Lysimachia barcae K. R. Wood & W. L. Wagner, 2025

Wood, Kenneth R., Wagner, Warren L., Fawcett, Susan & Heintzman, Scott, 2025, Lysimachia barcae (Primulaceae), a new endemic shrub from Wainiha, Kaua‘i, Hawaiian Islands, PhytoKeys 265, pp. 105-121 : 105-121

Lysimachia barcae K. R. Wood & W. L. Wagner sp. nov.

Figs 1 , 2 , 3 , 4

Diagnosis.

Lysimachia barcae is morphologically most similar to L. hillebrandii Hook. f. ex A. Gray from which it differs by its combination of mature stems villous to tomentose (vs. glabrate), petioles 1–3 mm long (vs. 4–10 mm), leaves cordate to subcordate or rounded at base, veins conspicuously raised on abaxial surface (vs. leaves cuneate to attenuate at base, veins only slightly raised on abaxial surface) and pedicels pendulous, 35–70 mm long (vs. erect, 12–45 mm).

Type.

USA. • Hawaiian Islands, Kaua‘i: Hanalei District, Wainiha , 22.093, - 159.533, 1150 m alt., 15 May 2025 (fl. & fr.), K. R. Wood, S. Heintzman & S. Deans 19754 ( holotype: PTBG 1000099430 !; isotypes: BISH!, US!) .

Description.

Shrubs, sprawling to 3.5 m long, 5 - to 15 - branched; diameter of lower stems ca. 1 cm near base, young and old stems terete, reddish-brown villous to tomentose. Leaves well-spaced, alternate, firm-chartaceous, ovate, rarely lanceolate, blade (35 –) 40–70 × (18 –) 20–45 mm, leaves abaxially and adaxially sparsely reddish-brown hirsute to pilose, often more densely so on veins, primary and secondary veins prominent on abaxial surface, purple-red, tertiary veins pellucid, margins entire, flat to weakly revolute, apex acuminate to attenuate, occasionally falcate, base cordate to subcordate or rounded, petioles 1–3 mm long, reddish-brown tomentose or pilose. Flowers solitary in leaf axils, 6 - to 7 - merous, pedicels slender, pendulous, 35–40 mm long, elongating to 60–70 mm long in fruit, with pilose hairs light tan to rusty; calyx 6 - to 7 - lobed, lobes persistent, lanceolate to broadly lanceolate, 5–6 × 2–3 mm, pilose to strigose; corolla campanulate, lobes obovate, 10–14 × 5–7 mm, purple, tinged yellowish on margins, veins dark purple, outer and inner surface glandular-punctate; filaments connate from base to 1 / 3 or 1 / 2 their length, 5–6 mm long, dark purple, anthers 1.2–1.4 mm long; stigma capitate, 1 × 1 mm, yellow-green, style 7–8 mm long, dark purple, ovary superior, glabrous, subglobose, ca. 2 × 2 mm, dark purple. Capsules subglobose, thick and woody, 6–9 mm long, dehiscent. Seeds dark brown, irregularly rhomboid, angled, 1–1.2 mm long.

Additional specimens examined

( paratypes). USA. Hawaiian Islands, Kaua‘i: Hanalei District, • Wainiha , 1158 m alt., 19 Jan 2016 (fl.), Wood, Perlman & Kishida 16724 ( BISH, PTBG) • loc. cit., 1158 m alt., 19 Jan 2016 (fr.), Wood, Perlman & Kishida 16725 ( BISH, NY, PTBG, US) .

Phenology.

Due to its extreme isolation, Lysimachia barcae has only been observed and vouchered on two occasions, January 2016 and May 2025 and, during those visits, plants were with both flower and fruit.

Etymology.

Lysimachia is named for Lysimachus (ca. 361–281 BC), King of Thrace and is derived from the Greek lysis (release from) and mache (strife) ( Wagner et al. 1990). The species epithet honours its discoverer, Nicolai Barca, Field Coordinator for The Nature Conservancy of Hawai‘i, Kaua‘i Program, in recognition of his many years of keen observations, hard work and dedication protecting the native forests of Kaua‘i.

Affinities.

Based on an analysis of the plastome phylogeny, Lysimachia barcae (represented by Wood 16724 and Wood 16725) is most closely related to a Kaua‘i collection of Lysimachia pendens K. L. Marr (100 % UFBoot support) and nested within a larger Kaua‘i clade, including L. hillebrandii , L. filifolia C. N. Forbes & Lydgate , L. iniki K. L. Marr and L. venosa (Wawra) H. St. John (Fig. 5 A – F ), with 99 % UFBoot support. However, the topologies derived from nuclear (Lichter-Marck et al., in prep) and plastid DNA showed a high degree of conflict, potentially further complicated by polyploidy, as the only two published chromosome counts for Hawaiian Lysimachia , L. glutinosa Rock and L hillebrandii (Fig. 5 A, G ) are both hexaploid ( 2 n = 72; Carr (1978); Kiehn (2005)). Other diverse Hawaiian endemic lineages have shown patterns of cytonuclear discordance ( Dunbar-Co et al. 2008; Yang et al. 2018; Knope et al. 2020; Baldwin et al. 2021), which may reflect chloroplast capture or ongoing hybridisation.

Morphologically, Lysimachia barcae is quite distinctive in comparison to all other currently described Lysimachia with its unique combination of mature stems villous to tomentose, petioles 1–3 mm long, leaves ovate, cordate to subcordate or rounded at base, with primary and secondary veins conspicuously prominent, purple-red, raised on abaxial surface, often densely hirsute to pilose and pedicels 35–70 mm long. It has some minor similarities to L. hillebrandii (Fig. 5 A ), with both being sprawling shrubs and having alternate leaves with some overlap in the length and width of leaves, yet L. barcae can be easily separated by features stated in the diagnosis. Superficially, the leaves of L. barcae have some overlap in length and width to the Moloka‘i species L. maxima (R. Knuth) H. St. John , yet differs from the latter species in having older stems villous to tomentose (vs. glabrate), leaves alternate, mostly ovate, with cordate to subcordate or rounded base (vs. leaves ternate, mostly obovate, with cuneate base) and pedicles 35–70 mm long (vs. 20–35 mm long). The unique cordate to subcordate or rounded leaf base of L. barcae has similarities to the cordate leaf base of L. iniki (Fig. 5 D, E ), yet differs from the latter species in having leaves ovate and flat or weakly revolute (vs. leaves obovate and cupped upwards), petioles 1–3 mm long (vs. sessile), stem tips non-viscid, tomentose (vs. viscid-hirsute), sprawling habit (vs. pendent), pedicels 35–70 mm long, pilose, pendulous (vs. 15–25 cm long, viscid-hirtellous, erect), calyx length 5–6 mm long (vs. 8–10 mm long) and corolla lobes purple with yellowish margin, 10–14 mm long (vs. white turning pink or purple towards base, 15–16 mm long) (see Table 1 ).

Distribution and ecology. Lysimachia barcae is narrowly endemic to the volcanic island of Kaua‘i where it has been documented around the north-central Alaka‘i plateau along a precipitously steep, moss-covered, talus-strewn ridge that descends into Wainiha Valley (Figs 6 , 7 ). This new species is known from only a single colony of ten mature individuals at ca. 1150–1190 m elevation. Rainfall in the immediate vicinity of the type locality averages between 6000 and 7000 mm a year. The forest has a closed to open canopy and is dominated by canopy trees of Metrosideros Banks ex Gaertn. ( Myrtaceae ) and Cheirodendron Nutt. ex Seem. ( Araliaceae ). The associated genera of understorey trees, shrubs, herbs and vines are floristically rich and include endemic species of Bidens L., Dubautia Gaudich. ( Asteraceae ); Clermontia Gaudich. ( Campanulaceae ); Perrottetia Kunth ( Dipentodontaceae ); Vaccinium L. ( Ericaceae ); Cyrtandra J. R. Forst. & G. Forst. ( Gesneriaceae ); Scaevola L. ( Goodeniaceae ); Hydrangea Gronov. ex L. ( Hydrangeaceae ); Geniostoma J. R. Forst. & G. Forst. ( Loganiaceae ); Myrsine L. ( Primulaceae ); Syzygium Gaertn. ( Myrtaceae ); Freycinetia Gaudich. ( Pandanaceae ); Peperomia Giseke , ( Piperaceae ); Coprosma J. R. Forst. & G. Forst. , Kadua Cham. & Schltdl. , Psychotria L. ( Rubiaceae ); Melicope J. R. Forst. & G. Forst. ( Rutaceae ); and Smilax L. ( Smilacaceae ). Genera of sedges and grasses include Carex L., Cyperus L., Machaerina Vahl ( Cyperaceae ); and Eragrostis Wolf. ( Poaceae ). Genera of ferns include Asplenium L., Hymenasplenium Hayata ( Aspleniaceae ); Deparia Hook. & Grev. , Diplazium Sw. ( Athyriaceae ); Sadleria Kaulf. ( Blechnaceae ); Cibotium Kaulf. ( Cibotiaceae ); Microlepia C. Presl ( Dennstaedtiaceae ); Dryopteris Adans. ( Dryopteridaceae ); Dicranopteris Bernh. ( Gleicheniaceae ); Hymenophyllum Sm. ( Hymenophyllaceae ); Adenophorus Gaudich. ( Polypodiaceae ); and Hoiokula S. E. Fawc. & A. R. Sm. ( Thelypteridaceae ). Wood (2007) reports high levels of floristic diversity in the greater Wainiha / Alaka‘i Region of Kaua‘i with ca. 266 native vascular plant taxa, including 92 single-island endemics.

Key to Hawaiian Lysimachia

The following key to Hawaiian Lysimachia has been modified from Wagner et al. (1990, pp. 1079–1080) to accommodate Lysimachia barcae , along with Lysimachia iniki , L. pendens and L. scopulensis K. L. Marr, which were discovered and described post Wagner et al. (1990).

Note: HI = Hawaiian Islands; H = Hawai‘i (Big Island); K = Kaua‘i; L = Lāna‘i; M = Maui; Mo = Moloka‘i; Ni = Ni‘ihau; O = O‘ahu.

Key to endemic Hawaiian Lysimachia on Kaua‘i

Preliminary conservation assessment. IUCN Red List Category

Lysimachia barcae falls into the Critically Endangered ( CR) category according to the IUCN criteria (B 1 ab (iii) + 2 ab (iii) + D) which reflects an EOO 1 km 2 and AOO of 1 km 2, a continuing decline in the quality of habitat and a population size estimated to number fewer than 50 mature individuals. It is well known that invasive plant and animal species threaten nearly all native flora throughout the Hawaiian Islands and Lysimachia barcae is no exception. The continued decline in quality of surrounding habitat where L. barcae occurs is evidenced by degradation from invasive non-native mammals such as pigs ( Sus scrofa L.), rats ( Rattus spp. ) and black-tailed deer ( Odocoileus hemionus columbianus Richardson ), in addition to the dense infestations of non-native plant species such as Erigeron karvinskianus DC. ( Asteraceae ) and Hedychium gardnerianum Sheph. ex Ker Gawl. ( Zingiberaceae ) which outcompete and suppress native bryophytes, seedlings and sporophytes through aggressive colonisation and shading. Additionally, Hedychium gardnerianum has established extensive rhizomatous networks that form dense, monotypic stands, to the extent that native habitats are unable to establish or persist. Lysimachia barcae is also highly susceptible to stochastic events such as landslides, which could result in significant habitat loss or population extirpation.

The lack of biotic regional data has become a serious barrier to sound management of the Earth’s remaining natural ecosystems and we hope that this formal description will stimulate future conservation and exploratory efforts to locate more colonies of Lysimachia barcae . There is still a large expanse of suitable, unexplored habitat around Wainiha’s rugged and highly variable physical geography (Fig. 7 ) and we predict that additional colonies of L. barcae will likely be found.

Seeds and cuttings of Lysimachia barcae have been collected by the Plant Extinction Prevention Program ( PEPP) and the National Tropical Botanical Garden ( NTBG) Science staff and plants are currently being cultivated by the Hawaii State Division of Forestry and Wildlife ( DOFAW) nursery, Kaua‘i, Hawai‘i.

We now estimate that over 130 Hawaiian vascular plant taxa have become extinct to date ( Wood et al. 2019) and the urgency to stem the extinction crisis becomes clearer when we realise that a significant number of endemic Kaua‘i taxa are limited to very small numbers, within a single valley or mountain range, with barely enough individuals to maintain viable populations for their long term survivorship. This, along with the understanding that each species is a masterpiece of evolution, extending back millions of years, profoundly demonstrates the urgency to support active conservation efforts and advance horticultural science for their cultivation.

Figures

Figure 1. Lysimachia barcae. A. Lower portion of habit; B. Upper portion of habit with flowers and immature capsules; C. Abaxial view of leaf blade with petiole; D. Node with pendulous flower and adaxial view of leaf; E. Flower bud; F. Flower showing petals with sepals removed; G. Flower with several petals removed showing stamens and pistil. Drawn from: A. Wood et al. 19754, holotype (PTBG); B. Field photo, 15 May 2025, Wainiha, Wood et al. 19754; C. Field photo, 19 January 2016, Wainiha, Wood et al. 16725; D. Field photo, 15 May 2025, Wainiha, Wood 19754; E. Field photo, 19 January 2016, Wainiha, Wood et al. 16725; F, G. Nursery photos by Tim Kroessig from plants grown from seed of paratype Wood, Perlman & Kishida 16725 (Illustration by Alice Tangerini).

Figure 2. Lysimachia barcae. A. Flower with several petals and sepals removed showing pistil and stamens with glands on staminal ring and filaments; B. Flower with petals intact and sepals removed showing pigmentation of petals. A, B. From plants grown from seed of paratype Wood, Perlman & Kishida 16725 (BISH, NY, PTBG, US). Photos by Tim Kroessig.

Figure 3. Lysimachia barcae. A. Branch, showing pendent immature capsules; B. Leaf, abaxial surface; C. Leaf, adaxial surface; D. Flower, early anthesis; E. Irregularly rhomboid seed. A – D. From Wood et al. 19754, holotype (PTBG) E. From Wood et al. 16725.

Figure 4. Lysimachia barcae. A. Sprawling growth habit; B. Floral buds showing indument on calyx lobes and pedicel; C. Young leaves showing prominent purple-red primary and secondary veins; D. Sprawling habit showing pendent pedicels and immature fruit. A, D. Field photos, 15 May 2025, Wainiha, Wood et al. 19754, holotype (PTBG); B. Field photo, 19 January 2016, Wainiha, Wood et al. 16725; C. Photo by Tim Kroessig from plant grown from seed of paratype Wood, Perlman & Kishida 16725 (BISH, NY, PTBG, US).

Figure 5. A. Lysimachia hillebrandii, erect with flower; B. L. pendens, pendent habit on wet cliff; C. L. filifolia, erect habit on stream bank; D. L. iniki, showing leaves cupped acroscopically; E. L. iniki, flowers fallen on moss with white corolla turning pink or purple towards base; F. L. venosa, with sessile leaves, purple corolla, and long calyx lobes; G. L. glutinosa, erect habit with cream corolla; H. L. daphnoides in bog habitat, erect habit and purple corolla; I. L. scopulensis, with purple calyx lobes and immature capsule. A. Field photo, 10 Jun 2010, Pi‘ina‘au, E Maui; B. Field photo, 14 Feb 2022, Blue Hole, Wailua, Kaua‘i; C. Field photo, 12 Jan 2008, Waikoko, Kaua‘i, Wood 12774 (PTBG); D. Field photo, 9 Apr 2024, Blue Hole, Wailua, Kaua‘i, Wood et al. 19481 (PTBG); E. Field photo, 21 Feb 2017, Blue Hole, Wailua, Kaua‘i, Wood et al. 17263 (PTBG); F. Field photo, 11 Jan 2012, Kawaikini, Kaua‘i, Wood 14845 (PTBG); G. Field photo, 30 Mar 2016, Kalalau, Kaua‘i; H. Field photo, 7 Nov 2024, Alaka‘i, Kaua‘i, Wood et al. 19649 (PTBG); I. Field photo, 4 Feb 2016, Kalalau, Kaua‘i, Wood et al. 16734 (PTBG).

Figure 6. Distribution map with red dot indicating single known location of Lysimachia barcae, Wainiha Valley, Kaua‘i, Hawai‘i.

Figure 7. Montane wet forest habitat of Lysimachia barcae, showing steep slopes and ridges around the valley rim of Wainiha, Kaua‘i. Field photos: A. View NW from Wainiha rim with vertical cliffs of Pali‘ele‘ele in far distance, 30 July 2014; B. View NE from Wainiha rim with crescent bay of Hanalei in far distance, 30 July 2014; C. View ENE from Wainiha rim with Mahinakēhau Ridge in centre and Nāmolokama Plateau in far right distance, 19 Jan 2016.