Macromitrium tongense Sull.

Thouvenot, Louis, 2019, A review of the genus Macromitrium Brid. (Orthotrichaceae, Bryophyta) in New Caledonia, Cryptogamie, Bryologie 20 (16), pp. 167-217 : 210-212

Macromitrium tongense Sull.

( Figs 2E , 22 , 23 )

United States Exploring Expedition Wilkes Musci 7: table 5 (1859).

Macromitrium villosum (Besch.) Broth., Naturlichen Pflanzenfamilien. I (3): 486. 1903. — Drummondia villosa Besch., Annales des Sciences naturelles, Botanique, sér. 5, 18: 207. 1873. syn. nov. — Types: New Caledonia, “Île des Pins”, Pancher 578 “Sud de la Nouvelle Calédonie”, Pancher 574; Mt Mou, Balansa 2979. (lecto-, designated here: Balansa 2979, [Ms CRY 2 p. 24, PC[PC0774037]! Bibliothèque de Botanique, MNHN, Paris]; isolecto-, PC[PC0695939, PC0695940, PC0695941]!; syn-, PC[PC0096505, PC0695938, PC0096513]! — Dasymitrium villosum (Besch.) A.Jaeger., Bericht über die Thätigkeit der St. Gallischen Naturwissenschaftlichen Gesellschaft 1877-1878: 423 1880).

M. villosum var. longisetum Thér. , Bulletin de l’Académie internationale de Géographie botanique 17: 308. 1907. — Type: New Caledonia, 1906, Franc s.n. com. Renauld (lecto-, designated here: PC[PC0695934]!; isolecto-, PC[PC0096504]!) syn. nov.

M. villosum var. elongatum Thér. , Bulletin de l’Académie internationale de Géographie botanique 17: 308. 1907. — Type: New Caledonia, 1906, Franc s.n. com. Renauld (lecto-, designated here: PC[PC0083740]!; isolecto-, PC[PC0096502]!) syn. nov.

M. villosum var. intermedium Thér. , Bulletin de l’Académie internationale de Géographie botanique 17: 308. 1907. — Type: New Caledonia, 1906, Franc s.n. com. Renauld (lecto-, designated here fide Guo in Sched. [2007]: «env. Nouméa» PC[PC0083741]!; isolecto-, PC[PC96503]!) syn. nov.

M. ludoviciae Broth. & Paris, Öfversigt af Finska Vetenskaps-Societetens Förhandlingar 53A (11):17. 1911. — Type: New Caledonia, “Île des Pins, Watchia”, L. Le Rat s.n. (lecto-, designated here fide Vitt in Sched. [1983]: H-BR[H-BR2563009]!; isolecto-, PC[PC137795]!, REN[REN000207]!) syn. nov.

M. densifolium Thér. , Bulletin de l’Académie internationale de Géographie botanique 18: 253. 1908. — Type: New Caledonia, 1907, Franc s.n. (lecto-, designated here PC[PC0137661]!, isolecto-, PC[PC0096532]!) syn. nov.

M. chrysoneuron Müll.Hal. nom. herb. (C.M. in Bescherelle’s herbarium), reference specimen: Wagap, Vieillard s.n. (PC: BESB1950!).

M. subvillosum Broth. & Paris Öfversigt af Finska Vetenskaps-Societetens Förhandlingar 51A (17): 16. 1909. — Type: New Caledonia, Mt Dzumac, A. Le Rat s.n. (lecto-, designated here fide Vitt in Sched. [1983] H-BR[H-BR2561008]!; isolecto, H-BR[H-BR2561005]!, PC[PC0096521]!) syn. nov.

TYPE. — Tonga. Tongatabu (Holotype:?; iso, PC [ PC 0695994, PC 0695995]!)

DISTRIBUTION IN NEW CALEDONIA. — Frequent at low to medium altitude in North and South Provinces.

TOTAL RANGE. — Western New Guinea, Polynesia ( Pitcairn Isl.), Tonga, Fiji, New Caledonia.

SELECTED SPECIMENS. — Macromitrium tongense : New Caledonia. Province Nord, Pouembout, Tiéa dry forest, 40 m, on trunks, 26.IX.2008, Thouvenot NC122 (PC); Forêt Plate near Ouendé waterfall, 300 m, epiphyt, 7.IX.2003, F. Müller NC755 (DR); Province Sud, Nouméa, Tina, mangrove edge, 1 m, on dead stump, 24.IX.2012, Thouvenot NC1451 (PC), on rock, 24.IX.2012, Thouvenot NC1444 (PC); Mont-Dore, Demazures wet forest, 400 m, on trunks, 28.IX.2016, Thouvenot NC2262 (PC); Farino, Grandes Fougères Nature Park, 400 m, 8.XII.2010, K. Reichel NC767 (DR); Bourail, Gouaro-Déva, Nindouri, 105 m, on trunks, 25.IX.2008, Thouvenot NC1124 (PC); Fiji, Malatta, 0-100 m, 29.III.1934, A.C. Smith 1443, det Bartram (PC0146832); Macromitrium chrysoneuron : New Caledonia. Île des Pins, Pancher s.n. (PC0137629); Macromitrium ludoviciae : New Caledonia. Île des Pins, Koumo, McKee 33758 (PC0096537); Macromitrium densifolium : New Caledonia. Province Nord, Balade, Vieillard 1733, PC0096500 (PC); Macromitrium subvillosum : New Caledonia. Province Sud, Mt Humboldt, trail to the hut below the summit, on stone, 800 m, 30.VIII.2003, F. Müller NC764 (DR); Macromitrium villosum var. intermedium : New Caledonia. Province Sud, Mont-Dore, Demazures forest, on trunks, 412 m, 28.IX.2016, Thouvenot NC2360 (PC);

South AFrica. Macromitrium serpens : Cape of Good Hope, Burchell s.n. type: E 00007638 ( E);

Tahiti. Macromitrium tahitisecundum : Nadeaud 266 (type PC 0695992).

DESCRIPTION

Pseudautoicous

Dwarf male plants on leaf axis of female branches.

Plant

Small, creeping stems with dense erect fusiform branches.

Branches

Short, 2-4(-10) mm long, simple, rarely innovating by fasciculate branchlets, when dry usually tightly funiculate, with leaves erect to obliquely appressed and spirally coiled, sometimes loosely so, stout costae prominent on the back, when moist patent to spreading, straight to slightly incurved, spirally inserted.

Branch leaves

Small, 1.1-1.6 mm long, (0.2-) 0.3-0.4 mm wide, carinate, ligulate above the more or less oblong wider bases, rarely lanceolate, upper parts opaque with a sharp transition, in inverted “v”, towards the basal parts which take up c. ½ the total leaf length, apices usually obtuse mucronate or apiculate, less frequently abruptly acute, costae strong, percurrent in apiculi or excurrent in stout mucrones, margins plane, subentire to crenulate, basal part plicate.

Upper cells

Small, (5-)8(-12) µm wide, irregularly multi-layered, the internal layers made of rounded-quadrate cells, thick walled, unevenly contiguous, in a slightly embossed surface, covered on both sides by more or less dense patches of spherical cells thick walled, bearing several small papillae, the internal cells with the same papillae when exposed. This pattern of cellular arrangement is variously developed on the upper half surfaces of the leaves, sometimes including the ventral side of the costae, but more often scattered, at least limited to the apices.

Lower cells

Rectangular elongate, 12-35 µm long, 7-10 µm wide, very thick walled, lumina narrow, variously wavy, single rounded papillae present, scattered or lined up on the plicae. Perichaetial leaves erect along the seta bases, not or slightly exceeding the vegetative leaves, oblong to wide lanceolate, smooth.

Calyptrae

Hairy.

Setae

Short to medium, 4-6(-10) mm long, rigid.

Vaginulae

Hairy.

Capsules

Elliptical to short cylindrical, 1.2-1.5(-2) mm long, smooth, with rims brown, small and erect, slightly plicate or smooth.

Peristomes

Single.

REMARKS

Macromitrium tongense is well characterized by:1) small branches fusiform, acute, usually simple; 2) leaves obliquely appressed, spirally coiled in dry condition, usually tightly so; 3) upper cells multi-layered with the continuous internal layers being covered on both sides by patches of rounded papillose cells; in transverse section the internal cells are arranged in staggered row, with additional cells in a discontinuous row on one or both sides; 4) basal cells rectangular elongate with thicker walls and sinuous narrow lumina; 5) perichaetia inconspicuous; 6) vaginulae and calyptrae hairy; 7) setae short to medium; and 8) oblong elliptical urns, mouth narrowed and usually smooth. It is easily distinguished from the Indian-African Macromitrium serpens Burch. ex Hook. et Grev. ) Brid., a species with longer lanceolate leaves, long acuminate, contorted in dry condition with fragile apices incurved so that the dry branches appear curly. Macromitrium tahitisecundum Margad. from Society Islands, should be a synonym of M. tongense as the distinguishing characters cited by Bescherelle (1898) and observed on types specimens are included within the variability observed in the later. Bescherelle himself stated that this species (first named Dasymitrium nadeaudii Besch. ) was very similar to Dasymitrium villosum .

All the syntype samples of Macromitrium villosum in PC, kept in the general herbarium of bryophytes as well as in the Bescherelle’s herbarium, have the characteristic features of M. tongense and the examination of many samples allows to evaluate the variability of the species, mainly varying in cover ratio of the upper laminae by patches of rounded cells which may cover nearly all the surface or be very scattered or limited to the apex (e.g. specimen Pancher 578). The lengths of the setae are evenly short, not exceeding 9 mm, but the var. longisetum , with setae 10-20 mm long, was isolated by Thériot on this single criterium. We do not consider here the single seta length as relevant, because it may be variable in some extant in many species of the genus. Thériot described M. villosum var. elongatum with longer branches, up to 7 mm, but a close examination reveals that this size regards branches innovating with fasciculate branchlets, while single branches do not exceed 4 mm. Branch innovations are rarely observed in the species. Since it is the single difference with the type, we include this variety within the species concept. Brotherus compared M. ludoviciae to M. cucullatum , synonym of M. francii , but the different type specimens actually match M. villosum , except for the branch dry habit that is variable, some specimens exhibiting very loosely spirally coiled branch leaves so that the typical fusiform spiralled habit of the branches is inconspicuous. In M. densifolium, Thériot emphasized the thick costae and mucrones, but it is a common feature in the species. M. subvillosum was isolated by Brotherus according to minor differences with M. villosum , namely the shape of the leaves, narrowly acuminate and acute, the rigid habit and larger cells. In the type specimens, we found no striking differences regardint to the two latter characters. However, leaves are variously spirally coiled in dry condition and the leaf upper parts are narrower and acute, upper cells are arranged as in M. villosum var. intermedium . The latter is distinguished from the other types brought together under the name M. tongense by the branch dry habit with very loosely spirally coiled leaves, branch leaves narrower, long ligulate, very obtuse to rounded, upper cells pluripapillose, single-layered except in the apices, setae 7-15 mm long. It represents a mix of extreme modes in the features of M. villosum . Recent samples matching to this variety have been collected at about 400 m, an elevation at the limit of the distribution range. Another sample matching with M. subvillosum , has been found at c. 800 m. Thus, these forms might represent extreme modes of variation in M. tongense characters and could be linked to ecological conditions.

Amongst the syntypes, the most accurate specimen, likely considered as typical of Drummondia villosa by Bescherelle, is the collection of Balansa n° 2979. Indeed, Bescherelle wrotes this reference in original documents found in his private herbarium: the part glued to his personnal sample book (Bescherelle 1873, Ms CRY 2) and the corresponding pencil sketches in a volume of plates (Bescherelle, s.d., Ms CRY 3-30, ined.), likely intended to illustrate the “Florule bryologique de la Nouvelle-Calédonie ” (Bescherelle 1873). Therefore, we select this part of the Balansa specimen in the Bescherelle herbarium as the lectotype and the other parts in PC are isolectotypes.

Macromitrium tongense is a frequent species in coastal, lowland and foothill areas, growing mainly on tree trunks but it can also be found on deadwood and rocks in various lowland habitats: mangroves, dry forests, wet forests, from 0 to 450, rarely up to 800 m a.s.l. These small plants seem adapted to harsh environments.

Figures

FIG. 2. — Dry branch habits of Macromitrium (II) A, M. sarasinii Thér.; B, M.humboldtense Thouvenot & Franck Müll.; C, F, M. panduraefolium Thouvenot; D, M. larrainii Thouvenot & K.T.Yong; E, M. tongense Sull.; G, M. subvillosum Broth. & Paris; H, M. rufipilum Cardot; I, M. aurescens var. caledonicum (Thér.) Thouvenot. From type specimens (A-D, F, H, I), from specimens Müller NC755 (E), NC764 (G). Scale bars: 1 mm.

FIG. 22. — Macromitrium tongense Sull.A, Dry branch with sporophyte;B, C, E, G, Branch leaves; D, Dwarf male plant;F, Upper cells;H, Basal cells; I, Perichae- tial leaf; J, Cells in upper half of basal par of branch leaf. All drawn from the M. villosum (Besch.) Broth. syntypes Pancher 574 (A, B, I), Pancher 578 (D), Balansa 2979 (C, E, F-H, J). Scale bars: A, 1 mm; B-D, E, G, I, 500 µm; F, H, J, 10 µm.

FIG. 23. — Macromitrium tongense Sull.: morphological diversity among the New Caledonian types with special emphasis on M. villosum var. intermedium (P-V). A-H, P, R, S, transverse sections in the top quarter of branch leaves;Q, transverse section at apex of branch leaf; I-O, U, V, branch leaves; T, dry branch.Drawn from the M. tongense isotype PC0695994 (A) and specimen of Smith 1443 (C), from the M. villosum (Besch.) Broth. syntypes Pancher 574 (B), Balansa 2979 (D, I), Pancher 578 (E-G), from the lectotype of M. subvillosum Broth. & Paris (H, J), lectotype of M. villosum var. intermedium Thér. (Q-S, U), lectotype of M. villosum var. elongatum Thér. (K), lectotype of M. ludoviciae Broth.& Paris (L, M), lectotype of M. densifolium Thér. (N, O), from the specimen M. villosum var.intermedium Thér. Thouvenot NC2311 (P, T, V). Scale bars: A-H, P-S, 10 µm; T, 1 mm; I-O, U, V, 500 µm.