Waiahulu schiedea (Schiedea waiahuluensis), a new species discovered by drone from rocky cliffs of Kaua’i, Hawaii

NEWS - Waiahulu schiedea (Schiedea waiahuluensis) is the only known species in the Waiahulu Valley cliffs in the Waimea Canyon of Kaua’i, Hawaiian Islands, and is placed in the broader sect. Leucocalyx. The new species brings the genus to 36 species endemic to Hawaii.

In a survey by a National Tropical Botanical Garden drone team in December 2021, the team observed the enigmatic Schiedea on a steep rocky cliff face in the Waiahulu Valley. A subsequent survey in March 2022 using a remote-controlled cutting tool suspended from a drone, the first specimen was collected of this cliff dweller that has never been described before.

The species has enlarged, whitish sepals that are similar to those of the cliff dweller S. attenuata, but differ significantly from all other species in the genus. The specimen also shares similarities with S. attenuata, namely woody, hermaphroditic flowers, colored nectaries and 5-7 or 8 stalks.

The specific epithet refers to Waiahulu in Waimea Canyon, the only location where the specimen was found. S. waiahuluensis is endemic to the Hawaiian Islands, restricted to the western side of Kaua’i with exposed cliffs, 1000-1500 mm/year rainfall, above Waiahulu Stream growing in a small tributary of the larger Waimea Canyon in Pu'u Ka Pele Forest Reserve.

The researchers determined the distribution of S. waiahuluensis to be approximately 5 km along basal cliffs above Waiahulu Stream with an estimated population of 345 individuals at elevations of 530-950 meters. Mostly on vertical rocks in small crevices with soil pockets, on rock shelves or under overhanging cliffs.

Although the native vegetation in Waimea Canyon has been severely damaged by goats (Capra hircus L.) since their introduction in the late 1790s, many endemic species remain in the more inaccessible parts of the reserve, especially the vertical dry cliffs. Native shrubs and trees grow alongside new species including Nototrichium sandwicense (A.Gray) Hillebr.

Then Peucedanum sandwicense Hillebr., Artemisia australis Less., Bidens sandvicensis Less. ssp. confusa Nagata & Ganders, Wollastonia fauriei H.Lév., Wilkesia gymnoxiphium A.Gray, Lobelia niihauensis H.St.John, Euphorbia celastroides Boiss. var. hanapepensis Sherff, Argemone glauca (Nutt. ex Prain) Pope, Dodonaea viscosa Jacq. and Neraudia melastomifolia Gaudich.

Two native grasses in this habitat include Eragrostis variabilis (Gaudich.) Steud. and Panicum lineale H.St.John, along with the ferns Doryopteris decora Brack. and Isodendrion pyrifolium A.Gray. A federally endangered small shrub previously undocumented from Kaua’i was also found growing alongside S. waiahuluensis with S. apokremnos H.St.John and S. spergulina A.Gray.

In addition to direct negative effects on native plant species, goats in this area facilitate the spread of invasive non-native plant species, most notably Pluchea carolinensis (Jacq.) G.Don, Hyptis pectinata (L.) Poit., Festuca bromoides L., Pentapogon micranthus (Cav.) P.M.Peterson, Romasch. & Soreng, Grevillea robusta A.Cunn. ex R.Br. and Lantana camara L.

S. waiahuluensis is assessed as endangered using IUCN criteria. Its limited geographic range, single location and declining habitat quality have led to its classification as Critically Endangered (CR). Establishment and replication of ex situ collections are ongoing, and additional collections from underrepresented subpopulations will provide a better understanding of the genetic diversity of this species.

Original research

Wagner WL, Weller SG, Sakai AK, Nyberg B, Wood KR (2024). Schiedea waiahuluensis (Caryophyllaceae), an enigmatic new species from Kaua’i, Hawaiian Islands and the first species discovered by a drone collection system. PhytoKeys 247: 111-121, DOI:10.3897/phytokeys.247.130241

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