Ptisana decipiens var. delicata Murdock & C.W. Chen, 2020

Murdock, Andrew G., Chen, Cheng-Wei, Huang, Yao-Moan & Glenny, David, 2020, Affinities of the fern genus Ptisana (Marattiaceae) in the Solomon Islands, with descriptions of two new species, PhytoKeys 170, pp. 1-23 : 1

Ptisana decipiens var. delicata Murdock & C.W. Chen var. nov. Figures 4D, E , 6C, H

Type.

Solomon Islands. Santa Isabel: Mt. Kobinitu, 600-1000 m, 16 Jul 2014, C.-W. Chen, T.-C. Hsu, M. Fanerii SITW05642. Holotype: BSIP. Isotypes: TAIF [473020, 473021], TNM.

Diagnosis.

Differs from P. decipiens var. decipiens in the small size of ultimate segments, and in bearing more synangia relative to the length of the segment and synangia with fewer locules. Differs from Ptisana melanesica (Kuhn) Murdock in having larger pinnules with submarginal synangia, smaller marginal teeth; differs from Ptisana kingii (Copel.) Christenh. in having stipes without prickles or other ornamentation and having glabrous receptacles.

Description.

Fronds 3-pinnate, up to 2 m long. Stipe up to 1 m long, round in cross-section, surface green to brown, darkening with age, with reddish-blackish scales, the broader scales being darker in color, lenticels raised. Fronds bearing 3-5 pairs of similarly sized pinnae on mature fronds, the terminal pair forking dichotomously at the frond apex, each pinna up to 80 cm long. Swollen pulvini present at the base of all segments, green, smooth. Ultimate segments 10-15 pairs per pinnule, alternating on the costulae, largest at apex of each pinnule, smaller at the base, ultimate segments 2.5-5 cm long × 0.5-1 cm wide, elliptic to oblong with an acuminate apex; pinnule costulae gently zigzagging and clearly winged between segments (Fig. 4D , 6H ). Laminae herbaceous-coriaceous, dark green above, pale below, with sparse brown-orange scales along the veins and midrib abaxially. Veins free, ca. 1 mm apart, rarely dividing once near the midrib. Leaf margin gently serrate, more conspicuous at apex (Fig. 6C ). Synangia green when immature, brown after opening, one per vein, submarginal, set back from leaf margin by ca 1 mm, ca. 1.2 mm long × 0.7 mm wide, 10-16 locules per synangium (Fig. 4E ), receptacles glabrous.

Selected specimens examined.

Solomon Islands. Guadalcanal: Popomanaseu, 1300-1750 m, 11 Sep 2015, H.-C, Hung, T.-C. Hsu & M. Fanerii SITW09774 (BSIP, TAIF [515246, 515247], TNM); New Georgia: Vahole, 250-100 m, 25 Sep 2012, C.-W. Chen SITW00523 (BSIP, TAIF [421034], TNM); Vangunu: Zaira Village to Mt. Vangunu camp site, 70-320 m, 5 Oct 2013, C.-W. Chen, T.-C. Hsu & M. Fanerii SITW03734 (BSIP, TAIF [451625], TNM); Rendova: Ughele village, 700-1000 m, 26 Aug 2013, C.-W. Chen, T.-C. Hsu & M. Fanerii SITW03381 (BSIP, TAIF [448701], TNM); Kolombangara: Ringgi, KFPL Nature Trail, 13 Aug 1991, D. Glenny 3177 (BSIP [22031], W [P017081]). Papua New Guinea. Bougainville: Korpei, 570 m, 1 Nov 1961, D.H. Nicolson 1531 (B, US [2415719]).

Etymology.

The epithet Ptisana delicata (delicate) refers to the less robust appearance of this variety.

Habitat and distribution.

Solomon Islands (Choiseul, Guadalcanal, Kolombangara, Santa Isabel, New Georgia, Nggatokae, Rendova); Bougainville. Lowland forest, most commonly in gullies, also on hillsides below ridges. Commonly found in association with Angiopteris microura Copel. Altitude range: 0-1550 m. Common. More common in the western islands (Western Province).

Preliminary conservation assessment.

As with the overall species, P. decipiens var. delicata , is widespread in the Solomon Islands and its habitat is not currently under significant threat. It is currently considered Least Concern (LC) based on IUCN (2012).

Figures

Figure 4. Ptisana decipiens var. decipiens: A type specimen, with characteristically large segments B stipe showing scales C adaxial surface of fertile segments, showing vein spacing, synangial distance from margin, and winged costa. Ptisana decipiens var. delicata: D type specimen, with characteristically small segments E abaxial surface of fertile segment with maturing synangia. Photos: C. - W. Chen.

Figure 6. Comparison of venation and margins (A-E) and apices of ultimate segments (F, G) of the Ptisana species in the Solomon Islands A, F P. ambulans B, G P. decipiens var. decipiens C, H P. decipiens var. delicata D, I P. papuana E, J P. smithii. Scale bars: 5 mm.