Bull. Natl. Mus. Nat. Sci., Ser. B, 46(4), pp. 145–175, November 20, 2020 Vascular Plants Collected from Eastern Provinces, the Solomon Islands Nobuyuki Tanaka1,*, Akihiro Seo2, Koji Sugimura3, Tetsuo Ohi-Toma4, †Tofu Pattson5 and Takashi Watanabe3 1 Department of Botany, National Museum of Nature and Science, 4–1–1 Amakubo, Tsukuba, Ibaraki 305–0005, Japan 2 Kochi Prefectural Makino Botanical Garden, 4200–6 Godaisan, Kochi 781–8125, Japan 3 Graduate School of Pharmaceutical Science, School of Pharmacy, Kumamoto University, 5–1 Oe, Chuo-ku, Kumamoto 862–0973, Japan 4 Nature Fieldwork Center, Okayama University of Science, 1–1 Ridai-cho, Kita-ku, Okayama-shi, Okayama 700–0005, Japan 5 The National Forestry Herbarium, Ministry of Forestry, Environment and Conservation, Honiara, Solomon Islands *E-mail: [email protected] (Received 14 August 2020; accepted 23 September 2020) Abstract The vascular plants collected by the field expeditions to the San Cristobal Islands and Malaita Islands, eastern Solomon Islands in 2011 and 2012 are enumerated as the materials towards the Flora of the Solomon Islands. The present paper records the occurrence of 20 species representing10 families of pteridophytes and 248 species representing 81 families of spermato- phytes. Among those, 10 taxa of spermatophytes namely: Ruellia blechum L., R. prostrata Poir, R. simplex C.Wright (Acanthaceae), Cyanthillium cinereum (L.) H.Rob., Canna indica L. var. warszewiczii (A.Dietr.) Nob.Tanaka (Cannaceae), Mecardonia procumbens (Mill.) Small (Plantag- inaceae), Persicaria barbata (L.) H.Hara (Polygonaceae), Discocalyx latepetiolata (Mez) Sleumer (Primulaceae), Smilax vitiensis (Seem.) A.DC. (Smilacaceae), and Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm., are newly recorded for the flora of the Solomon Islands. Keywords : inventory, Makira, Malaita, new record, Papuasia, San Cristobal. Whitmore (1966, 1969) reported the forest vege- Introduction tation features of the Solomon Islands. Hunt The Solomon Islands consisting of nearly (1969) published “Orchids of the Solomon 1,000 islands, covering a land area of 28,785 km2, Islands”, which was probably the first taxonomic extend in a southeast direction over a distance of account of the particular plant taxa in Solomon 1,450 km from Bougainville to Vanuatu and Islands. The basic reference of the total vascular 850 km from north to south (Mueller-Dombois account of this region is apparently “Flora of the and Fosberg, 1998). This archipelago has geo- Solomon Islands” by Hancock and Henderson graphical, biological and political affinities with (1988), in which 3210 vascular plant species the Papuan mainland (Kajewski, 1946). were enumerated. At the same time, Henderson The Solomon Islands is located easternmost and Hancock (1988) also published “A guide on edge of the Malesian floristic region, and appar- the useful plants of Solomon Islands”. ently one of the most under-collected countries. There is a single herbarium, Solomon Islands National Herbarium (BSIP), located in the Honi- © 2020 National Museum of Nature and Science ara Botanical Garden, the Guadalcanal Island, 146 Nobuyuki Tanaka et al. under the management of Department of For- Based on the identifications of the materials estry, Environment and Conservation, Ministry collected, the present paper recorded the occur- of Natural Resources. The fundamental materi- rence of 20 species representing10 families of als, a total of 26,000 herbarium specimens, for pteridophytes and 248 species representing 81 the flora of the Solomon Islands made by Han- families of spermatophytes from those regions. cock and Henderson, were deposited in BSIP Among those, 10 taxa were newly recorded from with duplicates in K, SING, etc. Hancock and the Solomon Islands. These data based on speci- Henderson (1988) estimated that there were at mens would be significant materials towards the least another 1,500 species in the Solomon publication of Flora of the Solomon Islands. Islands. Nevertheless, critical inventories for the flora of the Solomon Islands were not conducted Materials and Methods for almost twenty years after Hancock and Hen- derson (1988), which was a checklist rather than The floristic inventories mainly in lowland a flora book. tropical forests in San Cristobal (Makira) Island In October 2008, a joint expedition team from (Figs. 1, 2A) including Malaupaina of the Three the Royal Botanic Garden Edinburgh and the Sister Islands (Olu Malau Islands) (Figs. 1, 2B) Ministry of Forests, Honiara, Solomon Islands and Pio Island (Figs. 1, 2C), both of which are collected a large suite of specimens from most of located very close to the San Cristobal Island, the members of the Podocarpaceae known from Makira Ulawa Province, and Malaita Island, the Solomon Islands (Mill and Whiting, 2012). Malaita Province were carried out in September However, for the revision of the flora of the Sol- 2011 and February 2012 with collaboration of omon Islands, general collecting is indispens- the Ministry of Forests and Research, the Solo- able. A group of Taiwanese botanists carried out mon Islands. Collecting in the Guadalcanal the floristic inventory from 2012 to 2015, and Island was partially made. The collected speci- they published “Field Guide to the Plants of Sol- mens were morphologically examined. For 102 omon Islands” (Chiou et al., 2016). Although this specimens, following the recommendation of the guidebook gave a general overview of vascular CBOL Plant Working Group (2009), DNA bar- genera in the Solomon Islands, many taxa were coding was partially used to help in identifying still unidentified to the species rank in this publi- the genus and/or the family. Genomic DNA was cation. On the other hand, lycophytes and ferns extracted from dried leaf fragments using the were well studied and the pictorial book for these DNeasy Plant Mini Kit (Qiagen, Hilden). Then, taxa has been published (Chen et al., 2017). the target DNA regions of chloroplast rbcL and Probably thus far it could be said that the family matK were amplified and sequenced with respec- Orchidaceae is the most studied taxa in the coun- tive universal DNA barcoding primers (CBOL try in several decades (Hunt, 1969; Lewis and Plant Working Group, 2009). The obtained Cribb, 1991; Szlachetko and Margonska, 2000; sequences were used to query sequences in the Hsu et al., 2016). DNA Data Bank of Japan using Blastn. Overall, it is clear that still small number of The enumeration of the identified taxa with collections has been made from the eastern voucher specimens, distribution data and taxo- regions, Makira Ulawa Province, Malaita Prov- nomic notes is provided. Abbreviations of locali- ince, and Guadalcanal Island compared to west- ties for the specimen citation are used as follows: ern parts of the country based on the observa- SC as San Cristobal Island (Makira), PI as Pio tions of specimens in K, SING, and BSIP. Under Island, TS as Three Sisters Islands, M as Malaita such circumstances, we carried out floristic Island, and G as Guadalcanal Island. inventories mainly in San Cristobal (Makira) A first set of the voucher specimens is depos- Island and Malaita Island. ited in BSIP with duplicates in MBK and TNS. Vascular plants from Solomon Islands 147 Fig. 1. A map of the Solomon Islands showing the present study sites. The herbarium acronyms followed the Index are newly recorded for the flora of the Solomon Herbariorum (Thiers, 2016). Islands. The identified taxa are enumerated in alpha- betical order of families, genera and specific epi- Results and Discussion thets of pteridophytes, gymnosperms, and angio- Total of 740 specimens were collected. Based sperms respectively, with examined specimens on the identifications of the materials collected, citation as voucher, and distribution data the present study recorded the occurrence of 20 obtained chiefly from the related regional floris- species representing10 families of pteridophytes tic and monographic works (Hancock and Hen- and 248 species representing 81 families of sper- derson, 1988; Smith, 1991; Wu and Raven, 1994; matophytes from the eastern regions of the Solo- Ormerod, 2017; Hassler, 2019). Note including mon Islands. Among those, 10 taxa of spermato- taxonomic discussion is given for each taxon if phytes namely: Ruellia blechum L., R. prostrata available. Poir, R. simplex C.Wright (Acanthaceae), Cyant- hillium cinereum (L.) H.Rob. (Asteraceae), Canna List of the vascular plants collected from indica L. var. warszewiczii (A.Dietr.) Nob.Tanaka the Solomon Islands Expedition 2011–2012 (Cannaceae), Mecardonia procumbens (Mill.) PTERIDOPHYTES Small (Plantaginaceae), Persicaria barbata (L.) ASPLENIACEAE H.Hara (Polygonaceae), Discocalyx latepetiolata (Mez) Sleumer (Primulaceae), and Smilax vitien- Asplenium nidus L., Sp. Pl. 2: 1079 (1753). sis (Seem.) A.DC. (Smilacaceae), Alpinia zerum- Specimen examined:—SC: Garapusi Sand bet (Pers.) B.L.Burtt & R.M.Sm. (Zingiberaceae), Beach, Watanabe et al. 1881 (BSIP, MBK, TNS). 148 Nobuyuki Tanaka et al. Fig. 2. Vegetation of study sites. A. Lowland tropical forest of San Cristobal Island (Makira). B. Malaupaina Island, one of the Three Sister Islands. C. Pio Island. D. Grammatophyllum panthernum (Orchidaceae), grow- ing on ca. 20 m tree branches in the tropical forest, east of Kirakira, San Cristobal Island. Distribution: Malesia to N. Australia. Davallia solida (G.Forst.) Sw. in J. Bot. (Schrader) 1800(2): 87 (1801). Specimen examined:—TS: Malaupaina, Wata- DAVALLIACEAE nabe et al. 1822 (BSIP, MBK, TNS). Davallia heterophylla Sm. in Mém.