Ten subordinal names for flowering plants are established to complete a subordinal classification of the angiosperms.

The tribe Cunonieae comprises five genera and 214 species of shrubs and trees currently distributed in the Southern Hemisphere and the tropics, exhibiting an amphi-Pacific disjunct distribution shared with Araucariaceae, Myrtaceae, Nothofagaceae, Podocarpaceae, and Proteaceae, among others. To address the central question of how historical geological forces have shaped the distribution of plant diversity in the southern hemisphere, we aimed to provide evidence from the biogeographical history of Cunonieae. We generated the most densely sampled phylogenetic trees of Cunonieae available to date, with 121 samples and 81 species, based on 404 new sequences of plastid and nuclear DNA regions with high hierarchical phylogenetic signal (matK, trnL-F, rpl16, and internal transcribed spacer (ITS)). We included 184 samples of Rosids to estimate divergence times using fossil calibration points. For biogeographic inference, we employed a time-stratified model including fossils as tips. Cunonia and Pterophylla were paraphyletic in the ITS tree, and Cunonia was paraphyletic in the plastid tree. Pancheria, Vesselowskya, and Weinmannia were monophyletic, the latter with conflicting nuclear and plastid phylogenies. The crown group Cunonieae was dated at similar to 56 Ma, and its ancestral areas were Antarctica and Patagonia. Antarctica acted as a bridge between Australia and South America before the consolidation of the Antarctic Ice Sheet and the extinction of the lineage in Antarctica from the Oligocene to the Miocene. Following that, Cunonieae spread to lower latitudes via Zealandia/Oceania and Patagonia/South America. Geological changes during the Pliocene facilitated a further burst in diversification along the Andes, in Madagascar, and in New Caledonia, where at least three colonization events occurred.

Recent fieldwork has revealed a new species of Virotia, a genus of Proteaceae endemic to New Caledonia. This understory monocaulous shrub or tree was found in two nearby rainforests on ultramafic substrate in the Poro region. We report high concentrations of manganese (10,900 mg.g(-1)) and nickel (2,900 mg.g(-1)) in dry leaves of this species. This is one of the few cases of simultaneous hyperaccumulation of these metals in angiosperms. This rare micro-endemic species is given a conservation status of critically endangered due to the impact of nickel mining, fire and fragmentation on its habitat.

The era of molecular systematics has had a tremendous impact on taxonomy, with the increasing availability of phylogenetic trees allowing the recircumscription of higher taxa, particularly through the application of the monophyletic principle. Whether molecular phylogenetics has caused taxonomic instability has not been objectively assessed. Here, we used the flora of New Caledonia to monitor the evolution of the taxonomy of a tropical flora through four time windows from 1911 to 2024. This Pacific island's flora is renowned for its high species richness and endemism and includes 42% of the currently accepted flowering plant families, including the endemic Amborellaceae. We found that taxonomic changes, including changes in genera and families, have always been common, even in the pre-molecular era. If family changes were more important between 2001 and 2012, following the application of the classification proposed by the Angiosperm Phylogeny Group (APG), changes since then have been reduced to almost zero. Since the latest versions of the APG classification are almost identical, it seems that this classification can now be safely applied outside the world of scientific publication. Greater efforts are needed to achieve a stable generic classification, where collectives similar to APG could target such goals.

Dutailliopsis (Rutaceae) is a scarcely known monotypic genus from New Caledonia. It is one of the few genera of Rutaceae that has never been included in a molecular phylogenetic study. Based on Sanger sequencing of the markers ETS, ITS, and trnL-trnF, we conclude that Dutailliopsis is nested within the large genus Melicope and that it is most closely related to other New Caledonian species of Melicope. Previous molecular phylogenetic studies revealed that other New Caledonian genera - namely the endemic Comptonella, Dutaillyea, Picrella, and the near-endemic Sarcomelicope (only one out of the nine species is not endemic to New Caledonia) - are nested in Melicope as well and we propose nomenclatural changes to render Melicope monophyletic and develop a new classification system for the genus.

The taxonomy of Stenocarpus (Proteaceae: Stenocarpinae) in New Caledonia is reviewed. The name S. grunowii is re-instated at specific rank. Stenocarpus dumbeensis, S. gracilis, S. intermedius, and S. phyllodineus are treated as synonyms of S. umbelliferus. Stenocarpus x heterophyllus is considered as a hybrid taxon involving parents with multifid and entire leaves. A new species, S. deweae, with red rather than white to yellowish flowers, is described, illustrated and assessed as Endangered according to the IUCN Red List criteria. These changes reduce the number of species now recognized in this genus in New Caledonia from twelve to nine, and all are endemic. An identification key is provided and lectotypes are designated for several names. We also propose new combinations for the three Australian species of Strangea, which are phylogenetically nested within Stenocarpus, with the result that subtribe Stenocarpinae now contains a single genus only, Stenocarpus. Lectotypes are designated for the two names in Strangea based on Drummond's collections from Western Australia.

QuestionsHigh species richness is observed in certain shrublands on infertile substrates. Mineral nutrients are likely to be the primary limiting resources in these ecosystems, and below-ground plant interactions may be crucial to understanding their diversity. Using ionomics, we investigated whether there were nutritional variations between plant species that coexist in a shrubland located in an edaphically extreme environment.LocationNew Caledonia.MethodsWe set up a 20 m x 20 m plot in a diverse shrubland ("maquis") on ultramafic (infertile) substrate, in which we sampled all 475 plants taller than 1 m and characterized their ionome (22 elements).ResultsIn our study, 37 species were identified in the plot, representing all major forms of mycorrhizal symbioses, as well as nitrogen-fixing plants, cluster rooted and parasitic plants. Notably, both nickel hyperaccumulating and manganese hyperaccumulating species were present. Hypervolume approaches were used to assess ionome overlap among the nine most abundant species, with the results revealing limited overlap. Moreover, it was observed that the rarest species in the plot also had the most functionally distinct features.ConclusionsDifferent nutritional strategies were present in the plot, as demonstrated by the variety of root symbioses and leaf ionomes. Our findings indicate coexistence of multiple species within this infertile shrubland may be achieved by species partitioning into different highly specialized biogeochemical niches. The high species richness of certain shrublands on infertile substrates remains poorly understood. We designed a plot on ultramafic substrate in New Caledonia where we characterized the ionome (22 elements) of all 475 plants. We found a diversity of root symbioses (mycorrhiza) represented. Hypervolume and functional rarity analyses revealed differences in elemental spaces, including metal hyperaccumulation. Our results suggest that partitioning into different biogeochemical niches may account for the coexistence of multiple species.image

Background and Aims The geographical origin and evolutionary mechanisms underpinning the rich and distinctive New Caledonian flora remain poorly understood. This is attributable to the complex geological past of the island and to the scarcity of well-resolved species-level phylogenies. Here, we infer phylogenetic relationships and divergence times of New Caledonian palms, which comprise 40 species. We use this framework to elucidate the biogeography of New Caledonian palm lineages and to explore how extant species might have formed.Methods A phylogenetic tree including 37 New Caledonian palm species and 77 relatives from tribe Areceae was inferred from 151 nuclear genes obtained by targeted sequencing. Fossil-calibrated divergence times were estimated and ancestral ranges inferred. Ancestral and extant ecological preferences in terms of elevation, precipitation and substrate were compared between New Caledonian sister species to explore their possible roles as drivers of speciation.Key Results New Caledonian palms form four well-supported clades, inside which relationships are well resolved. Our results support the current classification but suggest that Veillonia and Campecarpus should be resurrected and fail to clarify whether Rhopalostylidinae is sister to or nested in Basseliniinae. New Caledonian palm lineages are derived from New Guinean and Australian ancestors, which reached the island through at least three independent dispersal events between the Eocene and Miocene. Palms then dispersed out of New Caledonia at least five times, mainly towards Pacific islands. Geographical and ecological transitions associated with speciation events differed across time and genera. Substrate transitions were more frequently associated with older events than with younger ones.Conclusions Neighbouring areas and a mosaic of local habitats shaped the palm flora of New Caledonia, and the island played a significant role in generating palm diversity across the Pacific region. This new spatio-temporal framework will enable population-level ecological and genetic studies to unpick the mechanisms underpinning New Caledonian palm endemism.

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods(1,2). A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome(3,4). Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins(5-7). However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes(8). This 15-fold increase in genus-level sampling relative to comparable nuclear studies(9) provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade.

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.

The assembly of island plant communities is the result of a number of processes: immigration (dispersal), speciation, and extinction. Using four plastid genes and one low-copy nuclear gene, we investigated the origin of the New Caledonian Grevillea (Proteaceae), an otherwise largely Australian genus. In the combined plastid analysis, the species form two distinct clades, the exul (four species) and gillivrayi groups (six species), within group 3 of Grevillea. All New Caledonian Grevillea display two distinct copies of PHYA, one copy in group 3, and another in group 4. Previously published chromosome counts for G. meisneri and two new genome size estimates of G. gillivrayi and G. rubiginosa suggest that these plants are tetraploids. Altogether, the current data available suggest that New Caledonian Grevillea are allotetraploids, resulting from one or two hybridisation events between two or three distinct parents. A possible scenario is that modern Grevillea has descended from a hybrid swarm that formed 9-13 Mya between multiple immigrants (now extinct) that reached the island. Grevillea can be added to the list of island plant radiations with an early history of hybridisation and polyploidy. The relative importance, location and timing of these two mechanisms remain to be elucidated. The two groups of New Caledonian Grevillea may be easily distinguished by their inflorescences, flowers and fruits, with the gillivrayi group displaying greater ecological and morphological diversity. The seed characteristics of New Caledonian Grevillea are consistent with their pioneer behavior.

Taxonomic notes are made on the Malpighiales of New Caledonia. The names Acridocarpus austrocaledonicus Baill. (Malpighiaceae), Crossostylis grandiflora Brongn. & Gris, C. multiflora Brongn. & Gris, C. sebertii Pancher ex Brongn. & Gris (Rhizophoraceae), and Erythroxylum novocaledonicum O.E.Schultz (Erythroxylaceae) are lectotypified. Based on published molecular phylogenetic and morphological evidence, Lasiochlamys Pax & K.Hoffm. is better treated as a synonym of Xylosma G.Forst. (Salicaceae), and five new combinations and one new name are provided to implement this change.

Proteaceae, the Macadamia nut family, are diverse in New Caledonia with c. 50 species distributed in nine genera in tribes Embothrieae, Macadamieae, Persoonieae, and Roupaleae, where they represent an important component of the rainforest and particularly the maquis. The family is also represented by a few species in the neighboring archipelagos of Vanuatu and Fiji, which marks the eastern limit of its distribution in the Pacific. Here, we address some issues regarding generic limits within Pacific Proteaceae, using new molecular data and a review of morphology. The generic limits within the tribe Macadamieae have long been problematic, particularly amongst Kermadecia, Sleumerodendron, and Turrillia, which are part of the subtribe Gevuininae. Molecular phylogenetics shows that they form a monophyletic group, while morphological data indicate that they are only weakly differentiated. We conclude that they are better treated as a single genus, Kermadecia, as has been done previously, with eight species. Kermadecia elliptica is placed in synonymy under K. rotundifolia for the first time, and several names in the genus are lectotypified. As previously observed, we found that the New Caledonian endemic Garnieria spathulifolia is nested in Persoonia (tribe Persoonieae) from which it differs only by the number of ovules and is therefore transferred to it and a lectotype is designated.

New Caledonia, an archipelago in the Southwest Pacific, is a biodiversity hotspot (Myers 1988; Myers et al. 2000) whose rich and unique flora has generally been associated with the diversity of geological substrates. New Caledonia has one of the largest extent of ultramafic rocks in the world (Garnica-Díaz et al. 2023). Ultramafic rocks are igneous rocks that are poor in silicon and rich in iron and magnesium. When weathered, they produce soils that impose difficult conditions for plant growth (Kazakou et al. 2008), and they have often been referred to as “ultrabasic rocks” or “serpentine” in the literature. The peculiarity of New Caledonia was noted by its earliest European visitors. In his journal, James Cook wrote that “our botanists did not complain for want of employment at this place; every day bringing something new in botany or other branches of natural history” (Cook 1777, p. 124). Although they did not visit ultramafic outcrops, the naturalists accompanying James Cook were also struck by the geological distinctiveness of New Caledonia. For instance, Georg Forster (1777, p. 576) anticipated that “there was some probability of meeting with rich and useful minerals upon this island, which, as far as we saw, distinguished itself from all those we had hitherto examined in the South Seas, in being entirely destitute of volcanic productions”. Georges’ father, Johann Forster (1778, p. 34), similarly wrote that “the mountains of New Caledonia are the most likely to contain the richest metallic veins”. Later, the geologist Jules Garnier explored more extensively the main island of New Caledonia noting the large areas of “terrains serpentineux” (serpentine terrains) and revealing the abundance of nickel ores (Garnier 1885). This dramatically changed the future of the island where the mining industry now plays a major role. The earliest European naturalists exploring New Caledonia focused on inventorying the diverse flora of the archipelago, and had limited interest or time to study its ecology, including plant–soil relationships. Robert Virot made the first substantial contribution to the ecology of the New Caledonian flora with his thesis “La végétation canaque” (Virot 1956). After spending several years on the island, he was able to give an overview of the biological forms, plant formations, and phytosociology of the flora. His work prefigures that of Tanguy Jaffré. In 1980, Tanguy Jaffré published his PhD thesis entitled « Etude écologique du peuplement végétal des sols dérivés de roches ultrabasiques en NouvelleCalédonie » (« Ecological study of the plant population of soils derived from ultrabasic rocks in New Caledonia »). Although it was published in French by ORSTOM (now IRD) with limited dissemination, this work has attracted a large and steady number of citations over the years (Figure 1). With this in mind, we thought it would be useful to make this work more accessible to the scientific community as a whole. Thanks to the support of the Société Botanique de France, an English translation is published in this special issue. The three thesis chapters, « les formations végétales des terrains ultrabasiques » (“Plant formations on ultramafic rocks”), « les groupements végétaux des maquis » (“Plant communities of the maquis”), and « phytogéochimie » (“Plant mineral nutrition”) representing about 73% of the pages of the original text, are published as three articles in this special issue. The figures were reformatted and are published in colour for greater clarity. The plant taxonomy was updated following the FLORICAL database (Morat et al. 2012; Munzinger et al. 2023) and the soil classification follows the World Reference Base (IUSS Working Group WRB 2015). Minor alterations to the text were made to avoid anachronisms with the current state of the art on the ecology of ultramafic vegetation and the New Caledonian flora. The first article entitled “Plant formations on ultramafic rocks in New Caledonia” (Jaffré 2023a) starts with a description of three contact zones between ultramafic rocks and other substrates. These suture zones have received little attention since, although they are interesting systems to study. They are known as areas of micro-endemism (Pintaud and Hodel 1998; Pillon et al. 2008; Gâteblé and Munzinger 2018). There, species with distinct soil preferences can co-occur and hybridize, which may trigger speciation (Pillon et al. 2009). The second part of the article describes the main plant formations occurring on ultramafic rocks in New Caledonia. Contrary to many other areas in the world (particularly temperate regions), ultramafic substrates of New Caledonia can harbour dense and diverse forests. The forests of New Caledonia have received significant attention (e.g. Jaffré and Veillon 1995; Ibanez et al. 2014; Birnbaum et al. 2015). The article also mentions several cases of monodominant formations, where one tree species represents a large proportion of the individuals reaching the canopy. A wide diversity of species can be dominant in New Caledonia (Pillon et al. BOTANY LETTERS 2023, VOL. 170, NO. 3, 333–337 https://doi.org/10.1080/23818107.2023.2234432

Purpose The Cunoniaceae are a major component of the New Caledonian flora with 91 endemic species that are highly unusual in that multiple metals are hyperaccumulated in different species. This makes it an ideal model system for studying the nature of the hyperaccumulation phenomenon. Methods X-ray fluorescence spectroscopy (XRF) scanning of all herbarium collections of the Cunoniaceae was undertaken at the Herbarium of New Caledonia to reveal incidences of nickel (Ni) and manganese (Mn) accumulation. Following on, the Mn hyperaccumulating P. reticulata and the Ni hyperaccumulating P. xaragurensis were selected for detailed follow-up investigations using synchrotron-based X-ray fluorescence microscopy (XFM). Results The systematic XRF screening of herbarium specimens showed that numerous species have high foliar Mn and Ni with species either accumulating Ni or Mn, but not both elements simultaneously. Soil 'extractable' Mn and Ni concentrations associated with Pancheria reticulata and P. xaragurensis greatly varies between the species. The XFM data shows that P. reticulata has a distinctive distribution pattern with Mn concentrated in large hypodermal cells. This contrasts with P. xaragurensis where Ni was mainly localized in and around the epidermis, and hypodermal cells were not observed. Conclusions Manganese and Ni accumulation are differently localized in Pancheria species growing on ultramafic soils, which is not explained by contrasting soils conditions, but represents different ecophysiological adaptations.

The remarkable capacity of plants to tolerate and accumulate tremendous amount of nickel is a complex adaptative trait that appeared independently in more than 700 species distributed in about fifty families. Nickel hyperaccumulation is thus proposed as a model to investigate the evolution of complex traits in plants. However, the mechanisms involved in nickel hyperaccumulation are still poorly understood in part because comparative transcriptomic analyses struggle to identify genes linked to this trait from a wide diversity of species. In this work, we have implemented a methodology based on the quantification of the expression of orthologous groups and phylogenetic comparative methods to identify genes which expression is correlated to the nickel hyperaccumulation trait. More precisely, we performed de novo transcriptome assembly and reads quantification for each species on its own transcriptome using available RNA-Seq datasets from 15 nickel hyperaccumulator and non-accumulator species. Assembled contigs were associated to orthologous groups built using proteomes predicted from completed plant genome sequences. We then analyzed the transcription profiles of 5953 orthologous groups from distant species using a phylogenetic ANOVA. We identified 31 orthologous groups with an expression shift associated with nickel hyperaccumulation. These orthologous groups correspond to genes that have been previously implicated in nickel accumulation, and to new candidates involved in this trait. We thus believe that this method can be successfully applied to identify genes linked to other complex traits from a wide diversity of species.

Tackling the complicated infrafamilial classification of the economically important Oleaceae requires a piecemeal approach that addresses generic circumscriptions. Here, focusing on the distinct clade formed by the generic complex Nestegis, Notelaea, Osmanthus, Phillyrea and Picconia in subtribe Oleinae, we aim to elucidate their boundaries and relationships and to evaluate their biogeographic history in light of their peculiar disjunct distribution in the Macaronesian, Mediterranean and Pacific regions. On the basis of phylogenomic data from plastid and nuclear DNA of an extensive sampling, the results show six subclades in this generic complex, which are also geographical segregates found in Australia (Notelaea), Hawaiian Islands (Nestegis sandwicensis), Macaronesia (Phillyrea and Picconia), Mediterranean Region (Phillyrea), New Caledonia (Osmanthus section Notosmanthus) and New Zealand (Nestegis s.s.). Accounting for broad morphological overlaps in this clade, we recognize three genera (Phillyrea, Picconia and Notelaea s.l.), subsuming all Pacific taxa under Notelaea. Molecular dating and biogeographic analyses indicate that this clade originated in Eurasia during the Early Miocene (mean 23.2 Mya, 95% HPD: 23.8-14.7). Finally, dispersal (rather than continental vicariance) is probably the main explanation for the global, disjunct distribution of this group, with island-hopping and local extinction as the hallmarks of its evolutionary history.

Background Relict lineages are an important component of biodiversity, but it is unclear under what circumstances these groups persist. A potential example of such a group is the Alseuosmineae (Asterales) of Oceania. This clade contains the three small families - Alseuosmiaceae, Argophyllaceae and Phellinaceae. The clade has highest diversity in New Caledonia, where there are extensive ultramafic substrates, creating an extreme edaphic environment. Aims Using several lines of evidence we aimed to show that Alseuosmineae qualify as a relict lineage, with specialised adaptations for ultramafic substrates. Methods Molecular phylogenetic and dating analyses were carried out on representatives from all Alseuosmineae genera. Metal concentration in 33 out of 44 Alseuosmineae species was measured in herbarium specimens with X-ray fluorescence spectrometry. Results Dating analyses indicated that Alseuosmineae began diversifying about 75-80 million years ago, and had much slower net diversification rates than other Asterales groups. One-third of the species occur on ultramafic substrates in New Caledonia. Six are categorised as nickel hyperaccumulators, and two as manganese hyperaccumulators. Conclusions Extinction was probably paramount in the history of Alseuosmineae, especially for continental species. We postulate that their adaptation to ultramafic substrates and metal accumulation may have contributed to their survival until today.