Acrolejeunea arcuata subsp. gradsteinii M.A.M.Renner, 2013

Renner, Matt A. M., 2013, A new subspecies of Acrolejeunea arcuata, and notes on typification, synonymy, and distribution of other Australasian Lejeuneaceae, Phytotaxa 83 (1), pp. 39-53 : 42-47

Acrolejeunea arcuata subsp. gradsteinii M.A.M.Renner , subsp. nov.

Differs from Acrolejeunea arcuata subsp. arcuata in its autoicous sexuality, with androecia on short lateral branches; the female bracts in one gyre, with rounded bract lobe apex, and bract lobes not reflexed; the perianths immersed within bracts at maturity; the longitudinally oblong underleaves c. 0.2× the shoot width; and the lobule second tooth longer than first tooth.

Type:— AUSTRALIA. Queensland: Cook District, summit area of Mount Bellenden Ker , 17° 16’ S 145° 52’ E, 1580 m, 7 July 2005, M. A. M . Renner 1912 & E. A. Brown (holotype: NSW871961 ! isotypes: BRI! CANB! F!) .

Forming loosely adherent patches of long and parallel red-brown shoots on tree trunks and branches. Shoots golden brown with reddish pigments when fresh, fading to warm brown in herbaria, medium sized for genus, to 30 mm long and 1.5 mm wide, branching infrequent and irregular, shoot system monomorphic, lateral branches similar in stature to parent branch. Branching Lejeunea- type, collar several discoid bracts, persistent. Stems with 11–17 rows of cortical cells, external and internal walls more or less continuously thickened and yellow pigmented, with bulging trigones at cell angles, medullar cells similar in size to cortical cells, in 12–22 rows, bulging trigones at cell angles, medial walls more or less continuously thickened, yellow-pigmented, ventral merophyte four cell rows wide. Rhizoids colourless. Dorsal leaf-free strip absent, leaf insertion interlocking across the dorsal cortical cell. Lobes asymmetrically ovate-oblong, sometimes weakly falcate, 610–760 µm long and 340 – 420 µm wide (free portion only), obliquely patent when moist, contiguous to weakly imbricate, stem partially visible between lobes in dorsal view. Lobe margins entire, basiscopic margin straight, curved through 90° to straight acroscopic margin, lobe apex rounded, weakly deflexed, lobe slightly concave. Cells of lobe smooth, lobe cell surfaces unornamented, cells arranged in diverging rows, cells with truncate ends, cell walls with strong, golden-to reddish-brown pigmented secondary thickenings as asymmetric cordate trigones confluent with strong medial wall thickenings on longer walls. Oil-bodies unknown. Lobules always normally developed, one third the lobe area, 560–680 µm long and 270–330 µm wide, obclavate, carinal region inflated along length of keel, progressively wider toward lobule base, narrowly obpyriform, cells smooth, keel emerging at angle of 60–90º from stem, pouchlike at base, rounded through 60–90º then straight, at an angle of 30–45° to stem, until slight arch at lobelobule junction. Lobule with two teeth, first tooth one- or two-celled, claw-like, inflexed behind lobule surface, tooth base united with adjacent lobule cells on their interior surface. Second tooth one- or two-celled, claw-like, inflexed behind lobule surface. Margin between second tooth and lobe-lobule junction slightly curved to notch at apex of carinal region, then extending as narrow triangular wing along lobe-lobule junction. Lobule antical margin minutely auriculate at stem insertion, then straight to second lobule tooth. Lobule papilla position unknown. Underleaves oblong-elliptic, 320–440 µm long and 280–360 µm wide, 1.5× long as wide, 2–3× stem width, 0.2× the shoot width, apex truncate or shallowly retuse, insertion transverse across 4 rows of ventral cortical cells, imbricate, margins entire. Asexual reproduction absent. Autoicous. Androecia on orthotropic lateral leafy branches with 4 – 6 pairs of androecial bracts, 360–470 µm long and 240–340 µm wide smaller than surrounding vegetative leaves, underleaves present throughout male portion of branch. Gynoecia terminal on orthotropic lateral leafy branches, usually without subfloral innovations, however unfertilised gynoecia occasionally subtended by a single Radula- type innovation. Female bracts in one pair, symmetrical, bract lobes obovate, 1000 – 1200 µm long and 580–680 µm wide at widest point, plane, margins entire, lobules elliptic 830 – 920 µm long and 210–280 µm wide, margins entire. Bract underleaf elliptical, apex truncate, 1000–1100 µm long and 400–550 µm wide, margins entire. Bracts and bract underleaf torsively arranged, bract-underleaf-bract, not underleaf-bract-bract as typical of most Lejeuneaceae , one bract lobule overlaps on the abaxial side of the bract underleaf. Perianth 1100–1400 µm long and 500–600 µm wide, immersed within bracts, isoplicate with 8–10 plicae extending down upper half, perianth slightly constricted below plicate, lower half smooth, abruptly contracted above into a prominent rostrum 6–8 cell tiers high. Sporophytes not known.

Additional specimens examined (paratypes):— AUSTRALIA. Queensland. Cook District, summit area of Mount Bellenden Ker , 17° 16’ S 145° 52’ E, 1580 m, 7 July 2005, M. A. M . Renner 1923 & E. A. Brown ( NSW871963 !); same locality, M. A. M . Renner 1925b & E. A. Brown ( NSW871984 !) .

Distribution and Ecology:— Trunk and branch epiphyte in tropical montane simple notophyll vine forests above 900 m in the Wet Tropics Bioregion of North-east Queensland, Australia. Typically grows on bark uncolonised by other bryophytes, in situations of high insolation.

Recognition:— Acrolejeunea arcuata is distinctive among Acrolejeunea species in its relatively large size, reddish colouration, its oblong-elliptic underleaves, and its crowded, narrowly obpyriform lobules held close to the stem, bearing two lobule teeth.

Acrolejeunea arcuata subsp. arcuata differs from A. arcuata subsp. gradsteinii in its 1) dioicy, vs. autoicy, 2) obtuse leaf lobe apices vs. rounded; 3) weakly obovate underleaves vs. oblong-elliptic; 4) obtuse-acute and reflexed female bract lobes vs. rounded and plane; 5) perianth emergent above the female bracts vs. immersed within the female bracts, 6) androecia intercalary on leading axes vs. on lateral branches.

The type of A. hians is exceptionally similar in gross morphology to A. arcuata subsp. gradsteinii , particularly in its large size, underleaf shape and lobule morphology. The A. hians form of A. arcuata differs from Australian material in the leaf gyre below the female bracts also has a bract-like form, the lobe and lobule apices of the inner gyre are obtuse-acute. Female bract shape, sexuality, and size are primary differences between the type of A. hians and Australian populations of A. arcuata .

Acrolejeunea pycnoclada subsp. pycnoclada differs from Acrolejeunea arcuata subsp. gradsteinii in 1) its smaller size, with shoots 0.8–1.0 mm wide vs. 1.2–1.5 mm; 2) its yellow green or grey-green colour, vs. reddish brown; 3) the rotund to slightly obovate underleaves vs. oblong elliptic underleaves; 4) the lobules bearing three teeth vs. two; 5) leaf lobe cells not arranged in radiating rows vs. so arranged; 6) female bracts and bract underleaf cucullate vs. plane; 7) perianth rostrum 8–12 cell tiers high vs. 6–8. The type of A. pycnoclada subsp. pycnoclada bears three teeth on each lobule, whereas the type of A. pycnoclada var. rostrata bears two.

Kodama & Kitagawa (1974) proposed a new species of Ptychocoleus for a plant from Borneo having perianths with five inflated carinae. Acrolejeunea arcuata subsp. gradsteinii differs in having 10 uninflated carinae on the perianths.