An Updated Checklist of the Genus Capparis L. (Capparaceae) in Vietnam, including a New Species from Hon Tre Island

The Indochinese Peninsula is a main center of speciation of Capparis, but the taxonomic treatment of the genus is still critical in this area. With regard to Vietnam, a discordant number of species was recorded by different authors during the last century, whereas various new species have been recently described. An updated checklist of the intrageneric taxa occurring in the country is here presented, including a new species from the island of Hon Tre, Khanh Hoa Province. The genus comprises in Vietnam 37 species, 9 subspecies and 3 varieties, all belonging to Capparis sect. Monostichocalyx. The study area, with 10 endemic species, is confirmed as one of the hotspots of the genus. Three lectotypes are also selected. The new species here described and illustrated, C. oxycarpa, is related to C. pranensis, differing in the few-flowered subumbels, narrower sepals, smaller petals, longer filaments and smaller, apiculate fruit; its affinities with related taxa and conservation status are discussed, and data on its ecology and phenology are given.


Introduction
The genus Capparis L. includes about 150 species [1], occurring in a wide range of habitats in the tropical and subtropical regions of the Old World, with outliers in the Mediterranean region and central Asia [2]. Jacobs [3] regarded the Indochinese Peninsula as a main center of speciation of the genus, reporting in this area 31 species, 7 of which are endemic. Recently, various new species have been described from Vietnam and Laos [4][5][6][7][8][9][10][11][12][13][14][15], as well as from other countries of southern Asia and the western Pacific, such as India [16,17], Thailand [18], China [19], Malaysia [20], Indonesia [21,22] and New Caledonia [23,24]. With regard to Vietnam, the taxonomic treatment of the genus is still critical, with a discordant number of intrageneric taxa recorded by different authors during the past century [3,[25][26][27]. All the species reported from this country belong to Capparis sect. Monostichocalyx Radlk., while other sections of the genus, i.e., sect. Capparis L., sect. Sodada (Forssk.) Endl. and sect. Busbeckea (Endl.) Benth. & Hook.f., are not represented in the Indochinese area [3,28,29]. In particular, sect. Capparis is distributed from southern Europe, southwestern Asia and Africa eastwards to Australia and the Pacific; sect. Sodada in Africa and southwestern Asia; and sect. Busbeckea in Australia with outliers in India, Sri Lanka, Indonesia, New Guinea and the western Pacific.
The present paper is aimed at providing an updated checklist of the genus in Vietnam, based on herbarium investigations as well as on the available bibliographic sources. Furthermore, during floristic research carried out in southern Vietnam, an unidentified population of Capparis was observed on Hon Tre Island, Khanh Hoa Province. Based on herbarium investigations, this population turned out to belong to a new species of sect. Craib, Bull. Misc. Inform. Kew 1922(8): 234 (1922. Distribution: India (including Andaman Islands), Sri Lanka, Nepal, China, Myanmar, Thailand, Laos, Cambodia, Philippines, Indonesia; northern, central and southern Vietnam. In Herb. L, P. Table 1 describes the main features of the Capparis population from Hon Tre Island and compares them with those of the related taxa belonging to the Subumbellates-Group [3], recorded from Vietnam. As reported in the diagnosis furnished in the Taxonomic treatment, the studied population is mainly related to C. pranensis, a species known from Thailand, Cambodia and Vietnam [3,28], resembling it in the vegetative features but differing in various characters of the inflorescence, flower and fruit ( Table 1). The Hon Tre population also shows affinities with C. thorelii Gagnep., recorded from Thailand, Cambodia and Vietnam, which is distinguished by the twigs pubescent, later glabrescent, subumbels up to 8-flowered often arranged in a panicle, stamens c. 35 with filaments c. (6-) 7-10 mm long and fruit 1.1-1.8 cm in diameter, not apiculate. In addition, C. sepiaria L., a wide-ranging species distributed from tropical Africa eastwards to southern Asia and Australia [3], shows some affinities with the studied population, differing in the twigs pubescent, later glabrescent, leaves mostly pubescent in the lower surface, subumbels up to 26-flowered, filaments 0.5-1 cm long, and fruit not apiculate. Several other species of the Subumbellates-Group, reported from Vietnam, are easily distinguished by both vegetative and reproductive characters (Table 1).

Discussion
As mentioned above, the diversity of the genus Capparis is still not exhaustively investigated in Vietnam, where a discordant number of species was recorded in the past by different authors. In particular, Gagnepain [25] reported 13 species from the area, while more recently Ho [26] and Ban and Dorofeev [27] respectively reported 34 and 30 species. Furthermore, during the past decade various new species were described and a few others were first recorded from Vietnam. Five new species, C. bachii, C. daknongensis, C. dongvanensis, C. gialaiensis and C. kbangensis, were described by Sy et al. [4][5][6][7][8] from different areas of the country, while three taxa, C. fengii, C. pubifolia and C. sikkimensis subsp. masakai, were first recorded [33,35,36]. Based on the checklist presented here, the genus includes in Vietnam 37 species, 9 subspecies and 3 varieties. With regard to the whole Asiatic continent, a comparable richness in species is reported from China with 37 species [19], and India with 34 species [37], while among the other countries of southeastern Asia, 26 species are recorded from Thailand [18,31], 22 from Laos [10], 11 from Malaysia [20] and 9 from Cambodia [10]. All the species of Capparis occurring in Vietnam belong to sect. Monostichocalyx. Within this section Jacobs [3], in his revision of the genus from the Indus to the Pacific, recognized some "tentative" groups, mainly distinguished by the inflorescence and flower characters; most species reported from Vietnam (20) belong to the Subumbellates-Group, which is characterized by flowers more or less neatly subumbellate, flowers medium-to small-sized (sepals 2-10 mm long), stamens under 70, ovary 1-3 mm long and 2-4 placentas [3]; in addition, 6 species belong to the Seriales-Group, 5 to the Brevispina-Group, 2 to the Trinervia-Group and Cataphyllosa-Group, and 1 to the Moonii-Group and Grandis-Group. Among the 37 species of Capparis occurring in Vietnam, 10 (27%) are endemics, i.e., C. annamensis, C. bachii, C. beneolens, C. daknongensis, C. dongvanensis, C. gialaiensis, C. kbangensis, C. oxycarpa, C. rigida and C. tonkinensis. Jacobs [3], p. 403, underlined that the endemicity is generally low within the genus, and regarded "the lowlands of the Indo-Chinese Peninsula, particularly of SE. Annam" as one of the main centers of speciation of Capparis; this statement is confirmed by our data, with seven species endemic to central Vietnam. Furthermore, the study of the historical herbarium collections carried out during the present research allowed us to designate the lectotypes of three species, i.e., C. floribunda, C. koioides and C. versicolor.
With regard to the new species here described, C. oxycarpa, it belongs to the Subumbellates-Group [3] and is easily distinguished from other taxa of the same group by the few-flowered inflorescence, with flowers in some cases solitary, and by the small, apiculate fruit. The latter character is so far known only from a few species of the genus, belonging to other groups of the ones recognized by Jacobs [3] within Capparis. As reported above, it is mainly related to C. pranensis in its vegetative characters, but differs from this species in various reproductive features (Table 1); furthermore, also the flowering period is differentiated, i.e., September in C. oxycarpa and March in C. pranensis [3]. The new species is so far known only from Hon Tre, an island lying a short distance from the Vietnamese coast, with highest elevation of about 460 m. Despite being influenced by anthropic impacts, large areas of Hon Tre Island are still covered by well-preserved forest communities. Finally, it is to be underlined that, based on herbarium collections, the genus Capparis is represented on this island by a few other species, i.e., C. floribunda Wight, C. micracantha DC. and C. zeylanica L.
Distribution and habitat: The new species is only known from Hon Tre Island ( Figure  2), where it has been observed in two close locations, in xerophytic scrub on sea faced dry slopes and in secondary lowland forest, up to 100 m elevation.
Phenology: Based on the available material flowering occurs in September, fruiting in November.
Conservation status: The new species is so far known from two locations of Hon Tre, in an area of occupancy less than 2 km 2 , and its population is estimated to number fewer than 1000 mature individuals. Following the IUCN Red List Categories and Criteria [38], it is here assessed as Vulnerable (VU D1).
Distribution and habitat: The new species is only known from Hon Tre Island (Figure 2), where it has been observed in two close locations, in xerophytic scrub on sea faced dry slopes and in secondary lowland forest, up to 100 m elevation.

Materials and Methods
Herbarium investigations were carried out on the collections of Capparis kept at HN, HNU, LE and P, coupled with research on the available online collections at A, BM, E, G, Phenology: Based on the available material flowering occurs in September, fruiting in November.
Conservation status: The new species is so far known from two locations of Hon Tre, in an area of occupancy less than 2 km 2 , and its population is estimated to number fewer than 1000 mature individuals. Following the IUCN Red List Categories and Criteria [38], it is here assessed as Vulnerable (VU D1). Additional

Materials and Methods
Herbarium investigations were carried out on the collections of Capparis kept at HN, HNU, LE and P, coupled with research on the available online collections at A, BM, E, G, GAC, GH, IBK, IBSC, K, KUN, L, LINN, MPU, NY, SING, U, US. The taxonomic treatment here adopted, as well as the main diagnostic characters within the genus, follow Jacobs [3]. The data on the distribution of the taxa are based on herbarium collections and on bibliographic sources [3][4][5][6][7][8][9][10]19,20,[24][25][26][27][28][29]33,35,36]. The species recognized in the study area are arranged in alphabetical order in the checklist. The herbarium acronyms follow Thiers [39], while authors and names of plants are based on the International Plant Names Index [40]. The examination of type specimens was carried out through electronic images available at JSTOR Global Plants [41] and through study of the historical collections at P. The new species here described was first observed and collected by one of us (L.A.) in November 1989 and later during September 1990, in the frame of field investigations carried out in southern Vietnam; the collections were kept at the Komarov Botanical Institute (LE). The description and illustration are based on herbarium material. The terminology of vegetative and reproductive structures is based on Jacobs [3]. The measurements of morphometric characters were carried out on the herbarium material using a digital caliper and the range of variation of each character, from the minimum to the maximum value, was reported in the description and Table 1. The data concerning the taxa related to the new species, reported in Table 1, were obtained from bibliographic sources [3,10,42]. The conservation status of the new species has been provisionally assessed according to IUCN Red List Categories and Criteria [38].