Genetically Depauperate in the Continent but Rich in Oceanic Islands: Cistus monspeliensis (Cistaceae) in the Canary Islands

BACKGROUND: Population genetic theory holds that oceanic island populations are expected to have lower levels of genetic variation than their mainland counterparts, due to founder effect after island colonization from the continent. Cistus monspeliensis (Cistaceae) is distributed in both the Canary Islands and the Mediterranean region. Numerous phylogenetic results obtained in the last years allow performing further phylogeographic analyses in Cistus. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed sequences from multiple plastid DNA regions in 47 populations of Cistus monspeliensis from the Canary Islands (21 populations) and the Mediterranean basin (26 populations). The time-calibrated phylogeny and phylogeographic analyses yielded the following results: (1) a single, ancestral haplotype is distributed across the Mediterranean, whereas 10 haplotypes in the Canary Islands; (2) four haplotype lineages are present in the Canarian Islands; (3) multiple colonization events across the archipelago are inferred; (4) the earliest split of intraspecific lineages occurred in the Early to Middle Pleistocene (<930,000 years BP). CONCLUSIONS/SIGNIFICANCE: The contrasting pattern of cpDNA variation is best explained by genetic bottlenecks in the Mediterranean during Quaternary glaciations, while the Canarian archipelago acted as a refugium of high levels of genetic diversity. Active colonization across the Canarian islands is supported not only by the distribution of C. monspeliensis in five of the seven islands, but also by our phylogeographic reconstruction in which unrelated haplotypes are present on the same island. Widespread distribution of thermophilous habitats on every island, as those found throughout the Mediterranean, has likely been responsible for the successful colonization of C. monspeliensis, despite the absence of a long-distance dispersal mechanism. This is the first example of a plant species with higher genetic variation among oceanic island populations than among those of the continent

The genomic basis of the plant island syndrome in Darwin’s giant daisies

Artículo escrito por un elevado número de autores. Solo se referencia el que aparece en primer lugar, el nombre del grupo de colaboración si hubiere y los autores pertenecientes a la UAMThe repeated, rapid and often pronounced patterns of evolutionary divergence observed in insular plants, or the ‘plant island syndrome’, include changes in leaf phenotypes, growth, as well as the acquisition of a perennial lifestyle. Here, we sequence and describe the genome of the critically endangered, Galápagos-endemic species Scalesia atractyloides Arnot., obtaining a chromosome-resolved, 3.2-Gbp assembly containing 43,093 candidate gene models. Using a combination of fossil transposable elements, k-mer spectra analyses and orthologue assignment, we identify the two ancestral genomes, and date their divergence and the polyploidization event, concluding that the ancestor of all extant Scalesia species was an allotetraploid. There are a comparable number of genes and transposable elements across the two subgenomes, and while their synteny has been mostly conserved, we find multiple inversions that may have facilitated adaptation. We identify clear signatures of selection across genes associated with vascular development, growth, adaptation to salinity and flowering time, thus finding compelling evidence for a genomic basis of the island syndrome in one of Darwin’s giant daisiesThis work was supported by the Norwegian Research Council via project number 287327 awarded to M.D.M., and a travel grant (project number 287327) granted to J.Ce. and M.D.M

Evolution of nectar spur length in a clade of Linaria reflects changes in cell division rather than in cell expansion.

BACKGROUND AND AIMS: Nectar spurs (tubular outgrowths of a floral organ which contain, or give the appearance of containing, nectar) are hypothesized to be a 'key innovation' which can lead to rapid speciation within a lineage, because they are involved in pollinator specificity. Despite the ecological importance of nectar spurs, relatively little is known about their development. We used a comparative approach to investigate variation in nectar spur length in a clade of eight Iberian toadflaxes. METHODS: Spur growth was measured at the macroscopic level over time in all eight species, and growth rate and growth duration compared. Evolution of growth rate was reconstructed across the phylogeny. Within the clade we then focused on Linaria becerrae and Linaria clementei, a pair of sister species which have extremely long and short spurs, respectively. Characterization at a micromorphological level was performed across a range of key developmental stages to determine whether the difference in spur length is due to differential cell expansion or cell division. KEY RESULTS: We detected a significant difference in the evolved growth rates, while developmental timing of both the initiation and the end of spur growth remained similar. Cell number is three times higher in the long spurred L. becerrae compared with L. clementei, whereas cell length is only 1.3 times greater. In addition, overall anisotropy of mature cells is not significantly different between the two species. CONCLUSIONS: We found that changes in cell number and therefore in cell division largely explain evolution of spur length. This contrasts with previous studies in Aquilegia which have found that variation in nectar spur length is due to directed cell expansion (anisotropy) over variable time frames. Our study adds to knowledge about nectar spur development in a comparative context and indicates that different systems may have evolved nectar spurs using disparate mechanisms

Evolución en el género Linaria: biogeografía, cambio morfológico y sistemático de Linaria sect. Versicolores

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid. Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 03-12-201

The evo-devo of plant speciation

Speciation research bridges the realms of macro- and microevolution. Evolutionary developmental biology (evo-devo) has classically dealt with macroevolutionary questions through a comparative approach to distantly related organisms, but the field later broadened in focus to address recent speciation and microevolution. Here we review available evidence of the power of evo-devo approaches to understand speciation in plants at multiple scales. At a macroevolutionary scale, evidence is accumulating for evolutionary developmental mechanisms giving rise to key innovations promoting speciation. At the macro microevolution transition, we review instances of evo-devo change underlying both the origin of reproductive barriers and phenotypic changes distinguishing closely related species. At the microevolutionary scale, the study of developmental variation within species provides insight into the processes that generate the raw material for evolution and speciation. We conclude by advocating a strong interaction between developmental biology and evolutionary biology at multiple scales to gain a deeper understanding of plant speciation.M.F.-M. has been supported by the Marie Curie Intra-European Fellowship LINARIA-SPECIATION (FP7-PEOPLE-2013-IEF, project reference 624396 to M.F.-M and B.J.G) and an Isaac Newton Trust Research Grant (Trinity College, Cambridge)

A synopsis of the Iberian clade of Linaria subsect. Versicolores (Antirrhineae, Plantaginaceae) based on integrative taxonomy

Integrative taxonomy, based on the combination of multiple lines of evidence, provides the foundations for a robust species delimitation. Here we provide a taxonomic synopsis of the Iberian clade of Linaria subsect. Versicolores based on recently published morphometric and phylogenomic data. This clade radiated in the Iberian Peninsula (western Mediterranean)during the Quaternary, and is being intensively studied from phylogenetic, evolutionary, biogeographic, ecological and developmental standpoints. Eight morphologically and genetically distinct species are recognized in the clade: L. algarviana, L. becerrae, L. clementei, L. incarnata, L. onubensis, L. salzmannii, L. spartea and L. viscosa. For each accepted species, the type material and notes on diagnostic characters, distribution, habitat and intraspecific variability are provided. Five names are typified (four neotypes and one lectotype are designated), and references to previous typifications are also presented. A distribution map and an identification key are presented. This synopsis will provide the basis for future research on speciation and evolution of the clade

A western representative of an eastern clade: phylogeographic history of the gypsum-associated plant Nepeta Hispanica

The preference of certain plant species for gypsum soils with a patchy distribution leads to disjunct population structures that are thought to generate island-like dynamics potentially influencing biogeographic patterns at multiple evolutionary scales. Here, we study the evolutionary and biogeographic history of Nepeta hispanica, a western Mediterranean plant associated with gypsum soils and displaying a patchy distribution with populations very distant from each other. Three approaches were used: (a) interspecific phylogenetic analyses based on nuclear DNA sequences of the ITS region to unveil the relationships and times of divergence between N. hispanica and its closest relatives; (b) phylogeographic analyses using plastid DNA regions trnS-trnG and psbJ-petA to evaluate the degree of genetic isolation between populations of N. hispanica, their relationships and their genetic diversity; and (c) ecological niche modelling to evaluate historical distributional changes. Results reveal that N. hispanica belongs to an eastern Mediterranean and Asian (Irano-Turanian) clade diversified in arid environments since the Miocene-Pliocene. This species represents the only lineage of this clade that colonised the western Mediterranean, probably through the northern Mediterranean coast (southern Europe). Present Iberian populations display a high plastid genetic diversity and, even if geographically distant from each other, they are highly connected according to the distribution of plastid haplotypes and lineages. This can be explained by a scenario involving a complex history of back-and-forth colonisation events, facilitated by a relative stability of suitable conditions for the species across the western Mediterranean throughout the QuaternaryThis work would not have been possible without the support of Julian ´ García, Rub´en de Pablo, Jesús del Río, Leonardo Guti´errez, Javier Puente, Javier Pavon ´ and Luis M. Medrano, who helped us with field sample collection; Leopoldo Medina, Cyrille Chatelain, Jesús Riera and Javier Hernandez, ´ who granted us permission to use specimens from the MA, G, VAL and SALA herbaria respectively; and Emilio Cano, who provided his invaluable help in the RJB-CSIC molecular systematics laboratory. Fieldwork was financed by the Universidad Autonoma ´ de Madrid with a grant to IRG’s Master thesis. Laboratory work was funded by a Juan de la Cierva fellowship to MF-M (Spanish Ministry of Economy and Competitiveness, reference IJCI-2015–23459

The Role of INAPERTURATE POLLEN1 as a Pollen Aperture Factor Is Conserved in the Basal Eudicot Eschscholzia californica (Papaveraceae)

This study was supported by the Spanish Ministry of Economy and Competitiveness (project CGL2015-70290-P to VS-S) and by the US National Science Foundation (MCB-1817835 to AD). IM-A was supported by a predoctoral grant (F.P.I. program) from the Spanish Government. BK was supported by the Ministry of Education, Youth and Sports of the Czech Republic (project LTC20050) and DH was supported by Czech Science Foundation (project 21-15856S).Pollen grains show an enormous variety of aperture systems. What genes are involved in the aperture formation pathway and how conserved this pathway is in angiosperms remains largely unknown. INAPERTURATE POLLEN1 (INP1) encodes a protein of unknown function, essential for aperture formation in Arabidopsis, rice and maize. Yet, because INP1 sequences are quite divergent, it is unclear if their function is conserved across angiosperms. Here, we conducted a functional study of the INP1 ortholog from the basal eudicot Eschscholzia californica (EcINP1) using expression analyses, virus-induced gene silencing, pollen germination assay, and transcriptomics. We found that EcINP1 expression peaks at the tetrad stage of pollen development, consistent with its role in aperture formation, which occurs at that stage, and showed, via gene silencing, that the role of INP1 as an important aperture factor extends to basal eudicots. Using germination assays, we demonstrated that, in Eschscholzia, apertures are dispensable for pollen germination. Our comparative transcriptome analysis of wildtype and silenced plants identified over 900 differentially expressed genes, many of them potential candidates for the aperture pathway. Our study substantiates the importance of INP1 homologs for aperture formation across angiosperms and opens up new avenues for functional studies of other aperture candidate genes.Spanish Ministry of Economy and Competitiveness CGL2015-70290-PNational Science Foundation (NSF) MCB-1817835Spanish Government European CommissionMinistry of Education, Youth & Sports - Czech Republic LTC20050Grant Agency of the Czech Republic 21-15856

Repeated asynchronous evolution of single-species endemics of ivies (Hedera L.) in Macaronesian archipelagos

Aim: Evolutionary studies of oceanic island endemics are usually focused on lineages that have experienced in situ radiation, while those that speciated once on the island or archipelago but have not further diversified (single-species endemics) remain understudied. The Macaronesian archipelagos, in the Atlantic Ocean, are home to significant numbers of single-species endemics. The genus Hedera L. (12 species) includes three single-species endemics from three Macaronesian archipelagos with putatively independent origins. Here, we tested the role of phylogenetic niche conservatism in their evolution. To that end, we (1) reconstructed the spatio-temporal origin of Macaronesian ivies using phylogenomics, and (2) assessed the role of climatic niche during their colonization and speciation. Location: Azores, Canary Islands, Madeira, western Mediterranean. Taxon: Hedera spp. Methods: We used 166 samples representing all Hedera species to generate genotyping-by-sequencing (GBS) libraries and performed time-calibrated phylogenomic and biogeographic analyses. Climatic preferences and climatic niche evolution were assessed using a geo-referenced database of the western ivy species (2,297 records). Results: Independent and asynchronous colonization and speciation were estimated for the three Macaronesian ivies, resulting in different degrees of phylogenetic and climatic niche differentiation: H. canariensis displayed an early divergence (7.5–12 Ma) and high phylogenetic and niche isolation; H. azorica had intermediate phylogenetic isolation and niche divergence from its closest relative H. helix (4.4–6.8 Ma) and H. maderensis was embedded within the climatically similar H. iberica (2.8–4.6 Ma). A strong phylogenetic signal was suggested for climatic niche in the western clade of Hedera, where the three Macaronesian ivies are placed. Main Conclusions: The three Macaronesian ivies represent the evolutionary stages leading to the emergence of single-species island endemics. Climatic niche conservatism appears to be involved in the evolution of single-species endemics, first by facilitating island colonization, and then by limiting in situ diversificationSpanish Ministry of Economy, Industry and Competitiveness, Grant/Award Number: CGL2017-87198-P and PID2019- 106840GA-C22; Universidad Autónoma de Madrid, Grant/Award Number: FPIUAM 201