The rediscovery of the rare Vietnamese endemic Eriophorum scabriculme redefines generic limits in the Scirpo-Caricoid Clade (Cyperaceae).

Julian R Starr,Étienne Léveillé-Bourret,Bruce A Ford,Vũ Anh Tài,Nguyê˜N Thị Kim Thanh

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.

Highlights

For those familiar with boreal bogs and wet tundra, species of Eriophorum L. (‘‘the cotton grasses’’) will undoubtedly represent some of the most striking and memorable taxa they have encountered
Both analyses placed Trichophorum alpinum, the T. subcapitatum agg. and T. scabriculme in the same clade with good support, but whereas maximum likelihood (ML) analyses had T. alpinum as sister to T. scabriculme (ML-BS 55%), this node was lacking in the strict consensus of parsimony analyses
Recent studies have consistently demonstrated that morphologically confusing Scirpus or Eriophorum species were typically separate generic lineages related to either species in the distantly related Ficinia Clade of Cypereae (Muasya et al, 2012; Yano et al, 2012; García-Madrid et al, 2015), or closely allied to Scirpus and Eriophorum within the SCC, a cosmopolitan group comprising eight major lineages (Dulichieae, Khaosokia, Calliscirpus, Sumatroscirpeae, Cariceae, Trichophorum Clade, Zameioscirpus Clade, and Scirpus+Eriophorum Clade; Dhooge, Goetghebeur & Muasya, 2003; Gilmour, Starr & Naczi, 2013; Léveillé-Bourret et al, 2015; Léveillé-Bourret, Starr & Ford, 2018; Semmouri et al, 2019)

Summary

Introduction

For those familiar with boreal bogs and wet tundra, species of Eriophorum L. (‘‘the cotton grasses’’) will undoubtedly represent some of the most striking and memorable taxa they have encountered. (‘‘the cotton grasses’’) will undoubtedly represent some of the most striking and memorable taxa they have encountered This small group of 20 Holarctic sedge species (Cyperaceae Juss.) is remarkable because its compound to unispicate infructescences form large, silky white to rusty-red cottony masses due to perianth bristles that elongate after anthesis. These bristles remain attached to the fruits and are probably involved in wind dispersal Conspicuous characters may be useful for dividing sedge diversity, but there is no guarantee that the groups they mark are natural (Starr, Harris & Simpson, 2004; Larridon et al, 2013; Starr, Janzen & Ford, 2015)

Methods

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Discussion

Conclusion