Bruguiera × dungarra N.C.Duke & Hidetoshi Kudo

Duke, N. C. & Kudo, H., 2018, Bruguiera × dungarra, a new hybrid between mangrove species B. exaristata and B. gymnorhiza (Rhizophoraceae) recently discovered in north-east Australia, Blumea 63 (3), pp. 279-285 : 283

Bruguiera × dungarra N.C.Duke & Hidetoshi Kudo , hybrid nov. — Fig. 1–4

Type: Hidetoshi Kudo 190916 A & Brian Venables (holo CNS; iso BRI), Australia, Queensland, Cairns , Machans Beach , mangrove, high intertidal zone, S16°51.674' E145°44.844', sea level, 27 Oct. 2016 .

Etymology. The location of the type of this new hybrid occurs on the ancestral lands of the Yirrganydji people. For these traditional custodians of the narrow coastal strip from Cairns to Port Douglas, the epithet Dungarra means, ‘belonging to Machans Beach area’.

Tree or shrub to 22 m high, evergreen, columnar or multi-stemmed, branching mostly sympodial, stem base with sinuous, finlike buttresses to 0.5 m high. Exposed breathing roots, pneu- matophores knee-like, to 15 cm long. Bark dark grey to palebrown, with horizontal and vertical fissures, with large corky lenticels of 1–2 cm diam, especially on buttresses. Foliage comprised of compact rosettes of paired leaves, clustered at 4–8 leaf scar nodes down from apical shoot, terminal, spicate, prominent, pink-green, 3–7 cm long. Interpetiolar stipules paired, narrowly ovate, green to yellowish, occasionally with pinkish tinge, enclose terminal bud to 7 cm long. Leaves opposite, simple, blade elliptic to elliptic-obovate, smooth, glossy green, 7–15 cm long, 3–6 cm wide, 4–8 cm shape length (see Table 2), length to width ratio 1.9–2.4, length to shape ratio 1.8–2 (see Table 2), base cuneate, margin entire, apex acute; petiole green, 2.1–3.8 cm long. Inflorescence axillary, 1-flowered (flowers solitary), buds generally nodding, matur- ing within leafy rosette; peduncle green, 8.4–16 mm long, 1.8–2.5 mm wide; mature buds present at 1 or 2 internodal segments below apical shoot; mature hypocotyls present at 3 or 4 internodal segments below apical shoot. Mature flower buds green with rosy blush to all green, 29.5–39.4 mm long, 4.9–7.4 mm wide around calyx tube, 7.8–11 mm wide at calyx lobes, distil tip acute; calyx tube turbinate, ribbed, with 9–11 lobes, slender pointed, longer than tube, 17.2–26 mm long, margins of lobes on closed mature buds antrorse to form ribs between adjoining lobes; petals 9–11, creamy white, turning orange-brown at anthesis, 14–18 mm long, 2.2–3 mm closed width, bilateral folded, 4.4–5.3 mm open width, bilobed; lobes 4.3–6.6 mm long, densely fringed with hairs along margin of outer side of petal lobe, apex of each lobe rounded with 2 or 3 bristles near apex, 0.5–1.8 mm long, sinus between lobes with hair-like spine, 2.4–3.9 mm long, about half lobe length, ratio of spine to petal lobe length 0.4–0.8; stamens 18–22, creamy white turning orange-brown at anthesis, 14.3–15.7 mm long, 0.2–0.6 mm wide, compressed pair within closed petal, dehiscing precociously when triggered, anthers linear, creamy pale yellow turning brown at anthesis, 5.5–8.5 mm long, 0.5–1 mm wide; style filiform, smooth, pale green, 17–23 mm long, 0.9–1.3 mm wide, stigma minutely 3-lobed, mounted centrally within calyx tube 3.2–4.6 mm wide, 3.9–4.9 mm long. Mature fruit cryptic within slightly enlarged calyx tube, turbinate, smooth to ribbed, 37–44 mm long, 13–16 mm wide, calyx lobes slightly reflexed, 17–20 mm long, 25–33 mm width; germination viviparous, hypocotyl emergent from calyx with maturation. Mature hypocotyl narrowly ovoid, straight, green, 5–16 cm long, 13–15 mm at widest point, 29–77 mm shape length (see Table 2), 4–7 mm width at plumule end, length to width ratio 3.9–11, length to shape ratio 0.9–4.1 (see Table 2), some longitudinal ribbing, distil end blunt, plumule 0.9–4.1 mm long, buoyant dispersal agent.

Distribution — Type location is Machans Beach (S16°52' E145°45'), near Cairns in Queensland, Australia. Other localities include Holloways Beach (S16°50' E145°44') also near Cairns in Queensland, Australia, south to around Hinchinbrook Channel (S18°29' E146°10') and Shoalwater Bay (S22°21' E150°10'), and further north to the Marrett River estuary (S14°31' E144°12') in Princess Charlotte Bay. Distribution elsewhere is likely, although possibly restricted to the zone of overlap of putative parents ( Fig. 3 ). Putative parent species co-occur in eastern Indonesia, Timor Leste, southern New Guinea and northern Australia. In Australia, B. × dungarra is likely to occur from Darwin Harbour in the Northern Territory (S12°25' E130°48') to Port Curtis in Queensland (S23°49' E151°22').

Ecology & Local influences — Uncommon hybrid in the mid-high intertidal zone of intermediate estuarine position (sensu Duke 2006). Often in proximity of stands of higher intertidal B. exaristata , and mid-high intertidal B. gymnorhiza .

Phenology — In Australia, flowering reported for July to September, and maturation of propagules in October to May.

Additional herbarium specimens and vouchers. AUSTRALIA, Queensland, Holloways Beach , mangrove, high intertidal, S16°49.825' E145°43.972',sea level, 27 Oct. 2016, Hidetoshi Kudo 190916 B & Brian Venables ( BRI, CNS) ; Queensland, Holloways Beach , mangrove near boat ramp, S16°49.826' E145°43.970', sea level, 6 Aug. 2018, Hidetoshi Kudo 3 to 6 ( BRI, CNS) ; Queensland, Holloways Beach, Willow Street ,mangrove edge, S16°50.815' E145°44.501', sea level, 6 Aug. 2018, Hidetoshi Kudo 7 to 10 ( BRI, CNS) ; Queensland, Holloways Beach street near mangrove edge, S16°50.206' E145°44.176', sea level, 6 Aug. 2018, Hidetoshi Kudo 11 to 14 ( BRI, CNS) ; Queensland, Machans Beach boat ramp, high intertidal mangroves, S16°51.675' E145°44.845', sea level, 6 Aug. 2018, Hidetoshi Kudo 15 to 18 ( BRI, CNS) ; Queensland, Machans Beach , Dungarra Reserve , mangrove, S16°51.601' E145°45.217', sea level, 6 Aug. 2018, Hidetoshi Kudo 19 to 22 ( BRI, CNS) .

Figures

Fig. 1 Two morphological multistate attributes, calyx lobe margin (distil view) and calyx tube surface (cross section), for all Bruguiera taxa, includ- ing B. × dungarra. All observations refer to fresh material listed in Table 1 and from material described by Duke 2006, 2013, 2014, Duke & Ge 2011. Note:taxa names in bold refer to the predominant or exclusive state; names underlined refer to a majority state; and names in regular font refer to a shared or minor state.

Fig. 2 Graphs of ‘a’ clustering and ‘b’ ordination analyses showing relationships between Bruguiera × dungarra, putative parent taxa, B. exaristata and B. gymnorhiza and outlier congeneric species, B. parviflora. Sympatric collections are shown in ‘b’ by blue lines linking data points between putative parents via the intermediate positioned hybrid at north-east Australian locations. The type location collection from Machans Beach (closed triangle symbol) is compared with other location records from Shoalwater Bay, Hinchinbrook Channel,Johnstone River estuary and Marrett River estuary in Princess Charlotte Bay (see Table 1). The clustering diagram and MDS multistate ordination plot were based on correlative relationships in 8 foliage and 33 mature floral characters (Table 2).

Fig. 3 Distributions of Bruguiera × dungarra (Δ – collection locations) and putative parental species, B. gymnorhiza (heavier line outline) and B. exaristata (lighter line outline).

Fig. 4 Bruguiera dungarra N.C.Duke & Kudo, hybrid nov. a. Foliage with inflorescences; b. trunk and exposed roots; c. habit; d. bark; e. leaves upper and lower surfaces; f. open and closed flower buds; g. leafy rosette with flower buds and mature propagule; h. mature hypocotyl; l. leaf scar node; j. colleter at inner base of interpetiolar stipule; k. petal dehisced and open; l. calyces of mature propagule,expended flower and closed flower bud; m. diagram of open petal (bar length = 10 mm); n. sectioned flower bud showing petals and style. — Collection field reference images for Hidetoshi Kudo & Brian Venables, HK190916A, (CNS!), Cairns, Machans Beach.