Lejeunea amphinephea 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 : 195-198

1. Lejeunea amphinephea M.A.M.Renner sp. nov.

Fig. 5 .

Diagnosis: Lejeunea amphinephea is distinguished by its rotund underleaves with a broad sinus with obtuse to rounded vertex; the round to ovate leaf-lobes whose apex is rounded; the smooth leaf cell surfaces; the lobules with a keel deeply and nearly continuously curved through 90 degrees, with a first lobule tooth always composed of a single-cell; 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 long stipe.

Type: New Zealand, Auckland Island, Hanfield Inlet near waterfall on southern side, 50°45’S 166°10’E, 23.II.1973, P. N . Johnson 23/5 (holotype: WELTH006349 )

Description: Plants mid- to brown-green, primary shoots large for genus, 30–40 mm long 1.2–2.0 mm wide, sparingly and irregularly branched, branching exclusively lateral-intercalary, branches with conspicuous irregularly lobed basal collar, loosely prostrate forming extensive patches on soil and rocks, in association with seepages and waterways or outcrops. Stems with seven or eight rows of larger cortical cells surrounding around 11–25 rows of smaller medullary cells; free external cell wall thickened, as are longitudinal radial cortical cell walls; medullar cell walls unthickened. Leaves contiguous to loosely imbricate, insertion attaining dorsal stem midline and overlapping across the dorsal-most cell row, dorsal leaf-free strip absent; lobes 617–942 (796 ± 90) µm long by 566–1055 (805 ± 172) µm wide, rotund to ovate, moderately convex, not obliquely spreading, outer portion arching ventrally, apex rounded to broadly obtuse, weakly falcate and obtusely notched at junction with keel; antical margin flared, not auriculate but crossing opposite stem margin, and overlapping adjacent lobes so obscuring the stem in dorsal view; margins entire. Lobules 192–345 (282 ± 44) µm long by 188–339 (271 ± 43) µm wide, 0.125–0.2× lobe area, not dimorphic though variable in size, carinal region broadly inflated, antical margin at most only weakly appressed against the lobe, keel evenly and continuously arched through 80–90° in maximally developed lobules, less arched to occasionally straight in others. Lobule first tooth single-celled, long axis orientated toward shoot apex, fused along all of its basal margin with a cell of similar size, and along 0.75 of the interior margin with a slightly larger cell, whose free margin defines a shallow notch between the first lobule tooth and the broadly rounded, indistinct second tooth; lobule antical margin interior of the second lobule tooth straight, marginal cells slightly elongate with long axes parallel with margin. Underleaves remote, at most contiguous on the largest shoots, rotund to ovate, 345–576 (485 ± 65) µm long by 377–580 (479 ± 58) µm wide, bifid to 0.3×, sinus broadly V- to U-shaped, vertex round- ed, sinus 109–209 (155 ± 32) µm deep, lobes triangular, obtuse, not spreading, margins entire to weakly and irregularly crenulate; underleaf insertion shallowly arched, on 2 stem cortical cells. Oil-bodies not seen. Asexual reproduction absent.

Paroicous. Androecia on short determinate lateral-intercalary branches, bearing two to three pairs of hyaline fertile bracts. Gynoecia produced on leading leafy shoots and lateral intercalary branches, subtended by a single Lejeuneoid innovation (Pycnolejeuneoid innovations were recorded for this species during the preparation of this description, but have not been confirmed due to restricted specimen access during the current pandemic — their presence would be anomalous within the Lejeuneinae). Female bracts rounded, bract lobules ligulate, apex rounded or obtuse; bracteole elliptic-oblong, bifid to 0.5×, lobes linear, not spreading, fused with bract lobules at base on one or both sides. Female bracteole similar to vegetative underleaves. Perianth 1152–1311 µm long overall with free perianth 593–690 µm long, equally pentacarinate, carinae unarmed, extending to near the base, rostrum 4–6 cells high. Immature perianths estipitate, mature perianths with a long, hyaline, basal stipe 530–621 µm long, comprised of leptodermous cells.

Distribution and Ecology: Currently known only from subantarctic Auckland Island and Adams Island, where it has been collected between sea level and 400 m elevation in a range of microsites, including on steep rocks of a lightly vegetated slip; on rocks in coastal stream; on dead stipes of Polystichum vestitum (Sw.) C.Presl ; on rocks in water of stream outfall, and on the eastern side of Cloudy Peak on a rock outcrop, partly sheltered by short scrub and Chionochloa antarctica (Hook.f.) Zotov. It is possible that Lejeunea amphinephea is endemic to the Auckland Islands, but as the Lejeuneaceae and the genus Lejeunea is generally poorly known and collected, the possibility that this species occurs elsewhere, including New Zealand, where it may yet be discovered in comparable microhabitats within the alpine zone, and southern South America cannot be excluded.

Recognition: A combination of characters will serve to distinguish L. amphinephea from other Lejeunea known from the New Zealand Botanical Region, and all should be checked to confirm the identity of plants under examination. The leaf cell surfaces are smooth; they do not bear a fine to coarse granular ornamentation as if found in some other large Lejeunea species such as L. flava and L. gracilipes . The leaf surface ornamentation of L. flava and L. gracilipes can be seen under around 400 times magnification on a compound microscope with appropriate diaphragm settings, and especially where airbubbles are trapped between the leaf surface and coverslip, they appear as small, usually scattered granules on the cell surface; and in life contribute to the opaque appearance of some, but not all, of the species that possess them. The leaf-lobes are rotund to ovate, and have a broadly and continuously rounded margin including the exterior margin, which is often reflexed. There is never a distinct obtuse apex as occurs in species with more ovate-triangular leaf lobes, for example L. thallasoides M.A.M.Renner & Glenny. The lobules of L. amphinephea are, when fully developed, distinctive in their relatively large size in comparison with the leaf-lobes, being around a sixth to an eighth the area of the lobe, and in their deeply and continuously curved keel, which is evenly cambered through nearly 90°, and whose base extends at right angles from the stem. The junction between the keel apex and the leaf-lobule forms a right angle, but is not notched. Shoot stature in L. amphinephea , as in many Lejeunea , is variable and diagnostic features associated with lobule shape are expressed best by the largest shoots, so these should be preferentially selected for inspection. Smaller-statured shoots often do not express diagnostic features, and tend to bear strong resemblance to the small- er shoots of other species, to the extent that plants comprising exclusively small-statured shoots may be difficult to assign to a species. Another distinctive feature of L. amphinephea is the long stipe at the base of fertilized perianths, this comprises half the overall perianth length and is 500–600 µm long and 6 or 7 tiers of leptodermous, hyaline, and inflated cells tall. The perianths are borne in gynoecia that are subtended by a single subfloral innovation that continues vegetative growth.

Among New Zealand Lejeunea species, Lejeunea amphinephea is most likely to be confused with L. thalassoides , because the two species are similar in stature, both have large underleaves with a broad sinus and the smaller stature shoots of both species bear a strong resemblance to one another. A useful feature for distinguishing smaller stature shoots of L. amphinephea from those of L. thalassoides , is found in the subfloral innovation, which in L. thalassoides are rudimentary and abortive; they do not continue vegetative growth while in L. amphinephea they do. The leaves of L. amphinephea have a continuously rounded free external margin, within which there is no trace of an obtuse apex, whereas the leaf lobe has a distinct obtuse apex in L. thallasoides , this character is best assessed by dissecting and slide-mounting leaf lobes so that their outline is unambiguous. The stem section may also provide assistance in distinguishing L. amphinephea from L. thalassoides ; the stems of L. amphinephea have seven cortical cell rows, or eight in the vicinity of stem insertion lines, whereas in L. thalassoides the larger stems have up to 10 cortical cell rows.

Etymology: from the ancient Greek ¢mfiknef»j ‘wrapped in darkness’ referencing both the long winter nights, expanse of surrounding deep open ocean, and dark green colour of the plants in herbarium material.

Conservation: Lejeunea amphinephea was listed as Lejeunea aff. flava (b) (WELT H006349; Auckland Islands) in de Lange et al. (2020). This species is currently known only from Auckland Island, where it has been collected at several localities in the early 1970’s.

Specimens examined: New Zealand, Auckland Island, Carnley Harbour, Camp Cove , 50°51’S 166°01’E, 30 m, 21.II.1973, P. N . Johnson 21/53 ( WELT-H006135 ); Waterfall Inlet 5049’ S 166°12’E, 12.II.1973, P. N . Johnson 12/22 ( WELT-H004955 ); Cloudy Peak , 50°53’S 166°09’E, 400 m, 14.II.1973, P. N . Johnson 14/41 ( WELT-H005213 ) Adams Island, 1 mile east of Fairchild’s Garden , 50°51’S 165°56’E, 18.II.1973, P. N . Johnson ( WELT-H005510 )

Figures

Fig. 5. Lejeunea amphinephea A: Lobule detail. B: Five underleaves showing size variation within a single shoot. C: Stem transverse section. D: Shoot in ventral view. E: Underleaf base. F: Dorsal stem surface showing leaf insertion lines, with dorsal stem midline indicated. G: Shoot in ventral view showing gynoecia production on small stature lateral branches. H: Cladograms, not to scale. I: Perianth transverse sections. J: A normal stature gynoecium bearing shoot showing normal leafy subfloral innovation. K: shoot bearing male branches. L: Shoot sector with gynoecia on small stature lateral branches, with long-stipitate perianths and small stature subfloral innovations. M: Two sets of female bracts and bracteoles. All from WELT-H6349, except K from WELT-H6135.