Selliguea kachinensis Hovenkamp, S. Linds., Fraser-Jenk., 2016

Khine, Phyo Kay, Lindsay, Stuart, Fraser-Jenkins, Christopher, Kluge, Juergen, Kyaw, Myint & Hovenkamp, Peter, 2016, Selliguea kachinensis (Polypodiaceae), a new fern species of uncertain affinity from Northern Myanmar, PhytoKeys 62, pp. 73-81 : 74-78

Selliguea kachinensis Hovenkamp, S. Linds., Fraser-Jenk. sp. nov.

Type.

Myanmar, Kachin State, Hponyin Razi, Quercus-Magnolia- Araliaceae forest, epiphyte. 27.601421°N, 96.988873°E, 1715 m, G. Miehe, P.K. Khine [ “Kine”], L. Shein, M. Kyaw, P. Ma, S. Lan Wan 13-094-159, 19 Nov. 2013 (holotype: L; isotype: SING).

Epiphytic.

Rhizome long-creeping, branched, 3.2-4.5 mm diam. when dry (c. 6 mm diam. after soaking in boiling water), black and shiny when dry with a glaucous waxy layer, the younger parts densely covered with scales, irregularly rooting from the ventral side, in cross-section with scattered sclerification in the peripheral, epidermal and subepidermal region; phyllopodia c. 2 cm distant, c. 1-3 mm high. Scales deciduous, mostly absent from older parts of the rhizome, basifixed and slightly to strongly auriculate, or pseudopeltate, or sometimes fully peltate, c. 0.5 × 2.0-3.5(-4.0) mm, gradually narrowed from the base to a long narrow acumen, brown or blackish near the attachment, central region brown and thick, the margin and acumen thinner and lighter, margin irregularly dentate, more strongly so towards the base. Fronds pendent, simple, monomorphic, stipitate, all parts densely hairy with multicellular, uniseriate, soft hairs to 1.5(-1.7) mm long, the longest hairs inserted on midrib and veins; sparse, long narrow pale strongly toothed scales present among the hairs on the abaxial midrib (particularly towards the base of the lamina), stipe 0.8-5.0 cm long, c. 1 mm thick; lamina 18-58 × 3.3-7.2 cm, oblong - narrowly elliptic, the basal 1-6 cm often narrowed, base truncate to cordate, apex acuminate, texture thin-herbaceous, glaucous when fresh, translucent when dry, margin very narrowly hyaline, without notches. Venation anastomosing, primary veins straight or slightly curved, at 60-90 degrees to the midrib, secondary veins hardly distinct, delimiting c. 5-6 rows of rectangular areoles with anastomosing tertiary veins and free veins in all directions, ending in hydathodes. Sori in a single row between each pair of primary veins, usually one per areole, but sometimes absent from the first one or two areolae closest to the midrib and occasionally two in areolae closest to the margin, c. 2 mm in diameter when ripe. Sporangia long-stalked, capsules c. 0.2 mm long, bearing 2-6 uniseriate, c. 0.4-0.8 mm long hairs, annulus with 14-16 indurated cells. Spores 29-46 × 25-34 µm in lateral view, perispore with a 0.1-0.3 µm thick, finely colliculate basal layer, rather densely set with narrow, fragile spines, spines c. 2 µm long by 0.5 µm thick at the base, somewhat narrowed to a blunt apex, apparently easily breaking off at the base leaving a low round scar.

Additional specimens seen.

Myanmar, Kachin State. Hponyin Razi: G. Miehe, P.K. Khine [ “Kine”], L. Shein, M. Kyaw, P. Ma, S. Lan Wan 13-096-034, 23 Nov. 2013, above 1300 m, road site (L); G. Miehe, P.K. Khine [ “Kine”], L. Shein, M. Kyaw, P. Ma, S. Lan Wan 13-131-013, 11 Nov. 2013, 1600 m, road site (SING).

Hponkan Razi: P.K. Khine [ “Kine”], J. Kluge, A.S. Lanwan, D.R. Lanwan, P. Lanwan 14-031-020, 14 Oct. 2014, 27.548702 N, 97.032742 E, 1565 m, evergreen broadleaved (L). Above Ziadam: P.K. Khine [ “Kine”], J. Kluge, A.S. Lanwan, D.R. Lanwan, P. Lanwan 14-047-022, 21 Oct. 2014, 27.585061°N, 97.104085°E, 1448 m, evergreen broadleaved (L, SING). Pisa District: Wang Jun & Zhou Lian Xuan 5431, 18 Apr. 2009, Pangjia (26°31.589'N, 98°18.473'E, 717 m) to Wuru (26°31.589'N, 98°18.473'E), in forest on a tree (CDBI). Ridan: Xia Nianhe, Deng Yunfei, Zhou Wei & Wu Linfang 1519, 20 Mar. 2009, around the Waqkure village, c. 2 miles from Ridan, E. side of Namai Kha river, 27°11.876'N, 98°15.165'E, 1400 m., in forest (CDBI).

Etymology.

The name derives from Kachin State, where the species is found.

Ecology.

Based on the specimens collected in the "northern forest complex", Selliguea kachinensis grows on heavily moss-covered trees in primary evergreen broadleaved forest (dominated by Fagaceae , Lauraceae , Araliaceae , and Magnoliaceae ) between 1300 m and 1715 m. It was found occasionally on trunks at 4 m from the ground (Figure 3 ), more frequently in the moss cover of trunks and thicker branches above 8 m and in the tree crowns, but is absent in the outer canopy. It is locally abundant together with Drynaria propinqua (Wall. ex Mett.) J.Sm. (Figure 4 ). It was not found growing on steep rock cliffs or open banks along trails. During our visits in November 2013, and October 2014 we did not observe any wilting of the fronds (in contrast to Oleandra neriiformis Cav. and Oleandra wallichii C.Presl which are lithophytes/epiphytes with a somewhat similar habit) and so could not assess whether it is deciduous or evergreen, but the herbaceous texture suggests that it is deciduous.

Climate.

The climate station nearest to the collection sites is Putao (450 m a.s.l) in an intramontane basin 50 km to the southeast. It records approximately 4000 mm rainfall between May and October with a pronounced dry season from November to January. We expect that the annual rainfall at altitudes between 1400 and 1800 m a.s.l. exceeds 5000 mm plus an unknown amount of fog precipitation from clouds shrouding the mountains between April and November.

Distribution, conservation and threats.

Selliguea kachinensis is currently known from five locations, all in the north of Kachin State, Myanmar. On the basis of these occurrences, the Extent of Occurrence is 4738 km2, while the known Area of Occupancy is 20 km2. However, as exploration of the area has been very fragmentary, we have little information on the actual occurrence of this species, which could well be more widely distributed along the rim of the Mali Kha / Irawaddy River basin. To date, forests where Selliguea kachinensis is found are among the least disturbed submontane evergreen broadleaved forests of the Southeastern Himalaya. Drastically increased population could extend swidden farming and might lead to a reduction of the population, but we have no information on any concrete and current threats to the habitat of the species. Accordingly, we propose a status of Data Deficient ( IUCN 2014).

Discussion: generic placement.

Selliguea kachinensis does not fit easily into the genus Selliguea , which contains mostly species with a more coriaceous texture and a distinctly cartilaginous, often notched, margin (although a thin-herbaceous texture is notably present in Selliguea pui Hovenkamp). An alternative position would be in the related genus Arthromeris . This would agree with the rather distinctive, glabrescent rhizome, which is similar to that of Arthromeris lehmanii (Mett.) Ching or Arthromeris tomentosa W.M.Chu, and with a number of other characters (Table 1 ) but it would seriously weaken the diagnostic value of that genus, as all species so far placed in Arthromeris have imparipinnate fronds with articulate pinnae ( Lu and Hovenkamp 2013; Tagawa and Iwatsuki 1989). There are several distinctive characters in Selliguea kachinensis that argue against placement in either of these genera, and for the erection of a new genus. The often somewhat lyrate base of the lamina of Selliguea kachinensis is distinctive and not encountered in any other species of either Selliguea or Arthromeris . The rhizome of Selliguea kachinensis is also distinct in that the cross-section shows sclerification only in the peripheral, subepidermal region (Figure 5a ). Sclerification occurs frequently in Selliguea , rarely in Arthromeris , but in both cases takes the form of sclerified strands in the central part of the rhizome, or a continuous, sclerified band well below the epidermis. The rhizome scales (Figure 5b ) do not show any distinctive characters. A dense indument of long hairs similar to the indument of Selliguea kachinensis (Figure 5c, d ) occurs in some species of Arthromeris , but in Selliguea , Selliguea trisecta (Baker) Fraser-Jenk. and Selliguea erythrocarpa (Mett. ex Kuhn) Hovenkamp, S. Linds., Fraser-Jenk. comb. nov. (basionym: Polypodium erythrocarpum Mett. ex Kuhn, Linnaea 36: 135. 1869) are also hairy, while Selliguea chrysotricha (C.Chr.) Fraser-Jenk. also has hairs (albeit short and stiff ones) on the capsules of the sporangia. The spore ornamentation (Figure 5e, f ) is matched in Selliguea by e.g. Selliguea quasidivaricata (Hayata) H.Ohashi & K.Ohashi and Selliguea yakushimensis (Makino) Fraser-Jenk. and in Arthromeris by e.g. Arthromeris tenuicauda (Hook.) Ching and Arthromeris lehmannii (Mett.) Ching ( Tryon and Lugardon 1991). Thus, there are arguments both for and against placement in Selliguea or in Arthromeris and there are arguments in favour of erecting a new genus. We have decided not to do the latter, as the generic taxonomy of the Selligueoid ferns is at the moment unsettled, has been burdened already by the erection of numerous small genera ( Hovenkamp 1998), and it is beginning to become clear that the best option to avoid paraphyletic groups may be to accept a large genus Selliguea ( He et al. in prep.). As alternative to a monotypic genus, we prefer a placement in the genus Selliguea over one in Arthromeris in anticipation of a generic reorganization along these lines.

Figures

Figure 3. Habitat of Selliguea kachinensis: a thick bryophyte covered trunk in Hponyin Razi at about 1,700 m (photograph by P. K. Khine).

Figure 4. Habitat of Selliguea kachinensis: a thick branch covered with other Polypodiaceae such as Drynaria propinqua, and Orchidaceae in Hponkan Razi at 1,600 m (photograph by P. K. Khine).

Figure 5. Selliguea kachinensis. A cross section of rhizome B rhizome scales C lamina margin D sporangium E spore F detail of spore, scale bar. All from the holotype, Miehe et al. 13 - 094 - 159 (L). Scale bar: 10 µm (A-E); 1 µm (F).