An account of the Cunoniaceae in the Solomon archipelago and Vanuatu

Five genera of the largely southern hemisphere family Cunoniaceae occur in the Solomon archipelago (Solomon Islands plus the Autonomous Region of Bougainville, Papua New Guinea): Geissois, Pterophylla (previously Weinmannia p.p.), Spiraeanthemum, Schizomeria and Ackama (including Spiraeopsis) (total of 12 species); the first three genera are also found in Vanuatu (total of four species). None of the genera is endemic to these two archipelagos although more than half the species are and Spiraeanthemum macgillivrayi Seem. is the only species common to both island groups. Along with keys to the genera and species, accounts are given for G. denhamii Seem. (throughout Vanuatu), G. pentaphylla C.T.White (restricted to the island of Vanikoro, Solomon Islands), and P. makiniae H.C.Hopkins, J.Bradford & Pillon sp. nov., from Vangunu and Kolombangara in the Solomon Islands. Most of the remaining taxa have been revised for generic treatments or flora accounts and for these, only a synopsis is given with notes on types for some names. Provisional conservation assessments are provided, with ecological summaries. Generic diversity in the Cunoniaceae decreases eastwards across the Pacific Ocean to the Marquesas and Austral Islands. The islands in the western Pacific have surprisingly few genera in common with Australia, and, compared with New Caledonia, Fiji or the Solomon archipelago, Vanuatu has fewer taxa than might be predicted from its location and size, presumably because of its young geological age.


Introduction
Treatments of the Cunoniaceae have been published relatively recently for Fiji, Malesia and New Caledonia (Hopkins & Hoogland 2002;Hopkins et al. 2014;Smith 1985).This paper provides an account of the family in the Solomon archipelago and Vanuatu to fill the geographical gap between these other island groups.
Cunoniaceae is a largely southern hemisphere family with a total of 27 genera and c. 335 species (Pillon et al. 2021a).Common though not universal characters include opposite or whorled decussate leaves that are simple or compound, the blades generally having toothed margins; stipules present and commonly interpetiolar; flowers poly-symmetric and hypogynous, with or without petals and having as many styles (stylodia) as carpels; and small capsular fruits containing winged or hairy seeds (Bradford et al. 2004).The greatest generic diversity is in eastern Malesia (nine genera in New Guinea), the islands of the south-west Pacific (11 genera) and eastern Australia (15 genera), with marked species richness in the Andes and Madagascar.
A recent phylogenetic study by Pillon et al. (2021a) indicated that changes should be made to generic limits affecting the names of two of the genera discussed here.Weinmannia L., the largest genus in the family, was shown to be polyphyletic and so was divided into two: Weinmannia s.s. is now confined to the Americas, including the islands of the Caribbean, plus the Mascarene islands (Indian Ocean); the remaining species, from Madagascar, Malesia and the islands of the western and central Pacific Ocean, were transferred to the resurrected genus Pterophylla D.Don.This study also found that the species previously placed in Spiraeopsis Miq.(Philippines to Solomon Islands) were nested within Ackama A.Cunn.(Australia and New Zealand) and so were transferred to the latter.
The area dealt with here comprises the Autonomous Region (A.R.) of Bougainville, which is politically part of Papua New Guinea, plus the Solomon Islands, which together form the Solomon chain or archipelago (sometimes referred to below just as "Solomons"), and Vanuatu (Map 1).Five genera of Cunoniaceae occur in the region, Ackama, Geissois Labill., Pterophylla, Schizomeria D.Don and Spiraeanthemum A.Gray, with a total of 15 species, 12 in the Solomon archipelago and four in Vanuatu (Table 1).
Bougainville A. R., previously known as North Solomons or Bougainville Province of Papua New Guinea, comprises the northernmost large island in the Solomon chain (Bougainville), the small island of Buka immediately to its north and a few remote atolls.It was not included in the area covered by Flora Malesiana, which extends east only to New Britain and New Ireland in the Bismarck archipelago.The checklist by Foreman (1971) included seven names in Cunoniaceae and cited collections but is now considerably out of date.
A brief treatment of the family in the Solomon Islands (excluding Bougainville) by Whitmore (1966a) recognised eight species, including one in Pullea Schltr.and he omitted Spiraeanthemum (Hoogland 1979: 504) -apparently a simple case of mistaken identity.The checklist of Hancock & Henderson (1988) recorded 12 species but included some synonyms.Relatively recent collections of Cunoniaceae include those by Bradford in 1997 and by a consortium of institutions from the Solomon Islands, Taiwan and Japan, especially from 2013 to 2015 (Flora of Solomon Islands, online).However, the main publication from this project (Chiou et al. 2016) does not include any members of this family.

Methods and Organisation of the Paper
For all genera, material at BM, K and P was seen, including many early BSIP (British Solomon Islands Protectorate) collections at K, plus some material from CANB, G, L, LAE, and NOU.For Pterophylla and Schizomeria, the herbaria consulted were given in the revisions cited.Images in the following online databases were also reviewed: Harvard University Herbaria (A), Bishop Museum (BISH), Naturalis (L, U), Linnean Collections -Smith Herbarium (LINN-SH), Tropicos (MO), C. V. Starr Virtual Herbarium (NY), Muséum National d'Histore Naturelle (P), Flora of Solomon Islands (TNM, only includes material from their recent expeditions), Taiwan Forestry Research Institute (TAIF), and the National Museum of Nature and Science, Japan (TNS).Some additional types were seen in Jstor Global Plants (online).Databases for the national herbaria of Papua New Guinea (LAE) (Conn et al. 2004 onwards) and Vanuatu (PVNH) (Flora of Vanuatu online; and see Vanuaflora online) list some additional collections but lack images.The National Herbarium of the Solomon Islands (BSIP) does not currently have an online database.
Within genera and sections, species are treated alphabetically irrespective of island group.The format for each genus varies according to what has been published elsewhere but for most taxa, only a synopsis is given.Except for basionyms, synonyms are listed only if the type is from the present region.When information on types is repeated from previous publications, herbarium barcodes have been added.All material cited has been seen, either in the herbarium or as an image, unless indicated "n.v.".Dimensions of leaves and other vegetative characters are taken primarily from fertile shoots; leaves on sterile collections are generally more variable in size, shape and indumentum.For species with unisexual flowers, m. = male, f. = female.When indicating the Table 1.species of Cunoniaceae in the solomon archipelago and Vanuatu, plus those from the Bismarck archipelago for comparison.Authors are given only for species not discussed in the text.

Bismarck archipelago: New Britain [NB], New Ireland [NI] and Manus [M]
Ackama celebica [NB, NI] Ceratotetalum succirubrum C.T. White [NB] Opocunonia nymanii (K.Schum.)Map outlines were made using Simplemappr (Shorthouse 2010, online).Under vernacular names, the local name has been taken from specimen field notes.This name is followed by the name of the language or tribal group, if known, in parentheses, and finally the collector's name and number of the specimen from which the information came.

Notes on Typification
For the new taxa of Cunoniaceae in Papuasia published by Perry (1949) (Spiraeanthemum kajewskii L.M.Perry, Weinmannia purpurea L.M.Perry, W. ysabelensis L.M.Perry), she stated that her paper was based on material at A and indicated certain collections as types.
If only a single sheet of these collections is known at A, it is cited as the holotype.Seemann (1865Seemann ( -1873) ) published the names of four species of Cunoniaceae from Vanuatu in his Flora vitiensis and cited the collection(s) on which each name was based although he did not mention the word "type".Three of the names are followed by the phrase "Seem.mss. in Herb.Mus.Brit." (once omitting "Herb.").For Geissois denhamii and Spiraeanthemum macgillivrayi, he mentioned only a single collection and the sheet at BM is cited here as the holotype.His other names, Weinmannia denhamii Seem.and W. macgillivrayi Seem., were lectotypified elsewhere.
Further notes on types are given in some species accounts.

Notes on Conservation Assessments
Conservation assessments using the IUCN Categories and Criteria (IUCN 2019, online) are based on the entire distribution of species.GeoCAT (online; Bachman et al. 2011) was used to derive the area of occupancy (AOO) and extent of occurrence (EOO), and to suggest the Red List category for some species, but not in cases where large areas of sea would have been included in the EOO; a measurement of AOH (area of habitat) would be more appropriate in these cases (Brooks et al. 2019).For calculating the EOO of widespread taxa in Vanuatu, a land surface area of 12190 km 2 for the archipelago was taken from World Bank data (online).
Assessments are preliminary for several reasons.First, some collections are old and their localities may now be of historical interest only due to habitat destruction, even though under criterion B this is not taken into account.Second, data on the distribution of less common species may not be comprehensive because of under-collecting on some islands.Third, local knowledge about the current extent of habitat loss and the ability of species to persist in secondary and logged forests is needed to make more meaningful assessments.Some Cunoniaceae have weedy tendencies and selective logging and small-scale habitat disturbance could result in population increases, though this is unlikely to be true in all cases.
Bougainville has been less affected by deforestation than many other parts of the region, partly because of its involvement in a civil war from 1988 to 1998, but several logging operations are planned or in progress (e.g.PNGexposed Blog 2014;Papua New Guinea Mine Watch 2018).The degree to which any Cunoniaceae are affected by this activity will depend on the type, extent and elevation of the logging.Mining for copper has also caused habitat destruction.No areas of forest on Bougainville currently have legal protection (UNEP-WCMC 2019).
Slash and burn agriculture has had a marked effect on the vegetation of the Solomon Islands over several centuries (Whitmore 1969), land has also been cleared for the cultivation of cash crops such as oil palm and cocoa, and considerable areas have been logged commercially.This continues at levels well above what is considered sustainable and at current rates of felling, commercially viable areas of forest are expected to be exhausted by 2036 (Global Witness 2018; Solomon Islands Government 2014).Logging makes a major contribution to the economy and, even if large-scale mining plays an increasing role in the future (Porter & Allen 2015), logging is likely to continue.Much current activity is for the export of round logs to China and some is said to be illegal and unmonitored (REDD in Solomon Islands 2014;Global Witness 2018).The proportion of forest selectively logged varies amongst the islands (Katovai et al. 2015: fig. 4) but on some, the lowland forest has already gone and so any large tree species is likely to have suffered a significant reduction in population and genetic diversity.Although a system of marine protected areas exists in the Solomon Islands, very little of the terrestrial environment has formal protection (UNEP-WCMC 2019).
Vanuatu has had relatively low forest loss compared with other countries in the region (REDD in Vanuatu 2013).However, significant areas of forest were lost on Santo when land was cleared for crops during WW2 and then subsequently for cattle raising (Pineda 2011).Widespread logging with some extensive forest degradation occurred from 1980 to 1998, when an export ban on round logs was introduced (King 2007); the islands most affected were Santo and Tanna (Herold et al. 2007: fig. 5).Although Vanuatu has a number of forest conservation areas, they cover < 5% of the land surface (UNEP-WCMC 2019).
Trees or sometimes shrubs.Indumentum of simple hairs, often with some minute curled trichomes and minute, red, spherical, "glandular" trichomes.Stipules intrapetiolar, 1 pair per node.Leaves opposite and decussate, petiolate, palmately compound; leaflets 3, 5, 7 or 9 (or rarely an even number), margins in adult plants entire or rarely toothed (not this region), in juvenile and shade foliage margins occasionally toothed; domatia sometimes present.Inflorescences ramiflorous or sometimes axillary, many-flowered, racemose, usually a monad (a single unbranched raceme on a peduncle) or rarely a triad (3 racemes on a common peduncle).Flowers pedicellate, bisexual; calyx 4-lobed, valvate in bud, bright red; corolla absent; stamens numerous (11 -28), in a single whorl, filaments bright red, extending far beyond calyx; disc annular, often yellow; gynoecium of 2 carpels, fused at level of ovary; locules and stylodia 2; ovules numerous, arranged in 2 rows in each locule.Capsules usually cylindrical (rarely ovoid, not this region), tapering towards and dehiscent from the apex; seeds numerous small, flat, winged.About 18 species, in the Solomon Islands (Vanikoro), Vanuatu, New Caledonia and Fiji; one species in the Solomon Islands and one in Vanuatu.For generic distribution maps see Hoogland (1984: no.263, excluding Australia) and Hopkins et al. (2013: fig. 5).Karrabina Rozefelds & H.C.Hopkins accommodates two Australian species at one time included in Geissois (Hopkins et al. 2013).HABITAT AND ECOLOGY.Geissois denhamii occurs in rain forest, moss forest, in scrub or thicket, at the forest edge, in pasture and near the strand line, from 10 -1300 m.Chew (1975) noted that some plants in Vanuatu, including Geissois, occurred mainly at higher elevations in the northern islands but were more abundant at lower altitudes on the southern islands.According to Wheatley (1992 and 2014) placed Geissois denhamii in the G. pruinosa -G.racemosa clade as sister to G. ternata A.Gray from Fiji.These two are rather similar as both commonly have relatively small trifoliolate leaflets on fertile shoots.Leaves on sterile shoots of G. denhamii often have slightly larger leaflets than those on fertile shoots.The leaflets were described by Wheatley (1992) as almost silvery green below with the stipules light green and conspicuous.Guillaumin (1937) distinguished Geissois parviflora by its large leaves (leaflet blades 21 × 11 cm) and small flowers (sepals 5.3 mm long; pedicels 2 -3 mm long, articulated at or near the apex).Although the type (Aubert de la Rüe s.n.) is unusual, it is not far outside the normal range for G. denhamii and so G. parviflora is not maintained as distinct.

Key to the species of
Variation in the density of the indumentum on the stipules and the ovary is not closely correlated (Map 2); where the indumentum is denser, the hairs are often longer.In the northern islands (Banks Isl. to Efate), the stipules are sparsely hairy, whereas in the southern islands (Erromango, Tanna, Aneityum) their indumentum is dense.Densely hairy ovaries occur in Espiritu Santo, Tanna and Aneityum, and more sparsely hairy ovaries are found in the northern islands (including Santo) and as far south as Tanna, meaning that the distributions of sparsely and densely hairy ovaries overlap.However, it is not yet confirmed that plants from the Banks Islands have sparsely hairy ovaries.White (1950: 86); Whitmore (1966a: 59).Type: Solomon Islands, Santa Cruz Group, Vanikoro, nr Lamia R., 30 Nov. 1945 (fr.), F. S. Walker BSIP 217 (holotype: BRI ×2 [both BRI-AQ0354924]; isotypes: A, K ×2 [K000739699, K000739700], LAE n.v.).Geissois pentaphylla C.T.White in F.S. Walker (1948: 110), nom.invalid., description in English.
Commercial logging for Kauri (Agathis macrophylla Mast.) occurred on Vanikoro from 1926 to 1964 (Bennett 2000;Whitmore 1966b) and new logging licences have been granted (Dawen & Cannon 2017) although meeting with some local opposition.Habitat destruction threatens several bird and bat species that are endemic to the Santa Cruz Islands (Pierce 2014) and no protected areas currently exist on Vanikoro.Although Geissois pentaphylla appears to survive in degraded habitats, the combination of its small EOO (probably < 150 km 2 ), presence at fewer than five locations and threats from loss of habitat suggests a provisional conservation assessment of Endangered (EN B1ab(i,ii,iii)).LOCAL NAME.Jaco wa tandoé, fide Cabalion 3338.NOTES.Geissois pentaphylla was not included in the phylogenetic analyses of Pillon (2011;Pillon et al. 2014) but its morphology suggests its affinities are with G. denhamii in the G. pruinosa -G.racemosa clade.
The type material at K and BRI is in poor condition making it difficult to verify some of the characters in the protologue, and discrepancies exist between the descriptions of White and material collected subsequently.For these reasons, unconfirmed characters from White's accounts have been excluded from the description here.According to White (in Walker 1948), the flowers have five sepals, but like others in the genus, this species normally has four.White (1950) described the young leaves as densely pubescent but in the only specimen we have seen with young leaves, Whitmore BSIP 1762, the emerging leaves are glabrous or almost so, and when hairs are present on the petioles and petiolules in adult leaves, they are sparse.White (1950) described the stipules as 3 cm long just before falling, but in subsequent collections they are shorter; however, in several species, including Geissois denhamii, the stipules appear to elongate just prior to being shed.
In addition to a few long, white, strigose hairs, the young leaf emerging from between the stipules on Whitmore BSIP 1762 (L) has some spherical, orange, gland-like structures, especially on the abaxial surface on either side of the prominent secondary veins.Similar but smaller structures are present on the pedicels and these "glands" occur occasionally in other species of Geissois.
The only collection mentioned in the protologue of Geissois pentaphylla was Walker BSIP 217 and in his introduction, White (1950) stated that types of his new species were at Queensland Herbarium, Brisbane, with isotypes at A, K and sometimes elsewhere.The two sheets of Walker BSIP 217 at BRI each have a label stating "holotype", and either "sheet 1 of 2", or "sheet 2 of 2", written by A. Bolin on 15 Nov. 1983.This holotype designation was erroneously changed in Hopkins (2006) and is corrected here.Trees or shrubs.Indumentum of simple hairs.Stems often slightly flattened at nodes.Stipules interpetiolar, 1 pair per node, usually caducous in fertile material.Leaves opposite and decussate (rarely whorled), simple, trifoliolate or imparipinnate, usually petiolate; in compound leaves, lateral leaflets usually opposite and sessile, sometimes asymmetric at base, terminal leaflets usually decurrent at base; margins of blades toothed or crenulate (rarely ± entire); domatia absent.Inflorescences manyflowered; racemes either simple and axillary (not this region) or arranged in groups on a sterile axis (peduncle), the basal segment(s) of which is either axillary or terminal, or a combination.Flowers bisexual, unisexual or a mixture, pedicellate, hypogynous or slightly perigynous; sepals 4 -5, imbricate in bud; petals 4 -5, elliptic or ovate, membranous, white to pale pink; stamens (5) 8 or 10, reduced in female flowers; disc annular or divided into lobes; gynoecium of 2 (3) carpels, united at the level of the ovary, locules and stylodia 2 (3); ovules 8 -16 per locule, in 2 rows, placentation axile; gynoecium reduced in male flowers.Capsules dehiscing from the apex, free central column often present, valves ± coriaceous, boatshaped, calyx lobes persistent or not.Seeds numerous, ellipsoid, comose or occasionally hairy all over.About 68 species in Madagascar and the Comoros, throughout Malesia and the islands of the southern Pacific as far east as the Marquesas and Austral Islands; absent from the Americas, Africa, mainland Asia (except Peninsular Thailand, Peninsular Malaysia) and Australia; six species in the Solomon archipelago and two in Vanuatu (Table 2).
Bradford (1998) divided Weinmannia s.l.(i.e. both New and Old World species) into five sections, four of which now comprise Pterophylla (Pillon et al. 2021a).Two sections, Pterophylla and Leiospermum, occur in the present area and the structure of the inflorescence is significant in distinguishing between them (see diagrams in Bradford 1998;Hopkins & Bradford 1998).
Some changes are made here to the species accounts in Hopkins & Bradford (1998) and Hopkins et al. (1998), including to the distribution of Pterophylla croftii, and we describe P. makiniae sp.nov.for material from the Solomon Islands previously identified as W. exigua A.C.Sm.Descriptions of most taxa were also given by Bernardi (1964, as Weinmannia).All species in the region have rather similar small flowers with petals 1 -2 mm long, and all have similar small, brown or reddish-brown fruits, 2 -4 (-6) × 1.5 -2 (-3) mm (plus style remnants 1 -2 mm).The specimens cited are recent collections or represent rare species.

Key to the species of Pterophylla in the Solomon archipelago and Vanuatu
1. Flowers grouped in small fascicles on the axis of a raceme, each fascicle in the axil of a small bract; inflorescence comprising 1 or 2 (3) pairs of opposite axillary dyads or tetrads (each formed of 2 or 4 racemes on a common peduncle) at the most distal leaf-bearing node of a shoot, i.e. inflorescence units lateral; if more than 1 pair of dyads or tetrads, these inserted in series……………………………………… sect.Pterophylla: 2 1'.Flowers inserted singly on the axis of a raceme, each flower in the axil of a small bract; inflorescence commonly a triad or pentad (each formed of 3 or 5 racemes on a common peduncle), these typically in a median position, sometimes with some additional axillary racemes at the base………………… sect.Leiospermum: 5 2. Petiole and rachis segments very narrowly winged………………………………………………………………………3 2'.Petiole and rachis segments not winged………………………………………………………………………………4 CONSERVATION STATUS.Overall LC (Least Concern); in the Solomon Islands, DD (Data Deficient).Despite the high level of logging in the Solomon Islands, the wide distribution of this species and the relatively large number of collections over its entire range suggest that it may not be threatened.It demonstrates weedy tendencies in Borneo, sometimes growing abundantly in roadside cuttings (Hopkins & Bradford pers. obs. 1996) and so can probably regenerate in gaps when forest is selectively logged.NOTES.The most widespread species of Pterophylla in Malesia and the Solomon Islands, P. fraxinea was reported by Whitmore (1966a, as Weinmannia blumei Planch.) as encountered occasionally in the Solomon Islands.Taken over its range as a whole, it is polymorphic, with variation in the size, thickness and number of leaflets per leaf (Hopkins & Bradford 1998).
The field notes of Bradford 830 reported that the flowers have a pale green calyx with the petals and filaments white and the nectary yellow, and the carpels and styles are white; the flowers are slightly sweetly fragrant and visited by bees.Shrub or tree to 20 m tall.Leaves imparipinnate, rachis terete, densely hairy on upper surface, segments not winged; lateral leaflets 4 -10 (-12) pairs, narrowly ovate to lanceolate, 2.2 -4.6 × 0.6 -1.3 cm, with base asymmetric, obtuse to rounded and apex acute, blades of the proximal 1 -3 pairs distinctly shorter than the distal ones, often with small, free 'ear' at the base.Smith 1952: 137), which at the time was known only from two collections, the type (Horne 632, Fiji, Vanua Levu, between Waiwai and Lomaloma, May 1878 (fl.& yfr.), K000739828) and Rangagone in Howard 89 (Fiji, Vanua Levu [BISH, K: "Pauliasi Rayaqona H.89"]). Similarities between the Whitmore collection and those from Fiji included leaves with small leaflets and the rachis segments narrowly winged, although those in Whitmore's material are more narrowly winged that those of Horne 632.Now the species from Fiji is represented by a further collection (Barrabé et al. 1132, Taveuni [K, P]), it is clear that Whitmore's specimen does not belong to the Fijian species and collections from the Solomon Islands by Bradford and Song et al., although sterile, confirm this.The other species of Pterophylla known from Kolombangara and Vangunu, P. croftii, has fewer, considerably larger leaflets that differ in shape from those of P. makiniae (compare Figs 6 and 7) and has an inflorescence structure typical of sect.Leiospermum rather than sect.Pterophylla.Pterophylla exigua should now be considered endemic to Fiji.Pillon et al. 2021aPillon et al. : 1198)).Weinmannia ysabelensis L.M. Perry (1949: 162) Tree 25 m tall.Leaves imparipinnate, rachis semi-terete, hairy along upper mid-line, distal rachis segments minutely winged; lateral leaflets in 1 -5 pairs, ovate to oblong, 1.3 -2 × 0.7 -0.8 cm, with base somewhat asymmetric and apex broadly acute; terminal leaflet markedly larger than laterals (3 -4.4 × 1 -1.3 cm).Flowers bisexual.Illustration: Hopkins et al. (1998: fig. 6).

Pterophylla ysabelensis (L.M.Perry) Pillon & H.C.Hopkins (in
DISTRIBUTION.Solomon Islands (Santa Isabel), known only from the type.HABITAT.Occurs in montane forest at 600 m and described as common.CONSERVATION STATUS.DD (Data Deficient).Further information is needed on distribution and abundance, as well as on its relationship with Pterophylla fraxinea.Large parts of Santa Isabel have been logged (Katovai et al. 2015: fig. 4), which is likely to have reduced the habitat available.NOTES.Pterophylla ysabelensis is similar to P. fraxinea but has much smaller leaflets.Although Whitmore (1966a) included them as two separate taxa in his key, he went on to imply they might be synonymous.Until we have more material from Santa Isabel, P. ysabelensis is maintained as distinct.sect.Leiospermum (D.Don) Engl.Pillon et al. 2021aPillon et al. : 1198)).Weinmannia croftii H.C. Hopkins (in Hopkins et al. 1998: 76) Tree or shrub, 2 -20 m high (to 10 m with trunk up to 1 m dbh in Solomons).Leaves trifoliolate or imparipinnate; petiole and rachis winged; lateral leaflets 1 -3 pairs (usually 1 -2 pairs in Solomons), lanceolate to narrowly elliptic, 2 -6.7 × 0.5 -1.7 cm (commonly 2 -4 × 0.5 -1.5 cm in Solomons, proximal leaflets slightly smaller than distal ones), with base asymmetric and apex acute; terminal leaflet somewhat longer and broader than largest laterals.On sterile shoots, lateral leaflets commonly in 3 pairs and slightly larger than on fertile shoots.Flowers unisexual and plants dioecious.Figs 1A, 7.

Pterophylla croftii (H.C.Hopkins) Pillon & H.C.Hopkins (in
DISTRIBUTION.Papua New Guinea (Manus, Karkar, New Britain, New Ireland; not mainland or Bougainville) and Solomon Islands (Kolombangara, Vangunu, Guadalcanal).SPECIMENS EXAMINED.SOLOMON ISLANDS.Guadalcanal Prov.: Guadalcanal: Popomanasiu, 2130 m, 23 Oct. 1965 (fl.), Corner RSS 89 (K, L).Western Prov.: New Georgia Group: Vangunu: NW of Vura along ridge to Mt Olasana, 8°42'S 158°01 'E, 700 m, 14 Nov. 1997 (fl.), Bradford 811 (K ×2, MO); ibid., 8°42'S 158°01 'E, 810 m, 15 Nov. 1997 (fr.), Bradford 822 (K ×2, MO).Kolombangara: Mt Duke, S of Mt Tapalamenggutu and N of Vila R., 7°58'S 157°06 'E, 1220'E, m, 20 Nov. 1997 (st.) (st.) 5 Nov. 1965 (st.), Hill RSS 9011 (K, L).HABITAT AND ECOLOGY.In the Solomon Islands, Pterophylla croftii is found on extinct volcanic mountains in wet, mossy montane forest, often on ridges, at 700 -2150 m.The field notes of Bradford 811 and 822 report it as common.CONSERVATION STATUS.Overall probably LC (Least Concern) although it may be under some threat locally as it has been found on only three of the Solomon Islands, all of which have been subject to logging.It appears to be quite common on Vangunu and Kolombangara, and the threats from logging may be mitigated by its occurrence on ridges at relatively high elevation and its tolerance of disturbance.NOTES.Hopkins et al. (1998) suggested that the Corner and Hill specimens from Kolombangara and Guadalcanal might either represent a new species (Weinmannia sp.(Solomons A)) or belong to P. croftii, but of the three collections then known, only Corner RSS 89 was fertile and sterile material of Pterophylla is notoriously variable.However, the subsequent collections by Bradford cannot be distinguished from P. croftii although the leaflets are slightly smaller than typical.Hill RSS 9011 has rounder, broader leaflets (laterals 3 -3.3× 1.8 -2 cm) and may be from an immature plant.
The field notes of Bradford 811 reported that the calyx was pale green, the petals and filaments white, the anthers dull yellow and that the flowers were barely fragrant; young foliage was pink to red, as commonly seen in Pterophylla.
3.6.Pterophylla denhamii (Seem.)Pillon & H.C.Hopkins (in Pillon et al. 2021a: 1198).Weinmannia denhamii Seem.(Seemann 1866: 109) as "denhami".Type: New Hebrides [Vanuatu], Aneiteum, Feb. 1859 (fl.), (MacGillivray) 45 (lectotype of Hopkins et al. (1998) Guillaumin (1931: 250) The overall elevational range is 120 -1800 m but the lowest recorded altitude varies by island.Pterophylla (as Weinmannia, species not indicated but likely to be this one) was another of the plants that Chew (1975) reported as occurring mainly at higher elevations in the northern islands of Vanuatu and at lower altitude in the southern islands.CONSERVATION STATUS.LC (Least Concern).The EOO is less than 20000 km 2 which could indicate a status of Vulnerable.However, this species is known from numerous herbarium collections and from almost all the larger islands of Vanuatu.Wheatley (1992) reported it from various secondary and disturbed habitats, indicating that it is able to persist or regenerate after selective logging and so LC is given for the present.NOTES.The leaves of Pterophylla denhamii are quite variable in the number of pairs of leaflets and their size and shape; when the leaflets are few, they are usually lanceolate and when numerous, they are shorter and relatively broader (Fig. 8).Specimens with the fewest leaflets are from Efate, Santo and Aneityum, and those with the most from Tanna and Ambae.On Santo, leaflets are smaller and stiffer with increasing elevation (Pillon pers. obs. 2006).Hopkins et al. (1998) stated that the types at P for the names Weinmannia kajewskii and W. tannaensis were holotypes.However, as Guillaumin (1931) did not specify this and several duplicates are known, these designations are amended here to lectotypes.Hopkins (in Pillon et al. 2021a: 1198).Weinmannia purpurea L.M. Perry (1949: 159).Type: [Papua New Guinea], Bougainville Is., Kupei Gold Field, 1000 m, 17 April 1930, S. F. Kajewski 1738 (lectotype, designated here: A [A00043371, fr.]; isolectotypes:
DISTRIBUTION.Papua New Guinea (Bougainville only: type) and Solomon Islands (Guadalcanal only: SW, Duidui area, 730 m, 9 Oct. 1968 (fl. & yfr.), Mauriasi BSIP 12092 (K, L)).HABITAT.Reported from rain forest, including well drained primary forest on a ridge top, at 730 -1000 m.CONSERVATION STATUS.Collected only twice, this species has a very small AOO and although its potential EOO is much larger (c.14000 km 2 ) if it were to occur throughout Bougainville and Guadalcanal, this may be misleading as the more recent of the collections was made more than 50 years ago.Although described as common in the field notes of Kajewski 1738, the lack of herbarium material probably indicates that it is in fact rare and likely to be threatened by habitat destruction.Clearly more information is needed but a provisional status of Vulnerable is assigned (VU B1a,b(i,ii,iii)).NOTES.Hopkins et al. (1998) stated that the holotype of Weinmannia purpurea was at A but as two sheets of Kajewski 1738 are shown on the Harvard University Herbaria website (online), the name is lectotypified here.Both sheets have good leaf material and the one chosen as the lectotype, with fruits, has previously been labelled as the holotype.
Tree 5 m tall.Leaves imparipinnate, to 5 cm long; rachis hirsute especially on upper surface, segments narrowly winged; lateral leaflets in 2 -5 pairs, elliptic, 0.7 -2 × 0.4 -0.7 cm, with base acute and apex broadly acute; terminal leaflet slightly larger than largest laterals.Flowers seen in bud only.Fruits unknown.
DISTRIBUTION.Papua New Guinea (Bougainville), known from a single locality.SPECIMENS EXAMINED.PAPUA NEW GUINEA.Bougainville A. R.: Bougainville: Mt Balbi, summit, 2400 m, 8 May 1988 (buds & old fr.?), Gideon LAE 78577 (K, LAE n.v.); Mt Balbi ("Bolbi"), 2440 m, Oct. 1963 (buds), Parker 6 (CANB, LAE n.v.).HABITAT.Reported as growing in forest, on the rim of an old volcanic crater.Said to be common as a canopy tree, reaching 5 m (field notes of Gideon LAE 78577).The elevation suggests montane forest.NOTES.This undescribed material has markedly smaller leaflets than other species in sect.Leiospermum in the region.Pterophylla croftii, which has not been collected on Bougainville, also has leaves with winged rachis segments and also grows on volcanic substrates but it typically has fewer, larger leaflets although they are sometimes similar in shape (e.g.Isles et al.NGF 34406, New Britain, 2000 m [A, BISH, K, L]).Although both collections of Pterophylla sp.(Solomons B) are from high elevation and there is a correlation in several Cunoniaceae between decreasing leaf(let) size and increasing elevation, it seems unlikely that this material is conspecific with P. croftii.However, further collections are needed to determine the range of variation in leaf characters before this taxon is described.

NOTES.
Material with small leaflets from Guadalcanal is equated here with Schizomeria ilicina but the fruits (1 × 0.8 cm) are smaller than typical for New Guinea (usually 1.6 -3 × 1.3 -2.5 cm); however, we do not know if the fruits on the material currently available from the Solomon Islands are mature.The inflorescence axes in the only flowering specimen, Corner RSS 88, are more sparsely hairy than usual for this species but the flowers have the typical glabrous ovaries.Both S. ilicina and S. serrata have terminal inflorescences and glabrous leaves and in New Guinea, S. ilicina replaces S. serrata at high elevations (Hopkins 2018: table 4) and it appears that the same occurs on Guadalcanal.However, it would be interesting to know whether plants of S. ilicina from Guadalcanal are genetically close to similar material from New Guinea or whether their characters of small leaves and glabrous ovaries have evolved independently in situ.
Trees or shrubs.Indumentum of simple hairs; red dots (apparently secretory glands) on under-surface of leaves in some species.Stipules interpetiolar, the number per node equal to the number of leaves.Leaves opposite and decussate, or whorled (not this region), simple, petiolate, margins entire or crenateserrate; domatia often present.Inflorescences manyflowered, axillary thyrses.Flowers pedicellate, either unisexual and then species dioecious, or bisexual (not this area), c. 2 mm long., commonly 4, valvate in bud; petals absent; stamens 6, 8 or 10 (12), reduced in female flowers; disc lobed, the lobes often united in pairs; ovary absent in male flowers, in female and bisexual ones apocarpous, carpels 2 -5 (-6), if more than 2 then number usually equal to that of sepals, ovoid, hairy; ovules 1 -4 (-6) per carpel.Fruit of 2 -5 (-6) follicle-like fruitlets, each dehiscent with boat-shaped valves, horned at apex.Seeds 1 -4 per carpel, glabrous, spindle-shaped or ellipsoid (and then with a tail at either end) or flattened and bearing a small membranous wing.
Nineteen species, from the Moluccas, New Guinea, the Bismarck and Solomon archipelagos, Vanuatu, New Caledonia, Fiji, Samoa and north-eastern Australia (see Pillon et al. 2009: fig.2); two species in the Solomon archipelago, one of which is also found in Vanuatu.
Based on DNA sequence data and morphology, Pillon et al. (2009) recognised three monophyletic groups within Spiraeanthemum s.l. and both S. bougainvillense Hoogland and S. macgillivrayi Seem.belong to Spiraeanthemum s.s.This group occurs in the Bismarck and Solomon archipelagos, Vanuatu, Fiji and Samoa and its members are all dioecious with opposite leaves, usually with toothed margins, ovate-elliptic stipules, hairy apical buds, and usually four free carpels in the female flowers, each of which contains two ovules that develop into spindle-shaped/ellipsoid seeds (Pillon et al. 2009: table 2).
The species concepts here follow Hoogland (1979), who recognised two species in the present region.The names of others, from Fiji and Samoa, have sometimes been used on herbarium specimens as their leaves are quite similar.Keys for Fiji and Samoa were provided by Smith (1952Smith ( , 1985) ) but a comprehensive key to the species of Spiraeanthemum s.s. is lacking.

Key to the species and subspecies of Spiraeanthemum in the Solomon archipelago and Vanuatu
1. Twigs with a dense, whitish or straw-coloured, pubescent to hirsute tomentum (hairs up to 1 mm long), usually quite persistent; similar indumentum also present on the petioles and midrib of the leaf (on lower leaf surface and upper surface at least towards the base of the blade); leaf blades 8 -19 × 5 -9.5 cm; domatia in the form of pockets or pouches with a tuft of longish hairs (Bougainville only)……… … ……… ……… In the protologue, Hoogland (1979) stated that the "type" was at CANB with numerous isotypes elsewhere.Jstor Global Plants (online) shows four sheets at CANB that each bear a printed holotype label and another label stating "sheet 1 of 4", "sheet 2 of 4" etc., showing that all four sheets together constitute the holotype.Tree or shrub 3 -12 (-20) m.Young twigs glabrous or almost so.Stipules ovate, to 10 × 5 mm, adaxial surface glabrous, abaxial surface with sparse white indumentum.Leaves: petioles 1.5 -3 cm long; blades ovate or narrowly ovate, rather variable in size, base cuneate to broadly cuneate, apex acute, both surfaces glabrous, margins toothed, tips of teeth conspicuous and drying dark (glandular when young?); venation craspedodromous; domatia in angle between secondary veins and midrib, and sometimes also where secondary veins split, drying dark.Inflorescences to 16 × 10 cm but often smaller, axes glabrous to sparsely hairy.Flowers white, pale green, yellowish, yellow-green or pale pink, with white stamens, scented.Fruits brown or red-brown.Fig. 9.

Discussion
Although no genus is confined to either the Solomon archipelago or Vanuatu (Table 3), more than half the species of Cunoniaceae in these two island groups are endemic.The non-endemics are Ackama celebica, Pterophylla croftii and P. fraxinea, Schizomeria ilicina and S. serrata, and Spiraeanthemum macgillivrayi, which are also found in New Guinea, or the Bismarck archipelago, or both.The only species common to both Vanuatu and the Solomon archipelago is Spiraeanthemum macgillivrayi, which is represented by a different subspecies in each island group.Additional collections would be useful for some of the less common species and from some of the less visited islands (e.g.Choiseul, Santa Isabel, Bougainville) to aid understanding of the variation, delimitation, distribution and abundance of some taxa.
Comparison with other island groups in the western Pacific Good (1969) and Thorne (1969) found that the flora of the Solomon Islands in general had its affinities with New Guinea, no doubt due to their geographical proximity and the presence of similar habitats.However, the flora of New Guinea is more closely allied with that in the rest of Malesia, rather than with the Bismarck archipelago and the Solomon Islands (Marsh et al. (2009).Among the genera of Cunoniaceae in the Solomon Islands and Bougainville, four are shared with the Bismarck archipelago (Table 1) and New Guinea.Both Ackama and Schizomeria have their greatest number of species in New Guinea and both also occur in eastern Australia.Schizomeria reaches its eastern limit in the Solomon Islands while Ackama extends south to New Zealand.Conversely, five genera that are found in New Guinea (Hopkins & Jennings 2021) are absent from the Solomon chain (Aistopetalum Schltr., Ceratopetalum Sm., Gillbeea F.Muell., Opocunonia Schltr., Pullea).Among these, Pullea has a curious disjunct distribution being found in eastern Malesia (Moluccas, New Guinea), north-eastern Australia and Fiji, but it is absent from the Bismarck and Solomon archipelagos and Vanuatu (map in Hoogland 1984).
Geissois is the only genus present in the Solomon Islands that does not also occur in New Guinea.Its greatest species richness is in New Caledonia and its northern limit is Vanikoro, at the southern edge of the Solomon Islands, with Fiji marking the eastern extent of its range.Vanikoro is closer to Vanua Lava (c.250 km), the more northerly of the two largest Banks Islands in Vanuatu, than it is to any of the large islands of the Solomon group, the nearest of which is Makira (= San Cristobal), about 500 km distant, and this may be a factor in why Geissois does not occur further north despite its wind-dispersed seeds.
Within the Solomon archipelago, Bougainville has the same four genera that are found on the other large islands.At species level, notable absences are Pterophylla fraxinea, which is found throughout much of Malesia, including New Guinea, New Britain and New Ireland, and on several of the large islands of the Solomon group, and P. croftii, which is known from the Bismarck archipelago and a few of the Solomon Islands.Endemic to Bougainville are Spiraeanthemum bougainvillense and Pterophylla sp.(Solomons B).
With only four species, the Cunoniaceae of Vanuatu are depauperate compared with other island groups in the western Pacific.Their affinities are largely with the Solomon Islands and/or Fiji, and only to a lesser extent with Vanuatu's close neighbour New Caledonia.As mentioned above, Geissois denhamii belongs to the G. pruninosa -G.racemosa clade, which is well represented in New Caledonia (Pillon 2011;Pillon et al. 2014), but the taxa of Spiraeanthemum and Pterophylla in Vanuatu are not especially closely related to their congeners in New Caledonia (Bradford 1998;Pillon et al. 2009).Spiraeanthemum s.s., to which the species from both the Solomon archipelago and Vanuatu belong, is often associated with quite recent volcanic substrates and the lack of these in New Caledonia may be a factor in the absence of Spiraeanthemum s.s.from that island.The other two groups in the genus, whose members were previously placed in Acsmithia Hoogland, are the "densiflorum" group (Moluccas, New Guinea, north-eastern Australia, New Caledonia), and the "brongniartianum" group (New Caledonia, Fiji) (Pillon et al. 2009).Only Fiji and New Caledonia have representatives of more than one species group.
Pterophylla has the largest number of species of any of the genera in the present region.Two of its four sections occur here, sect.Leiospermum, which is largely confined to Pacific islands plus some volcanic islands off the north coast of New Guinea, and sect.Pterophylla, which is largely Malesian but extends into the Pacific as far east as Fiji (Hopkins & Bradford 1998: fig.1).The members of both sections from the Solomon chain and Vanuatu are all morphologically typical of their sections whereas at least three of the four species from New Caledonia appear to form a unique group within sect.Leiospermum (Bradford 1998).
Compared with the Cunoniaceae found in the Solomon archipelago and Vanuatu, the family forms a distinctive and abundant element in the flora in New Caledonia, where it comprises some 90 species in seven genera, with three of the genera and all the species being endemic (Hopkins et al. 2014).Four genera from New Caledonia are absent from Vanuatu (Codia J.R.Forst.& G.Forst., Cunonia L., Hooglandia McPherson & Lowry, Pancheria Brongn.& Gris) and these four plus Pterophylla are also absent from Australia.
The marked difference in generic and species richness between Vanuatu and New Caledonia is likely to be the result of differences in geological age, history and substrates.The "high" islands of Vanuatu are largely composed of Tertiary volcanics (Oligocene to Quaternary, according to island) with some limestone, especially on Santo (Mallick 1975: fig. 1), and a few volcanoes are still active (including Mt Yasur on Tanna).Most of the current land mass of Vanuatu emerged from beneath the sea only in the last 2 million years (Mallick 1975: fig.2) although small areas of land have been above sea level from the end of the Oligocene.The recent origin of Vanuatu as an archipelago no doubt accounts for, or contributes to, the small number of species of Cunoniaceae found there.In contrast, the main island of New Caledonia is a much older and more geologically complex land mass (Pillon et al. 2021b) and about half the Cunoniaceae there occur on ultramafic substrates (mostly peridotites) (Hopkins et al. 2014).
Fiji has a relatively large number of species of Cunoniaceae (13) in four genera (Geissois, Pterophylla, Pullea, Spiraeanthemum;Smith 1985), which, except for Pullea, all occur in Vanuatu and the Solomon archipelago.Further east, the generic diversity of the Cunoniaceae decreases markedly across the Pacific (Table 3).Spiraeanthemum and Pterophylla are found in Samoa (Smith 1952) and the latter is the only genus whose distribution extends east of Samoa, to Rarotonga in the Cook Islands, and to the Society, Marquesas and Austral Islands (Hopkins & Florence 1989;Lorence & Wagner 2011) but the genus is always found on "high" islands.
Limestone is not generally favoured by members of the family, which are only rarely found on calcareous soils and are absent from coralline islands in the Pacific.
It is remarkable how few genera of Cunoniaceae Australia has in common with the islands of the western Pacific considering the number present (15, of which eight are endemic) and the fact that most members of the family appear to be wind dispersed (exceptions: Aistopetalum, Davidsonia F.Muell., Hooglandia, Schizomeria).Australia shares Ackama with the Solomon archipelago, as well as eastern Malesia, New Guinea and New Zealand, Spiraeanthemum with both Vanuatu and the Solomon archipelago plus New Guinea and New Caledonia, and has two genera in common with Fiji (Pullea, Spiraeanthemum).It is not surprising that it shares numerous genera with New Guinea (Ackama, Ceratopetalum, Gillbeea, Pullea, Schizomeria, Spiraeanthemum) considering their proximity and the recent terrestrial connection between them.
listed nine taxa of Cunoniaceae although five of these names are now considered synonyms.Brief descriptions with illustrations were provided by Wheatley Map 1. Archipelagos in the southwest Pacific Ocean.

Fig. 3 .
Fig. 3.A -G Spiraeanthemum bougainvillense.A leafy shoot with inflorescence at young fruiting stage; B leaf margin (adaxial surface); C detail of venation and domatia on abaxial surface of leaf; D male flower, one tepal removed; E female flower, one tepal removed (note reduced stamens); F mature fruit; G seed in face view (l) and side view (R).H -M Geissois denhamii.H leafy shoot and ramiflorous inflorescences; J flower; K young fruit; L mature dehisced fruit; M seed.A -C, E Schodde et al. 3850; D Cole 107; F, G Schodde et al. 3768; H Wheatley 723; J Bernardi 12932; K -M Wheatley 632).drawn by andrew brown.

Map 3 .
the solomon archipelago, showing the occurrence of Geissois pentaphylla and Pterophylla makiniae .

Fig. 6 .
Fig. 6.Pterophylla makiniae.A leafy shoot and inflorescence at young fruiting stage; B apex of a shoot, showing a pair of young leaves and the outer, hairy surface of a stipule; C apex of another shoot, showing opposite petioles and recurved stipules (note adaxial surface glabrous); D part of a leaf, adaxial surface, note very narrowly winged rachis; E part of a larger leaf, abaxial surface; F flower, lateral view; G half-flower; H petal, flattened: note that not all petals are notched; J two disc segments, one on either side of the base of a filament; K young fruit.A -K Whitmore BsiP 995.drawn by andrew brown.

Fig. 7 .
Fig. 7. Pterophylla croftii.A leafy shoot with inflorescence (triad) and part of another inflorescence behind it; B small leaf, abaxial surface, note that unusually, the rachis is unwinged; C tip of leaflet, abaxial surface; D abaxial surface of leaflet showing venation, sparse indumentum and "red dots" (hair bases?);E abaxial surface of larger leaf showing typical winged rachis; F stem with opposite petioles, base of median inflorescence axis and a pair of stipules; G part of a young inflorescence, note each flower is subtended by a bract; H flower, with 2 sepals, 2 petals and 4 stamens removed; J sepal; K petal; L mature fruit just starting to dehisce; M one half of a dehisced fruit with seeds in situ; N seed.A -F, H -K Bradford 811; G Corner Rss 89; L -N Bradford 822.drawn by andrew brown.

Table 2 .
species of Pterophylla in the solomon archipelago and Vanuatu according to section and island group.
Weinmannia L. sect.FasciculataeBernardi ex Hoogland  & H.C.Hopkins (in Hopkins & Bradford 1998: 21,  as "Fasciculata").Flowers unisexual or rarely bisexual and plants polygamodioecious.Fig.5 (and Hopkins et al. 1998: fig.7).macgillivrayi is rare elsewhere.These other populations might change the conservation status, perhaps to VU (Vulnerable), but more information is needed on its abundance on these other islands.NOTES.Pterophylla macgillivrayi is less widely distributed in Vanuatu than the more common P. denhamii.It appears closely related to P. fraxinea but is distinguished by its more numerous and smaller leaflets and by the "ears" that are frequent on the leaf rachis at the point of insertion of the lateral leaflets; in both species, the upper surface of the leaf rachis is often densely hairy.
The EOO is less than 20000 km 2 , which could indicate a status of Vulnerable but because of its wide distribution within Vanuatu, its ecological range and the number of collections, LC (Least Concern) appears to be more appropriate.Kajewski 2533 (BM, L, P); S coast (Duidui), Kolotsiri Ridge, 1040 m, 17 June 1968 (fr.), Sirute'e & collectors BSIP 10173 (K).Isabel Prov.: Santa Isabel: nr Maringe Lagoon, Mt Sasari, 800 m, 26 Oct. 1963 (fr.), Whitmore BSIP 2430 (K).This taxon has a relatively wide distribution, occurring on five islands, but nevertheless its EOO is estimated to be less than 5000 km 2 .It is not clear whether it could be under-collected because the flowers are relatively inconspicuous; if so, its EOO may in fact be greater.It occurs over a wide elevational range and at least some collections are from high elevation where the effects of logging are likely to be low.For these reasons, despite the low EOO, a conservation status of Vulnerable is assigned(VU B1a,b(i,ii,iii)).

Table 3 .
Generic distributions of Cunoniaceae worldwide.endemic genera are indicated by a spot (•) in main part of table, and by the number in parentheses in the line labelled "No. of genera".Most figures are from Pillon et al. (2021a).