Didymodon novae-zelandiae J.E.Beever & Fife, 2016

Beever, Jessica E. & Fife, Allan J., 2016, A new species of Didymodon (Pottiaceae, Bryophyta) and a key to New Zealand representatives of the genus, Phytotaxa 258 (3), pp. 279-286 : 279-283

Didymodon novae-zelandiae J.E.Beever & Fife , sp.nov.

Holotype:— NEW ZEALAND. North Auckland Land District: northern shore of Manukau Harbour , Ihumatao , ca. 1.5 m elev., 37°0.048ʹS, 174°45.108ʹE; on SW-facing, damp, vertical sea-cliff of volcanic tuff, lightly shaded under high pōhutukawa canopy, 15 May 1982, J. E. Beever 11-61 ( WELT M040251 ).

Paratypes:— at type locality, 17 February 2008, J. E. Beever 110-36 ( CHR 611390 ) ; at type locality, 2 June 2008, J. E. Beever 110-88 ( AK 356397 ) ; North Auckland Land District, northern shore of Manukau Harbour , Kaitarakihi Bay , 37°1′S, 174°35′E, on bare, eroding, fully exposed coastal cliff, in seepages, 15 September 2012, P. J. & T. J. de Lange 11094 ( AK 356398 ) ; Hawke’s Bay Land District, Kiwi [Station] near Wairoa , damp papa face in light bush, 6 January 1955, G. O. K. Sainsbury D 2 ( WELT M029610 ) ; Wellington Land District, Mākiekie Scenic Reserve , ca. 70 km ESE of Āpiti township, 20 January 2009, J. E. Beever 113-50c ( CHR 637235 ) .

Description:— ( Fig. 2 ). Plants brownish-green, gregarious, on damp vertical banks. Stems simple or sparsely branched, ca. 1–2 mm in length, brown, in cross-section rounded, without differentiated central strand, sclerodermis or hyalodermis. Leaves 0.5–1.0 mm, imbricate and appressed-incurved when dry, erect-spreading when moist, lingulate, concave in mid-leaf cross-section, obtuse-rounded and more or less flat at apex, with lamina unistratose throughout; margins papillose and crenulate by bulging laminal cells, plane or very weakly recurved at mid-leaf; upper laminal cells clear in outline, irregularly rounded-subquadrate to oblate, firm-walled, (7–)7.5–13.5(–15) × (7.5–)8–11(–15) μm, unipapillose or bipapillose on both surfaces, with papillae simple, rounded, and low (projecting ca. 3–5 μm); KOH colour reaction of upper laminal cell walls yellow; upper marginal cells not differentiated; basal cells differentiated, oblong-rectangular, mostly 2–4:1, more or less thin-walled, smooth, gradually transitioning to upper lamina. Costa failing several cells below leaf apex, with both abaxial and adaxial surface cells more or less oblong (from near base to mid-leaf), becoming quadrate on the abaxial face distally, but elongate adaxially; in cross-section at mid-leaf with 2–3(–4) guide cells and a weakly differentiated abaxial group of 4–6 smaller, thick-walled cells. Axillary hairs of ca. 4 cells, basal 1–2 usually brown. Sexuality presumed dioicous. Perichaetia terminal, the inner leaves sheathing the seta base and otherwise not differentiated from adjacent vegetative leaves. Male plants smaller, with stems ca. 0.4–0.7 mm, simple or branched (apparently by innovation), with perigonia terminal or on very short innovative branches, with bracts red-brown, the largest ca. 0.3 mm, lingulate from a broadly ovate base, surrounding ca. 2 antheridia and few paraphyses. Setae slender, twisted to the left, dark red at base, lighter or yellow above, becoming darker with age, 3–6 mm; capsules erect, short - cylindric, not constricted below the mouth, yellow-brown, becoming darker with age, 0.5–0.9 mm long; exothecial cells thin-walled, irregular; stomata apparently absent; annulus absent; operculum mammillate. Peristome absent. Calyptra cucullate. Spores spherical, smooth, (7.5–)10.5–14.0(–19.5) μm in diameter.

Etymology:— the epithet “novae-zelandiae ” refers to the New Zealand provenance of the species. A tag name “ Didymodon Ihu Pott ” has previously been used in herb. for this taxon.

Ecology:— At the type locality ( Fig. 1 ) Didymodon novae-zelandiae was found on a vertical sea-cliff formed of consolidated volcanic ash (tephra) from the eruption of nearby Maungataketake (Ellet’s Mountain) some 29,000 years ago ( Hayward & Hayward 1995). Present-day vegetation consists of a very thin strip of pōhutukawa at the top of the cliff, with associated coastal shrubs, including kawakawa ( Piper excelsum G. Forster (1786: 5)) and karamū ( Coprosma macrocarpa Cheeseman (1888: 147)) . A detailed account of the vascular vegetation of the site is provided by Cameron (1997).

Didymodon novae-zelandiae was found in bare areas on the tephra cliff face, with scattered Lobelia anceps Carl von Linnaeus filius (1782: 395), and wīwī ( Ficinia nodosa (C.F. Rottbøll 1772: 24) A.M.Muasya, D.A.Simpson & P.Goetghebeur (2000: 133)) . In slightly damper sites adjacent, the moss Bryum clavatum ( Schimper 1836: 148) Müll. Hal. (1848: 292) formed dense swards. Didymodon novae-zelandiae has not been positively identified during recent site visits (April 2012 and Feb. 2015), although minute non-fruiting Didymodon plants (not confidently identifiable to species level) were present among shoots of B. clavatum . Observations indicated that the much larger and denser B. clavatum may be extending its coverage and competing with the smaller moss. However, the cliff surface is exfoliating in patches, creating new moss-free areas, which could be suitable for colonisation by D. novae-zelandiae if spores were available. Potentially more disruptive to the site of the moss at Ihumatao are the changes wrought by wholesale collapse of sections of the cliff as mature pōhutukawa fall, and the establishment of the invasive grass kikuyu ( Cenchrus clandestinus (C.F.Hochstetter ex E. Chiovenda 1903: 41) Morrone in Chemisquy et al. 2010:127) on the colluvium. A search for the species along the Manukau Harbour northern foreshore located another colony, on eroding rock, ca. 14 km W of the type locality (P.J. & T.J. de Lange 11094, AK 356398). Here the substrate was fine silty material, in part derived from andesitic breccia and in part sedimentary (P.J. de Lange pers. comm. Sep. 2012).

A further specimen of D. novae-zelandiae has been located in the herbarium of G.O.K. Sainsbury (WELT M029610), collected by him near Wairoa (ca. 330 km SE of the type locality). A more recent collection (CHR 637235) was made from a damp cut roadside bank at the Mākiekie Scenic Reserve, ca. 100 km further south. Both of these specimens were from damp banks composed of the soft, blue-grey mudstone known regionally as ‘papa rock’.

Mosses found growing with D. novae-zelandiae include three other pottiaceous mosses: D. tophaceus , D. weymouthii and Tridontium tasmanicum Hook.f. in Hook. (1840: 248).

Conservation status:— Although known from only four sites ( Fig. 3 ), the moss is on a variety of substrates, in habitats that are not rare in the North Island of New Zealand. However, Didymodon novae-zelandiae is very small, even when fruiting, and therefore easily overlooked. A classification of ‘Data deficient and endemic’, according to the scheme of Townsend et al. (2008), is therefore recommended.

Figures

FIGURE 1. Type locality of Didymodon novae-zelandiae on Manukau Harbour foreshore. D. novae-zelandiae (position arrowed) on the cliff face, below a denser band of vegetation (mainly Bryum clavatum), some 1.5 m above high tide mark. The remains of trunks of trees buried by eruption of nearby Maungataketake can be seen in the cliff base both to the right and left of the standing figure. The large pōhutukawa tree (Metrosideros excelsa) to the right, above, has now fallen from the cliff. Photo R.E. Beever, 17 Feb. 2008.

FIGURE 2. Didymodon novae-zelandiae.A, habit with capsules. B–I, leaf cross-sections. J–K, stem leaves. L, leaf apex. M, mid laminal cells, at margin. N, lower laminal cells, margin to costa. O–P, stem cross-sections. Q–R, axillary hairs. Drawn from paratype material J.E. Beever 110-36, CHR 611390, by R. D. Seppelt.

FIGURE 3. Distribution map of Didymodon novae-zelandiae. The two northernmost sites are covered by a single symbol. Figure prepared by C. Pan.