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[Aim] Species with widespread distributions offer excellent opportunities for investigating recent biogeographical patterns across broad scales. Here, we tested the hypothesis that, due to its intermediate geographical location, NW Africa is pivotal in explaining the phylogeographical patterns of taxa with Mediterranean–Macaronesian distributions using a legume species with short generation times., [Location] Mediterranean, with a focus on NW Africa and the Canary Islands., [Taxon] Pitch trefoil (Bituminaria bituminosa)., [Methods] We generated genetic data and performed phylogeographical and demographic analyses at two geographical scales: Mediterranean Basin (MB), using plastid sequences (115 individuals), and Macaronesia, using plastid sequences (182 individuals) and 10 nuclear microsatellite loci (220 individuals). We also performed a literature survey focusing on phylogeographical studies of other circum-Mediterranean taxa., [Results] Northwest Africa was identified as a centre of genetic diversity (19 out of 38 haplotypes) and demographic expansion of B. bituminosa in the MB during the Pleistocene. Our literature review revealed two main phylogeographical patterns in widespread species: pre-Mediterranean evergreen sclerophylls versus Pleistocene facultative-deciduous (including Bituminaria) taxa, but on average, both functional groups show a similar, large genetic diversity (~40% of haplotypes) in NW Africa. At the Macaronesian scale, we found that Canarian Bituminaria is composed of two genetic sublineages that coexist and hybridize on the central islands and in the mainland Macaronesian enclave (Anti-Atlas region). Demographic analyses rejected the progression rule as the model of island colonization but strongly suggested that Anti-Atlas populations are the result of back-colonization from the easternmost islands before the Last Glacial Maximum (LGM)., [Conclusions] Bituminaria displays a pattern of Quaternary eastward expansion in the MB that appears to be paralleled by several members of its functional plant group. Thus, our study reveals a previously undescribed dual role of NW Africa in plant biogeography, acting both as a source of species expansion to the rest of the MB and a LGM refugium of plant populations with a Macaronesian island origin., This study was funded by a Vincenç Mut project (Govern de les Illes Balears and European Social Fund) and a research prize awarded to CG-V by Fundación Amurga.

Accurate inference in phylogeography requires appropriate sampling strategies. Complex questions demand a large sample size at both the population and genetic levels to obtain precise reconstructions. This is the case of the phylogeographic history of Cistus monspeliensis, a plant that displays low plastid (cpDNA) diversity in the Mediterranean Basin but high diversity in the Canary Islands. Here, we aimed to identify Mediterranean refugial areas and to accurately quantify inter-island colonization events in the Canaries. Using a previous study as starting point, we increased sample size in two ways: (i) additional sampling of plastid genetic markers (from 1041 to 1899 bp); and (ii) additional sampling of populations (from 47 to 69) in long-term persistence areas suggested by species distribution modeling (SDM). The synergy between SDM and extended population sampling helped find higher genetic diversity. Our deeper phylogeographic sampling of C. monspeliensis revealed the following: (i) potential refugia in long-term persistence areas with high cpDNA diversity in western Europe and the Canary Islands; and (ii) a significant increase (from 7 to 12) in the number of inferred inter-island colonization events across the archipelago. Our results stress the usefulness of SDM to identify the genetic signature associated with potential refugial areas. We herein propose a field sampling approach based on SDM that, in combination with a larger cpDNA sampling, can help answer a wide array of phylogeographic questions, such as the location of Quaternary refugia and number of colonizations across archipelagos.

The genus Dracaena in Macaronesia comprises two threatened species of arborescent monocots that are often associated with one of the most intriguing biogeographic disjunctions: the Rand Flora pattern. Molecular information is, however, largely missing for the Macaronesian Dracaena taxa (“MDT”, hereafter), and the biogeographic or population genetic patterns of this lineage have not yet been thoroughly assessed. To fill this gap, we generated plastid DNA sequence data of 14 Dracaena populations representing the entire natural distribution of MDT (including mainland Morocco and all recognized subspecies), 9 additional populations of subspontaneous origin, and a set of related species of the genus. We performed phylogenetic, biogeographic, and population genetic analyses at different spatial scales and conducted a comparative review on plant haplotype diversity in Macaronesian plants. The results of our phylogenetic analyses indicated the monophyly of the MDT and an origin separate from a clade of geographically distant species that so far were postulated as their closest living relatives (D. cinnabari, D. ombet, D. schizantha, D. serrulata). The results of our phylogeographic analyses indicated that diversification within D. draco occurred throughout the Pleistocene and that wild peripheral populations (Madeira, mainland Morocco) may have a recent origin from Canarian source populations. Recent dispersals, coupled with remarkably low levels of haplotype diversity, probably account for the weak phylogeographic signal observed across wild populations. However, our results suggested that human‐assisted expansion of Dracaena inflates the extant phylogeographic signal by non‐random translocation of a specific subset of haplotypes. Our study demonstrates that many of the previous biogeographic scenarios on MDT are not supported by molecular data. Instead, our results highlight (i) the impact that human activity may have on the phylogeographic pattern of island plants, and (ii) the need of a deeper taxonomic sampling in future investigations on MDT and close relatives., This research was funded by the European Regional Development Fund (Intereg projects CAVEGEN and ENCLAVES). JP was funded by the Marie Sklodowska‐Curie COFUND, Researchers’ Night and Individual Fellowships Global (MSCA grant agreement No 747238, “UNISLAND”’), and the Ramón y Cajal program (RYC‐2016‐20506). CG‐V was financially supported by a “Vicenç Mut” postdoctoral fellowship (Conselleria d'Innovació, Recerca i Turisme, Govern de les Illes Balears and the European Social Fund).

Oceanic islands are dynamic settings that often promote within-island patterns of strong population differentiation. Species with high colonisation abilities, however, are less likely to be affected by genetic barriers, but island size may impact on species genetic structure regardless of dispersal ability. The aim of the present study was to identify the patterns and factors responsible for the structure of genetic diversity at the island scale in Phoenix canariensis, a palm species with high dispersal potential. To this end, we conducted extensive population sampling on the three Canary Islands where the species is more abundant and assessed patterns of genetic variation at eight microsatellite loci, considering different within-island scales. Our analyses revealed significant genetic structure on each of the three islands analysed, but the patterns and level of structure differed greatly among islands. Thus, genetic differentiation fitted an isolation-by-distance pattern on islands with high population densities (La Gomera and Gran Canaria), but such a pattern was not found on Tenerife due to strong isolation between colonised areas. In addition, we found a positive correlation between population geographic isolation and fine-scale genetic structure. This study highlights that island size is not necessarily a factor causing strong population differentiation on large islands, whereas high colonisation ability does not always promote genetic connectivity among neighbouring populations. The spatial distribution of populations (i.e. landscape occupancy) can thus be a more important driver of plant genetic structure than other island, or species' life-history attributes.

[Premise] The endangered shrub Daphne rodriguezii (Thymelaeaceae) is endemic to the Balearic island of Menorca, where fragmentation and severe population decline are ongoing threats to this taxon. We developed a set of microsatellite markers to analyze the fine-scale genetics of its few extant populations., [Methods and Results] Fifteen microsatellite markers were obtained through Illumina high-throughput sequencing and tested in two populations. Twelve of these loci showed no evidence of null alleles and were highly polymorphic, with a mean number of 8.3 alleles per locus. Levels of observed and expected heterozygosity ranged from 0.100 to 0.952 and from 0.095 to 0.854, respectively. Seven to nine of these loci were successfully amplified in five other Daphne species., [Conclusions] This set of markers provides a useful tool for investigating the factors driving fine-scale population structure in this threatened species, and it represents a novel genetic resource for other European Daphne species., J.C.I. was funded by a GRUPIN research grant from the Regional Government of Asturias (Ref.: IDI/2018/000151), and C.G.‐V. was supported by a Vicenç Mut postdoctoral fellowship awarded by the Govern de les Illes Balears–Conselleria d'Innovació, Recerca i Turisme. The study was funded by the Ministerio de Economía, Industria y Competitividad (project Islet‐Foodwebs CGL2017‐88122‐P).

[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., C.G.-V. was supported by a ‘Juan de la Cierva’ fellowship (JCI-2012–15220), cofunded by the Ministerio de Economía y Competitividad and the Cabildo of Gran Canaria. This work was supported by the project ENCLAVES (MAC/3/C141).

Aim: The loss of dispersal on islands hypothesis (LDIH) posits that wind-dispersed plants should exhibit reduced dispersal potential, particularly if island populations are old. In this study, we tested this hypothesis using a detailed phylogeographical framework across different geographical scales. Location: Mainland and island areas of the Atlantic and Mediterranean regions, including Macaronesia (Canary Islands and Cape Verde) and Mediterranean islands in the strait of Sicily. Methods: Forty-five populations of Periploca laevigata, a wind-dispersed shrub, were sampled. Plastid and nuclear microsatellite data were used to reconstruct spatio-temporal patterns of island colonization, and estimates of seed terminal velocity used as a surrogate for dispersal ability under both field and common garden conditions. Results: Our findings did not provide evidence of loss of dispersability in any island lineage. In all of the regions considered, dispersal ability was similar on island and mainland populations, or higher on islands. Contrary to LDIH expectations, lineages inferred as the oldest (western Canaries and Cape Verde) converged towards the most dispersive seed phenotype. This pattern was supported by data obtained under common garden conditions. Within the western Canarian lineage, successful dispersal was shown to be very rare among islands and extensive within islands, but dispersability did not vary significantly from older to more recent sublineages. Considering all the study islands, we found a strong, positive correlation between dispersal ability and estimates of within-island habitat availability. Main conclusions: This study suggests that dispersal ability can be favoured on islands, possibly because traits enhancing wind dispersal are positively selected when habitat availability is high. Our results challenge broad generalizations of the LDIH, but we discuss how overlooking species′ phylogeographical history may give rise to misleading conclusions., PCT‐MAC Ministerio de Economia y Competitividad Cabildo de Gran Canaria. Grant Numbers: ENCLAVES (MAC/3/C141), JCI‐2012‐15220

Ecological studies have shown that island taxa often display novel phenotypic ranges relative to mainland congeners (i.e. character shift), but most examples come from behavioural and morphological traits in animals. In this study, I hypothesize that high levels of habitat diversity on oceanic islands would also provide opportunities for character shift in plant taxa with strong colonization ability. Habitat differentiation and phenotypic variation in two resource-use traits (leaf size and specific leaf area) were analysed in taxa showing widespread distributions in the Canary Islands and across mainland Mediterranean areas: Lavandula, Olea, Periploca and Cistus. Preliminary analysis of bioclimatic data indicated that islands show subtropical conditions that are not found among the mainland habitats occupied by these taxa, which could have favoured phenotypic differentiation between these two regions. Strong evidence of character shift, however, was only found in two cases. Phenotypic data in Lavandula suggested that evolution of growth form in the island setting was associated with the expression of novel leaf traits. Evidence of character shift was also related to ecological release, most notably in Periploca, when island populations occupy a range of ecological zones distant from typical mainland conditions (e.g. zones influenced by the humid, north-east trade winds). This study shows that widespread island taxa display convergent phenotypic responses to habitat shift, which strongly suggest an adaptive pattern and stress the deterministic nature of phenotypic variation. I further discuss how the identification of these patterns provides a promising framework for the testing of hypotheses on the evolutionary mechanisms involved in phenotypic adaptation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 399–411.

Premise of research. Hybridization is a mechanism frequently invoked to account for the spectacular radiations observed in oceanic islands, but, surprisingly, there is little empirical support for its ecological role in island plant radiations. Theory predicts that hybridization should provide individuals with the phenotypic novelty required for habitat shifts, thus promoting conditions for subsequent speciation. In this article, we studied the first stages of this process using two hybridizing species of Dubautia (Asteraceae), the most diversified genus of the Hawaiian silversword radiation.Methodology. Phenotypic and habitat differentiation were investigated in two recently derived species (Dubautia arborea and Dubautia ciliolata) and a hybrid zone. Morphological trait expression and physiological trait expression under field and common garden conditions and microclimatic variation were analyzed to address the patterns of differentiation among parental species and hybrids.Pivotal results. Our analyses s...

1. Canopy plasticity, the expression of different leaf phenotypes within the crown of an individual tree has complex functional and evolutionary implications that remain to be thoroughly assessed. We hypothesized that it can lead to disparity in how leaves in different positions of the canopy change with allometric growth and population genetic structure. 2. Leaf phenotypes of the inner and outer canopy were estimated using eight morphological and physiological characters. All traits were measured under field conditions in six populations of Olea europaea and again in a common garden for a subset of the genotypes. The same populations were characterized genetically with amplified fragment length polymorphisms (AFLP) genomic scans. With these data, we investigated the extent to which leaf phenotypes change with plant size, genetic processes and in response to environmental conditions inside and outside the canopy. 3. The size of trees measured in the field was clearly associated with the phenotype of sun but not to that of shade leaves. The phenotype of sun leaves depended on both direct and diffuse light, while that of shade leaves was found to correlate only with diffuse radiation. Additionally, light availability inside the canopy was conditioned by the shape of external leaves, and increasing elongation of sun leaves led to higher radiation in the inner canopy. 4. The field phenotypes of both inner and outer canopy leaves were correlated with genetic variation among populations. Conversely, in the common garden, the different genotypes expressed a homogeneous sun phenotype, while phenotypic differences among populations remained apparent in shade leaves. 5. We conclude that, in agreement with our working hypothesis, canopy plasticity is both cause and consequence of the environment experienced by the plant and might lead to the differential expression of genetic polymorphisms among leaves. Furthermore, we propose that it can contribute to buffer abiotic stress and to the partition of light use within the tree crown.

Trees are modular organisms that adjust their within-crown morphology and physiology in response to within-crown light gradients. However, whether within-plant variation represents a strategy for optimizing light absorption has not been formally tested. We investigated the arrangement of the photosynthetic surface throughout one day and its effects on the photosynthetic process, at the most exposed and most sheltered crown layers of a wild olive tree (Olea europaea L.). Similar measurements were made for cuttings taken from this individual and grown in a greenhouse at contrasted irradiance-levels (100 and 20% full sunlight). Diurnal variations in light interception, carbon fixation and carbohydrate accumulation in sun leaves were negatively correlated with those in shade leaves under field conditions when light intensity was not limiting. Despite genetic identity, these complementary patterns were not found in plants grown in the greenhouse. The temporal disparity among crown positions derived from specialization of the photosynthetic behaviour at different functional and spatial scales: architectural structure (crown level) and carbon budget (leaf level). Our results suggest that the profitability of producing a new module may not only respond to construction costs or light availability, but also rely on its spatio-temporal integration within the productive processes at the whole-crown level.

Trees have the ability to respond to local environmental cues by expressing particular phenotypes across their canopy through a mechanism known as intracanopy plasticity. In this study, intracanopy plasticity of Olea europaea subsp. europaea was analyzed by sampling leeward and windward canopy exposures of individuals occurring in an area with sustained strong wind conditions. A suite of morphofunctional and reproductive traits was measured at these contrasting canopy positions and, for comparison, also in wind-protected trees. Furthermore, the pattern of intracanopy plasticity of these plants was compared to that previously documented in a closely related species, Olea europaea subsp. guanchica. Plants exposed to strong winds displayed substantial differences between leeward and windward exposures in most of the study traits. Leeward exposures experienced a mean reduction of 73% in wind speed as compared to windward ones, and displayed a modular phenotype matching that observed in wind-protected plants. Wind-exposed plants, however, were comparatively smaller and had fewer and smaller inflorescences, since inflorescence size was positively associated with crown size. The two closely related species showed similar crown and leaf sizes between populations exposed to strong winds, and intracanopy responses were comparable for most traits. These observations suggest that intracanopy plasticity resulted in the expression of contrasting phenotypes within individuals, which allowed trees to persist under sustained wind stress, although at the cost of a reduced reproductive fitness. In addition, this study gives support to the idea that intracanopy responses are conserved among closely related taxa evolving in different habitats, but experiencing a comparable limiting factor.

Phenotypic variation of traits can reflect the ability of plants to adjust to particular environments, but how much of this variation is heritable is not frequently analyzed in natural populations. In the present paper, we investigated the patterns of phenotypic expression in light-related leaf traits of Olea europaea subsp. guanchica, a woody sclerophyllous species endemic to the Canary Islands. We explored phenotypic differentiation and heritable variation across several island populations differing in light environment. A suite of morpho-functional (leaf size, SLA and leaf angle) and physiological (pigment pools: Chl a/b ratio, xantophyll cycle and β-carotene) traits was measured in six populations on three islands. In addition, we estimated heritabilities for these traits following Ritland's method. Variation in morpho-functional, but not in physiological, traits was observed across the islands and was significantly related to the amount of diffuse light experienced by each population. In addition, significant heritabilities were found for morpho-functional traits, whereas expression of similar phenotypes among populations was accompanied by a lack of heritable variation in physiological traits. Most recently established populations did not exhibit lower heritabilities in quantitative traits than older populations, and apparently displayed congruent phenotypes under the local conditions. Our results strongly support the idea that different types of traits show contrasted levels of genetic and phenotypic variation in populations experiencing marked environmental differences.

Woody plants, as sessile and long-lived organisms, are expected to have effective mechanisms for dealing with recurrent environmental stresses. In the present study, we hypothesized that phenotypic plasticity (the ability to express alternative phenotypes) and integration (covariation among functionally related traits) are elicited in plants under stressful wind speed conditions. We investigated the within-crown variation of nine vegetative traits of a tree species (Olea europaea subsp. guanchica) in six populations that represented a gradient of wind speed exposures. Wind-exposed twigs in outer-canopy layers had smaller leaves; thinner, lighter, and shorter internodes; and a larger internode cross-sectional area to leaf area ratio. Comparison between field and greenhouse trials revealed that field differences among populations were mediated by phenotypic plasticity. Outer-canopy twigs expressed plastic responses in populations exposed to high wind speeds, whereas inner-canopy twigs displayed high phenotypic convergence among populations. In addition, phenotypic integration increased with wind exposure (outer canopy > inner canopy > greenhouse) and was consequently affected by canopy openness. We conclude that exposure to wind above a certain speed threshold in this woody species elicits a plastic response that is associated with increased integration among traits and involves mechanical and hydraulic rearrangements in more exposed parts of the trees.

Interspecific introgression is a well-known phenomenon in oaks whose ecological and evolutionary consequences, although relevant, are still unclear. We investigated molecular variation and any evidence for hybridisation in nine natural populations of kermes oak ( Quercus coccifera L.) from the Iberian Peninsula. Additive patterns in 59 nrDNA ITS sequences revealed that hybrid individuals showing intermediate genotypes between kermes and holm ( Q. ilex L.) oaks are very frequent, although intermediate morphotypes are uncommon. Bayesian analysis of ISSR fingerprinting patterns indicated extensive gene-flow among Q. coccifera populations and neighbouring Quercus taxa. Introgression appeared to be an active mechanism in the pair Q. coccifera – Q. ilex , but no conclusive evidence supporting hybridisation between Q. coccifera and other co-occurring Quercus species was found. The role of canalisation in the maintenance of stable morphological characters in the face of extensive introgression is discussed.

†Background and Aims Quercus coccifera, as a long-lived sprouter, responds plastically to environmental variation. In this study, the role of foliar plasticity as a mechanism of habitat selection and modification within the canopy and across contrasted habitats was characterized. An examination was made of the differential contribution of inner and outer canopy layers to the crown plasticity expressed in the field by adult individuals and its dependence on environmental and genetic factors. †Methods Within-crown variation in eight foliar traits was examined in nine populations dominated by Q. coccifera. The difference between mean trait values at the inner and outer canopy layers was used as a proxy for crown plasticity to light. Correlations between geographic distances, environmental differences (climatic and edaphic) and phenotypic divergence (means and plasticities) were assessed by partial Mantel tests. A subset of field measurements was compared with data from a previous common garden experiment. †Key Results Phenotypic adjustment of sun leaves contributed significantly to the field variation in crown plasticity. Plasticity in leaf angle, lobation, xanthophyll cycle pigments and b-carotene content was expressed in sun and shade leaves concurrently and in opposite directions. Phenotypic plasticity was more strongly correlated with environmental variation than mean trait values. Populations of taller plants with larger, thinner (higher specific leaf area) and less spiny leaves exhibited greater plasticity. In these populations, the midday light environment was more uniform at the inner than at the outer canopy layers. Field and common garden data ranked populations in the same order of plasticity. †Conclusions The expression of leaf plasticity resulted in a phenotypic differentiation that suggests a mechanism of habitat selection through division of labour across canopy layers. Signs of plasticity-mediated habitat modification were found only in the most plastic populations. Intracanopy plasticity was sensitive to environmental variation but also exhibited a strong genetic component.

Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island–mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long-standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant popula- tions.

Understanding how genetic diversity is structured on oceanic island taxa requires the integration of physical, biological and anthropomorphic factors. Founder effects coupled with limited dispersal over sea barriers typically result in low levels of genetic variation in island populations. In widespread species, restriction in gene flow across large areas leads to patterns of isolation by distance (IBD), but recent population-based studies indicate that genetic structure on islands can be complex even at local scales. Here, we investigated the patterns of genetic variation in a widespread island palm (Phoenix canariensis) displaying reproductive syndromes associated with extensive dispersal (wind pollination and zoochory). Genetic variation was assessed at eight nuclear microsatellite loci in 330 individuals of 15 Canarian populations. Our results showed that levels of within-population genetic diversity in P. canariensis depend on the island considered, with a strong decreasing pattern from the easternmost and oldest island to the westernmost and youngest islands. A Mantel test supported a stepping-stone model of differentiation across the archipelago that fits the sequence of island emergence, and results from ABC and clustering analyses also corresponded with this progression rule. In addition, our analyses were congruent with the idea that the only large population found on Lanzarote has an anthropogenic origin. Despite the high dispersal potential of P. canariensis, our analyses suggest that the geographical configuration of the Canary Islands and a relatively recent pattern of differentiation across islands appear to have had a primary influence on the genetic structure of this island taxon.

Evergreen oaks are an emblematic element of the Mediterranean vegetation and have a leaf phenotype that seems to have remained unchanged since the Miocene. We hypothesise that variation of the sclerophyll phenotype among Iberian populations of Quercus coccifera is partly due to an ulterior process of ecotypic differentiation. We analysed the genetic structure of nine Iberian populations using ISSR fingerprints, and their leaf phenotypes using mean and intracanopy plasticity values of eight morphological (leaf angle, area, spinescence, lobation and specific area) and biochemical traits (VAZ pool, chlorophyll and beta-carotene content). Climate and soil were also characterised at the population sites. Significant genetic and phenotypic differences were found among populations and between NE Iberia and the rest of the populations of the peninsula. Mean phenotypes showed a strong and independent correlation with both genetic and geographic distances. Northeastern plants were smaller, less plastic, with smaller, spinier and thicker leaves, a phenotype consistent with the stressful conditions that prevailed in the steppe environments of the refugia within this geographic area during glaciations. These genetic, phenotypic, geographic and environmental patterns are consistent with previously reported palaeoecological and common evidence. Such consistency leads us to conclude that there has been a Quaternary divergence within the sclerophyllous syndrome that was at least partially driven by ecological factors.

Background: Phylogenetic and phylogeographic investigations have been previously performed to study the evolution of the olive tree complex (Olea europaea). A particularly high genomic diversity has been found in north-west Africa. However, to date no exhaustive study has been addressed to infer putative polyploidization events and their evolutionary significance in the diversification of the olive tree and its relatives. Methods: Representatives of the six olive subspecies were investigated using (a) flow cytometry to estimate genome content, and (b) six highly variable nuclear microsatellites to assess the presence of multiple alleles at co-dominant loci. In addition, nine individuals from a controlled cross between two individuals of O. europaea subsp. maroccana were characterized with microsatellites to check for chromosome inheritance. Key Results: Based on flow cytometry and genetic analyses, strong evidence for polyploidy was obtained in subspp. cerasiformis (tetraploid) and maroccana (hexaploid), whereas the other subspecies appeared to be diploids. Agreement between flow cytometry and genetic analyses gives an alternative approach to chromosome counting to determine ploidy level of trees. Lastly, abnormalities in chromosomes inheritance leading to aneuploid formation were revealed using microsatellite analyses in the offspring from the controlled cross in subsp. maroccana. Conclusions: This study constitutes the first report for multiple polyploidy in olive tree relatives. Formation of tetraploids and hexaploids may have played a major role in the diversification of the olive complex in north-west Africa. The fact that polyploidy is found in narrow endemic subspecies from Madeira (subsp. cerasiformis) and the Agadir Mountains (subsp. maroccana) suggests that polyploidization has been favoured to overcome inbreeding depression. Lastly, based on previous phylogenetic analyses, we hypothesize that subsp. cerasiformis resulted from hybridization between ancestors of subspp. guanchica and europaea.