cm long claw) × ca 3-5 cm; bracts subtending lower partial infructescences similar to sterile bracts, diminishing in size and becoming narrowly triangular distally along the infructescence, the bract supporting the most basal partial infructescence ca 7 × 1 cm (incl. ca 1.5 cm long claw), fully reduced in uppermost partial infructescences; all bracts densely pale brown-grey flocculose; partial infructescences each comprising up to 4 branches at basal levels (gradually less with up to single branch towards the apex of the infructescence), branches arising simultaneously from the axil of the subtending bract, ca 2-3 mm in diam., usually unbranched, up to 5 cm long, with up to ca 10 fruits each. Female flowers scattered, solitary, sessile, all with an associated minute bracteole; perianth composed of 6 tepals in two whorls tightly clasping ovary/fruit in fresh material, all tepals with prominent bulbous thickening at base (more prominent in outer whorl), light green, margin ca 0.5-1 mm wide, hyaline translucent white (turning brown with age); outer tepals broadly ovate, ca 0.5-1 mm long, ca 1.5-2 mm broad, connate at base (only 0.2 mm), sparsely hairy; inner tepals almost orbicular, ca 3-3.5 mm long, 2.5-3 mm broad, basally imbricate but free, sparsely hairy; staminodes 6, in two whorls, pale green, triangular to narrowly triangular, outer staminodes ca 0.5-1 mm long, ca 0.3 mm broad at base, inner staminodes longer, ca 1.5-2 mm long, ca 0.5 mm at base, each basally sheathed with orbicular to broadly ovate, apically pointed to shallowly bilobed scale, ca 1-1.4 mm long, and 0.8-1.2 mm broad, apex and margins semitranslucent (when fresh) to light brown (when dry), gradually darker brown towards the base. Stigma 3-lobed, ca 2.5-3 mm in diam., each lobe ca 1.2-1.5 mm long (fruiting material), ovate to elliptic with slightly pointed apex curved upwards, lobes connate basally with somewhat raised centre, dark brown at fruiting stage, positioned terminally in ripe fruit. Ripe fruit globose, 8-12 mm in diam., dull purplish red, finally turning black; pulp 0.5-2 mm thick, pinkish-white to pinkish-yellow, fairly hard. Seed one per fruit, ca 5-6 × 4 mm, dark brown, ¾ globose to ellipsoid, deeply excavated, ostiole wedge-shaped accounting for ca ¼ of the seeds, without any discernible appendage on the rim, cavity filled with placental tissue.

Etymology.

The specific epithet is derived from Latin adjective deflexus (i.e. bend, deflexed) and referring to the position of infructescence, a rare character in hitherto described Hanguana species.

Distribution and habitat.

The species is known only from two localities in primary rainforest southeast of the village of Long Tuyo in Lawas district (northern Sarawak). Both populations occur on moderately steep slopes in altitudes around 600 m a.s.l.

Conservation status.

The species is so far known only from two small populations ca 1.4 km apart, each consisting of up to 10 adult individuals. Both populations, considered to be a single location (sensu IUCN Standards and Petitions Subcommittee 2019), are located in the forest with no legal protection and therefore threatened by potential logging. Although it is very likely, that H. deflexa occurs in suitable habitats in surrounding areas, it is also clear that the species is not widespread, since no other herbarium collections exist in any of the Hanguana major herbaria we have examined. Based on the IUCN criteria ( IUCN Standards and Petitions Subcommittee 2019), this species shall be provisionally treated as Critically Endangered (CR B2ab(iii); D) until more information is available for easing off this status.

Taxonomic remarks.

Based on the seed morphology, Hanguana deflexa belongs to the small forest species clade of Hanguana ( Niissalo et al. 2020) and therefore it is probably related to H. corneri Škorničk. & P.C.Boyce and H. neglecta Škorničk. & Niissalo ( Niissalo et al. 2014; Leong-Škorničková and Boyce 2015). However, it differs from both species by its deflexed (vs erect) infructescence. It further differs from H. corneri by leaf blade abaxially light green (vs purple red) and from H. neglecta by fruits ripening purplish red (vs fruits ripening black). The close relationship of H. deflexa to H. neglecta and H. corneri is confirmed in our phylogenetic reconstruction (Fig. 3 ); however, no other Bornean taxa are yet included in the matrix. The allele balance of H. deflexa has a distinctive peak at 25%, suggesting that the species is tetraploid, and, like another tetraploid species, H. anthelminthica , it may be capable of sexual reproduction ( Niissalo et al. 2020).

The deflexed infructescence is a very rare trait among known Hanguana species. Except of H. bakoensis Siti Nurfazilah, Sofiman Othman & P.C.Boyce and H. nana Randi & Škorničk., all Hanguana species have erect infructescences. The protologue illustration of H. loi Mohd Fahmi, Sofiman Othman & P.C.Boyce depicts a plant with deflexed infructescence, however, it is described as erect in the main text ( Mohd Fahmi et al. 2012). Larger individuals of H. deflexa may superficially remind H. loi by somewhat arching pseudopetioles and leaf blades (Fig. 1C ) and red ripe fruits but both species differ in lamina architecture, width of pseudopetioles, size of ripe fruits and infructescence arrangement as already outlined in the diagnosis. Another similar species, H. nana , shares with H. deflexa small overall size and red coloured fruits in somewhat sparse, deflexed infructescences but differs by stem evenly covered by leaves and bowl-shaped seeds ( Randi et al. 2021).

Hanguana deflexa is already the sixth described species of Hanguana known to occur in Sarawak ( Mohd Fahmi et al. 2012). Most species are known only from the south-western part of Sarawak, the only exception is Hanguana major Airy Shaw known from one locality in Lawas district in northern Sarawak. Our field observations suggest that the diversity of Hanguana in central and north-eastern parts of Sarawak is much greater and at least ten species occur in this area. However, these species cannot be described at present due to lack of complete photographic evidence and herbarium material of fruiting females necessary for their description.

Additional specimen studied (paratype).

Malaysia, Sarawak, Lawas district, Long Tuyo village, on slopes in primary rainforest above right bank of unnamed left-bank tributary of Tuyo river, ca 2 km SE of village, 4°27.37333'N, 115°29.22667'E, ca 620 m a.s.l., 23 Jan 2020; M. Hroneš & M. Dančák 452020 (OL).

Figures

Figure 1. Hanguana deflexa Hrones & Dancak A-C habit in-situ D structure of infructescence E lamina F adaxial and G abaxial surface of lamina. Photographed by M. Hrones (all except C from Hrones & Dancak 422020, C from Hrones & Dancak 452020).

Figure 2. Hanguana deflexa Hrones & Dancak A rhizome with fibre remnants of leaf sheaths B stem covered by leaf sheaths C floccose indumentum on abaxial side of pseudopetiole D peduncle with pale brown-grey floccose indumentum E structure of infructescence with sterile and fertile bracts F top view of fruit showing detail of stigma G side view of fruit H basal part of fruit with tepals I detail of inner tepals, staminodes and staminodial scales J longitudinal section of fruit K cross-section of fruit L side view of seed M top view of seed N bottom view of seed. The smallest grid (where applicable): 1 x 1 mm. Photographed by M. Hrones (A, B, D, G-O from Hrones & Dancak 422020, C, E, F from Hrones & Dancak 452020).

Figure 3. Genomic analyses of Hanguana deflexa Hrones & Dancak, using ddRADseq A maximum likelihood phylogenetic reconstruction using RAxML 7.2.8 (Stamatakis 2006). Sequences were added to a data matrix first published in Niissalo et al. (2020). Outgroups are not shown B allele balance, supporting tetraploid status of the species, measured using Smudgeplot v. 0.2.3 dev (Ranallo-Benavidez et al. 2020), using kmer length of 21, minimum kmer coverage of 20 and maximum kmer coverage of 10,000.