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Valcarcel V.,Pablo De Olavide University | Vargas P.,Real Jardin Botanico de Madrid
American Journal of Botany

Premise of the study: The use of continuous morphological characters in taxonomy is traditionally contingent on the existence of discrete diagnostic characters. When plant species are the result of recent divergence and gene flow and/or hybridization occur, the use of continuous morphological characters may help in species identification and delimitation. Between nine and 15 species have been recognized in the last treatments of Hedera. The recent divergence of the species and the involvement of allopolyploidization as the main force in this process may have greatly impeded the establishment of clear limits and contributed to multiple taxonomic proposals. Methods: A multivariate statistical decision-making procedure was applied to 56 quantitative morphological characters and 602 specimens to identify and delimit Hedera species under the general lineage concept. Species' exclusive genetic ancestry was evaluated with the genealogical sorting index from the Bayesian inference trees of 30 Hedera ITS sequences. Key results: The decision-making procedure allowed recognizing 12 species and two groups (stellate and scale-like trichome groups) in Hedera and provided statistical support for making decisions about long-standing taxonomic controversies. Common ancestry was detected for the populations of three species even in the absence of the species monophyly. Conclusions: Quantitative variation supports discrete variation and provides statistical support for the taxa recognized in some recent proposals of Hedera. The need of explicit analysis of quantitative data are claimed to reduce taxonomic subjectivity and ease decision-making when qualitative data fail. © 2010 Botanical Society of America. Source

Valente L.M.,Imperial College London | Vargas P.,Real Jardin Botanico de Madrid
Journal of Biogeography

Aim: The Cape of southern Africa and the Mediterranean Basin, two of the world's five mediterranean-climate biodiversity hotspots, are exceptionally species-rich and constitute a well-described example of ecological convergence. However, the area-adjusted plant species diversity of the Cape is on average more than double that of the Mediterranean Basin. Here, we investigate the causes of this diversity asymmetry by drawing on phylogenetic information from a variety of plant groups and focusing on three competing hypotheses: diversity disparities arising from differential clade ages, diversification rates or diversity limits. Location: Cape of southern Africa and the Mediterranean Basin. Methods: We reviewed a variety of studies in order to contrast the geography, geomorphic history, biogeographical connectivity and ecological context in the two hotspots. We also tested the relationship between clade age and species richness in both regions based on phylogenetic information from 39 clades. Results: Clades are on average older in the Cape than in the Mediterranean Basin. Clade age is a strong predictor of species diversity in the Cape, suggesting that diversity-dependent regulatory mechanisms may be weak. In contrast, we failed to find a relationship between age and diversity in the Mediterranean Basin, indicating that a diversity limit may have been achieved in multiple clades. Main conclusions: The Cape has a higher species density than the Mediterranean Basin owing to a combination of older clade ages, high rates of diversification in certain lineages and an exceptionally high upper limit to diversity. High richness in the Cape is linked to long-term lineage persistence in a heterogeneous but stable evolutionary context. In contrast, the climatically unstable Mediterranean Basin has offered fewer opportunities for diversity accumulation in the long term (owing to high extinction rates), but appears to be a hotspot of recent rapid speciation. © 2013 John Wiley & Sons Ltd. Source

Garcia-Verdugo C.,University of California at Berkeley | Calleja J.A.,Autonomous University of Madrid | Vargas P.,Real Jardin Botanico de Madrid | Silva L.,University of The Azores | And 2 more authors.
Molecular Ecology

Refugia are expected to preserve genetic variation of relict taxa, especially in polyploids, because high gene dosages could prevent genetic erosion in small isolated populations. However, other attributes linked to polyploidy, such as asexual reproduction, may strongly limit the levels of genetic variability in relict populations. Here, ploidy levels and patterns of genetic variation at nuclear microsatellite loci were analysed in Prunus lusitanica, a polyploid species with clonal reproduction that is considered a paradigmatic example of a Tertiary relict. Sampling in this study considered a total of 20 populations of three subspecies: mainland lusitanica (Iberian Peninsula and Morocco), and island azorica (Azores) and hixa (Canary Islands and Madeira). Flow cytometry results supported an octoploid genome for lusitanica and hixa, whereas a 16-ploid level was inferred for azorica. Fixed heterozygosity of a few allele variants at most microsatellite loci resulted in levels of allelic diversity much lower than those expected for a high-order polyploid. Islands as a whole did not contain higher levels of genetic variation (allelic or genotypic) than mainland refuges, but island populations displayed more private alleles and higher genotypic diversity in old volcanic areas. Patterns of microsatellite variation were compatible with the occurrence of clonal individuals in all but two island populations, and the incidence of clonality within populations negatively correlated with the estimated timing of colonization. Our results also suggest that gene flow has been very rare among populations, and thus population growth following founder events was apparently mediated by clonality rather than seed recruitment, especially in mainland areas. This study extends to clonal taxa the idea of oceanic islands as important refugia for biodiversity, since the conditions for generation and maintenance of clonal diversity (i.e. occasional events of sexual reproduction, mutation and/or seed immigration) appear to have been more frequent in these enclaves than in mainland areas. © 2013 Blackwell Publishing Ltd. Source

Escudero M.,Pablo De Olavide University | Vargas P.,Real Jardin Botanico de Madrid | Arens P.,Plant Research International | Ouborg N.J.,Radboud University Nijmegen | LuceNo M.,Pablo De Olavide University
Molecular Ecology

Coastal plants are ideal models for studying the colonization routes of species because of the simple linear distributions of these species. Carex extensa occurs mainly in salt marshes along the Mediterranean and European coasts. Variation in cpDNA sequences, amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs) of 24 populations were analysed to reconstruct its colonization history. Phylogenetic relationships indicate that C. extensa together with the South American Carex vixdentata and the southern African Carex ecklonii form a monophyletic group of halophilic species. Analyses of divergence times suggest that early lineage diversification may have occurred between the late Miocene and the late Pliocene (Messinian crisis). Phylogenetic and network analyses of cpDNA variation revealed the monophyly of the species and an ancestral haplotype contained in populations of the eastern Mediterranean. The AFLP and SSR analyses support a pattern of variation compatible with these two lineages. These analyses also show higher levels of genetic diversity and differentiation in the eastern population group, which underwent an east-to-west Mediterranean colonization. Quaternary climatic oscillations appear to have been responsible for the split between these two lineages. Secondary contacts may have taken place in areas near the Ligurian Sea in agreement with the gene flow detected in Corsican populations. The AFLP and SSR data accord with the 'tabula rasa' hypothesis in which a recent and rapid colonization of northern Europe took place from the western Mediterranean after the Last Glacial Maximum. The unbalanced west-east vs. west-north colonization may be as a result of 'high density blocking' effect. © 2009 Blackwell Publishing Ltd. Source

Lado C.,Real Jardin Botanico de Madrid | Wrigley De Basanta D.,Real Jardin Botanico de Madrid | Estrada-Torres A.,University of Tlaxcala | Stephenson S.L.,University of Arkansas
Fungal Diversity

The results obtained from two expeditions to survey the biodiversity of myxomycetes in Central Chile are reported in this paper. The surveys were carried out as part of Global Biodiversity of Eumycetozoans project funded by the National Science Foundation (USA) and the Myxotropic project funded by the Spanish Government. The expeditions were made to the temperate zone of the central part of the country between 23 and 39 South latitudes, which is characterized by Mediterranean vegetation, as well as to the transition areas between the arid and semi-arid regions of northern Chile, and the humid, cold Valdivian and Andean-Patagonian forests of the far South. Eight of the fifteen regions of the country, from Antofagasta to Araucanía, in selected areas where the native vegetation is well preserved, were included in these surveys. Over 600 collections were obtained, and a total of 110 species of myxomycetes representing 29 genera have been identified. Two of these (Dianema succulenticola, Didymium chilense) are species new to science and are described in this paper, 12 species (Collaria nigricapillitia, Comatricha alta, Cribraria oregana, Dianema depressum, Didymium eximium, D. nivicolum, Enerthenema melanospermum, Lepidoderma chailletii, Macbrideola ovoidea, Physarum clavisporum, Ph. newtonii and Trichia alpina) were previously unknown for either the Neotropics or South America, and 49 additional species are new records for Chile. Comments are provided on the morphology, distribution and ecology of selected species and light and SEM micrographs of the most significant species are included. An evaluation of the biodiversity of myxomycetes in Chile, with special emphasis on the endemic plants that provided the substrates with which they were associated, and a comparative analysis of our results with those from other countries of South America is presented. © 2012 The Mushroom Research Foundation. Source

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