 |
| Trichophorum scabriculme (Beetle) J. R. Starr, Lév.-Bourret & B. A. Ford
in Starr, Léveillé-Bourret, Tài, et al., 2019.
DOI: 10.7717/peerj.7538
|
Abstract
For those familiar with boreal bogs and wet tundra, species of Eriophorum (“the cotton grasses”) will undoubtedly represent some of the most striking and memorable taxa they have encountered. This small genus of 20 Holarctic sedge species (Cyperaceae) is remarkable because its inflorescences produce large, brilliantly white to rusty-red cottony masses when its flowers develop a perianth of highly elongated bristles after anthesis. In this study, we document the rediscovery of Eriophorum scabriculme, a narrow Vietnamese endemic known from only two collections made approximately 7 km apart near Sa Pa in Lào Cai Province over 75 years ago. Using plastid DNA sequences (matK, ndhF), embryology, and morphology, we test whether E. scabriculme is aligned within the Scirpo-Caricoid Clade (genus Khaosokia and tribes Cariceae, Dulichieae, Scirpeae, and Sumatroscirpeae) or the Ficinia Clade (Cypereae), and we determine whether its unique character combinations (≥10 elongated bristles, reduced sheathing basal leaves, 1–4 spikelets) could be evidence for a new genus or simply mark it as an unusual species within currently recognised genera. In addition, we document the discovery of seven new populations, and we extend its range westward to Lai Châu Province and southward in Lào Cai Province by more than 47 km. Our results demonstrate that Eriophorum scabriculme is best treated in the genus Trichophorum, thus re-circumscribing both genera and their limits with Scirpus s.str. In addition, we emend the description of Trichophorum scabriculme (Beetle) J.R.Starr, Lév.-Bourret & B.A. Ford, provide the first pictures and accurate illustration of the species, and assess its conservation status in Vietnam (VU, Vulnerable). Our study corroborates the fact that in such a diverse and taxonomically difficult family like the sedges, conspicuous characters like highly elongated bristles may be useful for dividing diversity, but they are no guarantee that the groups they mark are natural.
Keywords: Vietnam, Trichophorum, Eriophorum, Conservation, Embryology, Phylogeny, Scirpus, Morphology, Cyperaceae, cpDNA
 |
| Figure 3: Illustration of Trichophorum scabriculme. (A) Habit. (B) Inflorescence with three spikelets. (C) Bract with antrorsely scabrous awn. (D) Glume (proximal) with awn, abaxial and lateral views. (E) Flower with developing bristles (note single stamen). (F) Bristles, showing minute distally antrorse barbs. (G) Stamen, adaxial and abaxial views. (H) Gynoecium (note style branches with abundant large papillae as long as wide). (I) Nutlet (mature) with full length bristles. (J) Nutlet (mature), close up with abbreviated bristles. Nutlet (mature), in cross-section and with abaxial and lateral views.
Drawn from Ford 1227A & al. (WIN). Illustration by Bobbi Angell.
|
Trichophorum scabriculme (Beetle) J. R. Starr, Lév.-Bourret & B. A. Ford comb. nov.
Type: Indo-chine (Vietnam), Tonkin, Chapa. Parois siliceuses du ravin à la Cascade, vers 1,200 m. Février 1931, A. Pételot 6128 (holotype, GH!); isotypes P!, VNM (Photo!).
Basionym: Scirpus scabriculmis Beetle, American Journal of Botany 33: 665–666 (1946).
Eriophorum scabriculme (Beetle) Raymond (1957: 147).
Recognition: The type was originally identified as Scirpus subcapitatus Thwaites & Hook. (=Trichophorum subcapitatum (Thwaites & Hook.) D.A. Simpson), but it differs markedly from this species and all other southern Chinese and Vietnamese Trichophorum by culms scabrous on one edge from their base to apex versus culms smooth or scabrous apically only; by bracts with long scabrous awns (4–10 mm long) versus bracts lacking awns or shorter (0–5 mm long), and by fruits subtended by long bristles exsert from glumes versus bristles only slightly exceeding glume length or entirely lacking, amongst other characters. Like all Trichophorum species, it cannot be confused with Eriophorum or Scirpus because all its leaves are basal, and with highly reduced blades (except in T. planifolium), whereas species of Eriophorum and Scirpus have both well-developed basal and cauline leaves, with few exceptions.
Trichophorum scabriculme has also been provisionally determined as a Carex (D.K. Harder et al. 6826), a Fimbristylis (A. Pételot 5498, Fimbristylis cf. pauciflora; Fimbristylis sp. for all specimens in Hoàng Liên National Park Herbarium) and an Eleocharis (N.T. Hiep, P.H. Hoang & L. Averyanov 2846). This is understandable as it can superficially resemble single-spiked Carex species, and Fimbristylis and Eleocharis species with inflorescences composed of single spikelets. Carex can be distinguished from T. scabriculme by unisexual flowers and the presence of a perigynium; Eleocharis by distinct, thickened and persistent style-bases (tubercles) and eligulate leaves, and Fimbristylis by the absence of bristles and a deciduous style. It could also be possible to confuse T. scabriculme with Isolepis species that have just one or a few spikelets, but like Fimbristylis species, they lack bristles.
 |
| Figure 5: Habitat of Trichophorum scabriculme. (A) The largest population observed in Vietnam on the right bank of the suô´i Vàng (Gold Stream). The arrows indicate plants on cliff face. The picture is taken from the type locality for Trichophorum scabriculme (“La Cascade”) with the French power station constructed in 1925 visible in the lower left corner. (B) Plants growing in fissures on edge of waterfall. (C) Plants growing in mossy substrate.
Photo credit: Julian Starr.
|
Distribution: Việt Nam, Hoàng Liên Mountains, Lào Cai province from Sa Pa District south to Văn Bàn District and Lai Châu Province, from Tam Ðường District south to Tân Uyên District.
Habitat: Mountains (612 m to 2,878 m) in full sun on vertical rock walls and road cuts, along steep cascading streams and on the edges and foot of waterfalls where moisture is present. Plants typically grow within a moss substrate. Carex hypolytroides and Scirpus ternatanus Reinwardt ex Miquel were seen at all localities near Sa Pa where this species was collected (Ford et al. 1225, 1227, 1256).
Conservation status: Vulnerable (VU) category of IUCN (2012) based on criterion B1 (a, b). Only nine populations are known (<10) and the extent of occurrence is 252.8 km2 (<20,000 km2). Owing to intense anthropogenic activity near most populations (roads, agriculture, fish farming, tourism), there is reason to believe that subpopulations could be lost or a significant decline in the number of mature individuals could occur in the near future.
Etymology: The epithet scabriculme combines the Latin word for rough or scabrous (scabri-) with the Latin for culm (culmus) in reference to the culms of T. scabriculme that are scabrous from their base to their apex, a character that is unique in Trichophorum.
Conclusions:
Although Trichophorum scabriculme possesses a unique combination of characters within sedges, DNA data, morphology and embryology strongly support its position within the Scirpo-Caricoid Clade including its placement within the genus Trichophorum. Trichophorum now consists of 14 species, but it is likely that future studies will conclude that its limits include species of Cypringlea and Oreobolopsis as well. Eriophorum s.str. now consists of approximately 18 species, but it is likely that future studies will find that the aberrant E. transiens is best aligned with elements in the Ficinia Clade. Eriophorum is nested in Scirpus s.str. but further research is required to determine whether the limits of Scirpus are appropriately defined.
Despite discovering seven new populations and extending its range westward to Lai Châu Province and southward in Lào Cai Province by more than 47 km, the conservation status of Trichophorum scabriculme in Vietnam is Vulnerable (VU). Only 56% of populations are found in protected areas and intense anthropogenic activity continues to threaten the existence of this unique sedge species.
Julian R. Starr, Étienne Léveillé-Bourret, Vũ Anh Tài, Nguyễn Thị Kim Thanh and Bruce A. Ford. 2019. The Rediscovery of the Rare Vietnamese Endemic Eriophorum scabriculme redefines Generic Limits in the Scirpo-Caricoid Clade (Cyperaceae). PeerJ. 7:e7538. DOI: 10.7717/peerj.7538
