New Guinea has the world's richest island flora.

New Guinea is the world's largest tropical island and has fascinated naturalists for centuries1,2. Home to some of the best-preserved ecosystems on the planet3 and to intact ecological gradients-from mangroves to tropical alpine grasslands-that are unmatched in the Asia-Pacific region4,5, it is a globally recognized centre of biological and cultural diversity6,7. So far, however, there has been no attempt to critically catalogue the entire vascular plant diversity of New Guinea. Here we present the first, to our knowledge, expert-verified checklist of the vascular plants of mainland New Guinea and surrounding islands. Our publicly available checklist includes 13,634 species (68% endemic), 1,742 genera and 264 families-suggesting that New Guinea is the most floristically diverse island in the world. Expert knowledge is essential for building checklists in the digital era: reliance on online taxonomic resources alone would have inflated species counts by 22%. Species discovery shows no sign of levelling off, and we discuss steps to accelerate botanical research in the 'Last Unknown'8.

An updated infra-familial classification of Sapindaceae based on targeted enrichment data.

PREMISE: The economically important, cosmopolitan soapberry family (Sapindaceae) comprises ca. 1900 species in 144 genera. Since the seminal work of Radlkofer, several authors have attempted to overcome challenges presented by the family's complex infra-familial classification. With the advent of molecular systematics, revisions of the various proposed groupings have provided significant momentum, but we still lack a formal classification system rooted in an evolutionary framework. METHODS: Nuclear DNA sequence data were generated for 123 genera (86%) of Sapindaceae using target sequence capture with the Angiosperms353 universal probe set. HybPiper was used to produce aligned DNA matrices. Phylogenetic inferences were obtained using coalescence-based and concatenated methods. The clades recovered are discussed in light of both benchmark studies to identify synapomorphies and distributional evidence to underpin an updated infra-familial classification. KEY RESULTS: Coalescence-based and concatenated phylogenetic trees had identical topologies and node support, except for the placement of Melicoccus bijugatus Jacq. Twenty-one clades were recovered, which serve as the basis for a revised infra-familial classification. CONCLUSIONS: Twenty tribes are recognized in four subfamilies: two tribes in Hippocastanoideae, two in Dodonaeoideae, and 16 in Sapindoideae (no tribes are recognized in the monotypic subfamily Xanthoceratoideae). Within Sapindoideae, six new tribes are described: Blomieae Buerki & Callm.; Guindilieae Buerki, Callm. & Acev.-Rodr.; Haplocoeleae Buerki & Callm.; Stadmanieae Buerki & Callm.; Tristiropsideae Buerki & Callm.; and Ungnadieae Buerki & Callm. This updated classification provides a backbone for further research and conservation efforts on this family.

Generic delimitations, biogeography and evolution in the tribe Coleeae (Bignoniaceae), endemic to Madagascar and the smaller islands of the western Indian Ocean.

This study presents the most complete generic phylogenetic framework to date for the tribe Coleeae (Bignoniaceae), which is endemic to Madagascar and the other smaller islands in the western part of the Indian Ocean. The study is based on plastid and nuclear DNA regions and includes 47 species representing the five currently recognized genera (including all the species occurring in the western Indian Ocean region). Bayesian and maximum likelihood analyses supported (i) the monophyly of the tribe, (ii) the monophyly of Phylloctenium, Phyllarthron and Rhodocolea and (iii) the paraphyly of Colea due to the inclusion of species of Ophiocolea. The latter genus was also recovered paraphyletic due to the inclusion of two species of Colea (C. decora and C. labatii). The taxonomic implications of the mutual paraphyly of these two genera are discussed in light of morphological evidence, and it is concluded that the two genera should be merged, and the necessary new nomenclatural combinations are provided. The phylogenetic framework shows Phylloctenium, which is endemic to Madagascar and restricted to dry ecosystems, as basal and sister to the rest of the tribe, suggesting Madagascar to be the centre of origin of this clade. The remaining genera are diversified mostly in humid ecosystems, with evidence of multiple dispersals to the neighboring islands, including at least two to the Comoros, one to Mauritius and one to the Seychelles. Finally, we hypothesize that the ecological success of this tribe might have been triggered by a shift of fruit-dispersal mode from wind to lemur.

A long distance dispersal hypothesis for the Pandanaceae and the origins of the Pandanus tectorius complex.

Pandanaceae (screwpines) is a monocot family composed of c. 750 species widely distributed in the Paleotropics. It has been proposed that the family may have a Gondwanan origin with an extant Paleotropical distribution resulting from the breakup of that supercontinent. However, fossils supporting that hypothesis have been recently reassigned to other families while new fossil discoveries suggest an alternate hypothesis. In the present study, nuclear and chloroplast sequences were used to resolve relationships among Pandanaceae genera. Two well-supported fossils were used to produce a chronogram to infer whether the age of major intra-familial lineages corresponds with the breakup of Gondwana. The Pandanaceae has a Late Cretaceous origin, and genera on former Gondwanan landmasses began to diverge in the Late Eocene, well after many of the southern hemisphere continents became isolated. The results suggest an extant distribution influenced by long-distance-dispersal. The most widespread group within the family, the Pandanus tectorius species complex, originated in Eastern Queensland within the past six million years and has spread to encompass nearly the entire geographic extent of the family from Africa through Polynesia. The spread of that group is likely due to dispersal via hydrochory as well as a combination of traits such as agamospermy, anemophily, and multi-seeded propagules which can facilitate the establishment of new populations in remote locations.

Antiproliferative Compounds from Cleistanthus boivinianus from the Madagascar Dry Forest.

The two new lignans 3α-O-(ß-D-glucopyranosyl)desoxypodophyllotoxin (1) and 4-O-(ß-D-glucopyranosyl)dehydropodophyllotoxin (2) were isolated from Cleistanthus boivinianus, together with the known lignans deoxypicropodophyllotoxin (3), (±)-ß-apopicropodophyllin (4), (-)-desoxypodophyllotoxin (5), (-)-yatein (6), and ß-peltatin-5-O-ß-D-glucopyranoside (7). The structures of all compounds were characterized by spectroscopic techniques. Compounds 1, 4, and 5 showed potent antiproliferative activities against the A2780 ovarian cancer cell line, with IC50 values of 33.0 ± 3.6, 63.1 ± 6.7, and 230 ± 1 nM, respectively. Compounds 2 and 7 showed only modest A2780 activities, with IC50 values of 2.1 ± 0.3 and 4.9 ± 0.1 µM, respectively, while compounds 3 and 6 had IC50 values of >10 µM. Compound 1 also had potent antiproliferative activity against the HCT-116 human colon carcinoma cell line, with an IC50 value of 20.5 nM, and compound 4 exhibited modest antiproliferative activity against the A2058 human caucasian metastatic melanoma and MES-SA human uterine sarcoma cell lines, with IC50 values of 4.6 and 4.0 µM, respectively.

Neolignans and other metabolites from Ocotea cymosa from the Madagascar rain forest and their biological activities.

Ten new neolignans including the 6'-oxo-8.1'-lignans cymosalignans A (1a), B (2), and C (3), an 8.O.6'-neolignan (4a), ococymosin (5a), didymochlaenone C (6a), and the bicyclo[3.2.1]octanoids 7-10 were isolated along with the known compounds 3,4,5,3',5'-pentamethoxy-1'-allyl-8.O.4'-neolignan, 3,4,5,3'-tetramethoxy-1'-allyl-8.O.4'-neolignan, didymochlaenone B, virologin B, ocobullenone, and the unusual 2'-oxo-8.1'-lignan sibyllenone from the stems or bark of the Madagascan plant Ocotea cymosa. The new 8.O.6'-neolignan 4a, dihydrobenzofuranoid 5a, and the bicyclo[3.2.1]octanoid 7a had in vitro activity against Aedes aegypti, while the new compounds 5a, 7a, 8, and 10a and the known virolongin B (4b) and ocobullenone (10b) had antiplasmodial activity. We report herein the structure elucidation of the new compounds on the basis of spectroscopic evidence, including 1D and 2D NMR spectra, electronic circular dichroism, and mass spectrometry, and the biological activities of the new and known compounds.

Bioactive compounds from Stuhlmannia moavi from the Madagascar dry forest.

Bioassay-directed fractionation of the leaf and root extracts of the antiproliferative Madagascar plant Stuhlmannia moavi afforded 6-acetyl-5,8-dihydroxy-2-methoxy-7-methyl-1,4-naphthoquinone (stuhlmoavin, 1) as the most active compound, with an IC50 value of 8.1 µM against the A2780 human ovarian cancer cell line, as well as the known homoisoflavonoid bonducellin (2) and the stilbenoids 3,4,5'-trihydroxy-3'-methoxy-trans-stilbene (3), piceatannol (4), resveratrol (5), rhapontigenin (6), and isorhapontigenin (7). The structure elucidation of all compounds was based on NMR and mass spectroscopic data, and the structure of 1 was confirmed by a single crystal X-ray analysis. Compounds 2-5 showed weak A2780 activities, with IC50 values of 10.6, 54.0, 41.0, and 74.0 µM, respectively. Compounds 1-3 also showed weak antimalarial activity against Plasmodium falciparum with IC50 values of 23, 26, and 27 µM, respectively.

Antiproliferative and antiplasmodial dimeric phloroglucinols from Mallotus oppositifolius from the Madagascar Dry Forest (1).

Bioassay-guided fractionation of an ethanol extract of the leaves and inflorescence of Mallotus oppositifolius collected in Madagascar led to the isolation of the two new bioactive dimeric phloroglucinols mallotojaponins B (1) and C (2), together with the known mallotophenone (3). The structures of the new compounds were determined on the basis of spectroscopic evidence, including their 1D- and 2D-NMR spectra, mass spectrometry, and an X-ray crystal structure. Compounds 1 and 2 showed potent antimalarial activity against chloroquine-resistant Plasmodium falciparum, with IC50 values of 0.75 ± 0.30 and 0.14 ± 0.04 µM, while 3 was inactive in this assay. Compounds 1-3 also displayed strong antiproliferative activity against the A2780 human ovarian cancer cell line (IC50 1.10 ± 0.05, 1.3 ± 0.1 and 6.3 ± 0.4 µM, respectively).

Structure elucidation of antiproliferative bisbenzylisoquinoline alkaloids from Anisocycla grandidieri from the Madagascar dry forest.

Antiproliferative bioassay-guided fractionation of the ethanol extract of the stems of Anisocycla grandidieri led to the isolation of the known alkaloids stebisimine (1), (+)-1,2-dehydrotelobine (2), (+)-2'-norcocsuline (3) and puetogaline B (4). Herein, we report the full NMR assignments of all compounds and the X-ray crystallography of single crystals of compounds 1 and 3. Compounds 2 and 3 showed moderate antiproliferative activity against the A2780 human ovarian cancer cell line with IC50 values of 4.1 ± 0.3 and 2.7 ± 0.3 µM, respectively, and they also displayed selective activity toward the H460 (large cell lung cancer), MCF-7 (breast ductal carcinoma), and UACC-257 (melanoma) cell lines.

Phylogenomic analyses of Sapindales support new family relationships, rapid Mid-Cretaceous Hothouse diversification, and heterogeneous histories of gene duplication.

Sapindales is an angiosperm order of high economic and ecological value comprising nine families, c. 479 genera, and c. 6570 species. However, family and subfamily relationships in Sapindales remain unclear, making reconstruction of the order's spatio-temporal and morphological evolution difficult. In this study, we used Angiosperms353 target capture data to generate the most densely sampled phylogenetic trees of Sapindales to date, with 448 samples and c. 85% of genera represented. The percentage of paralogous loci and allele divergence was characterized across the phylogeny, which was time-calibrated using 29 rigorously assessed fossil calibrations. All families were supported as monophyletic. Two core family clades subdivide the order, the first comprising Kirkiaceae, Burseraceae, and Anacardiaceae, the second comprising Simaroubaceae, Meliaceae, and Rutaceae. Kirkiaceae is sister to Burseraceae and Anacardiaceae, and, contrary to current understanding, Simaroubaceae is sister to Meliaceae and Rutaceae. Sapindaceae is placed with Nitrariaceae and Biebersteiniaceae as sister to the core Sapindales families, but the relationships between these families remain unclear, likely due to their rapid and ancient diversification. Sapindales families emerged in rapid succession, coincident with the climatic change of the Mid-Cretaceous Hothouse event. Subfamily and tribal relationships within the major families need revision, particularly in Sapindaceae, Rutaceae and Meliaceae. Much of the difficulty in reconstructing relationships at this level may be caused by the prevalence of paralogous loci, particularly in Meliaceae and Rutaceae, that are likely indicative of ancient gene duplication events such as hybridization and polyploidization playing a role in the evolutionary history of these families. This study provides key insights into factors that may affect phylogenetic reconstructions in Sapindales across multiple scales, and provides a state-of-the-art phylogenetic framework for further research.

Isolation and synthesis of two antiproliferative calamenene-type sesquiterpenoids from Sterculia tavia from the Madagascar rain forest.

Investigation of the endemic Madagascan plant Sterculia taiva Baill. (Malvaceae) for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of two new bioactive calamenene-type sesquiterpenoids, named tavinin A (2) and epi-tavinin A (3) together with the known sesquiterpenoid mansonone G (1). The structures of the two new compounds were elucidated based on analysis of their 1D and 2D NMR spectra and mass spectrometric data, and were confirmed by de novo synthesis. The three isolated sesquiterpenoids (1-3) had modest antiproliferative activities against the A2780 ovarian cancer cell line, with IC(50) values of 10.2, 5.5 and 6.7 µM, respectively.

Antiproliferative acetogenins from a Uvaria sp. from the Madagascar dry forest.

Investigation of the endemic Madagascan plant Uvaria sp. for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of two new acetogenins. The structures of these two compounds were elucidated on the basis of analysis of their 1D and 2D NMR spectra, circular dichroism, and mass spectrometric data, together with chemical modification. The two acetogenins display weak antiproliferative activity against the A2780 ovarian cancer, the A2058 melanoma, and the H522 lung cancer cell lines.

A TAXONOMIC REVISION OF GOUANIA (RHAMNACEAE) IN MADAGASCAR AND THE OTHER ISLANDS OF THE WESTERN INDIAN OCEAN (THE COMORO AND MASCARENE ISLANDS, AND THE SEYCHELLES).

A taxonomic revision of the genus Gouania Jacq. (Rhamnaceae) is presented for Madagascar and the other western Indian Ocean islands. Seventeen species are recognized, of which nine are described and published as new (all endemic to Madagascar): G. ambrensis Buerki, Phillipson & Callm., G. callmanderi Buerki, G. cupreifolia Buerki, Phillipson & Callm., G. cupuliflora Buerki, Phillipson & Callm., G. gautieri Buerki, Phillipson & Callm., G. perrieri Buerki, Phillipson & Callm., G. phillipsonii Buerki, G. taolagnarensis Buerki, Phillipson & Callm., and G. zebrifolia Buerki, Phillipson & Callm. Sixteen species occur in Madagascar, of which 13 are endemic and three are common to Madagascar and one or more of the smaller Indian Ocean islands. The latter include G. laxiflora Tul., a species which is also present on mainland Africa. One species, G. mauritiana Lam., is endemic to Réunion Island. We recognize two subspecies within G. scandens (Gaertn.) R. B. Drumm.: G. scandens subsp. scandens and G. scandens subsp. glandulosa (Boivin ex Tul.) Buerki, Phillipson & Callm., the latter transferred from G. glandulosa Boivin ex Tul. Past confusion about the identity of this species is discussed. Five names are lectotypified: G. aphrodes Tul., G. glandulosa [= G. scandens subsp. glandulosa], G. laxiflora, G. lineata Tul., and G. tiliifolia Lam. Both lectotype and epitype are designated for G. mauritiana. Conservation assessments are provided for all species within their primary areas of occurrence.

Isolation and synthesis of antiproliferative eupolauridine alkaloids of Ambavia gerrardii from the Madagascar Dry Forest.

Investigation of the Madagascan endemic plant Ambavia gerrardii for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of the three new alkaloids 8-hydroxyeupolauridine (1), 9-methoxyeupolauridine 1-oxide (2), and 11-methoxysampangine (3) and the three known alkaloids 4-6. The structures of 1 and 2 were confirmed by synthesis. Compounds 3, 4, and 6 showed moderate to good antiproliferative activities, with IC50 values of 10.3, 3.5, and 0.60 µM, respectively, against the A2780 human ovarian cancer cell line and with IC50 values of 0.57, 1.77, and 0.58 µM, respectively, against the H460 human lung cancer cell line.

The genus Ophiocolea H. Perrier in northern Madagascar with description of four new species and two lectotypifications.

A recent review of Bignoniaceae for the "Catalogue of the vascular plants of Madagascar" has revealed new species in most of the genera present on the island. We provide descriptions of four new species in the genus Ophiocolea H. Perrier, a genus that is endemic to the Malagasy region: Ophiocolea ambrensis Callm. & Phillipson, Ophiocolea darainensis Callm., Phillipson & Nusb., Ophiocolea pauciflora Callm., Phillipson & Razan. and Ophiocolea ratovosonii Callm. & Phillipson. Field photographs and line drawings are provided for each of these four new species. Two species described previously, Ophiocolea decaryi H. Perrier and Ophiocolea velutina H. Perrier, are lectotypified. For all six treated species, we provide a short discussion on morphological affinities and eco-geography, and perform a conservation threat analysis based on the IUCN Red List Categories and Criteria.

Antiproliferative compounds from Pongamiopsis pervilleana from the Madagascar Dry Forest.

Bioassay-guided fractionation of an ethanol extract of the roots of the endemic Malagasy plant Pongamiopsis pervilleana led to the isolation of the three new compounds (2'R)-4'-hydroxyemoroidocarpan (1), pongavilleanine (3), and epipervilline (4) together with two known compounds, identified as emoroidocarpan (2) and rotenolone (5). The structures of all compounds were determined by physical, chemical, and spectroscopic evidence. The stereochemistry at C-2' of the previously reported compound emoroidocarpan was determined to be R by the observation of a negative Cotton effect at 474 nm in the CD spectrum of its osmate ester derivative. Compounds 2-5 displayed moderate antiproliferative activity against the A2780 human ovarian cancer cell line, and rotenolone also showed micromolar antiproliferative activity toward the breast cancer BT-549, prostate cancer DU 145, NSCLC NCI-H460, and colon cancer HCC-2998 cell lines.

Four diphenylpropanes and a cycloheptadibenzofuran from Bussea sakalava from the Madagascar dry forest.

Investigation of the endemic Malagasy plant Bussea sakalava for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of the four new diphenylpropanes 1-4 and the new cycloheptadibenzofuran 5; compound 5 has a previously unreported natural product skeleton. The structure elucidation of these compounds was based on the analysis of their 1D and 2D NMR and mass spectroscopic data. Compounds 1-5 were tested for antiproliferative activity against the A2780 human ovarian cancer cell line.

A new species of Pandanaceae from northern Madagascar, Pandanus ankaranensis.

A new species, Pandanus ankaranensis Callm. & Laivao (Pandanaceae), is described from the karst region of Ankarana in northern Madagascar. It resembles P. grallatus B. C. Stone, another member of Pandanus sect. Mammillares H. St. John occurring in the area. The new taxon can be distinguished by its larger and wider leaves that are persistent on the branches, the stipe often lying on the rocks where plants grow, and its larger syncarps. Pandanus ankaranensis is classified as Vulnerable based on the IUCN Red List criteria.

Plastid and nuclear DNA markers reveal intricate relationships at subfamilial and tribal levels in the soapberry family (Sapindaceae).

The economically important soapberry family (Sapindaceae) comprises about 1900 species mainly found in the tropical regions of the world, with only a few genera being restricted to temperate areas. The infrafamilial classification of the Sapindaceae and its relationships to the closely related Aceraceae and Hippocastanaceae - which have now been included in an expanded definition of Sapindaceae (i.e., subfamily Hippocastanoideae) - have been debated for decades. Here we present a phylogenetic analysis of Sapindaceae based on eight DNA sequence regions from the plastid and nuclear genomes and including 85 of the 141 genera defined within the family. Our study comprises 997 new sequences of Sapindaceae from 152 specimens. Despite presenting 18.6% of missing data our complete data set produced a topology fully congruent with the one obtained from a subset without missing data, but including fewer markers. The use of additional information therefore led to a consistent result in the relative position of clades and allowed the definition of a new phylogenetic hypothesis. Our results confirm a high level of paraphyly and polyphyly at the subfamilial and tribal levels and even contest the monophyletic status of several genera. Our study confirms that the Chinese monotypic genus Xanthoceras is sister to the rest of the family, in which subfamily Hippocastanoideae is sister to a clade comprising subfamilies Dodonaeoideae and Sapindoideae. On the basis of the strong support demonstrated in Sapindoideae, Dodonaeoideae and Hippocastanoideae as well as in 14 subclades, we propose and discuss informal groupings as basis for a new classification of Sapindaceae.

Antiproliferative and antimalarial anthraquinones of Scutia myrtina from the Madagascar forest.

Bioassay-guided fractionation of an ethanol extract of a Madagascar collection of the bark of Scutia myrtina led to the isolation of three new anthrone-anthraquinones, scutianthraquinones A, B and C (1-3), one new bisanthrone-anthraquinone, scutianthraquinone D (4), and the known anthraquinone, aloesaponarin I (5). The structures of all compounds were determined using a combination of 1D and 2D NMR experiments, including COSY, TOCSY, HSQC, HMBC, and ROESY sequences, and mass spectrometry. All the isolated compounds were tested against the A2780 human ovarian cancer cell line for antiproliferative activities, and against the chloroquine-resistant Plasmodium falciparum strains Dd2 and FCM29 for antiplasmodial activities. Compounds 1, 2 and 4 showed weak antiproliferative activities against the A2780 ovarian cancer cell line, while compounds 1-4 exhibited moderate antiplasmodial activities against P. falciparum Dd2 and compounds 1, 2, and 4 exhibited moderate antiplasmodial activities against P. falciparum FCM29.