Alessandro Rapini

Asclepiadeae classification: evaluating the phylogenetic relationships of New World Asclepiadoideae (Apocynaceae)

To provide an overview of New World Asclepiadoideae, we here evaluate Asclepiadeae classification by comparing the taxonomic arrangement of subtribes with a topology obtained through analyses of two plastid DNA regions (trnL intron and trnL-F intergenic spacer) for 111 species of Asclepiadoideae representing the major lineages of the subfamily. Without Jobinia, Nephradenia and Barjonia, Asclepiadeae are not monophyletic. The monotypic African genus Eustegia, with pendent pollinia, may represent the sister clade of MarsdenieaeCeropegieae, the group composed of plants with erect pollinia. Metastelmatinae including African plants are also non-monophyletic, and the circumscription of the recently re-instated Cynanchinae should be studied further. Overall, Asclepiadeae are composed of three main clades. The Old World Astephaninae are the sister group of the other Asclepiadeae, which are divided into the ACTG (Asclepiadinae, Cynanchinae, Tylophorinae and Glossonematinae) and MOG (Metastelmatinae, Oxypetalinae and Gonolobinae) clades. According to this study, the New World Asclepiadoideae fall into just four clades: (1) Marsdenia(Marsdenieae), (2) Asclepias (Asclepiadinae, Asclepiadeae), (3) Cynanchum subgenus Mellichampia(Cynanchinae, Asclepiadeae), and (4) MOG, the clade comprising the majority of New World Asclepiadoideae.

Phylogenetics of the New World Subtribes of Asclepiadeae (Apocynaceae—Asclepiadoideae): Metastelmatinae, Oxypetalinae, and Gonolobinae

Abstract Analysis of the trnT-trnL spacer, the trnL intron, the trnL-trnF spacer, and the rps16 intron of 106 species in 34 of the 45 genera of New World Asclepiadeae in the former subtribes Metastelmatinae, Oxypetalinae, and Gonolobinae shows that these genera form a well-supported clade (“MOG”). The small Andean genus Pentacyphus is sister to the remaining MOG clade. The former Gonolobinae form a well-supported subclade closely related to members of Tassadia, Funastrum, and former Oxypetalinae. The only genera that are monophyletic as presently circumscribed are Tassadia and Funastrum. The separation of Tweedia from Oxypetalum is justified by our results. Philibertia is monophyletic only if Amblystigma, Fontellaea, Melinia, Mitostigma, and Podandra are also included. Most species of Blepharodon and Hemipogon are not monophyletic with the respective type species. Some former Astephanus and Cynanchum species as well as the monotypic Grisebachiella are imbedded in Diplolepis (D. descolei, D. geminiflora, D. hieronymi, D. boerhaviifolia, and D. nummulariifolia). The neglected tribe Orthosieae is recognized at subtribal level, Orthosiinae. Chromosome numbers (as far as known) indicate a tendency for reduction in several clades. This study provides a framework for future study of the American MOG genera and highlights areas that need further attention.

DIVERSIFICATION OF ASCLEPIADOIDEAE (APOCYNACEAE) IN THE NEW WORLD1

Abstract Plastid sequences of trnL-F are used to estimate the age of biogeographical events in New World Asclepiadoideae. These data suggest that the subfamily arose somewhere in the Old World in the Late Eocene (40 million years ago (Ma)) and that there were at least four independent episodes of dispersal to the New World. The MOG clade, comprising Metastelmatinae, Oxypetalinae, and Gonolobinae, probably colonized South America through transoceanic dispersal from Africa at 32 Ma. The three subtribes emerged at 24 Ma, radiating 15–16 Ma. Cynanchum L. subg. Mellichampia (A. Gray) Woodson (Cynanchinae) only arrived in the New World at 24 Ma and has since diversified gradually. Asclepias L. (Asclepiadinae) probably arrived in the New World through the Bering Strait at 20 Ma, dispersing to South America before the emergence of the Isthmus of Panama. More recently, tropical Marsdenia R. Br. (Marsdenineae) probably arrived in the New World by long-distance dispersal at 16 Ma. Most diversification in New World Asclepiadoideae is estimated to have occurred during the Miocene. The synchrony of events suggests an environmental influence on the diversification of the lineages. Nevertheless, individual rates of diversification point out the importance of intrinsic factors.

Phylogenetics of South American Asclepiadoideae (Apocynaceae)

According to analyses of plastid DNA, New World Asclepiadoideae (Apocynaceae) fall into four clades; most species, however, are included in just one clade endemic to the New World that comprises Metastelmatinae, Oxypetalinae and Gonolobinae (the MOG clade). Looking for better support and resolution inside the MOG core group, we sequenced the nuclear ribosomal DNA region ITS and increased the number of plastid regions (trnS-G and matK) sequenced. Because of high levels of intra-individual polymorphisms and complex alignment among subtribes, ITS could not be used at the subtribal level. According to combined analysis of the plastid regions, Blepharodon lineare and Funastrum clausum are confirmed as sister group to the rest of Metastelmatinae and Oxypetalinae, respectively. The analysis indicates that Ditassa is polyphyletic. A highly supported clade composed of shrubby species with minute leaves that were traditionally classified in Ditassa comes out as sister to the rest of the subtribe apart from B. lineare. These data clearly support the recognition of a new genus in Metastelmatinae.

Amazon plant diversity revealed by a taxonomically verified species list

Significance Large floristic datasets that purportedly represent the diversity and composition of the Amazon tree flora are being widely used to draw conclusions about the patterns and evolution of Amazon plant diversity, but these datasets are fundamentally flawed in both their methodology and the resulting content. We have assembled a comprehensive dataset of Amazonian seed plant species from published sources that includes falsifiable data based on voucher specimens identified by taxonomic specialists. This growing list should serve as a basis for addressing the long-standing debate on the number of plant species in the Amazon, as well as for downstream ecological and evolutionary analyses aimed at understanding the origin and function of the exceptional biodiversity of the vast Amazonian forests. Recent debates on the number of plant species in the vast lowland rain forests of the Amazon have been based largely on model estimates, neglecting published checklists based on verified voucher data. Here we collate taxonomically verified checklists to present a list of seed plant species from lowland Amazon rain forests. Our list comprises 14,003 species, of which 6,727 are trees. These figures are similar to estimates derived from nonparametric ecological models, but they contrast strongly with predictions of much higher tree diversity derived from parametric models. Based on the known proportion of tree species in neotropical lowland rain forest communities as measured in complete plot censuses, and on overall estimates of seed plant diversity in Brazil and in the neotropics in general, it is more likely that tree diversity in the Amazon is closer to the lower estimates derived from nonparametric models. Much remains unknown about Amazonian plant diversity, but this taxonomically verified dataset provides a valid starting point for macroecological and evolutionary studies aimed at understanding the origin, evolution, and ecology of the exceptional biodiversity of Amazonian forests.

Centres of Endemism in the Espinhaço Range: identifying cradles and museums of Asclepiadoideae (Apocynaceae)

Although the high diversity of neotropical plants is often associated with rain forests, another important location is open vegetation at mountain tops. In the present study, we investigated the phytogeographic patterns of the Espinhaço Range, in eastern Brazil, a region characterized by campos rupestres and marked by high levels of plant richness and endemism. Based on the occurrence of Asclepiadoideae (Apocynaceae) in a grid of 0.5º × 0.5º cells, we conducted cluster analyses and parsimony analysis of endemicity (PAE). We also calculated indexes of diversity and endemism and examined the distribution of palaeo- and neo-endemics. According to our data, the topographic gap between the Espinhaço Range of Minas Gerais and Bahia seems to be an important constraint for the dispersion of endemics, and the floristic similarity between northern Minas Gerais and Bahia is a result of species with broad distribution. Based on the seven areas of endemism that emerged from PAE, we defined five principal centres of endemism in the Espinhaço Range, including the region comprising Serra do Cipó and the Diamantina Plateau, in Minas Gerais, as the major Asclepiadoideae cradle, and Chapada Diamantina, in Bahia, as an Asclepiadoideae museum.

Spatial analyses of the phylogenetic diversity of Minaria (Apocynaceae): assessing priority areas for conservation in the Espinhaço Range, Brazil

The protection of areas that shelter high evolutionary diversity represented by geographically and phylogenetically isolated lineages is becoming an important conservation strategy. Nevertheless, the spatial distribution of this component of biodiversity is still unknown for most groups, which limits its application for selecting priority areas to conserve. In the present study, we reconstructed the phylogeny of Minaria (Apocynaceae) based on plastid (trnH-psbA, rps16, trnS-trnG and trnD-trnT) and nuclear (ITS and ETS) DNA markers and 34 morphological characters, and analysed the geographic distribution of the phylogenetic diversity (PD) and endemism (PE) in this genus. Minaria includes 21 species that are highly concentrated in the Espinhaço Range, in eastern Brazil, most of which (∼75%) are narrowly distributed. The spatial analyses of PD and PE of Minaria indicate four evolutionary relevant areas in this region. The Serra do Cipó and the Diamantina Plateau contain 10 endemic species and present the highest levels of PD. However, the two other areas also deserve special attention. Rio de Contas has high levels of PE, because of two endemic sister species that represent a phylogenetically isolated lineage and the Southern Espinhaço Range houses the most critically endangered species of the genus. Most endemic species of Minaria occur in vegetation islands on rocky outcrops (campos rupestres). These low-fuel areas are less susceptible to fire, suggesting that the Espinhaço Range has served as a historical refuge for fire-sensitive lineages. Our results suggest that conservation units in the Espinhaço Range cover a great proportion of the evolutionary diversity of Minaria and that fire management is probably an important strategy to preserve this endemic biodiversity.

Taxonomic Considerations on Metastelmatinae (Apocynaceae) Based on Plastid and Nuclear DNA

Abstract The Metastelmatinae (Asclepiadoideae, Apocynaceae) include 13 genera and approximately 260 species with complex morphological affinities that are broadly distributed in the Neotropics. This study investigated phylogenetic relationships within this subtribe using plastid (trnT-F, trnS-G, trnH-psbA, trnD-T, rps16, and matK) and nuclear (ITS) markers. The taxonomic sampling focused on the South American species, and included approximately 25% of the subtribe. Individual data partitions, and combined datasets were analyzed using Bayesian inference, maximum likelihood, and maximum parsimony. The results indicated that most genera of Metastelmatinae are not monophyletic. Internal relationships in the subtribe and key morphological characters used in the taxonomy of the group are discussed. The lack of resolution in the molecular phylogeny, incongruent phylogenetic signals between plastid and nuclear datasets, and the lack of morphological features for individual clades prevented major taxonomic changes in this group, those of which were restricted to the inclusion of Barjonia harleyi and Hemipogon harleyi into Minaria forming the new combinations Minaria harleyi and M. volubilis , and the synonymy of Macroditassa under Peplonia with the new combinations Peplonia adnata and P. macrophylla .

The new genus Minaria (Asclepiadoideae, Apocynaceae)

Combined analyses of plastid regions indicate that the genus Ditassa (Asclepiadoideae, Apocynaceae) is polyphyletic and reveal a highly supported clade composed of shrubby species with minute leaves. These molecular data provide clear support for the recognition of a segregate genus from Ditassa, which we propose here as Minaria. Keys to distinguish Minaria from closely related genera and to identify the species of Minaria are provided. Eighteen nomenclatural combinations are proposed and the new species M. campanuliflora is described. The new genus is centred on eastern Brazil with two more widely distributed species extending as far as eastern Bolivia and NE Argentina. All the species occur in the state of Minas Gerais, Brazil, and it is from Minas that the name is derived; fourteen are endemic to the Espinhaco Range, and most are narrow endemics.

Plant diversification in the Espinhaço Range: Insights from the biogeography of Minaria (Apocynaceae)

The Espinhaco Range, eastern Brazil, is a region with remarkable floristic diversity and endemism, which are mainly concentrated in the campo rupestre. Minaria (Apocynaceae) is a genus with 21 species, most of which are endemic to the Espinhaco Range. In the present study, we investigated the biogeography of Minaria as the basis for understanding the origin and maintenance of plant diversity and endemism in the campo rupestre of the Espinhaco Range. We assessed the ecological divergence between clades, reconstructed the historical biogeography and dated the phylogeny of Minaria based on plastid and nuclear DNA. According to our estimates, Minaria arose in the Espinhaco Range during the Neogene. Its distribution is postulated to have been driven by a trend toward long-term retraction, interrupted by a few episodes of expansion. Ecologically, Minaria species do not present any obvious innovations that could explain their diversification by adaptive radiation. Appar- ently, the higher-altitude rocky savannas in the Espinhaco Range have offered stable environments in which dry seasons and fire regimes are less intense than in savannas at lower altitudes. Isolated on rocky outcrops, lineages would be more likely to differentiate by non-adaptive radiation, which may result in high plant diversity and endemism.