Lejeunea demissa M.A.M.Renner, 2021

Renner, M. A., de, Lange P. J. & Glenny, D. S., 2021, A synopsis of Aotearoa / New Zealand Lejeunea (Lejeuneaceae: Jungermanniopsida) and new species in the Lejeunea epiphylla Colenso complex, Arctoa 30 (2), pp. 187-212 : 199-202

6. Lejeunea demissa M.A.M.Renner sp. nov. Fig. 6 , 7.

Diagnosis: Lejeunea demissa is distinguished by its ovate underleaves with a V-shaped sinus with obtuse to acute vertex; the ovate leaf-lobes whose apex is broadly obtuse to acute; the smooth leaf cell surfaces; the lobules with a keel shallowly curved, with a first lobule tooth composed of two cells and moniliform; the dimorphic shoot systems with branches smaller in stature than the primary shoot; gynoecia borne on short lateral branches subtended by a single subfloral innovation that continues vegetative growth; and the perianths with a short stipe.

Type: New Zealand, North Island, Coromandel Ecological Region, Te Aroha Ecological District, Mt Te Aroha summit, along track to Dog Kennel Flat, SW side of summit, in Nothofagus menziesii (Hook.f.) Oerst. and Griselinea littoralis Raoul forest, 37°32’S 175°45’E, 940 m, 12.III.1995, J.E. Braggins 95/201 (holotype: AK255268)

= Lejeunea epiphylla Colenso Trans. & Proc. New Zealand Instit. 21: 73. 1889. nom illeg. non Mitten J. Proc. Linn. Soc., Bot. 5: 118. 1861. pro parte.

Original material: Hab. Epiphytical on Hymenophyllum (sps.), woods, Dannevirke, County of Waipawa; 1888, W. C.

Description: Plants forming mostly pure patches on tree trunks and branches, also epiphyllous, particularly on Hymenophyllum demissum (G.Forst.) Sw. Shoots yellow green, to 25 mm long, medium sized for genus (1.0–) 1.2–1.6(–2.0) mm wide, irregularly pinnately branched. Stems with external and internal walls unthickened except for weak concave trigones of primary wall around cell wall junctions, seven cortical cells and around 10 medullary cell rows, cortical cell walls evenly and continuously thickened, medulla cell walls unthickened, hyaline. Leaves imbricate, insertion reaching the dorsal stem mid-line, dorsal leaf free strip absent. Lobes ovate, 211–610 (464 ± 68) µm long by 269–648 (483 ± 78) µm wide, imbricate to contiguous, obliquely spreading and patent, not squarrose when dry, convex, margin entire, apex rounded to obtuse. Lobules 41–200 (136 ± 35) µm long and 56–240 (160 ± 42) µm wide, with explanate and normal morphs, lobules not strictly dimorphic, typically intergrading along shoots, explanate morphs infrequent, normal lobules barely extending beyond the width of the underleaves, mostly obscured, keel straight at antical and postical ends, mostly arched in the middle, through 80° in total; lobule arch 4 cells, angle between arch and keel 50–90° at lobe-lobule juncture, arch meeting base of lobule tooth in plane with lobule; first lobule tooth variably 1 cell, or two moniliform cells, pointing in direction of shoot apex, all lobules on a shoot may have one-celled teeth, or two-celled first teeth; first tooth basal cell fused with two or three subtending cells, the

Fig. 7. Lejeunea demissa Four shoot sectors showing variation in lobule stature and teeth, and underleaf size and shape, within a single specimen, WELT-H10971

marginal of which are larger than surrounding cells, the interior of which is situated in a shallow rectangular notch that separates the first and second lobule teeth; second lobule tooth of one or two cells, obtuse; antical margin beyond first tooth plane or weakly in-rolled, straight then curved toward stem insertion at interior end; carinal region inflated primarily along the keel. Explanate lobules of 10–14 cells bearing a single-celled apical tooth. Underleaves contiguous to imbricate, ovate, broadest at or slightly below mid-point, 155–399 (302 ± 52) µm long and 140–399 (284 ± 46) µm wide, one third to one half the shoot width, bifid to 0.3×, sinus 64–168 (107 ± 27) µm deep, broadly to narrowly V-shaped, vertex rounded to acute, lobes not divergent, acute when small, increasingly obtuse and rounded as stature increases, rounded on largest underleaves. Underleaves attached to 2 or 3 ventral cortical cells, insertion transverse to weakly arched, underleaf base not cordate. Lobe cell walls with small triangular trigones and 1 or 2 small but distinct medial wall thickenings per wall. Lobe cell surface unornamented. Oil-bodies 16–35 per cell, small, ellipsoidal, internally homogeneous, colourless, smooth, in a loose submarginal ring. Asexual reproduction lacking.

Paroicous. Antheridia on short, determinate, achlorophyllous lateral branches bearing 3 bracts, 2 of which contain a single antheridia each, with an underleaf at branch base. Gynoecia produced on lateral branches immediately after branch initiation, the female bracts being the first leaf gyre produced by the branch, the branch then terminating, gynoecia also produced occasionally in the middle of leafy axes. Gynoecia subtended by one Lejeuneoid subfloral innovation of smaller stature than main leafy shoot that continues vegetative growth. Female bracts fused with bract underleaf on both sides. Perianths 805–983 µm long overall, with free perianth 760–910 µm long, pentacarinate, carinae with crenulate ridges through bulging cells, extending from apex one half to two thirds the way down the perianth sides; rostrum relatively short but distinct; with a short basal stipe 46–80 µm long, of two or three cell tiers. Sporophytes not seen.

Distribution and Ecology: Lejeunea demissa is endemic to New Zealand, where it is widely distributed throughout the North and South Islands with known records from the Bay of Islands in Northland to south Westland, however Lejeunea demissa is likely to be more widely distributed to the north and south of these northern and southern reports. Lejeunea demissa is an epiphyte or facultative epiphyll on tree trunks, branches, twigs and leaves between sea level and 1000 m. Common host species for epiphyllous growth are Beilschmiedia tawa (A.Cunn.) Kirk and Hymenophyllum demissum . At Coromandel L. demissa grew on the trunk of Dacrydium cupressinum in Agathis Salisb. forest, with Lopholejeunea (Spruce) Steph. and Radula allisonii Castle. At Mt Te Aroha L. demissa was collected as an epiphyte on a trunk of Schefflera digitata J.R.Forst. & G.Forst. At Rangitata River L. demissa was an epiphyte in low stature broadleaf forest, and at South Westland an epiphyte on tree trunks in alluvial forest.

Recognition: Lejeunea demissa is a fairly characteristic plant that is unlikely to be confused with other Lejeunea species in New Zealand, so long as it is examined carefully. Microhabitat provides a good first clue to identity, L. demissa is an epiphyte or epiphyll, it is not known to grow on rock, soil, or leaf litter and this, in combination with the smooth leaf lobe cell surfaces, the two-celled first lobule tooth and pentacarinate perianths are sufficient for confidant identification. Lobules, when well developed bear a 2-celled moniliform first lobule tooth that spreads away from the shoot axis, often at 45° or more. Above the first lobule tooth is a prominent triangular second lobule tooth. Sometimes explanate lobules also produce a 2-celled moniliform first lobule tooth. Some searching may be required along shoots to find lobules whose apex is visible, alternatively focusing up and down within clean shoot sectors may suffice to detect the first lobule tooth. Three of the other Lejeunea species in New Zealand with a moniliform first lobule tooth ( L. colensoana , L. oracola and L. rhigophila ) have inflated, ecarinate perianths while the fourth ( L. helmsiana ) has a first lobule tooth of three of four cells and has smaller, rotund, and remote to contiguous underleaves. The only species that is likely to be confused with L. demissa is L. perichymidia , especially when smaller plants expressing a high percentage of explanate lobules are at hand. Small and large shoots of Lejeunea demissa can be distinguished from those of L. perichymidia by the leaf-lobes having a distinct rounded to obtuse apex, whereas the leaf-lobes of L. perichymidia are continuously rounded; and the underleaves of L. demissa are ovate while those of L. perichymidia tend to be more rotund. It may co-occur with L. perichymidia , and with it form mixed patches, in which case identification may be challenged if the mixture is overlooked.

Etymology: From Latin demissa, hanging, applied in reference to the frequent colonisation of leaves of the fern Hymenophyllum demissum , where it co-occurs with Radula demissa .

Conservation: Lejeunea demissa is widely distribut- ed throughout cool wet forests of both main islands, so we suggest it may be suitable for listing as ‘Not Threatened’ following criteria in Townsend et al. (2008).

Specimens examined: New Zealand: North Island: Eastern Northland and Islands Ecological Region and District , Bay of Islands , Russell State Forest , Waihaha Stream, 35°21.323’S 174°12.129’E, 45 m, 14. I.2009, M. A. M . Renner 4150 & D. S . Glenny ( AK314701 ); Coromandel Peninsula, Horomanga Block , Waiwawahi Stream , 36°54’S 175°31’E, 25.II.1973, N. M . Adams ( WELT-H011249 ); South Island: Canterbury, Rangitata Riv- er, Rata Stream, 760 m, 25.VII.2013, M . Crowe ( CHR 589304 ); South Westland , 2 miles above Haast River Bridge, 11.VII.1969, R. K . Dell ( WELT-H003005 , WELT-H003007 ) ; New Zealand, without specific locality, Colenso a.2127 ( WELT-H003133 ) .

Figures

Fig. 6. Lejeunea demissa A: Four lobules showing variation in lobule teeth. B: Ten underleaves showing size and shape variation within a single shoot. C: Underleaf base. D: Shoot in ventral view. E: Shoot in ventral view, note difference in size and stature of underleaves and lobules. F: Dorsal stem surface showing leaf insertion lines, with dorsal stem midline indicated. G: Stem transverse section. H: Cladogram, not to scale. I: Lobule pair and underleaf comprising a single module, with underleaf partially cut away. J: Shoot sector with gynoecia on small stature lateral branches. K: Perianth transverse section. L: Perianth viewed from above, same scale as K. M: Shoot sector with gynoecia on lateral branch, with subfloral innovation. N: Shoot sector bearing gynoecia and androecia. A, B, C, E, H, K, M from WELT-H10971; D, F G, I, J, N from AK255268; L from AK300050; N from CHR589304.