Phylogenomics and phylogeographic model testing using convolutional neural networks reveal a history of recent admixture in the Canarian Kleinia neriifolia.

Multiple-island endemics (MIE) are considered ideal natural subjects to study patterns of island colonization that involve recent population-level genetic processes. Kleinia neriifolia is a Canarian MIE widespread across the archipelago, which exhibits a close phylogenetic relationship with species in northwest Africa and at the other side of the Sahara Desert. Here, we used target sequencing with plastid skimming (Hyb-Seq), a dense population-level sampling of K. neriifolia, and representatives of its African-southern Arabian relatives to infer phylogenetic relationships and divergence times at the species and population levels. Using population genetic techniques and machine learning (convolutional neural networks [CNNs]), we reconstructed phylogeographic relationships and patterns of genetic admixture based on a multilocus SNP nuclear dataset. Phylogenomic analysis based on the nuclear dataset identifies the northwestern African Kleinia anteuphorbium as the sister species of K. neriifolia, with divergence starting in the early Pliocene. Divergence from its sister clade, comprising species from the Horn of Africa and southern Arabia, is dated to the arid Messinian period, lending support to the climatic vicariance origin of the Rand Flora. Phylogeographic model testing with CNNs supports an initial colonization of the central island of Tenerife followed by eastward and westward migration across the archipelago, which resulted in the observed east/west phylogeographic split. Subsequent population extinctions linked to aridification events, and recolonization from Tenerife, are proposed to explain the patterns of genetic admixture in the eastern Canary Islands. We demonstrate that CNNs based on SNPs can be used to discriminate among complex scenarios of island migration and colonization.

Multiplexed shotgun genotyping (MSG) data resolve phylogenetic relationships within and among archipelagos in Macaronesian Tolpis.

PREMISE: Plants endemic to oceanic archipelagos are suitable for studying evolution, being isolated on substrates of different ages. Evolution has been recent, rendering traditionally employed sequences insufficiently variable for resolving relationships. This study includes sampling in the genus Tolpis (Asteraceae) from the Azores, Madeira, and Cape Verde, and expands upon an earlier study demonstrating the efficacy of multiplexed shotgun genotyping (MSG) for resolving relationships in Canarian Tolpis. METHODS: Genomic libraries for 90 accessions of Tolpis and two from the outgroup were generated for genotyping individuals using MSG. Loci were de novo assembled with iPyrad, which clusters MSG loci within and between samples. A maximum likelihood phylogeny was generated with RAxML. Ancestral area reconstruction was inferred using R package BioGeoBEARS. RESULTS: MSG data recovered a highly resolved phylogeny from population to inter-archipelago levels. Ancestral area reconstruction provided biogeographic hypotheses for the radiation of Macaronesian Tolpis. CONCLUSIONS: Four major clades were resolved. The Madeiran endemic T. macrorhiza is sister to other Tolpis. Species from the Canaries, Cape Verdes, and the continent are sister to T. succulenta from Madeira, which has a sister subclade of Azorean populations composed of T. succulenta and T. azorica. Population-level resolution suggests unrecognized taxa on several archipelagos. Ancestral reconstruction suggests initial dispersal from the continent to Madeira, with dispersal to the Azores, then dispersal from Madeira to the Canary Islands, with both subsequent dispersal to the Cape Verdes and back-dispersal to the continent. Single-island radiations and inter-island dispersal are implicated in divergence in Macaronesian Tolpis.

Molecular phylogenetics of Lotus (Leguminosae) with emphasis in the tempo and patterns of colonization in the Macaronesian region.

With a wide distribution range including Europe and Asia, Lotus (Leguminosae) represents the largest genus within Loteae. It is particularly diverse in the Mediterreanean region and in the five archipelagos of Macaronesia (Atlantic Ocean). However, little is known about the relationships among the 14 sections currently recognized within Lotus and about the timing and patterns of its colonization in the Macaronesian region. In this investigation, we use four DNA regions (nuclear ribosomal ITS plus three plastid regions) in the most comprehensive sampling of Lotus species to date (some endemic species within the Canary Islands were poorly represented in previous phylogenetic analyses) to infer relationships within this genus and to establish patterns of colonization in Macaronesia. Divergence time estimates and habitat reconstruction analyses indicate that Lotus likely diverged about 7.86 Ma from its sister group, but all colonization events to Macaronesia occurred more recently (ranging from the last 0.23 to 2.70 Ma). The diversification of Lotus in Macaronesia involved between four and six independent colonization events from four sections currently distributed in Africa and Europe. A major aspect shaping the current distribution of taxa involved intra-island colonization of mainly new habitats and inter-island colonization of mostly similar habitats, with Gran Canaria and Tenerife as the major sources of diversification and of further colonization events. Section Pedrosia is the most diverse in terms of colonization events, number of species, and habitat heterogeneity, including a back-colonization event to the continent. Subsections within Pedrosia radiated into diverse habitat types recently (late Pleistocene, ca 0.23-0.29 Ma) and additional molecular markers and sampling would be necessary to understand the most recent dispersal events of this group within the Canary Islands and Cape Verde.

How repeatable is microevolution on islands? Patterns of dispersal and colonization-related plant traits in a phylogeographical context.

BACKGROUND AND AIMS: Archipelagos provide a valuable framework for investigating phenotypic evolution under different levels of geographical isolation. Here, we analysed two co-distributed, widespread plant lineages to examine if incipient island differentiation follows parallel patterns of variation in traits related to dispersal and colonization. METHODS: Twenty-one populations of two anemochorous Canarian endemics, Kleinia neriifolia and Periploca laevigata, were sampled to represent mainland congeners and two contrasting exposures across all the main islands. Leaf size, seed size and dispersability (estimated as diaspore terminal velocity) were characterized in each population. For comparison, dispersability was also measured in four additional anemochorous island species. Plastid DNA data were used to infer genetic structure and to reconstruct the phylogeographical pattern of our focal species. KEY RESULTS: In both lineages, mainland-island phenotypic divergence probably started within a similar time frame (i.e. Plio-Pleistocene). Island colonization implied parallel increases in leaf size and dispersability, but seed size showed opposite patterns of variation between Kleinia and Periploca species pairs. Furthermore, dispersability in our focal species was low when compared with other island plants, mostly due to large diaspore sizes. At the archipelago scale, island exposure explained a significant variation in leaf size across islands, but not in dispersability or seed size. Combined analyses of genetic and phenotypic data revealed two consistent patterns: (1) extensive within-island but very limited among-island dispersal, and (2) recurrent phenotypic differentiation between older (central) and younger (peripheral) island populations. CONCLUSIONS: Leaf size follows a more predictable pattern than dispersability, which is affected by stochastic shifts in seed size. Increased dispersability is associated with high population connectivity at the island scale, but does not preclude allopatric divergence among islands. In sum, phenotypic convergent patterns between species suggest a major role of selection, but deviating traits also indicate the potential contribution of random processes, particularly on peripheral islands.

A tale of two forests: ongoing aridification drives population decline and genetic diversity loss at continental scale in Afro-Macaronesian evergreen-forest archipelago endemics.

Background and Aims: Various studies and conservationist reports have warned about the contraction of the last subtropical Afro-Macaronesian forests. These relict vegetation zones have been restricted to a few oceanic and continental islands around the edges of Africa, due to aridification. Previous studies on relict species have generally focused on glacial effects on narrow endemics; however, little is known about the effects of aridification on the fates of previously widespread subtropical lineages. Methods: Nuclear microsatellites and ecological niche modelling were used to understand observed patterns of genetic diversity in two emblematic species, widely distributed in these ecosystems: Canarina eminii (a palaeoendemic of the eastern Afromontane forests) and Canarina canariensis (a palaeoendemic of the Canarian laurel forests). The software DIYABC was used to test alternative demographic scenarios and an ensemble method was employed to model potential distributions of the selected plants from the end of the deglaciation to the present. Key Results: All the populations assessed experienced a strong and recent population decline, revealing that locally widespread endemisms may also be alarmingly threatened. Conclusions: The detected extinction debt, as well as the extinction spiral to which these populations are subjected, demands urgent conservation measures for the unique, biodiversity-rich ecosystems that they inhabit.

MtDNA metagenomics reveals large-scale invasion of belowground arthropod communities by introduced species.

Using a series of standardized sampling plots within forest ecosystems in remote oceanic islands, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large-scale species introductions by humans. Species of beetle and spider were sampled almost exclusively from single islands, while soil-dwelling Collembola exhibited more than tenfold higher species sharing among islands. Comparison of Collembola mitochondrial metagenomic data to a database of more than 80 000 Collembola barcode sequences revealed almost 30% of sampled island species are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. Patterns of mtDNA relatedness among Collembola implicate human-mediated species introductions, with minimum estimates for the proportion of introduced species on the sampled islands ranging from 45% to 88%. Our results call for more attention to soil mesofauna to understand the global extent and ecological consequences of species introductions.

Surviving in isolation: genetic variation, bottlenecks and reproductive strategies in the Canarian endemic Limonium macrophyllum (Plumbaginaceae).

Oceanic archipelagos are typically rich in endemic taxa, because they offer ideal conditions for diversification and speciation in isolation. One of the most remarkable evolutionary radiations on the Canary Islands comprises the 16 species included in Limonium subsection Nobiles, all of which are subject to diverse threats, and legally protected. Since many of them are single-island endemics limited to one or a few populations, there exists a risk that a loss of genetic variation might limit their long-term survival. In this study, we used eight newly developed microsatellite markers to characterize the levels of genetic variation and inbreeding in L. macrophyllum, a species endemic to the North-east of Tenerife that belongs to Limonium subsection Nobiles. We detected generally low levels of genetic variation over all populations (H T = 0.363), and substantial differentiation among populations (F ST = 0.188; R ST = 0.186) coupled with a negligible degree of inbreeding (F = 0.042). Obligate outcrossing may have maintained L. macrophyllum relatively unaffected by inbreeding despite the species' limited dispersal ability and the genetic bottlenecks likely caused by a prolonged history of grazing. Although several factors still constitute a risk for the conservation of L. macrophyllum, the lack of inbreeding and the recent positive demographic trends observed in the populations of this species are factors that favour its future persistence.

High genetic diversity and population structure in the endangered Canarian endemic Ruta oreojasme (Rutaceae).

Insular species are expected to have low genetic diversity, for their populations are often small and isolated, and characterized by restricted gene flow and increased incidence of inbreeding. However, empirical results do not always match this expectation. For example, population genetic analyses of several Canarian endemics, based mainly on allozymes, show levels of genetic diversity exceptionally high for insular species. To investigate whether genetic variation in rare species endemic to Canary Islands is low, as predicted by theoretical expectations, or high, as documented in some previous studies, we analysed genetic diversity of the endangered Ruta oreojasme, a rare endemic of the island of Gran Canaria, using microsatellite markers, which are more variable than allozymes. Our analyses identified very high levels of genetic diversity (A = 7.625, P = 0.984, H o = 0.558, H e = 0.687) for R. oreojasme. Even though the distribution of the species is restricted to the South of Gran Canaria, only one population shows low genetic diversity, isolation and signs of a recent bottleneck/founder event. Some intrinsic characteristics of R. oreojasme (hermaphroditism, proterandry and polyploidy), the relative climatic stability of the Canarian archipelago during Quaternary glacials/interglacials, the size of most populations (thousands of individuals), its age, and the relative proximity of the archipelago to the mainland might have contributed to the high diversity that characterises this endemic. As expected, given the marked topographic complexity of Gran Canaria, we found marked genetic structure in R. oreojasme populations. Our results support the observation that Canarian endemics are characterised by unexpectedly high genetic diversity and provides important insights for potential applications to the conservation of R. oreojasme.

Multiplexed-shotgun-genotyping data resolve phylogeny within a very recently derived insular lineage.

PREMISE OF THE STUDY: Endemic plants on oceanic islands have long served as model systems for studying patterns and processes of evolution. However, phylogenetic studies of island plants frequently illustrate a decoupling of molecular divergence and ecological/morphological diversity, resulting in phylogenies lacking the resolution required to interpret patterns of evolution in a phylogenetic context. The current study uses the primarily Macaronesian flowering plant genus Tolpis to illustrate the utility of multiplexed shotgun genotyping (MSG) for resolving relationships at relatively deep (among archipelagos) and very shallow (within archipelagos) nodes in this small, yet diverse insular plant lineage that had not been resolved with other molecular markers. METHODS: Genomic libraries for 27 accessions of Macaronesian Tolpis were generated for genotyping individuals using MSG, a form of reduced-representation sequencing, similar to restriction-site-associated DNA markers (RADseq). The resulting data files were processed using the program pyRAD, which clusters MSG loci within and between samples. Phylogenetic analyses of the aligned data matrix were conducted using RAxML. KEY RESULTS: Analysis of MSG data recovered a highly resolved phylogeny with generally strong support, including the first robust inference of relationships within the highly diverse Canary Island clade of Tolpis. CONCLUSIONS: The current study illustrates the utility of MSG data for resolving relationships in lineages that have undergone recent, rapid diversification resulting in extensive ecological and morphological diversity. We suggest that a similar approach may prove generally useful for other rapid plant radiations where resolving phylogeny has been difficult.

In defence of the entity of Macaronesia as a biogeographical region.

Since its coinage ca. 1850 AD by Philip Barker Webb, the biogeographical region of Macaronesia, consisting of the North Atlantic volcanic archipelagos of the Azores, Madeira with the tiny Selvagens, the Canaries and Cabo Verde, and for some authors different continental coastal strips, has been under dispute. Herein, after a brief introduction on the terminology and purpose of regionalism, we recover the origins of the Macaronesia name, concept and geographical adscription, as well as its biogeographical implications and how different authors have positioned themselves, using distinct terrestrial or marine floristic and/or faunistic taxa distributions and relationships for accepting or rejecting the existence of this biogeographical region. Four main issues related to Macaronesia are thoroughly discussed: (i) its independence from the Mediterranean phytogeographical region; (ii) discrepancies according to different taxa analysed; (iii) its geographical limits and the role of the continental enclave(s), and, (iv) the validity of the phytogeographical region level. We conclude that Macaronesia has its own identity and a sound phytogeographical foundation, and that this is mainly based on three different floristic components that are shared by the Macaronesian core (Madeira and the Canaries) and the outermost archipelagos (Azores and Cabo Verde). These floristic components are: (i) the Palaeotropical-Tethyan Geoflora, formerly much more widely distributed in Europe and North Africa and currently restricted to the three northern archipelagos (the Azores, Madeira and the Canaries); (ii) the African Rand Flora, still extant in the coastal margins of Africa and Arabia, and present in the southern archipelagos (Madeira, the Canaries and Cabo Verde), and (iii) the Macaronesian neoendemic floristic component, represented in all the archipelagos, a result of allopatric diversification promoted by isolation of Mediterranean ancestors that manage to colonize Central Macaronesia and, from there, the outer archipelagos. Finally, a differentiating floristic component recently colonized the different archipelagos from the nearest continental coast, providing them with different biogeographic flavours.

A review of the allozyme data set for the Canarian endemic flora: causes of the high genetic diversity levels and implications for conservation.

Background and Aims Allozyme and reproductive data sets for the Canarian flora are updated in order to assess how the present levels and structuring of genetic variation have been influenced by the abiotic island traits and by phylogenetically determined biotic traits of the corresponding taxa; and in order to suggest conservation guidelines. Methods Kruskal-Wallis tests are conducted to assess the relationships of 27 variables with genetic diversity (estimated by A, P, Ho and He) and structuring (GST) of 123 taxa representing 309 populations and 16 families. Multiple linear regression analyses (MLRAs) are carried out to determine the relative influence of the less correlated significant abiotic and biotic factors on the genetic diversity levels. Key Results and Conclusions The interactions between biotic features of the colonizing taxa and the abiotic island features drive plant diversification in the Canarian flora. However, the lower weight of closeness to the mainland than of (respectively) high basic chromosome number, partial or total self-incompatibility and polyploidy in the MLRAs indicates substantial phylogenetic constraint; the importance of a high chromosome number is feasibly due to the generation of a larger number of linkage groups, which increase gametic and genotypic diversity. Genetic structure is also more influenced by biotic factors (long-range seed dispersal, basic chromosome number and partial or total self-incompatibility) than by distance to the mainland. Conservation-wise, genetic structure estimates (FST/GST) only reflect endangerment under intensive population sampling designs, and neutral genetic variation levels do not directly relate to threat status or to small population sizes. Habitat protection is emphasized, but the results suggest the need for urgent implementation of elementary reproductive studies in all cases, and for ex situ conservation measures for the most endangered taxa, even without prior studies. In non-endangered endemics, multidisciplinary research is needed before suggesting case-specific conservation strategies. The molecular information relevant for conservation should be conserved in a standardized format to facilitate further insight.

A local dormancy cline is related to the seed maturation environment, population genetic composition and climate.

BACKGROUND AND AIMS: Seed dormancy varies within species in response to climate, both in the long term (through ecotypes or clines) and in the short term (through the influence of the seed maturation environment). Disentangling both processes is crucial to understand plant adaptation to environmental changes. In this study, the local patterns of seed dormancy were investigated in a narrow endemic species, Centaurium somedanum, in order to determine the influence of the seed maturation environment, population genetic composition and climate. METHODS: Laboratory germination experiments were performed to measure dormancy in (1) seeds collected from different wild populations along a local altitudinal gradient and (2) seeds of a subsequent generation produced in a common garden. The genetic composition of the original populations was characterized using intersimple sequence repeat (ISSR) PCR and principal co-ordinate analysis (PCoA), and its correlation with the dormancy patterns of both generations was analysed. The effect of the local climate on dormancy was also modelled. KEY RESULTS: An altitudinal dormancy cline was found in the wild populations, which was maintained by the plants grown in the common garden. However, seeds from the common garden responded better to stratification, and their release from dormancy was more intense. The patterns of dormancy variation were correlated with genetic composition, whereas lower temperature and summer precipitation at the population sites predicted higher dormancy in the seeds of both generations. CONCLUSIONS: The dormancy cline in C. somedanum is related to a local climatic gradient and also corresponds to genetic differentiation among populations. This cline is further affected by the weather conditions during seed maturation, which influence the receptiveness to dormancy-breaking factors. These results show that dormancy is influenced by both long-and short-term climatic variation. Such processes at such a reduced spatial scale highlight the potential of plants to adapt to fast environmental changes.

The origin of bird pollination in Macaronesian Lotus (Loteae, Leguminosae).

The four red-flowered, apparently bird-pollinated Lotus species from the Canary Islands have previously been classified in their own genus, Rhyncholotus. Currently, they are considered as a separate section within genus Lotus, distinct from other herbaceous Canarian congeners which are yellow-flowered and bee-pollinated. A combined analysis of four nuclear regions (including ITS and three homologues of CYCLOIDEA) and three plastid regions (CYB6, matK and trnH-psbA) nests the four bird-pollinated species within a single extant species of bee-pollinated Lotus (L. sessilifolius), in a very extreme example of species paraphyly. Therefore, our data compellingly support the hypothesis that the Macaronesian Lotus species with a bird pollination syndrome are recently derived from entomophilous ancestors. Calibration of the phylogenetic trees using geological age estimates of the most recent islands (La Palma and El Hierro) together with oldest ages of Fuerteventura indicates that bird pollination evolved ca. 1.7 Ma in the Canarian Lotus. These four bird-pollinated species share a most recent common ancestor (MRCA) with L. sessilifolius that dates to about 2.2 Ma. Our analyses further suggest that the evolution of the bird pollination syndrome was likely triggered by the availability of new niches in La Palma and Tenerife as a result of recent volcanic activity.

Temporal and palaeoclimatic context of the evolution of insular woodiness in the Canary Islands.

Insular woodiness (IW), referring to the evolutionary transition from herbaceousness toward woodiness on islands, has arisen more than 30 times on the Canary Islands (Atlantic Ocean). One of the IW hypotheses suggests that drought has been a major driver of wood formation, but we do not know in which palaeoclimatic conditions the insular woody lineages originated. Therefore, we provided an updated review on the presence of IW on the Canaries, reviewed the palaeoclimate, and estimated the timing of origin of woodiness of 24 insular woody lineages that represent a large majority of the insular woody species diversity on the Canaries. Our single, broad-scale dating analysis shows that woodiness in 60%-65% of the insular woody lineages studied originated within the last 3.2 Myr, during which Mediterranean seasonality (yearly summer droughts) became established on the Canaries. Consequently, our results are consistent with palaeoclimatic aridification as a potential driver of woodiness in a considerable proportion of the insular woody Canary Island lineages. However, the observed pattern between insular woodiness and palaeodrought during the last couple of million years could potentially have emerged as a result of the typically young age of the native insular flora, characterized by a high turnover.

Fostering Conservation via an Integrated Use of Conventional Approaches and High-Throughput SPET Genotyping: A Case Study Using the Endangered Canarian Endemics Solanum lidii and S. vespertilio (Solanaceae).

Islands provide unique opportunities to integrated research approaches to study evolution and conservation because boundaries are circumscribed, geological ages are often precise, and many taxa are greatly imperiled. We combined morphological and hybridization studies with high-throughput genotyping platforms to streamline relationships in the endangered monophyletic and highly diverse lineage of Solanum in the Canarian archipelago, where three endemic taxa are currently recognized. Inter-taxa hybridizations were performed, and morphological expression was assessed with a common-garden approach. Using the eggplant Single Primer Enrichment Technology (SPET) platform with 5,093 probes, 74 individuals of three endemic taxa (Solanum lidii, S. vespertilio subsp. vespertilio, and S. vespertilio subsp. doramae) were sampled for SNPs. While morphological and breeding studies showed clear distinctions and some continuous variation, inter-taxon hybrids were fertile and heterotic for vigor traits. SPET genotyping revealed 1,421 high-quality SNPs and supported four, not three, distinct taxonomic entities associated with post-emergence geological, ecological and geographic factors of the islands. Given the lack of barriers to hybridization among all the taxa and their molecular differences, great care must be taken in population management. Conservation strategies must take account of the sexual and breeding systems and genotypic distribution among populations to successfully conserve and restore threatened/endangered island taxa, as exemplified by Solanum on the Canary Islands.

The molecular phylogeny of Matthiola R. Br. (Brassicaceae) inferred from ITS sequences, with special emphasis on the Macaronesian endemics.

Matthiola (Brassicaceae) is a genus that is widespread in the Mediterranean and Irano-Turanian regions and includes two species that are endemic to the archipelagos of Madeira and the Canaries in Macaronesia, which is an insular oceanic hotspot of biodiversity harboring many radiating endemic plant lineages. Sequence analyses of the nuclear ITS-1 and ITS-2 regions in a comprehensive geographical sample of Matthiola, encompassing all the endemic Macaronesian populations known to date, suggest independent Mediterranean and NW African origins of the taxa in Madeira and the Canaries, respectively. These molecular data reveal a complex evolutionary landscape that converges with morphological analyses in the recognition of two new Madeiran species. The data also suggest that the Canarian infra-specific endemic taxa described thus far have high (but non-diagnostic) levels of morphological and genetic diversity, and should be included in the single endemic Matthiola bolleana. In agreement with earlier investigations that revealed a high genetic differentiation between the populations of Matthiola in Fuerteventura and Lanzarote, our phylogeny supports independent founder events from the same mainland congener to either island. The consistently derived position of the Moroccan populations within a mostly Canarian clade suggests a further back-colonization of the continent. Notably, the ITS sequence resolution offered by Matthiola is higher than that found in many of the radiating Canarian endemic lineages for which molecular phylogenetic studies abound. Hence, our research discovers largely unexplored pathways to understand plant diversification in this oceanic insular hotspot through the investigation of non-speciose endemics.

An expanded molecular phylogeny of Plumbaginaceae, with emphasis on Limonium (sea lavenders): Taxonomic implications and biogeographic considerations.

Plumbaginaceae is characterized by a history of multiple taxonomic rearrangements and lacks a broad molecular phylogenetic framework. Limonium is the most species-rich genus of the family with ca. 600 species and cosmopolitan distribution. Its center of diversity is the Mediterranean region, where ca. 70% of all Limonium species are endemic. In this study, we sample 201 Limonium species covering all described infrageneric entities and spanning its wide geographic range, along with 64 species of other Plumbaginaceae genera, representing 23 out of 29 genera of the family. Additionally, 20 species of the sister family Polygonaceae were used as outgroup. Sequences of three chloroplast (trnL-F, matK, and rbcL) and one nuclear (ITS) loci were used to infer the molecular phylogeny employing maximum likelihood and Bayesian analyses. According to our results, within Plumbaginoideae, Plumbago forms a non-monophyletic assemblage, with Plumbago europaea sister to Plumbagella, while the other Plumbago species form a clade sister to Dyerophytum. Within Limonioideae, Ikonnikovia is nested in Goniolimon, rejecting its former segregation as genus distinct from Goniolimon. Limonium is divided into two major clades: Limonium subg. Pteroclados s.l., including L. sect. Pteroclados and L. anthericoides, and L. subg. Limonium. The latter is divided into three well-supported subclades: the monospecific L. sect. Limoniodendron sister to a clade comprising a mostly non-Mediterranean subclade and a Mediterranean subclade. Our results set the foundation for taxonomic proposals on sections and subsections of Limonium, namely: (a) the newly described L. sect. Tenuiramosum, created to assign L. anthericoides at the sectional rank; (b) the more restricted circumscriptions of L. sect. Limonium (= L. sect. Limonium subsect. Genuinae) and L. sect. Sarcophyllum (for the Sudano-Zambezian/Saharo-Arabian clade); (c) the more expanded circumscription of L. sect. Nephrophyllum (including species of the L. bellidifolium complex); and (d) the new combinations for L. sect. Pruinosum and L. sect. Pteroclados subsect. Odontolepideae and subsect. Nobiles.

The potential role of hybridization in diversification and speciation in an insular plant lineage: insights from synthetic interspecific hybrids.

Hybridization is recognized as an important process in plant evolution, and this may be particularly true for island plants where several biotic and abiotic factors facilitate interspecific hybridization. Although rarely done, experimental studies could provide insights into the potential of natural hybridization to generate diversity when species come into contact in the dynamic island setting. The potential of hybridization to generate morphological variation was analysed within and among 12 families (inbred lines) of an F4 hybrid generation between two species of Tolpis endemic to the Canary Islands. Combinations of characters not seen in the parents were present in hybrids. Several floral and vegetative characters were transgressive relative to their parents. Morphometric studies of floral, vegetative and fruit characters revealed that several F4 families were phenotypically distinct from other families, and from their parents. The study demonstrates that morphologically distinct pollen-fertile lines, potentially worthy of taxonomic recognition if occurring in nature, can be generated in four generations. The ability of the hybrid lines to set self-seed would reduce gene flow among the lines, and among the hybrids and their parental species. Selfing would also facilitate the fixation of characters within each of the lines. Overall, the results show the considerable potential of hybridization for generating diversity and distinct phenotypes in island lineages.

Molecular taxonomic identification in the absence of a 'barcoding gap': a test with the endemic flora of the Canarian oceanic hotspot.

We use a comprehensive subset of Canarian angiosperms corresponding to 23 families, 35 genera and 60 Canarian endemic taxa to test whether this flora is suitable to taxonomic identification with the two proposed plant DNA barcode sequences and whether these sequences may reveal the existence of cryptic species overlooked by morphology. The rate of discrimination success between the insular congeneric samples using the rbcL+matK combination and a 'character-based' approach (where we use only the combination of nucleotide positions in an alignment that allows unambiguous species identification) is higher (82.29%) than that obtained with the 'distance-based' approach (80.20%) used by the CBOL Plant Working Group in 2009 and also when compared with tests conducted in other floras. This suggests that the molecular identification of the Canarian endemic flora can be achieved as successfully as in other floras where the incidence of radiation is not as relevant. The facts that (i) a distance-based criterion was unable to discriminate between congeneric and conspecific comparisons and (ii) only the character-based discrimination criterion resolved cases that the distance-based criterion did not, further support the use of a character discrimination approach for a more efficient DNA barcoding of floras from oceanic islands like the Canaries. Thus, a barcoding gap seems not to be necessary for the correct molecular characterization of the Canarian flora. DNA barcodes also suggest the possible existence of cryptic taxa to be further investigated by morphology and that the current taxonomic status of some of the taxa analysed may need revision.