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Biological invasions in remote areas that experience low human activity provide unique opportunities to elucidate processes responsible for invasion success. Here we study the most widespread invasive plant species across the isolated islands of the Southern Ocean, the annual bluegrass, Poa annua. To analyse geographical variation in genome size, genetic diversity and reproductive strategies, we sampled all major sub-Antarctic archipelagos in this region and generated microsatellite data for 470 individual plants representing 31 populations. We also estimated genome sizes for a subset of individuals using flow cytometry. Occasional events of island colonization are expected to result in high genetic structure among islands, overall low genetic diversity and increased self-fertilization, but we show that this is not the case for P. annua. Microsatellite data indicated low population genetic structure and lack of isolation by distance among the sub-Antarctic archipelagos we sampled, but high population structure within each archipelago. We identified high levels of genetic diversity, low clonality and low selfing rates in sub-Antarctic P. annua populations (contrary to rates typical of continental populations). In turn, estimates of selfing declined in populations as genetic diversity increased. Additionally, we found that most P. annua individuals are probably tetraploid and that only slight variation exists in genome size across the Southern Ocean. Our findings suggest multiple independent introductions of P. annua into the sub-Antarctic, which promoted the establishment of genetically diverse populations. Despite multiple introductions, the adoption of convergent reproductive strategies (outcrossing) happened independently in each major archipelago. The combination of polyploidy and a mixed reproductive strategy probably benefited P. annua in the Southern Ocean by increasing genetic diversity and its ability to cope with the novel environmental conditions.

Phenotypic plasticity (i.e. the ability to express different phenotypes under changing environmental conditions) is thought to play a key role in habitat adaptation, but little is known about how trait plasticity evolves following dispersal into novel island habitats. We hypothesize that shifts from seasonal Mediterranean climates to more stable (subtropical) island conditions would promote a net reduction in trait plasticity over time. To test this hypothesis, we set two common gardens with contrasting environmental (low resource vs. mesic) conditions, where we grew seedlings of wild olive (Olea europaea var. sylvestris) populations that represented two Canary Island lineages with different colonization times (old vs. young) and their Mediterranean ancestral lineage (N = 275 individuals). Plasticity was assessed for 12 morphological, photosynthetic and chemical traits by (i) subjecting half of the seedlings to simulated herbivore browsing (50% of aerial biomass removal) and (ii) comparing phenotypic values between both common garden settings. Simulated herbivore browsing induced few plastic responses, mostly restricted to photosynthetic traits, but these were similarly displayed by all lineages. Comparisons between common gardens revealed a contrasting response between the Mediterranean and both subtropical island lineages in leaf phenotypes. Furthermore, the older island lineage showed an overall lack of plasticity (i.e. environmental canalization) in morphological and chemical traits. These results suggest that, unlike photosynthetic traits that are fundamental for fast acclimation to environmental shifts, some developmental traits may lose plasticity over time as a result of phenotypic adjustment to subtropical insular conditions.

Aim: It is predicted that insular plant taxa have evolved reduced defences in response to lower herbivore pressure on islands. However, the few studies testing this hypothesis have addressed variation in individual defensive traits, without paying attention to patterns of correlated trait expression (i.e. defence syndromes). Location: Balearic and Canary Islands. Taxon: Ninety-one woody plant species. Methods: We tested whether plant species with contrasting histories of insularity (namely, endemics, non-endemic natives and exotics) differed in their defensive syndromes using a suite of morphological, physical, and chemical traits putatively associated with herbivory. For this, we measured eight leaf traits of 42 endemic, 29 native non-endemic and 20 introduced species for which specimens were sourced from botanical gardens found in two archipelagos: the Balearic and Canary Islands. Results: We conducted phylogenetic-controlled analyses which showed that, contrary to predictions, insular taxa (endemics and non-endemic natives) across both archipelagos were more defended (thicker, smaller leaves with less nutrients) than exotic species. There were no differences in chemical defence (phenolic compounds) between endemics, non-endemic natives and exotics. Finally, we also found different defence syndromes between archipelagos: whereas species from the Balearic Islands were more physically defended, on average, those from the Canary Islands had higher chemical defences. Main conclusions: Overall, these results point to a defence syndrome based on low-nutrient and physically defended leaves characteristic of insular plant taxa that is indistinct for endemic and non-endemic taxa, relative to introduced species, as well as quantitative and qualitative differences in defences between archipelagos owing to changes in species composition and likely also to different histories of biotic or abiotic pressure.

Aim: We explore the idea that most pre-glacial non-endemic Canarian flora became endemic to the archipelago by the extinction of its mainland populations during the late Pleistocene glaciations, implying that the extant non-endemic flora is mostly post-glacial: the ‘late Pleistocene endemicity increase hypothesis’. Taxon: The native flora of the Canarian archipelago. Methods: We statistically compare the distributions of 2087 Canarian endemic and native non-endemic plants across islands. We also carry out connectivity analyses using their dispersal paths, obtained by connecting all the islands of occurrence for each taxon. Results: While the distribution of the endemic flora is strongly L-shaped (with a much higher proportion of Single-Island Endemics than Multiple-Island Endemics), that of the native non-endemics is U-shaped (i.e. similar prevalence of single-island taxa and taxa distributed on all islands). The native non-endemics have a significantly lower proportion of single-island taxa and a higher proportion of widespread taxa than the endemics. Most dispersal paths in the endemics connect the central and western islands, whereas they are extended across all islands in the native non-endemics. Main conclusions: The contrasting distributional patterns of the endemics and the native non-endemics support an outstanding role of species diversification in the endemic flora, but a still negligible influence of the insular selective and stochastic pressures (including extinction) in the native non-endemic flora, arguably due to its recent origin. Our results suggest that the high endemicity levels of the extant Canarian flora can be explained by two complementary processes: (i) high diversification rates throughout the ontogeny of the archipelago, often from colonisers that attained a widespread distribution prior to speciation, and (ii) an ‘endemicity increase’ during the late Pleistocene glaciations, whereby most of the pre-glacial non-endemic Canarian flora becam

Project NEXTGENDEM (MAC2/4.6d/236, https://lupus.itccanarias.org/nextgendem/es/) complements multiple research disciplines to provide verified and validated scientific data that help managers make more informed conservation decisions. As a result of the mobilization and enrichment of the sample and data banks of the Jardín Botánico Canario “Viera y Clavijo” -UA CSIC and the Instituto Nacional de Investigação e Desenvolvimento Agrário de Cabo Verde, tools will be developed for the estimation of phylogenetic diversity of the terrestrial endemic flora of these islands, the approximation to the molecular taxonomic identification of samples, phylogenetic reconstruction, and territorial analysis merging biotic and abiotic variables. Our main objective is to organise, analyse and apply the most relevant scientific knowledge to guide in situ and ex situ actions to improve the conservation status of the flora of Gran Canaria (Canary Islands) and Santiago (Cape Verde), although we plan to incorporate other Macaronesian territories in future projects, El proyecto NEXTGENDEM (MAC2/4.6d/236, https://lupus.itccanarias.org/nextgendem/es/) complementa múltiples disciplinas de investigación para proporcionar datos científicos contrastados y validados que faciliten a los gestores la toma de decisiones de conservación más informadas. A consecuencia de la movilización y el enriquecimiento de los bancos de muestras y datos del Jardín Botánico Canario ¿Viera y Clavijo¿ ¿ UA CSIC y del Instituto Nacional de Investigação e Desenvolvimento Agrário de Cabo Verde, se pondrán a punto herramientas para la estimación de la diversidad filogenética de la flora terrestre insular, la aproximación a la identificación taxonómica molecular de muestras, la reconstrucción de filogenias, y el análisis territorial integrado con variables bióticas y abióticas. Nuestro objetivo principal es organizar, analizar y aplicar el conocimiento científico más relevante para guiar actuaciones in situ y ex situ que mejoren el estado de conservación de las floras de Gran Canaria (Islas Canarias) y Santiago (Cabo Verde), aunque prevemos incorporar otros territorios macaronésicos en futuros proyectos

[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.

[Aim] Plants on islands are often subjected to lower levels of herbivory relative to those found at mainland sites. As a consequence, island plants are predicted to exhibit lower levels of physical or chemical defences, which renders them more susceptible to introduced herbivores. Yet, instances of high pressure by superabundant herbivores native to islands have been reported in many insular systems, which presumably would result in heightened plant defences. To date, no quantitative review has been conducted to determine how common these contrasting patterns are and their implications for the evolution of plant-herbivore interactions., [Location] Islands worldwide., [Taxon] Plants, insects, molluscs, mammals., [Methods] We conducted a meta-analysis of insularity effects on herbivory and plant defences by including studies that involved island-mainland comparisons of the same plant species in both environments (90% of cases), or insular endemics versus mainland congeners (10% of cases). We tested for differences between mammalian and invertebrate (mollusc or insect) herbivory as well as between plant chemical and physical defences by specifying comparisons based on the type of herbivore (vertebrate or invertebrate) or plant trait included in the study., [Results] Mammalian herbivory was significantly higher on islands than on mainlands. In contrast, no significant effect was observed on invertebrate herbivory. In addition, we found no significant difference in either plant physical or chemical defences between insular and mainland plants, though physical defences tended to be higher for plants on islands., [Main conclusions] All analysed mammal studies focused on species introduced to islands, suggesting greater susceptibility of insular plants to exotic mammals, whereas the lack of effects in the case of invertebrate herbivory suggests no difference in susceptibility to molluscs or insects between insular and mainland plants. Interestingly, plant trait patterns suggest a trend for increased physical defences by insular plants, possibly due to heightened pressure by exotic mammalian herbivores on islands, whereas chemical defences appear uncorrelated to differences in herbivory. These findings call for further experimental and observational studies measuring defences and herbivory for multiple sympatric plant species occurring at both mainland and island sites within a system, or comparing insular endemics to congeneric mainland species.

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.

[Aim] One of the main goals of functional biogeography is to examine distribution patterns of trait diversity, and islands provide excellent study cases for this emerging field. We tested the hypothesis that multiple dispersals from a common mainland pool would promote functional similarity among island systems when environmental conditions are similar, but also novel phenotypic traits related to colonization history and exploitation of new habitats., [Location] Mediterranean Basin and Macaronesian islands., [Taxon] Wolfbane (Periploca laevigata), [Methods] We used the well‐known biogeographical history of a woody plant complex (P. laevigata s.l.) to examine trait variation and how it relates to climatic conditions of mainland and subtropical island settings. In a common garden experiment, we measured a suite of leaf physiological and anatomical traits tightly related to plant performance in 320 seedlings representing 21 populations of five sublineages—the oldest (2.6 my) island colonization (western Canary Islands) as a reference, three sublineages stemming from independent events of island colonization in the last 0.5 my from NW Africa (Cape Verde, Fuerteventura, Lanzarote) and their widespread Mediterranean mainland counterpart., [Results] We observed strong phenotypic divergence between island and mainland sublineages linked to contrasting climatic conditions. Mediterranean mainland populations displayed a very specialized leaf phenotype characteristic of arid plants (i.e. small leaves, amphistomaty, isobilateral mesophyll, high photosynthetic rates). In turn, low seasonality on islands was linked to the recurrent expression of a phenotype characterized by larger leaves and lower photosynthetic rates. Our analyses showed that the high investment in secondary compounds (i.e. tannins) on islands decouples photosynthesis from growth rates. Despite this pattern of parallel differentiation, each island sublineage displayed a distinctive phenotype, with some traits related to colonization time, which resulted in a mosaic of functional variation across island systems., [Main conclusions] Our data suggest that the studied subtropical islands promote expression of traits specific to certain sublineages and other common traits that are no longer adaptive in the original mainland pool due to Pleistocene climatic shifts. These findings ultimately extend the role of islands as biodiversity refugia and hotspots of plant functional diversity.

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 (

Aim: Research on plant–herbivore interactions has shown that islands typically have low abundances and diversity of herbivores because of barriers to dispersal, isolation and reduced land area. Islands commonly have lower levels of herbivory relative to mainland regions, and, as a consequence, insular plants should exhibit lower levels of defences than their mainland counterparts. Despite these predictions, there are significant gaps in our understanding of insularity effects on plant–herbivore interactions. For instance, most work addressing the effects of insularity on plant–herbivore interactions have compared one or a few islands with a single mainland site. In addition, studies have measured herbivory or plant defences but not both, and the influence of abiotic factors has been neglected. Location: Mediterranean Basin (from Spain to Greece). Taxon: Quercus ilex L. Methods: We conducted a large-scale study to investigate whether insect leaf herbivory and plant chemical defences in holm oak (Quercus ilex L.) differ between insular versus mainland populations. We further investigated mechanisms by which insularity effects on herbivory may take place by assessing the influence of defences and climatic variables on herbivory. Results: We found that insular populations exhibited lower herbivory and higher defences (condensed tannins) than their mainland counterparts. Our analyses, however, suggest that these concomitant patterns of insect herbivory and plant defences were seemingly unrelated as island versus mainland differences in defences did not account for the observed pattern in herbivory. Furthermore, climatic factors did not explain insularity effects on either herbivory or plant defences. Main conclusions: Overall, this study provides one of the most robust assessments to date on insularity effects on herbivory and builds towards a better understanding of the ecology and evolution of plant–insect interactions in insular ecosystems.

[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.

[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.

[Premise of the Study] We tested a hypothesis that predicts loss of chemical defenses on island plant populations (LCDIH) as an evolutionary response to limited herbivore pressures., [Methods] Using a common garden approach, we grew 16 populations (N = 286 seedlings) of Periploca laevigata, a Mediterranean shrub for which previous studies suggested that animal browsing elicits defensive responses mediated by tannins. Our experimental setting represented a wide latitudinal gradient (37–15°N) encompassing three island systems, virtually free of large herbivores, and three mainland areas. Putative chemical defenses were estimated from tannin–protein precipitation assays, and inducible responses in growth and chemical traits were assessed between seasons and by subjecting plants to a pruning treatment., [Key Results] We failed to find support for the LCDIH, since island populations (Canary Islands, Cape Verde) had increasingly higher constitutive levels of tannins at lower latitudes. Seasonality, but not experimental pruning, induced variation in levels of tannins in a consistent pattern across populations. Thus, net differences in leaf tannin concentration remained similar among geographical areas regardless of the factor considered, with latitude being the best explanatory factor for this trait over seasonal growth patterns., [Conclusions] Geographical variation in total tannin pools appears to be mediated by factors other than herbivore pressure in P. laevigata. We hypothesize that abiotic correlates of latitude not considered in our study have promoted high constitutive levels of leaf tannins across Macaronesian populations, which ultimately may explain the pattern of seasonal variation and latitudinal increase from Mediterranean to subtropical Cape Verde populations.

Subtropical islands are often viewed as refuges where Quaternary climatic shifts driving global episodes of extinction were buffered. Island biodiversity, however, may have been impacted by climatic fluctuations at local scales, particularly in spatially heterogeneous island systems. In this study, we generated a conceptual framework for predicting the potential impact of Pleistocene extinctions on the biogeographical pattern of the Canarian spermatophyte flora, with a focus on the easternmost Canarian islands (ECI). Then, we performed an exhaustive bibliographic revision (270 studies) to examine whether taxonomic, phylogenetic and phylogeographical data support our predictions. Although molecular information is limited for many lineages, the available data suggest that the majority of extant ECI plant taxa may be the result of relatively recent (<1 Ma) dispersal from surrounding insular and mainland areas. Different lines of evidence are compatible with the idea of a Pleistocene period of frequent lineage extirpation on ECI. Extinction may thus have provided new ecological opportunities for recent (re)colonization, with some cases of recent establishment mediated by facilitation. Considering background extinction on ECI, we describe five general patterns of colonization for Canarian plant lineages. In addition to factors related to island ontogeny and long-distance dispersal, we suggest that Pleistocene extinctions may have significantly contributed to extant biogeographical patterns in the Canarian archipelago, such as the biased distribution ranges of island plants and the low endemic richness on ECI. This new scenario provides testable hypotheses for future studies dealing with the phylogeography, taxonomy and conservation of terrestrial biodiversity on the Canarian islands, and possibly, on other near-shore islands.

Los días 1 y 3 de febrero se celebró en Mallorca la XV Reunión anual de ECOFLOR (http://webecoflor.webs.uvigo.es) (Fig. 1), red temática y grupo de trabajo sobre ecología y evolución floral de la Asociación Española de Ecología Terrestre (AEET). Fue organizada por el grupo de Ecología Terrestre del Instituto Mediterráneo de Estudios Avanzados (IMEDEA-CSIC, http://imedea.uib-csic.es/icg/ecol_ terr/cast/group.html).