Radula strangulata Hook.f. et Taylor London Journal of Botany 5: 377. 1846.
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https://dx.doi.org/10.3897/phytokeys.27.5523 |
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https://treatment.plazi.org/id/17CE3281-526D-5DA1-8672-EA796E7A86EB |
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Radula strangulata Hook.f. et Taylor London Journal of Botany 5: 377. 1846. |
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Radula strangulata Hook.f. et Taylor London Journal of Botany 5: 377. 1846. View in CoL Figs 28 View Figure 28 -32 View Figure 32
Radula strangulata Type: New Zealand: J.D. Hooker, 1840, ex herb Taylor (holotype: FH00258850! isotypes: ex herb. Lehmann S-B43503! S-B43504! S-B43505!).
Radula levieri Steph. Species Hepaticarum. 4: 227. 1910.
Radula strangulata Type: New Zealand: damp forest, Westland, Kelly’s Range, Perry Ridge, 1903, leg. T.W.N. Beckett 298 ex Hb. Levier No. 4612 in Hb. Steph. (lectotype (designated by Castle 1967, p. 74): G00067466!)
Radula silvosa E.A.Hodgs. et K.W.Allison in Hodgson, Transactions and Proceedings of the Royal Society of New Zealand 74: 286. 1944.
Radula strangulata Type: New Zealand: Te Tiki Station, Wairoa ca. 1500 ft, No.24766 P.R.B. Herb. (holotype: MPN!)
Radula parviretis E.A.Hodgs. Transactions of the Royal Society of New Zealand. Botany 3: 87. 1965.
Radula strangulata Type: New Zealand: Rakiura [Stewart Island]: landing for Tin Range, Port Pegasus, 10 Jan 1949, W. Martin, herb. Hodgson 9746. (holotype: MPN!)
Description.
[From CHR579214] Forming interwoven mats of shoots, glaucous yellow-green to brown-green in life, brown in herbarium; shoot systems regularly pinnately branched in male plants and sterile female plants, but pseudodichotomous in fertile female plants due to production of pairs of subfloral innovations below gynoecia, monomorphic, 1.0-2.0 mm wide and up to 40 mm long, branches initially smaller in stature than parent shoot and attaining similar stature by third to fifth pair of leaves; older shoot sectors retaining leaf-lobes. Stems 115-175 µm diameter, with cortical cells in a single tier of 16-25 rows, cell walls yellow-brown to brown pigmented, external free cortical cell wall heavily and continuously thickened, radial longitudinal walls thin, inner tangential walls thin or continuously thickened; medulla cells in 18-35 rows, cell walls yellow-brown pigmented, sometimes deepening to brown pigmented on old shoot sectors, cell walls with small triangular trigones, walls between trigones lacking thickenings. Cortical cells on dorsal stem surface arranged in straight longitudinal rows on young and mature shoot sectors. Leaf insertion not reaching dorsal stem mid-line, leaving four or five dorsal cortical cell rows leaf-free; leaf insertion not attaining the ventral stem mid-line, leaving two or three ventral cortical cell rows leaf-free. Leaf lobes elliptic-ovate, 550-1050 µm long by 400-830 μm wide, remote to contiguous, not falcate, acroscopic base not sharply deflexed away from stem, flat, lying in plane with stem, not interlocking over the dorsal stem surface, stem visible between leaf lobes in dorsal view; margins irregularly but minutely repand, minutely crenulate, the interior lobe margin not or at most shallowly ampliate, hardly covering the dorsal stem surface and not reaching the opposite stem margin, antical margin curved, exterior margin curved through nearly 100°, postical margin straight; angle between postical lobe margin and keel c. 135°. Lobules quadrate when small to oblong, one twelfth to one sixth the lobe area, 270-490 µm long by 140-270 μm wide; keel straight to shallowly arched, angle between keel and stem 135-150°, keel turning through 90° at keel-lobe junction, keel apex and postical lobe margin flush; interior lobule margin free for one fifth to one quarter its length, free portion not ampliate in small stature lobules to moderately ampliate on large lobules, extending at most half way across the ventral stem surface; acroscopic margin S-shaped, apical portion perpendicular to stem; apex obtuse to apiculate; free exterior margin straight, margins plane, crenulated; lobe-lobule junction well postical to the acroscopic end of stem insertion; attached to stem along 0.75 to 0.8 of the interior margin, stem insertion more or less straight, not curved at acroscopic or basiscopic ends, not revolute; lobule apex bearing a single papilla, with another two papilla situated on the interior lobule margin above the stem insertion. Leaf lobe cells rounded-oblong, not arranged in rows, unequally sized, 10-25 µm long by 9-19 μm wide, thin walled with small triangular trigones, medial wall thickenings absent; cells of lobe margin smaller than those of leaf middle, quadrate to rectangular, 9-15 µm long and wide, interior and exterior cell walls not differential thickened, cell lumen bulging medially; leaf lobe cell surface unornamented, smooth. Oil-bodies two or three per cell, ellipsoidal, filling cell lumen, light-brown, surface granular, internally homogeneous or with a hyaline droplet. Asexual reproduction usually absent, however two specimens have been observed producing bud-like shoot primordia from leaf lobe margins. Dioicous. Androecia on indeterminate branches that continue vegetative or reproductive growth, androecial bracts in 4-∞ pairs, lobules epistatic, keel deeply curved, bucket-like, free apical portion triangular, apex obtuse, moderately deflexed, lobes rounded, not caducous, antheridia not seen. Gynoecia terminal on leading shoots, subtended by two full subfloral innovations that are usually full-sized and again fertile; archegonia 130-155 µm tall, archegonia neck five or six cell columns, 6-8 per gynoecium on a small disc of tissue, not encompassed by the protoperianth; female bracts in one pair, slightly asymmetrical, tightly imbricate, elliptic-ovate, weakly falcate, lobe 840-1015 μm long by 460-545 μm wide, margins entire; lobules rhomboid to trullate, one quarter to one half the lobe area, apex acute to acuminate, keel straight to arched, margins entire; bract insertion lines interlocking dorsally and ventrally, insertion equitant. Perianths 3200-3800 µm long and 840-980 µm at mouth, mouth entire to irregularly lobed, perianth shape variable, either broadening from mouth to widest point at approximately one third to one half length above base, where 850-950 µm wide, then tapering to base, or tapering from mouth to base; perianth walls unistratose above, with bistratose collar 3 or 4 cell tiers high above the perianth-calyptra junction; long stem perigynium present, 5-6 stratose, cell walls not thickened or pigmented, perianth-calyptra fusion elevated above female bracts on 9-15 tiers of cells; calyptral perigynium present, base of calyptra bistratose, unistratose above, unfertilised archegonia elevated on surface of calyptra.
Etymology.
Strangulating, in reference to the entwining growth about a shoot of Weymouthia cochlearifolia exhibited by the type specimen.
Distribution and ecology.
Radula strangulata is widely distributed throughout the New Zealand Botanical Region, from the Kermadec Islands in the north, throughout the North, South, and Stewart Islands, south to the Auckland and Campbell Islands, and east to the Chatham Islands. Radula strangulata occupies an elevational range from sea level to c. 800 mencompassing lowland to montane habitats, including coastal scrub, mature and regenerating lowland podocarp-broadleaf forest and beech forest on both sides of the main axial ranges in North and South Islands. Radula strangulata also has a broad ecological amplitude, occupying a range of microsites from tree trunks and bases, exposed tree roots on the forest floor, to rotting logs, exposed clay on forest banks, dripping rocks adjacent to waterfalls, and on rocks within stream beds, sometimes under running water. In hyperhumid locations Radula strangulata may grow epiphyllously on fern fronds. This is the only Radula species in New Zealand commonly encountered growing aquatically, typically submerged on basaltic boulders within cool, clear, fast flowing streams. It is also the only Radula species encountered in suburban areas where it is opportunistic in a range of man-made habitats in suitably moist sites, for instance the surfaces of rotting wooden roof tiles.
Radula strangulata is the most commonly collected species of Radula in New Zealand, and despite this accessibility bias, is probably the most common species of Radula in New Zealand.
When growing on naked bark Radula strangulata forms tightly adherent mats, and usually grows admixed with Radula allisonii . Radula strangulata also grows in epiphytic turfs with Radula plicata , Radula demissa , Archilejeunea olivacea , various Cheilolejeunea species, Plagiochila spp. In terrestrial habitats and on rotting logs, Radula strangulata occurs with a wide variety of bryophytes, including the mosses Pendulothecium punctatum , Echinodium umbrosum , Catharomnion ciliatum , Fissidens tenellus var. australiensis, and the liverworts Heteroscyphus spp., Chiloscyphus spp., Saccogynidium and many other species. On rocks and tree roots on the forest floor with Pendulothecium oblongifolium , Pendulothecium punctatum , Acromastigum colensoanum , Chiloscyphus muricatus , Radula marginata .
Variation.
Radula strangulata exhibits a broad amplitude of morphological variation, as might be expected from the diverse array of habitats occupied by this species. This, in conjunction with the relatively deep phylogenetic divergences between groups of individuals suggests Radula strangulata , as circumscribed here, could well be a complex of weakly morphologically differentiated sister species. Variation in gametophyte morphology appears at least partly correlated with moisture regime of the occupied microsite. Plants growing in dry habitats and microsites have contiguous to imbricate leaf lobes, small rhomboid lobules, and are glaucous green. The origin of this glaucous colouration is not known, however it is not due to cell surface ornamentation. The type material of Radula silvosa is typical of plants growing in dry sites. Plants growing at the wet end of the moisture spectrum have remote leaf lobes, large rectangular lobules with a well developed ampliate interior margin when large, and are dark green. The type material of Radula levieri is typical of plants from wet sites.
Part of the justification presented by Hodgson (1944) for the recognition of Radula silvosa was that the perianths abruptly inflated above a tubular base, as opposed to gradually narrowed from mouth to base in Radula levieri (a species she accepted). The former feature is apparent in juvenile perianths, but is lost as the stem perigynium subtending the perianthium grows and matures prior to eruption of the sporophyte from the calyptra. All perianths we have seen wherein the sporophyte has ruptured are gradually tapered from apex to base. In addition to developmental changes in perianth shape, perianth length at maturity varies, and this variation is positively correlated with capsule valve length (R 2=0.368, F (1, 22)=12.81, P =0.0017) ( Fig. 33 View Figure 33 ).
Recognition.
Despite the variability exhibited by Radula strangulata this species is relatively easy to recognize. Radula strangulata inhabits forest interiors, frequently in microsites on or close to the forest floor, and often in relative shade. The other species of the Radula buccinifera complex with which Radula strangulata could be confused on morphological grounds occupy quite different microsites. Radula australiana inhabits subalpine and alpine habitats typically dominated by shrubland, tussockland or grassland, and almost always above tree-line. Like Radula strangulata , Radula demissa is a forest inhabitant, but is typically an epiphyte on tree trunks, branches, twigs and occasionally leaves, in reasonable light. When fresh, plants of Radula strangulata growing in relatively dry microsites have a distinct glaucous bloom. This is a distinctive character that, in combination with microsite can facilitate identification in the field. However, not all plants are glaucous, and microsite differences from other members of the complex are not absolute.
The most accessible morphological character by which Radula strangulata differs from Radula demissa is the orientation of the leaf lobes. In Radula strangulata the leaves lay in plane and alongside the stem, such that the dorsal stem surface is at least partially visible from above. In Radula demissa the leaves are obliquely-patent, and spread upward away from the stem and overlap one another across the dorsal stem surface, such that the dorsal stem surface is not usually visible from above.
If this character proves ambiguous, lobule shape is a source of diagnostic differences. Radula strangulata has lobules with a straight keel, and the carinal region is a weakly inflated mound set back from the keel. In contrast, Radula demissa typically has a curved keel, and the carinal region is strongly inflated along the length of the keel. Radula strangulata expresses a range of lobule morphologies within a single population, from small rhomboidal lobules to large rectangular lobules. In rhomboidal lobules the apex lies close to the stem, and the exterior margin is noticeably inclined toward the stem and the exterior margin is straight. In Radula demissa , lobule morphology is more conservative, with the smallest lobules being approximately quadrate such that the apex is closer to the keel apex, and the exterior margin is not noticeably inclined toward the stem. The exterior margin of Radula demissa is curved. Another useful difference is found in the junction of the lobule and the lobe. In Radula strangulata this junction forms a simple angle of c. 135°, and the postical lobe margin then continues perpendicular to the stem in a straight line. In Radula demissa this junction forms a notch, and the postical margin is weakly to strongly falcate, and curved. Diagnostic differences between Radula strangulata and Radula demissa can also be derived by counting the number of rows of dorsal cortical cells that are not crossed by the leaf insertion lines. In Radula strangulata 2-5 rows are leaf-free, whereas no rows are leaf free in Radula demissa .
Radula strangulata has been confused with two other Radula , Radula australiana and Radula buccinifera . As noted above Radula australiana is primarily an alpine species. Lobule shape provides the best morphological differences between Radula strangulata and Radula australiana . Whereas the lobules in Radula strangulata are rhomboid to longitudinally rectangular, in Radula australiana they are more or less quadrate. Lobules in Radula australiana are typically larger in comparison to the lobe size than in Radula strangulata , and may be up to one quarter the lobe area. The lobule keel and its junction with the leaf lobe also differentiate these two species. In Radula strangulata the keel is straight, and forms an angle of c. 135° at the junction with the lobe, the postical lobe margin then continues perpendicular to the stem in a straight line. In Radula australiana the keel is curved, and continues evenly into the rounded outline of the leaf without forming a notch or angle at the junction. Diagnostic differences between Radula strangulata and Radula australiana can again be derived by counting the number of rows of dorsal cortical cells that are not crossed by the leaf insertion lines. In Radula strangulata 2-5 rows are leaf-free, whereas no rows are leaf free in Radula australiana .
As far as is known, Radula buccinifera does not occur in New Zealand. However, it is always worth checking unusual plants against either of these species, particularly as the vagrant occurrence of Radula buccinifera in New Zealand cannot be ruled out. The reverse is also true, and some aquatic forms of Radula buccinifera are difficult to differentiate from Radula strangulata , and both species occur in Tasmania and south-east Australia. For guidance on separating Radula strangulata and Radula buccinifera , see the recognition section of Radula buccinifera .
Remarks. The variation in morphology exhibited by Radula strangulata seems to have encouraged the description of several species that we retain in synonymy. The type of Radula strangulata consists of small male plants on Weymouthia cochlearifolia , the lobules on this individualrepresent only a part of the range of variation expressed by the species. The other end of lobule shape variation, having heavily ampliate lobule base extending over the ventral stem surface, is found in the type specimen of Radula levieri . This specimen also has remote leaves and in these two characteristics corresponds to morphotypes associated with microsites that are permanently saturated. The type of Radula silvosa possesses lobules of the same shape range as exhibited by the type of Radula strangulata , however the plants are larger and female. Hodgson’s (1944) application of names is explained by her stated belief that the type of Radula strangulata was the male plant of Radula levieri . The type of Radula parviretis exhibits variable leaf size on single shoots, reddish pigments, variable leaf cell size, and grows on peat. Variation in cell size within leaves is not atypical of Radula strangulata . The collections made on peat may reflect occupancy of a rarely explored habitat. Radula parviretis is known from only two specimens, both from Port Pegasus on Rakiura (Stewart) Island. Reddish pigments are not known in other specimens of this species, and have not been observed in the field.
The plants illustrated for Radula buccinifera and Radula silvosa in Allison and Child (1975) are actually both Radula strangulata . The material illustrated for Radula buccinifera corresponds to a hygromorphic phenotype whereas the material illustrated for Radula silvosa corresponds with plants occupying drier microsites. Both drawings illustrate clearly how the dorsal stem surface is visible between the leaves, however as described above the perianth differences illustrated for these two species are misleading.
Hodgson (1944) identified a monoicous specimen of Radula silvosa collected by N. Kemble Walsch. This specimen (CHR587344) contains a packet labeled 'perianth showing monoecious [sic]' containing three shoots two of which are male and one of which is female. If the female shoot was ever attached to either of the male shoots, it was not so attached at the time of this investigation. Although the apex of one of the male shoots is missing, the sequence of leaves suggests that the female shoot does not comprise that apex, as the male shoot ends with an entire right leaf, and the female shoot begins with a fragment of the same. Furthermore, the remainder of the specimen consists of shoots that are either male, or female, or sterile. There is no definite evidence that this specimen is not a mixture of a male and a female individuals, a common occurrence for this, and other dioicous Radula species.
The specimen of Radula strangulata collected by J.D. Hooker in 1840 held in herb. Taylor (FH) can be regarded as the holotype, as it is cited in the protologue, is the only collection in herb. Taylor, and there are no additional collections in herb. Hooker derived from the Erebus & Terror voyage in either FH or BM. Duplicates of this specimen in S can be considered isotypes.
Specimens examined.
New Zealand: Kermadec Islands: Raoul Island, Ravine 8, Hebe Site, 29°14'0"S, 177°56'0"W, 147 m, 9 May 2009, P.J. de Lange K373 & D.C. Havell, AK313880; North Island: Te Paki Ecological Region and District, Te Paki, Tomokanga, Tomokanga Stream, 34°25'S, 172°57'E, 60 m, 22 Oct 2009, P.J. de Lange 8503, AK309079;Te Paki Ecological Region and District, Te Paki, Radar Bush, 34°28'03"S, 172°51'15"E, 160 m, 19 Sep 2011, P.J. de Lange NC14 & M.A.M. Renner, NSW970841; North Auckland, Waitakere Ranges, Cascade track, mid reaches of Cascade Stream, 36°53'37"S, 174°31'08"E, 124 m, 24 Feb 2012, M.A.M. Renner 6265, NSW896405; Hauraki Gulf, Rakitu (Arid) Island, Reserve Valley, 36°7'S, 175°30'E, 100 m, 4 Jan 1981, E.K. Cameron 3, AK312200; Coromandel Ecological Region, Colville Ecological District, Te Moehau, Moehau camp, track from Hope Stream, 36°33'S, 175°24'E, 580 m, 24 Nov 1971, J.E. Braggins, AK282576;Tainui Ecological Region, Raglan Ecological District, Te Akamu Waimai-Waikorea Road, 37°38'S, 174°49'E, 20 m, 17 Feb 2009, P.J. de Lange 7813, AK304757; Colenso 2161, ex herb. Hooker, NY01178967, as Radula buccinata Taylor; New Zealand, Stephenson, NY0118968 p.p.; New Zealand, Hutton & Kirk, NY01178969; New Zealand, J.D. Hooker, NY01178970; Auckland Ecological Region, Waitakere Ecological District, Waitakere Range, Spraggs Bush, 36°55'S, 174°32'E, 360 m, 4 Jan 2002, M.A.M. Renner 02/11, AK280392; Tongariro Ecological Region and District, Whakapapa River at Dropshaft, 39°8'S, 175°28'E, 700 m, 23 May 1989, J.E. Braggins 89/008B, AK255891;North Island, Hawkes Bay, Morere Hotel, Morere, on treefern trunk in dense bush, 21 Aug 1964, R.E. Hatcher 3, F;Otari Reserve, Wellington, April 1932, Miss N. Kemble Welch No. 3, CHR587344; Otari Reserve, Wadestown, Wellington, 13 Apr 1969, B.G. Hamlin 1055, WELT-H000470; South Island: Marlborough, Pelorus River catchment, head of Elvy Stream, 41°18'52"S, 173°34'24"E, 270 m, 12 Feb 2012, M.A.M. Renner 6082, NSW895357; Nelson, The Grove Scenic Reserve, Golden Bay, Pohara, 40°50'53"S, 172°52'13"E, 55 m, 19 Feb 2012, M.A.M. Renner 6259, NSW896393; Westland Land District, Croesus Track, Barrytown, 150 m, 9 Jun 1999, D. Glenny 7841, CHR525056; Whataroa Ecological Region, Hokitika Ecological District, south of Lake Kaniere on SE side of Mt Upright and north of Styx River, on alpine fault, 42°52'S, 171°9'E, 130 m, 26 Nov 1995, J.E. Braggins 95654C, AK286375; Westland, Paparoa National Park, Fox River., 42°02'26"S, 171°23'58"E, 20 m, 18 Feb 2012, M.A.M. Renner 6222, NSW895673; Westland, Arthurs Pass, McGrath Stream, above road bridge, 42°55'44"S, 171°33'22"E, 810 m, 14 Feb 2012, M.A.M. Renner 6092, NSW895367;
Australia: New South Wales: North Coast, Dorrigo National Park, west of Coffs Harbour, 30°22'S, 152°48'E, 550 m, 14 Apr 2011, M.A.M. Renner 5265, NSW875811; Tasmania: West Coast, Waratah-Savage River Road, Arthur River catchment, unnamed stream, 41°27'52"S, 145°25'26"E, 490 m, 28 Jan 2012, M.A.M. Renner 6016 & E.A. Brown, NSW909416.
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