Smooth actions of connected compact Lie groups with a free point are determined by two vector fields

Consider a smooth action $\mathbf G\times M \rightarrow M$ of a compact connected Lie group $\mathbf G$ on a connected manifold $M$. Assume the existence of a point of $M$ whose isotropy group has a single element (free point). Then we prove that there exist two complete vector field $X,X_1$ such that their group of automorphisms equals $\mathbf G$ regarded as a group of diffeomorphisms of $M$ (the existence of a free point implies that the action of $\mathbf G$ is effective). Moreover, some examples of effective actions with no free point where this result fails are exhibited.Comment: 30 pages, no figures. V2: Major revision. Exposition improved and added a new section presenting some open question

Latitudinal environmental niches and riverine barriers shaped the phylogeography of the central Chilean endemic Dioscorea humilis (Dioscoreaceae)

The effects of Pleistocene glaciations and geographical barriers on the phylogeographic patterns of lowland plant species in Mediterranean-climate areas of Central Chile are poorly understood. We used Dioscorea humilis (Dioscoreaceae), a dioecious geophyte extending 530 km from the Valparaíso to the Bío-Bío Regions, as a case study to disentangle the spatio-temporal evolution of populations in conjunction with latitudinal environmental changes since the Last Inter-Glacial (LIG) to the present. We used nuclear microsatellite loci, chloroplast (cpDNA) sequences and environmental niche modelling (ENM) to construct current and past scenarios from bioclimatic and geographical variables and to infer the evolutionary history of the taxa. We found strong genetic differentiation at nuclear microsatellite loci between the two subspecies of D. humilis, probably predating the LIG. Bayesian analyses of population structure revealed strong genetic differentiation of the widespread D. humilis subsp. humilis into northern and southern population groups, separated by the Maipo river. ENM revealed that the ecological niche differentiation of both groups have been maintained up to present times although their respective geographical distributions apparently fluctuated in concert with the climatic oscillations of the Last Glacial Maximum (LGM) and the Holocene. Genetic data revealed signatures of eastern and western postglacial expansion of the northern populations from the central Chilean depression, whereas the southern ones experienced a rapid southward expansion after the LGM. This study describes the complex evolutionary histories of lowland Mediterranean Chilean plants mediated by the summed effects of spatial isolation caused by riverine geographical barriers and the climatic changes of the Quaternary

Museomics Unveil the Phylogeny and Biogeography of the Neglected Juan Fernandez Archipelago Megalachne and Podophorus Endemic Grasses and Their Connection With Relict Pampean-Ventanian Fescues

Oceanic islands constitute natural laboratories to study plant speciation and biogeographic patterns of island endemics. Juan Fernandez is a southern Pacific archipelago consisting of three small oceanic islands located 600–700 km west of the Chilean coastline. Exposed to current cold seasonal oceanic climate, these 5.8–1 Ma old islands harbor a remarkable endemic flora. All known Fernandezian endemic grass species belong to two genera, Megalachne and Podophorus, of uncertain taxonomic adscription. Classical and modern classifications have placed them either in Bromeae (Bromus), Duthieinae, Aveneae/Poeae, or Loliinae (fine-leaved Festuca); however, none of them have clarified their evolutionary relationships with respect to their closest Festuca relatives. Megalachne includes four species, which are endemic to Masatierra (Robinson Crusoe island) (M. berteroniana and M. robinsoniana) and to Masafuera (Alejandro Selkirk island) (M. masafuerana and M. dantonii). The monotypic Podophorus bromoides is a rare endemic species to Masatierra which is only known from its type locality and is currently considered extinct. We have used museomic approaches to uncover the challenging evolutionary history of these endemic grasses and to infer the divergence and dispersal patterns from their ancestors. Genome skimming data were produced from herbarium samples of M. berteroniana and M. masafuerana, and the 164 years old type specimen of P. bromoides, as well as for a collection of 33 species representing the main broad- and fine-leaved Loliinae lineages. Paired-end reads were successfully mapped to plastomes and nuclear ribosomal cistrons of reference Festuca species and used to reconstruct phylogenetic trees. Filtered ITS and trnTLF sequences from these genomes were further combined with our large Loliinae data sets for accurate biogeographic reconstruction. Nuclear and plastome data recovered a strongly supported fine-leaved Fernandezian clade where Podophorus was resolved as sister to Megalachne. Bayesian divergence dating and dispersal-extinction-cladogenesis range evolution analyses estimated the split of the Fernandezian clade from its ancestral southern American Pampas-Ventanian Loliinae lineage in the Miocene-Pliocene transition, following a long distance dispersal from the continent to the uplifted volcanic palaeo-island of Santa Clara-Masatierra. Consecutive Pliocene-Pleistocene splits and a Masatierra-to-Masafuera dispersal paved the way for in situ speciation of Podophorus and Megalachne taxa

Corrigendum: Museomics Unveil the Phylogeny and Biogeography of the Neglected Juan Fernandez Archipelago Megalachne and Podophorus Endemic Grasses and Their Connection With Relict Pampean-Ventanian Fescues

In the original article, there was amistake in Table 1, Figures 2A, 2B, 3A, 3B and 5, Supplementary Figures 1A, 1B, 1C, 1D, 2A, 2B, 2C and 3, and Supplementary Tables 1 and 2A as published. The name and authorship of Festuca fontqueri St-Yves were misspelled as Festuca fontqueriana (St-Yves) Romo. In addition, the GenBank accession codes of ITS, trnLF and trnTL DNA sequences of Avena fatua, Oryza sativa, Poa alpina, Secale cereale and Triticum aestivum were wrong in Supplementary Table 1. The corrected Table 1, Figures 2A, 2B, 3A, 3B and 5 appear below and corrected Supplementary Figures 1A, 1B, 1C, 1D, 2A, 2B, 2C and 3, and Supplementary Tables 1 and 2A are published. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated. © 2021 Moreno-Aguilar, Arnelas, Sánchez-Rodríguez, Viruel and Catalán

Diversification into novel habitats in the Africa clade of Dioscorea (Dioscoreaceae): erect habit and elephant's foot tubers

Background: Dioscorea is a widely distributed and highly diversified genus in tropical regions where it is represented by ten main clades, one of which diversified exclusively in Africa. In southern Africa it is characterised by a distinct group of species with a pachycaul or "elephant''s foot" structure that is partially to fully exposed above the substrate. In contrast to African representatives of the genus from other clades, occurring mainly in forest or woodland, the pachycaul taxa and their southern African relatives occur in diverse habitats ranging from woodland to open vegetation. Here we investigate patterns of diversification in the African clade, time of transition from forest to more open habitat, and morphological traits associated with each habitat and evaluate if such transitions have led to modification of reproductive organs and mode of dispersal. Results: The Africa clade originated in the Oligocene and comprises four subclades. The Dioscorea buchananii subclade (southeastern tropical Africa and South Africa) is sister to the East African subclade, which is respectively sister to the recently evolved sister South African (e. g., Cape and Pachycaul) subclades. The Cape and Pachycaul subclades diversified in the east of the Cape Peninsula in the mid Miocene, in an area with complex geomorphology and climate, where the fynbos, thicket, succulent karoo and forest biomes meet. Conclusions: Diversification out of forest is associated with major shifts in morphology of the perennial tuber (specifically an increase in size and orientation which presumably led them to become pachycaul) and rotation of stem (from twining to non-twining). The iconic elephant''s foot morphology, observed in grasslands and thicket biomes, where its corky bark may offer protection against fire and herbivory, evolved since mid Miocene. A shift in pollination trait is observed within the forest, but entry into open habitat does not show association with reproductive morphology, except in the seed wing, which has switched from winged all round the seed margin to just at the base or at the apex of it, or has been even replaced by an elaiosome

Genome-wide footprints in the carob tree (Ceratonia siliqua) unveil a new domestication pattern of a fruit tree in the Mediterranean

Intense research efforts over the last two decades have renewed our understanding of plant phylogeography and domestication in the Mediterranean basin. Here we aim to investigate the evolutionary history and the origin of domestication of the carob tree (Ceratonia siliqua), which has been cultivated for millennia for food and fodder. We used >1000 microsatellite genotypes to delimit seven carob evolutionary units (CEUs). We investigated genome-wide diversity and evolutionary patterns of the CEUs with 3557 single nucleotide polymorphisms generated by restriction-site associated DNA sequencing (RADseq). To address the complex wild vs. cultivated status of sampled trees, we classified 56 sampled populations across the Mediterranean basin as wild, seminatural or cultivated. Nuclear and cytoplasmic loci were identified from RADseq data and separated for analyses. Phylogenetic analyses of these genomic-wide data allowed us to resolve west-to-east expansions from a single long-term refugium probably located in the foothills of the High Atlas Mountains near the Atlantic coast. Our findings support multiple origins of domestication with a low impact on the genetic diversity at range-wide level. The carob was mostly domesticated from locally selected wild genotypes and scattered long-distance westward dispersals of domesticated varieties by humans, concomitant with major historical migrations by Romans, Greeks and Arabs. Ex situ efforts to preserve carob genetic resources should prioritize accessions from both western and eastern populations, with emphasis on the most differentiated CEUs situated in southwest Morocco, south Spain and eastern Mediterranean. Our study highlights the relevance of wild and seminatural habitats in the conservation of genetic resources for cultivated trees