Lejeunea

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 : 193-195

KEY TO LEJEUNEA OF NEW ZEALAND AND TASMANIA

Tips for using the key to Lejeunea species.

1. Check whether or not the specimen is a mixed gathering. Lejeunea species may form mixed patches, so always be aware of whether or not your specimen comprises one species, as this will save a lot of time and confusion. Differences among species may be subtle, involving differences in underleaf and lobule shape, in addition to leaf cell surface ornamentation and oil-bodies, so several shoots from across the specimen should be checked.

2. Choose several of the largest shoots for examination. Character expression within Lejeunea species is often correlated with size, such that diagnostic features are borne on the largest shoots only. Two studies have explicitly addressed allometric patterns of quantitative character expression in leafy liverworts, and both have found significant allometric relationships in which diagnostic shape variation is maximally expressed on the largest structures (Renner et al., 2013, 2018). The point is that patterns of expression are critical and require nuanced understanding not adequately captured by the reduction of variation to simple ranges, including the allometric components to the expression of variation in both qualitative and quantitative variation. Just because, due to their structural simplicity and allometric variation, small shoots of different species are indistinguishable does not mean the species to which those shoots belong are the same. The complex realities of morphological variation expressed by leafy liverworts is itself an argument against overly typological and formulaic operational species criteria, in particular those based on simple morphological discontinuity. The expression of diagnostic characters associated with lobule shape and dentition may be variable within and among shoots, and it is often necessary to search a number of shoots for lobules whose expression is optimal before an effective assessment of character manifestation can be made.

3. Count oil-bodies close to the shoot apex. Oil-body number in Lejeunea and Cololejeunea species can increase with distance from the shoot apex. In some Lejeunea species with granular oil-bodies 5-7 oil-bodies are present in cells of mature leaves at the shoot apex, while 12-24 oil-bodies are present in cells of leaves further down the shoot. Oil-body number in the key refers to counts from cells close to the shoot apex. The difference between homogeneous and granular oil-bodies in Lejeunea is somewhat subtle. Homogeneous oil-bodies have smooth surfaces, and no discernible internal structure, they also tend to be fusiform in shape. These homogeneous oil-bodies tend to be numerous within each cell, and are often arranged in a distinct submarginal ring ( Fig. 4A ). Granular oil-bodies, on the other hand, have a finely granular surface and discernable internal structure. Granular oil-bodies tend to be few in number, usually less than 20, per cell and may be scattered or arranged in a loose submarginal ring ( Fig. 4 B-C). Granular oil-bodies occur in species which also possess a granular leaf-lobe cell surface ornamentation, which can be fine and indistinct ( Fig. 4D ).

4. Two of the couplets in the key are based solely on whether perianths are carinate or not. In specimens where perianths are absent, we recommend the following proceedure. Firstly check through older portions of the specimen, including those overgrown by younger shoots, for old perianths. These are sometimes present, but buried within, the specimen. Failing that try keying the specimen in both directions. Subsequent couplets contain sufficient detail that the forcing of your specimen through one, or the other, should become clear through the mismatch between characters described in each and those borne by the plant at hand.

5. It has been claimed that perianth stipe expression in Lejeuneaceae is variable within individuals, and even within single shoots, and that this inconsistency of expression renders this feature worthless for species circumscription. While at face value the observation of variable perianth stipe expression is correct, extending that claim to inconsistency is incorrect because it neglects ontogenetic patterning in the expression of perianth stipes. The perianth stipe character requires careful interpretation, the stipe evidently develops during the later stages of perianth growth, perhaps close to the maturity of the sporophyte enclosed by the perianth. This delayed development means that on a single shoot perianths with and without stipes may be present, but the perianths without stipes will always be the youngest, containing inconspicuous sporophytes. Perianth stipe length may be variable on perianths in close proximity, see for example Fig. 5L , this is due to differences in perianth age, which themselves likely relate to differences in when the archegonium was fertilized, the event which ultimately triggers perianth development. Within the New Zealand Lejeunea flora variation in stipe length at perianth maturity is rare, and known only to occur in Lejeunea rhigophila , in which perianths bearing erupted sporophytes may or may not have a stipe ( Renner et al., 2010). The demonstration of true variability in stipe expression against common ontogenetic markers is, however, rare for Lejeuneaceae . For the purposes of this key, perianth maturity is reached when the enclosed sporophyte has ceased cell division. In practical terms, this means that mature perianths are those from which the sporophyte has emerged, or is at the point of rupturing the calyptra, in other words the sporophyte is conspicuous, swollen, and dark if the calyptra remains intact.

1. Leaf cell surfaces bearing granular ornamentation, sometimes sparse; oil-bodies (where known) granular, generally fewer than 10 per leaf lobe cell; plant colour often whitish-green, opaque ...................... 2

— Leaf cell surfaces smooth, without ornamentation; oil-bodies (where known) homogeneous, fusiform, small, numbering upward of 30 per leaf-lobe cell and often arranged in a sub-marginal ring; plant colour green, yellow-green, or brown-green, clear ........ 11

2. Perianth inflated, carinae faint or absent ............. 3

— Perianth inflated or compressed, pentacarinate but always at least four carinae conspicuous ............... 5

3. Underleaves ovate, divided from 0.5 to 0.75 their length; plants usually comprised loose, radiating patches; shoots mid-green, or if white-green then small, up to 0.6 mm wide ...................................... 4

— Underleaves more or less rotund to ovate, divided to 0.5, usually less, underleaf lobes triangular; plants usually comprised long, sparingly branched shoots arranged in parallel, positively geotropic and often forming pure turfs on tree or palm trunks; shoots bright pale green when fresh, drying to a whitish brown ................................... 9. Lejeunea gracilipes

4. Perianth with remnants of 5 carinae, each taking the form of 2 rows of raised and paired cells; mature perianths usually weakly pentagonal in end-view; lobe–lobule junction lying postical to the base of the first lobule tooth; lobule arch (the lobule margin between the lobe-lobule insertion and the base of the first lobule tooth) of 3 or 4 cells (for illustrations of this character compare the following figures in Renner et al., 2010: Fig. 8 B, 8 C, 9 B); a trunk epiphyte in lowland (<300 m) forest from Northland south to Nelson – Marlborough. .......... 21. Lejeunea tumida

— Perianth without carinae remnants as described above, laterally dilated with suture or grove on median dorsal surface, ventral surface smooth; lobe–lobule junction lying antical to the apex of the first lobule tooth; lobule arch of 4–7 cells; epiphytic or epiphyllous on trunks, branches, twigs and leaves in lowland through montane forest and scrub from North Auckland to South Westland ................... 4. Lejeunea colensoana

5. Leaf apex acuminate .............................................. 6

— Leaf apex rounded ................................................. 7

6. Leaves contiguous, apex spreading at right angles to shoot axis; shoots typically comprising either all normal or explanate leaves, without abrupt and numerous transitions among lobule forms within a single shoot ...................................... 2. Lejeunea apiculata

— Leaves remote, apex spreading toward shoot apex; shoots comprised a mixture of explanate and normal leaves ...........................................7. Lejeunea exilis

7. Leaf lobe elliptic-ovate, nearly parallel sided close to the stem, tapering gradually to a more or less tightly rounded apex, overall wider than long; lobules small in comparison to leaf lobe size; underleaves ovate, on larger shoots imbricate, and obscuring lobules in entirety in ventral view .... 8. Lejeunea flava

— Leaf lobe ovate-rotund, margins more or less continuously curved, progressively and evenly rounded at apex, approximate as long as wide, or slightly wid- er; lobules small or large in comparison to leaf lobe size, but not obscured by underleaves in ventral view; underleaves various .............................................. 8

8. Leaves dislocating from stem 16. Lejeunea schusteri

— Leaves not dislocating from the stem................... 9

9. Leaf cells bulging, leaf lobe margin crenulate with bulging cells; plants not flattened against the substrate; underleaves rotund, divided to less than 0.5×, sinus narrow, underleaf lobes triangular ................. ... 18. Lejeunea sp. (s) (AK306857; Surville Cliffs)

— Leaf cells not bulging, leaf lobe margin entire; plants flattened against substrate; underleaves ovate, divided to 0.5× or more, sinus narrow or broad, if broad then lobes spreading, underleaf lobes lanceolate ........ 10

10. First lobule tooth multicellular on larger lobules ... ...................................... 11. Lejeunea hodgsoniana

— First lobule tooth always unicellular regardless of lobule size ......................... 3. Lejeunea anisophylla

11. Lobules nearly uniformly explanate; underleaves rotund, remote to contiguous; plants on basalt, soil, or decaying wood within and alongside streams ......... ......................................... 19. Lejeunea subelobata

— Plants without the above combination of characters; lobules at least sometimes fully developed, or if not then variable in size and not uniformly explanate; underleaves rotund or, more often, ovate ............ 12

12. Plants with lobule first tooth at least sometimes multicellular, formed by two or three moniliform cells, at least on the largest lobules .............................. 13

— Plants with lobule first tooth consistently unicellular, including on the largest lobules .................... 16

13. Perianth tumid, without carinae .......................... 14

— Perianth pentacarinate ......................................... 15

14. Leaf lobes squarrose when dehydrated, markedly altered from hydrated conformation; underleaves remote to contiguous, underleaf bases not cordate; lobules with antical margin around the first lobule tooth visible in ventral view, not strongly inrolled; the first lobule tooth consistently with 2 cells, usually inclined outward, away from the shoot apex, lobe–lobule junction lying postical to the base of the first lobule tooth, lobule arch usually of 3 (ranging from 2 to 4) cells ............................................... 12. Lejeunea oracola

— Leaf lobes maintaining hydrated conformation when dry, not squarrose; underleaves imbricate, underleaf bases cordate; lobules with antical margin inrolled, margin around the first lobule tooth not visible in ventral view; the first lobule tooth consistently of 3 or 4 cells, usually inclined inward, towards the shoot apex, lobe–lobule junction lying above the base of the first lobule tooth, lobule arch consistently of 4 cells ............................... 15. Lejeunea rhigophila

15. First lobule tooth variably 1- to 3-celled, when three celled orientated nearly parallel with the stem axis, antical lobule margin strongly inrolled and obscured in ventral view; leaf apex evenly rounded, keel half the lobe width or more; underleaves remote, rotund to elliptic, about twice the stem width .................... ........................................... 10. Lejeunea helmsiana

— First lobule tooth variably 1- or 2-celled, antical lobule margin inflated but not inrolled, and so visible in ventral view; leaf apex broadly obtuse, keel half the lobe width or less; underleaves remote to contiguous, elliptic to ovate, about three times the stem width ....................................... 6. Lejeunea demissa

16. Plants with blue oil-bodies 5. Lejeunea cyanophora

— Plants with hyaline or pale grey oil-bodies ......... 17

17. Shoots 1.2 mm or more wide across leaves when hydrate ..................................................................... 18

— Shoots less than 1.0 mm wide across leaves when hydrated, typically 500–600 µm ......................... 20

18. Subfloral innovations absent, or small-stature in comparison to parent shoot; underleaves on large shoots ovate, imbricate, wider than lobules, which are obscured in ventral view; leaf lobes ovate-triangular, apex often obtuse, lobule keel straight to slightly curved; lobules trapezoidal, keel nearly straight; ventral merophyte 2 to 4 cells wide .............................. ....................................... 20. Lejeunea thalassoides

— Subfloral innovations present and similar in stature to the parent shoot; underleaves on large shoots nearly rotund, narrower than the lobules, which are visible in ventral view; leaf lobes elliptic, apex rounded;;obules broadly ovate, lobule keel curved; ventral merophyte 2 cells wide ....................................... 19

19. Mature perianths (those containing a sporophytes whose cell divisions are completed, or nearly completed) sessile or with a short, inconspicuous stipe; bracteole narrow ovate to nearly rectangular; plants dark green to brown green, on rocks or tussock bases on Auckland Islands ...... 1. Lejeunea amphinephea

— Mature perianths (those containing a sporophytes whose cell divisions are completed, or nearly completed) sessile or with a short, inconspicuous stipe; bracteole ovate; plants mid- to bright-green, on soil, tree trunks, branches, and leaves in the North and South Islands of New Zealand, and Tasmania ........ ...................................... 13. Lejeunea perichymidia

20. Cladia present, produced by lateral-intercalary branching, and dislocating leaving the basal collar of leaf-like appendages intact on the parent shoot; lobe apex sometimes obtuse; underleaves as long as wide, appearing squat on larger shoots with a wide sinus ............................... 14. Lejeunea primordialis

— Cladia not produced; lobe apex always rounded; underleaves longer than wide, appearing ovate on larger shoots with a narrow sinus ...................................... ......... 17. Lejeunea sp. (p) (AK286681; Mangere).

Figures

Fig. 4. A: Oil-bodies of Lejeunea thalassoides (Glenny 14482). B: Oil-bodies of Lejeunea primordialis (Glenny 14464). C: Oil-bodies of Lejeunea flava (Glenny 14457). D: Leaf-lobe cell surface of Lejeunea flava (Glenny 14457), please note the focal plane of this image is on the leaf cell surface, not the middle of the cell lumen, the associated intereference effects and blurring of background objects explains the apparent differences in oil-body morphology between this figure and Fig. 4C. Compare the oil-bodies in this image with those in the background of Fig. 4C for demonstration of this point. All images to same scale, 10 micron scale bar indicated in A, B, C.

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.