Ptisana ambulans Murdock & C.W. Chen, 2020
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publication ID |
https://dx.doi.org/10.3897/phytokeys.170.59471 |
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persistent identifier |
https://treatment.plazi.org/id/75559201-8109-5B24-B4E9-07B90D57F0AB |
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treatment provided by |
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scientific name |
Ptisana ambulans Murdock & C.W. Chen |
| status |
sp. nov. |
Ptisana ambulans Murdock & C.W. Chen sp. nov. Figures 3 View Figure 3 , 6A, F View Figure 6
Type.
Solomon Islands. Vahole, New Georgia Island, Western Province, Solomon Islands. Under forest. 250-350 m. 28 Sep 2012. C.-W. Chen & T.-C. Hsu SITW00629. Holotype: BSIP. Isotypes: TAIF [421080], TNM.
Diagnosis.
Differs from Ptisana decipiens in having costae without prominent wings, nearly marginal synangia; ultimate segments ovate (versus elliptic to oblong), veins tightly spaced (ca. 0.8 mm, compared to 1.3 mm in P. decipiens ), lamina thick, margins entire, serrated only at apex, revolute when dry, apex abruptly acuminate, uniseriate hairs subtending synangia.
Description.
Fronds 3-pinnate, up to 2.5 m long. Stipe circular in cross-section (stipe coloration and indument not observed). Fronds bearing 3 pairs of similarly sized pinnae on mature fronds, the terminal pair forking dichotomously at the frond apex, each pinna up to 1 m long. Swollen pulvini present at the base of all segments, green, smooth. Ultimate segments 6.5-8 cm long × 1.3-1.5 cm wide, oblong with abruptly acuminate apices (Fig, 6F); pinnule costulae slightly zigzagging and wingless (Fig. 3A, B View Figure 3 ). Laminae dark green above, pale whitish-green below, thick and coriaceous, with occasional brown-orange scales abaxially along veins and midribs (Fig. 3C, D View Figure 3 ). Veins free, ca. 0.8 mm apart, rarely dividing once near the midrib (Fig. 6A View Figure 6 ). Leaf margin entire, serrate only at apex, slightly revolute when dried. Synangia green when immature, brown after opening, one per vein, nearly marginal, set back from leaf margin by ca. 1 mm, ca. 1.5 mm long × 0.8 mm wide, 10-14 locules per synangium (Fig. 3C View Figure 3 ), receptacles bearing short, uniseriate hairs.
Etymology.
The epithet Ptisana ambulans (walking) refers to the wingless costae.
Selected specimens examined.
Only known with certainty from one collection from New Georgia (see type above).
Habitat and distribution.
Low elevation forest. Altitude range: 250-350 m. Only known with certainty from one population. Solomon Islands (New Georgia).
Preliminary conservation assessment.
There is currently only one collection and observation of this species, but this is likely due to its similarity to the more widespread P. decipiens , and consequent under-collection. It is currently considered Data Deficient (DD) based on IUCN (2012).
Note.
In the field, this species was thought to be an atypical form of P. decipiens , but further examination found that both morphology and sequence data are clearly distinct, and no intermediates have been found. The presence of uniseriate hairs on the receptacle in P. ambulans is a character that is common in Ptisana but notably absent in P. decipiens . The rigid, thickened laminae with tightly spaced veins are reminiscent of P. rigida (Alderw.) Murdock, a highland species from West Papua. Together with the fact that the DNA sequences from this taxon contain unique autapomorphies, we consider this taxon sufficiently distinctive to recognize as a species. However, due to the available characters apparent on the one collection, the description here is limited and further observation is needed to supplement our understanding of this species. Examination of other collections from the Solomon Islands and Papua New Guinea have so far found no other collections of this wingless species, but we anticipate that the range likely extends beyond New Georgia.
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