Schiedea haakoaensis W. L. Wagner, Weller & A. K. Sakai, 2022

Wagner, Warren L., Weller, Stephen G., Sakai, Ann K., DeMent, Tom & VanDeMark, Josh, 2022, Schiedea haakoaensis, a new facultatively autogamous species of Schiedea sect. Mononeura (Caryophyllaceae) from the Hawaiian Islands, PhytoKeys 210, pp. 135-141 : 135

Schiedea haakoaensis W. L. Wagner, Weller & A. K. Sakai sp. nov.

Fig. 1

Type.

Hawaiian Islands: Hawai`i: Hawai‘i County, North Hilo District , Laupahoehoe Section of Hilo Forest Reserve , windward Mauna Kea , Mauka of Ha'akoa and Pāhale Streams, 5020 ft (1530 m), Cult. material harvested July 2021, Tom DeMent & Josh VanDeMark s.n. (holotype: US-3742219!) .

Description.

Erect to strongly ascending subshrubs 7-10 dm tall or in wild perhaps more; stem single or sometimes with few short side branches, conspicuously quadrangular, pale green, but distal internodes often purple-tinged, glabrous except internodes of inflorescence, bracts and sepals. Leaves opposite; blades 3-18 cm long, 1.2-4.5 cm wide, narrowly or broadly elliptic, sometimes lanceolate to oblanceolate, pale green to yellowish green, sometimes younger ones purple-tinged, slightly thickened and rubbery, chartaceous when dry, with only the midvein evident, the midvein ± slightly excentric, margin entire, slightly thickened becoming weakly involute toward the apex, apex acute to acuminate; petioles 0.5-1 cm long, weakly grooved. Inflorescence terminal, 40-50 cm long, with up to 80 or more flowers, diffuse, erect, the lateral branches 11-18 cm long, ascending, each with 6-20 flowers, the tertiary and higher level internodes, usually ascending or appressed, with pedicels usually spreading at anthesis, sometimes with a few minute curved hairs along the inflorescence internodes; bracts usually yellowish green, foliaceous, and nearly as large as the leaves in the lowest portions of the central axis, those in the upper part of the inflorescence and subtending the flowers, subulate, purple and usually yellowish green near base, margins ciliate; pedicels 4-6 mm long at anthesis, elongating slightly in fruit, conspicuously asymmetrically flattened and weakly quadrangular, sometimes with a few hairs toward the base. Flowers hermaphroditic, facultatively autogamous. Sepals 3-4.1 mm long, lanceolate, purple, and sometimes greenish toward the base, concave to shallowly navicular toward the apex, oriented at ca. 30° to 60°angle to the pedicel, abaxial side smooth and rounded, glabrous, margins weakly scarious, ciliate, apex attenuate. Nectary shaft 1.5-2.1 mm long, gently recurved, apex weakly bifid. Stamens 10; filaments weakly dimorphic, the antisepalous whorl 2.5-3.1 mm long, the alternate whorl 1.5-2.6 mm long; anthers ca. 0.3 mm long, yellow, apparently dehiscing after flower opens. Styles 3, stigmas elongated and apparently receptive when flower opens, and anthers are dehiscing. Capsules 4.3-5 mm long, ovoid. Seeds 0.8-1.0 mm long, suborbicular, slightly asymmetrical, compressed, brown, the surface rugose. Chromosome number unknown.

Distribution.

Schiedea haakoaensis was known from only a single plant from Hawaiian Islands, on the northeastern side of Hawai‘i Island, in the Laupāhoehoe Section of Hilo Forest Reserve. No individuals are currently known from the wild but progeny from one of the two individuals grown from seed collected at the type locality are in cultivation at locations in Hilo and Irvine, California, with outplantings anticipated soon.

Habitat.

The only known plant of Schiedea haakoaensis was discovered in 2016 in the montane wet forests of windward Mauna Kea and died of natural causes shortly thereafter. Montane wet forests in this area are dominated by closed canopies of Metrosideros polymorpha Gudich. and Acacia koa A. Gray with a sub-canopy comprised of Cheirodendron trigynum (Gaudich.) A. Heller subsp. trigynum , Melicope sp., Myrsine lessertiana A. DC., Myrsine sandwicensis A. DC., Ilex anomola Hook. & Arn., Coprosma sp., Phytolacca sandwicensis Endl., and Vaccinium calycinum Sm. The thick and dense vegetation of the understory host Rubus hawaiiensis A. Gray, Hydrangea arguta (Gaudich.) Y. De Smet & Granados, Cibotium glaucum (Sm.) Hook. & Arn., Cibotium menziesii Hook., Cibotium chamissoi Kaulf., and a rich diversity of additional ferns including Adenophorus tamariscinus (Kaulf.) Hook. & Grev. var. tamariscinus , Asplenium polyodon G. Forst., Asplenium aethiopicum (Burm. f.) Bech., Athyrium microphyllum (Sm.) Alston, Diplazium sandwichianum (C. Presl) Diels, Dryopteris wallichiana (Spreng.) Hyl., Microlepia strigosa (Thunb.) C. Presl, Polypodium pellucidum Kaulf. var. pellucidum , Sadleria sp., and the uncommon Asplenium schizophyllum C. Chr. The forests of this area have a low number of non-native species, most of which occur in the understory and consist of non-native grasses and shrubs including Cenchrus clandestinus (Hochst. ex Chiov.) Morrone, Ehrharta stipoides Labill., Rubus argutus Link, Passiflora tarminiana Coppens & Barney and Juncus sp. The terrain and topography of the region are carved by seasonal and perennial streams with gulches varying in depth from a few meters to very large river gulches at lower elevations. The area of the previously known individual, ~5000 ft (1525 m) elevation, lies uphill from the dominant streams of Ha‘akoa and Pāhale with a mean annual rainfall of ~115 inches (292 cm; Rainfall Atlas of Hawaii).

Threats.

Habitat degradation by feral pigs continues to threaten species that grow at ground level in the understory of these forests, which remain unprotected by ungulate-proof exclusionary fences. Currently, a ~1200-acre fenced unit is being constructed in the area and once completed will encompass the area where Schiedea haakoaensis was discovered. The sole individual of S. haakoaensis was naturally protected from feral pig damage due to its location on a log elevated 3-4 ft (0.9-1.2 m) above the ground. Although ungulate damage was not the cause of death other threats to extremely rare species exist. The only individual of S. haakoaensis was probably affected by a prolonged period of drought and its particular location on the log.

Breeding system.

Facultative autogamy is indicated by the occurrence of abundant seed production of the one plant that has so far flowered at the VRPF. The plant is growing in an enclosed facility, but some pollinator access is possible. Most species in the VRPF that have floral adaptations for pollinator attraction do not produce fruits unless pollinated, suggesting that the abundant fruit production of S. haakoaensis is likely to result from self-pollination. Nearly all wet forest species of Schiedea are facultatively or obligately autogamous with self-pollination and subsequent self-fertilization facilitated by synchrony between stigma receptivity and release of pollen from anthers.

Conservation assessment.

IUCN Red List Category. When evaluated using the IUCN criteria for endangerment, Schiedea haakoaensis falls into the Extinct in the Wild (EW) category. Surveys of the surrounding area and habitat have failed to locate additional individuals although it is possible more exist in the vast and remote landscape of the windward Mauna Kea wet forests. Future surveys of the area should concentrate on the adjacent US Fish & Wildlife Maulua Tract, the Laupāhoehoe Section of Hilo Forest Reserve, and the Laupāhoehoe Natural Area Reserve. Future protection and feral ungulate exclusion in these areas will help preserve habitat for this species should it be rediscovered, and for individuals of S. haakoaensis restored to the area.

Figures

Figure 1. Schiedea haakoaensis W. L. Wagner, Weller & A. K. Sakai A habit, stem with leaves and inflorescence B habit of plant in habitat C stem internode, showing sparse hairs D stem internode with leaf bases E branch of inflorescence with developing fruit and flower F bract G flower at full anthesis H branch of inflorescence, post anthesis I capsule J seed. Drawn from photograph of cultivated individual from which holotype was taken (A), drawn from field photograph and cropped to fit plate (B), drawn from holotype (C, D, H, I, J), and from the holotype and photographs (E, F, G). Coloration added to plate figures from photographs. Illustration by Alice Tangerini.