Ptisana papuana (Alderw.) 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 papuana (Alderw.) Murdock & C.W. Chen comb. nov. Figures 5A, C, E , 6D, I

Marattia papuana Alderw., Bull. Jard. Bot. Buitenzorg, sér. 2, 23: 17. 1916. Type: New Guinea. Constantinhafen: Hollrung 613 (holotype: BO, photo BM!; isotype: BM!).

Description.

Fronds 2-pinnate, 2.4-4.0 m long. Stipe 1.5-2.0 m long, 3-6 cm diameter at the base, circular in cross-section, slightly flattened on the dorsal side, surface brown to greenish-black, densely matted with lacerate rusty orange-red scales at the base, mixed with occasional dark, undivided scales. Fronds bearing 6-8 pairs of pinnae, well-spaced on the rachis, the terminal pair forking dichotomously at the frond apex, proximal pinnae reduced in size (Fig. 5A ). Swollen pulvini present at the base of all segments, dark, often with a dorsal ridge (Fig. 5E ). Ultimate segments 15-18 cm long × 1.7-2.5 cm wide, narrowly oblong, base rounded but asymmetric, more cuneate acroscopically, apex acuminate (Fig. 6I ). Laminae texture thick, dark green above, pale below, with occasional ragged orange scales along the veins and midrib abaxially. Veins free, ca. 1.3 mm apart, rarely dividing once near the midrib. Leaf margin strongly serrate, more pronounced at the apex, gently repand (Fig. 6D ). Synangia submedial-medial, 2.0 mm long × 0.9 mm wide, 16-24 locules per synangium (Fig. 5C ), receptacle bearing short hairs.

Selected specimens examined.

Solomon Islands. Kolombangara: Camp 3 to Mt. Veve, 1500-1790 m, 15 Oct 2013, C.-W. Chen, T.-C. Hsu & M. Fanerii SITW04892 (BSIP, TAIF [465293], TNM); Makira: Materato to Mt. Gasi, 910 m, 1 Jul 2015, C.-W. Chen, H.-C. Hung & M. Fanerii SITW06913 (BSIP, TAIF [482836], TNM); Rendova: Ughele Village, 700-1000 m, 26 Aug 2013, C.-W. Chen, T.-C. Hsu & M. Fanerii SITW03385 (BSIP, TAIF [448705], TNM); Ughele, Rendova Peak, 11 Sep 1991, D. Glenny 3234 (BSIP [21770], W [P017133]). Papua New Guinea. Madang Province: Constantinhafen, 1887, M.U. Hollrung 613 (BM); Manus Province: Manus Island, Falls of Lorengau River, Nov 1945, D.F. Grether & W.H. Wagner Jr. 4130 (UC [UC728759], US [1918547]); Milne Bay Province: Misima Island, Mt. Oia-Tau, 700 m, 27 Mar 1979, J.R. Croft 71409 (US [3341352]).

Habitat and distribution.

Montane forest, in gullies and on hillslopes. Altitude range: 810-1550 m. Uncommon. Solomon Islands (Kolombangara, Makira, Rendova); eastern Papua New Guinea, Misima and Manus Island.

Preliminary conservation assessment.

Ptisana papuana is uncommon in the Solomon Islands, but its habitat is not currently under significant threat, and additional populations exist in Papua New Guinea. It is currently considered Least Concern (LC) based on IUCN (2012).

Note.

This species has been previously identified as both Ptisana smithii (Mett. ex Kuhn) Murdock (type from Vanuatu) and Marattia andaiensis Alderw. (type from eastern Papua New Guinea). Molecular analysis confirms that this is not related to P. smithii but is instead nested in the Sambucina clade (Fig. 2 ), with Malesia/New Guinea affinities. After comparison with the type specimen and the protologue of M. andaiensis , Solomon Islands material is a better match instead for Marattia papuana Alderw., described in the same publication ( Van Alderwerelt Van Rosenbergh 1916). Marattia andaiensis is white spotted on the underside of the pinnules, has a frond that is broadest in the middle, with smaller, submarginal sori. The type collection of Marattia papuana was originally identified as Marattia smithii , a confusion echoed in the Solomon Islands.

Figures

Figure 2. Phylogeny of Ptisana based on rps 4 - trnS and trnSGG plastid sequence data. Bayesian consensus tree, with branch support values (ML bootstrap support / Bayesian posterior probability); • = 100. The four species recognized in the Solomon Islands are marked by colored bars. Key clades discussed in text marked by arrows.

Figure 5. Comparison of Ptisana papuana (left column) and Ptisana smithii (right column) A, B whole plants Ptisana smithii B showing its distinctively repand margins C, D fertile segments with mature synangia. Ptisana papuana (left) has longer synangia that reach nearly the midpoint between the margin and the midrib, and conspicuously serrate margins E, F Pulvini, closeup.

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.