Investigadors de l’ IBB participen en un estudi que avala el perill de desaparició de l’espècie Cheirolophus uliginosus

Noticia publicada en la web institucional del Instituto Botánico de Barcelona el 19 de noviembre de 2015 -- Disponibles PDFs en español y catalán y capturas de pantalla de la noticia en la web.Peer reviewe

Key processes for the rapid diversification of Cheirolophus (Asteraceae) on Macaronesian archipelagos

19 p. -- Presentación utilizada para el seminario científico celebrado en el Instituto Botánico de Barcelona el 27 de mayo de 2014.Volcanic islands are excellent natural laboratories to test speciation and diversification hypotheses. For this reason, in the last decades the Macaronesian archipelagos have become a key subject for several evolutionary studies in many diverse plant groups. The genus Cheirolophus (Asteraceae), comprising c. 20 endemic species to the Canary and Madeira archipelagos, represents an ideal study case for discussing diversification on islands. The analyses based on AFLP markers confirmed the evolutionary distinctiveness of these species. Our phylogeographical analyses based on plastidial and nuclear sequences and using the latest Bayesian-based phylogenetic tools indicate that this radiation started c. 2 Mya. It represents one of the most remarkable examples of plant diversification in oceanic islands so far reported. This extraordinary process could be explained by the combined action of allopatric speciation, incipient adaptive radiation and hybridisation. Finally, our results suggest the important role of insularity, geological history, habitat isolation and plant features in generating the rapid diversification of Cheirolophus within such a small area.Peer reviewe

Key processes for the rapid diversification of Cheirolophus (Asteraceae) on Macaronesian archipelagos

19 p. -- Presentación utilizada para el seminario científico celebrado en el Instituto Botánico de Barcelona el 27 de mayo de 2014.Volcanic islands are excellent natural laboratories to test speciation and diversification hypotheses. For this reason, in the last decades the Macaronesian archipelagos have become a key subject for several evolutionary studies in many diverse plant groups. The genus Cheirolophus (Asteraceae), comprising c. 20 endemic species to the Canary and Madeira archipelagos, represents an ideal study case for discussing diversification on islands. The analyses based on AFLP markers confirmed the evolutionary distinctiveness of these species. Our phylogeographical analyses based on plastidial and nuclear sequences and using the latest Bayesian-based phylogenetic tools indicate that this radiation started c. 2 Mya. It represents one of the most remarkable examples of plant diversification in oceanic islands so far reported. This extraordinary process could be explained by the combined action of allopatric speciation, incipient adaptive radiation and hybridisation. Finally, our results suggest the important role of insularity, geological history, habitat isolation and plant features in generating the rapid diversification of Cheirolophus within such a small area.Peer reviewe

Progress in the study of genome size evolution in Asteraceae: analysis of the last update

The Genome Size in Asteraceae database (GSAD, http://www.asteraceaegenomesize.com) has been recently updated, with data from papers published or in press until July 2018. This constitutes the third release of GSAD, currently containing 4350 data entries for 1496 species, which represent a growth of 22.52% in the number of species with available genome size data compared with the previous release, and a growth of 57.72% in terms of entries. Approximately 6% of Asteraceae species are covered in terms of known genome sizes. The number of source papers included in this release (198) means a 48.87% increase with respect to release 2.0. The significant data increase was exploited to study the genome size evolution in the family from a phylogenetic perspective. Our results suggest that the role of chromosome number in genome size diversity within Asteraceae is basically associated to polyploidy, while dysploidy would only cause minor variation in the DNA amount along the family. Among diploid taxa, we found that the evolution of genome size shows a strong phylogenetic signal. However, this trait does not seem to evolve evenly across the phylogeny, but there could be significant scale and clade-dependent patterns. Our analyses indicate that the phylogenetic signal is stronger at low taxonomic levels, with certain tribes standing out as hotspots of autocorrelation between genome size and phylogeny. Finally, we also observe meaningful associations among nuclear DNA content on Asteraceae species and other phenotypical and ecological traits (i.e. plant habit and invasion ability). Overall, this study emphasizes the need to continue generating and analyzing genome size data in order to puzzle out the evolution of this parameter and its many biological correlates

Phylogeographic insights of the lowland species Cheirolophus sempervirens in the southwestern Iberian Peninsula

5 p., gráf, mapasThe southwestern Iberian Peninsula is an important biogeographic region, showing high biodiversity levels and hosting several putative glacial refugia for European flora. Here, we study the genetic diversity and structure of the Mediterranean, thermophilous plant Cheirolophus sempervirens (Asteraceae) across its whole distribution range in SW Iberia, as a tool to disentangle some of the general biogeographic patterns shaping this southern refugia hotspot. Null genetic diversity was observed in the cpDNA sequencing screening. Nonetheless, AFLP data revealed high levels of among-population genetic differentiation correlated to their geographic location. Our results suggest longer species persistence in southern Iberian refugia during glacial periods and subsequent founder effects northwards due to colonizations in warmer stages (i.e., the southern richness to northern purity pattern). Additionally, our phylogeographic analyses indicate the presence of two separate genetic lineages within Ch. sempervirens, supporting the hypothesis of multiple minor refugia for SW Iberia in agreement with the refugia within refugia model.This work has been supported by the Dirección General de Investigación Científica y Técnica (Spanish Government; projects CGL2010-22234-C02-01 and 02/BOS and CGL2013-49097-C2-2-P) and the Generalitat de Catalunya (“Ajuts a grups de recerca consolidats” 2009SGR0439 and 2014SGR514).Peer reviewe

Molecular insights into the diversification of Cheirolophus (Asteraceae) in Macaronesia

Podeu consultar el llibre complet a: http://hdl.handle.net/2445/67430The diversification of Cheirolophus in Macaronesian archipelagos constitutes a paradigmatic example of radiation on oceanic islands. Phylogenetic and molecular dating analyses indicate an extraordinarily fast process, showing one of the highest speciation rates ever found on plants from oceanic islands. Such radiation has been recently studied employing phylogeographic, population genetic and molecular cytogenetic approaches. Here, the main potential patterns and processes involved in the diversification of the genus in the Canary Islands and Madeira are reviewed and discussed as a whole

Genetic structure and seed germination in Portuguese populations of Cheirolophus uliginosus (Asteraceae): Implications for conservation strategies

Cheirolophus uliginosus is a threatened species, endemic to the Atlantic coast of the Iberian Peninsula, where it occupies a few restricted localities. In our study we analysed the patterns of cpDNA haplotypes variation and reproductive success germinability among seven Portuguese populations of varying size. The aim was to examine the reproductive performance of Ch. uliginosus related to genetic structure and population size. The results showed very low within-population variability of cpDNA markers. Our study indicates that the germination rate is significantly reduced in small populations ( 250 individuals) do not show any constraint. In the search for plausible causes explaining the lower germination success in the smallest populations, ecological concerns and genetic isolation must be taken into account. Besides, in large-sized populations of Ch. uliginosus (> 250 plants) a higher incidence of predispersal seed predation was observed, maybe affecting their sexual reproductive response. Finally, smaller populations presenting a reduced reproductive success contain also the most evolutionary distant haplotypes, so their conservation should be a priority

Phylogeography of Dictyota fasciola and Dictyota mediterranea (Dictyotales, Phaeophyceae): unexpected patterns on the Atlantic-Mediterranean marine transition and taxonomic implications

The Atlantic-Mediterranean marine transition is a fascinating biogeographic region, but still very poorly studied from the point of view of seaweed phylogeography. Dictyota fasciola and D. mediterranea (Dictyotales, Phaeophyceae) are two currently recognized sister species that share a large part of their distribution along the Mediterranean Sea and the Atlantic Ocean, representing a unique study model to understand the diversification processes experienced by macroalgae during and after Messinian at this marine region. In this study, we sampled 102 individuals of D. fasciola and D. mediterranea from 32 localities along their distribution range and sequenced the mitochondrial cox1 and the chloroplast rbcL-rbcS DNA regions for all the samples. Our data do not support the occurrence of two sister species but a morphologically variable and highly genetic diverse species or a complex of species. Most of the observed genetic diversity corresponds to the Mediterranean populations, whereas the Atlantic ones are much more homogeneous. The early-diverged lineages inferred from both mtDNA and cpDNA phylogenetic reconstructions were constituted by samples from the Mediterranean Sea. Together, these results suggest that the Mediterranean Sea acted as a refugium for the D. fasciola-D. mediterranea lineage during the geologic and climatic changes occurred on the region since the Miocene, subsequently dispersing to the Atlantic Ocean

The explosive radiation of Cheirolophus (Asteraceae, Cardueae) in Macaronesia

Considered a biodiversity hotspot, the Canary Islands have been the key subjects of numerous evolutionary studies concerning a large variety of organisms. The genus Cheirolophus (Asteraceae) represents one of the largest plant radiations in the Canarian archipelago. In contrast, only a few species occur in the Mediterranean region, the putative ancestral area of the genus. Here, our main aim was to reconstruct the phylogenetic and biogeographic history of Cheirolophus with special focus on explaining the origin of the large Canarian radiation. Results: We found significant incongruence in phylogenetic relationships between nuclear and plastid markers. Each dataset provided resolution at different levels in Cheirolophus: the nuclear markers resolved the backbone of the phylogeny while the plastid data provided better resolution within the Canarian clade. The origin of Cheirolophus was dated in the Mid-Late Miocene, followed by rapid diversification into the three main Mediterranean lineages and the Macaronesian clade. A decrease in diversification rates was inferred at the end of the Miocene, with a new increase in the Late Pliocene concurrent with the onset of the Mediterranean climate. Diversification within the Macaronesian clade started in the Early-Mid Pleistocene, with unusually high speciation rates giving rise to the extant insular diversity. Conclusions: Climate-driven diversification likely explains the early evolutionary history of Cheirolophus in the Mediterranean region. It appears that the exceptionally high diversification rate in the Canarian clade was mainly driven by allopatric speciation (including intra-and interisland diversification). Several intrinsic (e.g. breeding system, polyploid origin, seed dispersal syndrome) and extrinsic (e.g. fragmented landscape, isolated habitats, climatic and geological changes) factors probably contributed to the progressive differentiation of populations resulting in numerous microendemisms. Finally, hybridization events and emerging ecological adaptation may have also reinforced the diversification process

Contribution to the knowledge of genome size evolution in edible blueberries (genus Vaccinium)

BACKGROUND: Vaccinium is one of the largest genera (ca. 500 species) of Ericaceae, well known for its edible and ornamental uses. Although there is certain karyological knowledge, information about genome size (GS) is scarce in the genus. OBJECTIVE: The main goal is providing GS data for several Vaccinium species with prevalence in Europe and Western Asia and analysing global GS variation in the genus, considering available data and phylogenetic context. METHODS: New GS assessments were obtained by flow cytometry and chromosome counts were verified. Phylogenetic analyses (using nuclear ITS, and chloroplastic matK and ndhF) were performed by Bayesian inference and reconstruction of ancestral GS by maximum parsimony. RESULTS: We obtained GS data for five Vaccinium species (13 populations). Three species are reported for the first time. Values (2C) ranged between 1.16-1.47 pg at the diploid (2n = 24) and between 3.13-3.16 pg at the tetraploid (2n = 48) levels. The five species here investigated have been placed and analysed in a reconstructed phylogenetic background (including 68 taxa). CONCLUSIONS: GS values of Vaccinium can be considered "very small". The preliminary reconstruction of ancestral GS would point to a reduction in Vaccinium, although more data is needed to establish global GS evolutionary trend in the genus