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Questions: Pollen traits (e.g., size, wall thickness, number of apertures) have been suggested to be relevant in terms of pollination mechanisms and the ability of the male gametophyte to withstand desiccation. We examined the spatiotemporal distribution of pollen traits related to dispersal (ornamentation and dispersal unit) and desiccation tolerance (wall thickness, presence of furrows and pores and pollen size). Specifically, we address two questions: how are the pollen traits distributed in relation to different levels of aridity? And, how did the pollen trait composition change with changing past environmental conditions?. Location: Laurel forests of La Gomera and Tenerife (Canary Islands). Methods: We used pollen rain from 19 forest plots on an elevational gradient of 1050 m and all laurel forest types (cold, dry, humid and ridge crest) to quantify pollen trait composition using community-weighted means. In addition, we used fossil pollen to examine the composition of pollen traits over 9600 years in response to known intervals of regional past climate change. Results: Our results demonstrated increased prevalence of desiccation tolerance-related pollen traits over drier areas of the laurel forest distribution. We also found increased prevalence of rich pollen grain ornamentation in the core of the laurel forest distribution. Holocene pollen functional diversity increased during a trend towards drier conditions as did the proportion of pollen grains with apertures and thicker walls to indicate desiccation tolerance. Conclusions: Our study provides the first step towards understanding the role of pollen traits when quantifying the dynamics of different plant communities.

The Walker and Syers model predict that phosphorus (P) availability decreases with time leading to a final stage known as retrogression. We tested the validity of the Walker and Syers model in the Canary Islands, a soil chronosequence ranging from 300 years to 11 million years under recurrent episodes of atmospheric dust-containing P inputs. In particular, we compared our results with those from the volcanic soil chronosequences described in the Hawaii Islands and in Arizona, as they share key biological and/or geological characteristics. In three islands of the Canarian Archipelago, we selected 18 independent sites dominated by mature Pinus canariensis forests and grouped them into six age classes. For each site, soil samples were analyzed for known proxies of soil nitrogen (N), P and cations availability. We also analyzed the P. canariensis needles for N, P and cation contents. We found tendencies similar to those observed in other soil chronosequences: maximum N and P concentrations at intermediate ages and lower P concentrations in the older soils. The nutrient dynamics suggested that the older sites may indeed be approaching the retrogression stage but at lower rates than in other similar chronosequences. Differences from other chronosequences are likely due to the drier Canarian climate, the higher P deposition rates originating from the nearby Sahara Desert and the top soil horizon studied. Our results confirm the validity of the Walker and Syers model for the Canary Islands despite the influence that the high P deposition rates and the seasonally dry climate may have on soil development and P pools in P. canariensis ecosystems.

Plants on oceanic islands can evolve insular syndromes such as secondary woodiness, a generalized trend found in island floras worldwide. This phenomenon occurs through evolution in situ. It is triggered by ecological and physiological stimuli that transform herbaceous annuals into woody perennials. However, well-dated and informative fossils that could help track and frame the evolution of this syndrome are lacking. Remarkably, in Madeira Island (Portugal), there are good examples of Apiaceae that evolved secondary woodiness, like the giant neoendemic Melanoselinum (≡ Daucus). Apiaceae has a very scarce fossil record, despite being a cosmopolitan family and an economically important crop. Here we describe the oldest Daucus s.l. fossil known to date and the first fossil evidence of a plant with insular woodiness. The fossils are preserved as mummified/compressed mericarps within 1.3-million-year-old fluvio-lacustrine sediments of the Funchal unit, Upper Volcanic complex, near Porto da Cruz. We assign them to the extant neoendemic species Melanoselinum (≡ Daucus) decipiens. The mericarp morphology shows remarkable stasis since the Calabrian stage of the Early Pleistocene. Our results demonstrate that in the Madeiran Daucinae clade, insular woodiness developed at least 1.3 million years ago, indicating a coeval or earlier immigration to Madeira Island of a Daucus sp. Our results reinforce the role of palaeobotanical research in oceanic islands, supported by stratigraphy and geochronology studies, as a key element for the understanding of plant palaeobiogeography, ecology and evolution worldwide. We expect this contribution to shed light on the evolutionary origins of carrots, and related plant groups, an important element of human food, and to better comprehend the evolution of plant insular woodiness.

Terceira Island (Azores archipelago, central Atlantic Ocean) presents a unique but poorly studied Quaternary palaeobotanical record. Among the sites referenced in the literature, Fanal Bay, within Angra do Heroismo city, is known at least since the 1940s. Field prospection in the summer of 2016 revealed two layers of leaf fossils with an unexpected fossil abundance. The preliminary results showed that these represented autochthonous or para-autochthonous (T0) fossil assemblages, preserved by the emplacement of ash or lapilli layers by volcanic events, in a leaf litter of a laurel palaeoforest. Unfortunately, in 2018, the site was destroyed due to development works to consolidate and requalify the Fanal Bay cliff from further sea erosion. This prevented a detailed study and the ex situ preservation of an important palaeontological site, within the Azores UNESCO Global Geopark. With this work, we hope to call the attention to the need of implementing geoconservation strategies in order to prevent the destruction of important geoheritage within the Azores Islands and to transpose this warning to other geoconservationists in oceanic islands worldwide.

The extinction of iconic species such as the dodo and the deforestation of Easter Island are emblematic of the transformative impact of human colonization of many oceanic islands, especially those in the tropics and subtropics. Yet, the interaction of prehistoric and colonial-era colonists with the forests and forest resources they encountered can be complex, varies between islands, and remains poorly understood. Long-term ecological records (e.g., fossil pollen) provide the means to understand these human impacts in relation to natural change and variability pre- and postcolonization. Here we analyze paleoecological archives in forested landscapes of the Canary Islands and Cabo Verde, first colonized approximately 2,400 to 2,000 and 490 y ago, respectively. We demonstrate sensitivity to regional climate change prior to human colonization, followed by divergent but gradual impacts of early human settlement. These contrast with more rapid transformation in the colonial era, associated with significant increases in anthropogenic pressures. In the Canary Islands, at least two native tree taxa became extinct and lowland thermophilous woodlands were largely converted to agricultural land, yet relictual subtropical laurel forests persisted with limited incursion of nonnative species. In Cabo Verde, in contrast, thermophilous woodlands were depleted and substituted by open landscapes and introduced woodlands. Differences between these two archipelagos reflect the changing cultural practices and societal interactions with forests and illustrate the importance of long-term data series in understanding the human footprint on island ecosystems, information that will be critically important for current and future forest restoration and conservation management practices in these two biodiversity hotspots.

Research Article Aim: Palaeoecological data provide an essential long-term perspective of ecological change and its drivers in oceanic islands. However, analysing the effects of multi-scalar and potentially co-occurring disturbances is particularly challenging in dry islands. Here, we aim to identify the ecological consequences of the integrated impacts of a regional drying trend, volcanic eruptions and human mass migrations in a spatially constrained environment—a small, dry oceanic island in Macaronesia. Location: Brava Island, Republic of Cabo Verde. Taxa: Terrestrial vegetation and fungi. Methods: We use palaeoecological analyses applied to a caldera soil profile that dates back to 9700 cal yr BP (calibrated years before the present). Analyses include pollen (vegetation history), non-pollen palynomorphs (changes in fern and fungal communities), grain-size distribution, loss-on- ignition and geochemistry (sedimentology and erosion regimes), microscopic tephra shards (volcanic ash deposition) and charcoal (fire regime). Results: A regional drying trend after c. 4000 cal yr BP caused increased erosion but had limited immediate impacts on highland grassland vegetation. The expansion of fern-rich woody scrubland was contemporaneous with significant deposition of volcanic ash and erosion between 1800 and 650 cal yr BP. About 300 cal yr BP, exogenous plants expanded, grazing and fires increased, and there was a decrease of native vegetation cover. Main conclusions: Throughout the Holocene, highland vegetation in Brava was characterized by the presence of open landscapes dominated by herbaceous species (e.g. Poaceae, Forsskaolea), with some presence of woody native taxa (e.g. Ficus, Dodonaea). A regional drying trend was a driver of erosion since the Mid Holocene but did not have an immediate influence on highland vegetation. Tephra deposition is a possible driver of vegetation change. Inter-island mass migration after volcanic events in Fogo Island c. 1680 CE potentially triggered land use change and intensification, causing a reduction of native vegetation in Brava info:eu-repo/semantics/publishedVersion

Aim Long‐term ecological data provide a stepped frame of island ecosystem transformation after successive waves of human colonization, essential to determine conservation and management baselines. However, the timing and ecological impact of initial human settlement on many islands is still poorly known. Here, we report analyses from a 4800‐year sedimentary sequence from Gran Canaria (Canary Islands), with the goal of disentangling forest responses to natural fire from early human pressure on the island. Location La Calderilla, a volcanic maar caldera at 1,770 m a.s.l. on Gran Canaria. Taxon Plants and fungi. Methods A core from the caldera infill was analysed for sediment properties, pollen, micro‐ and macrocharcoal, with radiocarbon and biochronology dating. Fossil data were statistically zoned and interpreted with the help of cross‐correlation and ordination analyses. Surface samples and a pollen–vegetation training set were used as modern analogues for vegetation reconstruction. Results Before human settlement (4,800–2,000 cal. yr bp), pine (Pinus canariensis) pollen dominated. Extensive dry pine forests characterized the highlands, although with temporary declining phases, followed by prompt (sub‐centennial scale) recovery. Towards 2,280 cal. yr bp there was a shift to open vegetation, marked by an increase in coprophilous spores. Coincidental with independent evidence of human settlement in the pine belt (2,000–470 cal. yr bp) there was a decline of pine and a peak in charcoal. Following historic settlement (470–0 cal. yr bp), pollen producers from anthropogenic habitats, secondary vegetation and coprophilous fungi increased in abundance, reflecting higher pressure of animal husbandry and farming. Modern moss polsters reflect extensive reforestation since 1950 ce (Common Era). Main conclusions From 4,800 cal. yr bp, the pristine vegetation covering the Gran Canaria highlands was a mosaic of dry pine forests and open vegetation. The pine forests sustained intense fires, which may well have promoted habitat diversity. Human interference was initiated around 2,280 cal. yr bp probably by recurrent cultural firing and animal husbandry, triggering a steady trend of forest withdrawal and expansion of grasses and scrubs, until the final disappearance of the pine forest locally in the 20th century. Grasslands were found to be of ancient cultural origin in the summit areas of Gran Canaria, although they underwent an expansion after the Castilian Conquest.

Accelerating ecosystem disruption Oceanic islands are among the most recent areas on Earth to have been colonized by humans, in many cases in just the past few thousand years. Therefore, they are important laboratories for the study of human impacts on natural vegetation and biodiversity. Nogué et al. provide a quantitative palaeoecological study of 27 islands around the world, focusing on pollen records of vegetation composition before and after human arrival. The authors found a consistent pattern of acceleration of vegetation turnover after human invasion, with median rates of change increasing by a factor of six. These changes occurred regardless of geographical and ecological features of the island and show how rapidly ecosystems can change and how island ecosystems are set on new trajectories. Science , this issue p. 488

Islands contribute enormously to global biodiversity, but their species and ecosystems are highly threatened and often confined to small patches of remaining native vegetation. Islands are thus ideal microcosms to study the local dimensions of global change. While human activities have drastically transformed most islands, the extent to which societal and environmental conditions shape differences in land cover remains unclear. This study analyses the role of contrasting environmental and societal conditions in affecting the extent of native vegetation cover on 30 islands in five Atlantic Ocean archipelagos (Azores, Madeira, Canary Islands, Cape Verde, Gulf of Guinea Islands). We adopt a mixed-method approach in which we combine a statistical analysis of environmental and societal variables with a qualitative reconstruction of historical socioeconomic trends. Statistical results indicate that terrain ruggedness predominantly shapes the extent of remaining native vegetation cover, suggesting that topography constrains human impacts on biodiversity. Overall, environmental variables better explain differences in native vegetation cover between islands than societal variables like human population density. However, throughout history, islands experienced large changes in demography and socioeconomic trends, and therefore modern patterns of native vegetation might also partly reflect these past conditions. While anthropocene narratives often present humans as a global geophysical force, the results show that local environmental context strongly mitigated the degree of human impact on biodiversity. These findings call for integrative approaches to understand the contributions of local human-environment interactions to ongoing global change. Portuguese National Funds, through Fundação para a Ciência e a Tecnologia (PD/BD/114380/2016); Portuguese Government through Fundação para a Ciência e a Tecnologia (FCT/MCTES) (SFRH/BPD/91494/2012); Royal Geographical Society; European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant (700952); University of Amsterdam starting grant; Faculty Research Cluster 'Global Ecology'; cE3c FCT Unit fund (UID/BIA/00329/2019). info:eu-repo/semantics/publishedVersion

In Tenerife (Canary Islands), the laurel forest is considered one of the most biodiverse ecosystems of the archipelago. This study aims at providing useful information about tree species strategies and their natural dynamics in order to improve understanding of the functioning of this ecosystem. The knowledge gained would be of great importance for laurel forest conservation, not only in the Canaries, but also in Madeira and the Azores. Our main research question is: ‘Are the ecological groups of laurel forest tree species, described in earlier studies based exclusively on regeneration strategies, consistent with species functional traits, growth patterns and spatial distributions?’ We used data from six 50 × 50 m permanent plots established in 1999 and re-measured in 2015, combined with information on twelve functional traits from newly produced data or extracted from previous studies. For each species, we analyzed the abundance of seedlings/suckers, saplings and adults inside the permanent plots. Two ordination methods were used to assess multivariate differences in functional traits between species. Different mixed-effect models were tested to investigate effects of sites, individual tree size and competition on tree growth rates. Finally we analyzed the spatial distribution of both saplings and adults and their interaction within the six permanent plots. Our results were consistent with a classification of species into different ecological groups based on (1) their shade tolerance: light-demanding versus shade-tolerant species and (2) their reproductive strategies: sexual (i.e., seedlings), asexual (i.e., suckers) or both. These differences between light-demanding versus shade-tolerant and/or seedling-producing species versus sucker-producing species were consistently observed across the species functional traits, growth patterns and spatial distributions. Only one species, Viburnum rigidum Vent., presented singularities compared with its previously established group. Because V. rigidum is mostly an understory species, we proposed to add a third aspect to the classification scheme: understory versus canopy species. This led to a total of six ecological groups within fourteen laurel forest tree species. Finally, this study also showed that the Tenerife laurel forest is still maturing and becoming richer in species, which outlines the importance of its preservation.

Plant fossils are known from the Azores Islands, yet poorly studied. We present a comprehensive bibliographical review for the archipelago. A first pre-scientific reference dates from late fifteenth century, while the first scientific description was reported in 1821, accounting for trunks in pyroclastic units and silicified plants within hydrothermal deposits. Throughout the second-half of the nineteenth century and the first-half of the twentieth century, prospection by naturalists and geological mapping work, led to the discovery and description of plant fossils in most islands. From the 1970s onwards, the taxonomic interest ceased, and plant fossils were used mainly for 14C dating. Recently, sediment cores from lakes and peatlands were used for palaeoecological reconstructions and to measure anthropogenic impacts. Generally, plant fossils are younger than 50 ka, although older fossils may exist. Azorean plant fossils include somatofossils of leaves, stems, logs and seeds preserved as impressions, compressions, adpressions, permineralizations, lava tree casts and mummifications. The taphonomy of macrofloral elements is usually related to explosive volcanic activity, while palynological record is associated with lake sediments and peat bogs. The persistence in palaeobotanical and palaeopalynological studies will decisively contribute to disentangle the paleodiversity, palaeoecology, and add crucial information on insular plant phylogeny and biogeography

Endemics–Area Relationships (EARs)are fundamental in theoretical and applied biogeography for understanding distribution patterns and promoting biodiversity conservation. However, calculating EARs for vascular plant species from existing data is problematic because of biased knowledge of endemic species distributions and differences between taxonomies. We aimed to overcome these challenges by developing a new standardized global dataset based on expert knowledge to produce a set of global EARs. We developed a nested circle design, with grain sizes of 10 4 , 10 5 , 10 6 , 10 7 , and 10 8 km 2 , respectively, and a global distribution of plots based on a stratified random scheme. The number of vascular plant species endemic to each circle was then estimated independently by five experts randomly chosen from a pool of 23, as both a minimum and a maximum value (lower and upper bounds of the estimation), taking into account the limitations of current knowledge and varied species concepts in existing taxonomies. This procedure resulted in a dataset of 3000 expert estimates. Based on the data, we produced three global EARs for endemic species richness using minimum, maximum and average estimates. As a validation, we used all three models to extrapolate to the entire world, producing estimates of 284,493 (minimum), 398,364 (maximum)and 312,243 (average)vascular plant species. These figures conform to the range of taxonomists’ estimates. From the models, we calculated the average area needed to harbour a single endemic species as 12,875 km 2 (range 9675–20,529). The global vascular plant EARs we calculated represent the first standardized, quantitative expectations of plant endemism at any given scale (sampling unit size). These EARs allow us to provide a clear answer to a long-standing but elusive biogeographical question: how to assess whether any area on the surface of the Earth is rich or poor in endemics relative to the average.

Tropical dry islands are currently facing major challenges derived from anthropogenic and climatic pressures. However, their trajectories of environmental change, which could provide relevant information applicable to biodiversity conservation, remain understudied. This is mainly due to poor micro-fossil preservation and irregular sediment deposition. Multi-proxy palaeoecological analyses spanning decades to 1000s of years can add perspective as to how vegetation, fungal communities, and the fauna responded to previous natural and anthropogenic disturbances. In Sao Nicolau, Cabo Verde, we used palaeoecological methods to analyse a highland soil profile (1000 m asl) dated to 5900 cal yr BP. We analysed how vegetation (abundances in pollen of native and introduced species, and leaf wax n-alkanes), ferns and fungal communities (abundance of non-pollen palynomorphs) varied over time in relation to fire (charcoal concentration) and erosion regimes (grain sizes and elemental composition). Between 5000 and 400 cal yr BP the highlands held native woody taxa such as Euphorbia tuckeyana, Dracaena draco subsp. caboverdeana, and Ficus, taxa that can be used for future reforestation programmes. From 400 cal yr BP to the present day, replacement of native taxa by introduced and cultivated taxa (Pinus, Eucalyptus, Asystasia, Opuntia) has occurred. Vegetation burning and grazing caused loss of vegetation and erosion, acting as conjoined drivers of scrubland degradation. This dataset helps to set historically contextualised restoration goals such as the re-introduction of native species, monitoring of recently introduced species and control of free grazing. This can serve as a model system for the conservation of tropical dry islands' biodiversity.

Cabo Verde was the first tropical archipelago colonized by Europeans. Historians have suggested that the first colonizers initiated archipelago-wide ecosystem degradation, loss of vegetation cover, and erosion. However, the human–environment interactions that led to the archipelago's current environmental status remain poorly understood. Here, we report the first palaeoecological study of past vegetation change and disturbance regimes for Cabo Verde. We present a 2130-yr old sediment sequence from a volcanic caldera (Cova de Paul) located at ~1200 m asl on Santo Antao Island, for which we analyzed fossil pollen, non-pollen palynomorphs (NPPs), charcoal, silica bodies, and grain size distribution. Our analyses do not show evidence of the presence of temperate, tropical or subtropical forests growing on the summits of Santo Antao in pre-human times. The pollen record shows that scrubland and grasslands dominated the highlands and underwent compositional changes ca. 1850 and 1300 cal yr BP. These shifts overlap with erosion phases and are linked to intensified seasonality. Steady rates of sedimentation marked the period 1230 to ca. 350 cal yr BP, but an increase in charcoal concentrations indicate a drying phase. Increases in regional and local fire, peaks of coprophilous fungi and the presence of New World crop pollen (Zea mays) are interpreted as the onset of Portuguese settlement of the highlands after 450 BP. Sustained erosion between ca. 350 and 100 cal yr BP indicate soil degradation, and the pollen record shows the increase in introduced herbaceous taxa (Rosaceae, Centaurea, Verbenaceae) and exotic tree taxa (e.g. Pinus), while shifting abundances of coprophilous fungi indicate changes in land-use. The record shows stabilization of soils in the last century due to recent afforestation of the highlands. Further palaeoecological studies have the potential to provide further detail of the long-term dynamics of Cabo Verde ecosystems and to inform conservation initiatives.

Oceanic islands remained free of humans until relatively recent times. On contact, humans encountered pristine environments with unique ecosystems and species highly vulnerable to novel impacts. In the course of rendering an island habitable, the new settlers transformed it through fire, deforestation, hunting and introduction of pests and weeds. The result, as described for many oceanic islands globally, has been a catastrophe for biodiversity. Here we present the case of the Canary Islands, an Atlantic archipelago renowned for its exceptional biodiversity, and show that these islands have been no exception to the general rule. We review the archaeological, palaeoecological, palaeontological and ecological literature for the archipelago and discuss the ecological consequences – in particular habitat transformation and biodiversity loss – of human settlement. In contrast to previous views that prehistoric humans had only limited impacts on these islands, we show that vegetation change, increased fire, soil erosion, species introductions and extinctions follow the familiar oceanic pattern. Timing of human settlement of the Canary Islands has been controversial, with revised archaeological dates suggesting a relatively late arrival at the beginning of the Common Era, while palaeoecological and palaeontological evidence favours a presence several centuries earlier. While the matter is still not settled, we suggest that settlement sometime between 2400 and 2000 cal years BP is a possibility.

A new checklist of the terrestrial biota from the easternmost islets from Canary Islands (Roque del Este, Roque del Oeste, Montaña Clara, Alegranza, La Graciosa and Lobos) isprovided as a result of a wide bibliographic and database compilation. The checklist includes bryophytes, vascular plants, fungi, chordates, arthropods and mollusks. Additionally, a short analysis of the fauna and flora species richness reveals that there are slightly more than 700 terrestrial species in the islets, the big majority of them being native, with > 25% endemics and < 10% exotics, what argues in favour of the high conservation quality of this protected area. By far, the more important taxa contributing to this biodiversity are arthropods and vascular plants, as happen in the rest of the archipelago. Up to seven different taxa, four spiders, one bird –already extinct–, one snail and one vascular plant, have been found to be endemic to the islets. Finally, the availability of this new checklist will contribute significantly towards more accurate biogeographic analyses of the Canarian biota, because until now the islets’ biota distribution was not disaggregated of the main islands, Lanzarote and Fuerteventura, to which politically belong. Se presenta un nuevo listado de la biota terrestre de las isletas más orientales del archipiélago canario (Roque del Este, Roque del Oeste, Montaña Clara, Alegranza, La Graciosa y Lobos) resultado de una exhaustiva recopilación bibliográfica y de bases de datos. El listado incluye briófitos, plantas vasculares, hongos, cordados, artrópodos y moluscos. Un breve análisis estadístico de la flora y fauna de los islotes revela que existen algo más de 700 especies en el conjunto de los mismos, la gran mayoría de ellas nativas, con más de un 25% de endemismos y menos de un 10% de especies exóticas, lo que avala la alta calidad de estos espacios protegidos. Con diferencia los taxa que más contribuyen a la biodiversidad inventariada son los artrópodos y las plantas vasculares, como ocurre en el resto del archipiélago. Hasta siete taxones diferentes, cuatro especies de araña, un ave –ya extinta–, un molusco y una planta vascular, son endémicos de estas isletas. La disponibilidad de esta lista contribuirá a la realización de análisis biogeográficos más rigurosos, pues hasta ahora la biota de las isletas no se encontraba desagregada de las islas mayores, Lanzarote y Fuerteventura, a las que pertenecen políticamente.

The general dynamic model of oceanic island biogeography (GDM) predicts the immigration, speciation and extinction of terrestrial biota through geological time on oceanic islands. Additionally, the glacial-sensitive model of island biogeography (GSM) also predicts extinction due to eustatic and climate change within islands. However, well-documented and natural pre-Holocene plant extinctions are almost unknown for oceanic islands worldwide. To test these predictions, we have sampled the Early Pleistocene Porto da Cruz lacustrine and fluvial sediments for plant fossils that could confirm the GDM and GSM extinction predictions. Additionally, two new 40Ar/39Ar geochronological analyses were performed, constraining the age of the sediments to 1.3 Ma (Calabrian). Among the fossils, Eurya stigmosa (R.Ludw.) Mai (Theaceae) seeds were recognised and studied by scanning electron microscopy (SEM). E. stigmosa is the first report of a natural (non-anthropogenic) extinct plant in the fossil record for Madeira Island, and for an oceanic island, confirming the GDM and GSM predictions. Eurya spp. palaeobiogeography indicates wider distribution in Europe until the end of the Pliocene (2.58 Ma), becoming extirpated to small refugia and extinct thereafter. The Madeiran record expands the formerly unknown presence of E. stigmosa to the Macaronesian realm. The new dating of the deposit at 1.3 Ma (Calabrian) means that E. stigmosa in Madeira was already in a refugium. The extinction in Madeira is most probably a combination of island ontogeny and climate change due to Pleistocene glaciations. The palaeoecological role of this extinct shrub or tree is currently unknown, but it was a probably an element of the Madeiran laurel forest, as this community was already present in Madeira at least 1.8 My ago. This new information corroborates the predictive power of GDM and GSM and adds a new view on the importance of studying oceanic island palaeobotany, specially palaeocarpofloras.

Presentación

Confined to the humid cloud belt of the Macaronesian Islands the Laurel-forests are sensitive to climate changes. Intense natural disturbances are rare and regeneration includes asexual regeneration and dominance of shade intolerant species in the seedling bank. Long-term monitoring of the seedling bank showed that even under these relatively stable conditions high variations occurred. Studies point out to a downward shift of the trade winds cloud belt that confined laurel cloud forests. Only long-term studies can detect the effects of rare extreme events or the influence of slow processes on seedling dynamics. In nine 10 × 10 m plots (six in windward and three in leeward) we monitored the seedling bank monthly from 2000 to 2003 and recount it in 2005 and 2011. Our aim was to estimate seedling dynamics in a Laurel forest. We hypothesized that this forest seedling bank is relatively stable over time. Under present mild temperate climate, we hypothesized that this forest seedling bank is relatively stable over time; seedling recruitment will be positively related to rainfall; sprouting-species will be poorly represented in the seedling bank and growth rate will be higher than observed in other forests. Composition and abundance in seedling bank were stable across 2000–2003. The fluctuation in density, recruitment and mortality for Laurus novocanariensis was determinant for seedling community dynamic, and composition and abundance in seedling bank were stable across first three years and relative seeding growth rate is higher than observed in another subtropical wet montane forests. There was no significant relationship between mortality and recruitment and precipitation. However, in the 2011 count, an increase in density for all species. Except for a hot year in 2010 and a humid one in 2009 for the Canary Islands, there was no record of exceptional weather events or large-scale disturbance episodes in the previous eight years, and these are unlikely to explain the observed increase. Species with seedling banks were more abundant. Nonetheless, few seedlings survive more than two years. We emphasise the importance of long-term studies with fine-scale disturbance monitoring for understanding the dynamic processes of this unique forest.

Understanding patterns of community structure and the causes for their variation can be furthered by comparative biogeographic analyses of island biotas. We used woody plant data at the local scale to investigate variations in species rarity, alpha, beta, and gamma diversity within and between three islands from the oceanic archipelagoes of Azores, Canaries and Mascarene. We used standardized protocols to sample ten 50 m × 50 m forest plots in each of the three islands with contrasting climate and regional species pools: Terceira (Azores), Tenerife (Canaries), and Reunion (Mascarene Islands). Occupancy frequency distributions and species abundance distributions were used to investigate rarity. The partitioning of beta diversity in a distance-decay framework was used to test for spatial patterns of community composition. Rarity was much more pronounced in the highly diverse islands of Tenerife and Reunion than in the regionally poorer island of Terceira. The number of species rose faster with increasing sample area in both Tenerife and Reunion. The slope of the species rank abundance curve was steeper in Terceira whereas the richer island assemblages approached a lognormal model. Compositional changes according to spatial distance were mostly due to replacement of species in Terceira and Reunion. Our results point to important differences in the community structure of Terceira, which is the less diverse and temperate region in comparison to Tenerife and Reunion which are highly diverse., This research was supported by the ERA-Net Net -Biome research framework, financed through the: Canary Islands Government ACIISI grants SE-12/02 (PO), SE-12/03 (JCC), SE-12/04 (BE), co-financed by FEDER; Portuguese FCT-NETBIOME grant 0003/2011 (PB); French ANR-NETBIOME grant n°11-EBIM-001-01 (CT); Région Reunion council for research activities (DS), Universitéde La Reunion contract DGADD/PE/20120585 (DS). CR, FR and IRA were supported by grants from Fundação da Ciência e Tecnologia - FCT-SFRH/BPD/91357/2012, FCT-PTDC/BIA-BIC/119255/2010, FCT-SFRH/BPD/102804/2014 respectively. MF has been funded by Direcção Regional da Ciência e Tecnologia, DRCT-M3.1.7/F/002/2011 and the Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq (401045/2014-5), Programa Ciência sem Fronteiras; the current MF’s contract is supported by the Universidad de Alcalá. The work of LBD in this manuscript was performed within the scope of the project MOMENTOS (PTDC/BIA-BIC/5558/2014).

Aim: The majority of documented extinctions world-wide in the last four centuries are of species endemic to islands. However, the phenomenon of delayed extinctions as a result of habitat loss has rarely been assessed on oceanic islands. In this study, we tested whether extinction debt (ED), in general, occurs on islands and for which taxonomical groups this phenomenon is most pronounced by assessing ED for multiple endemic taxa and for each of the main altitudinal ecosystems in a well-studied oceanic archipelago. Location: Canary Islands. Methods: We characterized habitat preferences for all endemic species of several taxonomic groups (vascular plants, ground and darkling beetles, flies and land snails). Using generalized linear mixed models and available data about habitat distributions, we tested for all taxa and habitat types to determine whether past habitat area better explained current richness of habitat specialists than current habitat area. If so, an extinction debt can be assumed. Results: For all five major habitat types and five taxonomic groups studied, present-day richness of habitat specialists fitted better with past than current habitat area, evidencing habitat-and taxon-specific extinction debts. This pattern was consistent for both long-lived vascular plants and short-lived invertebrates. Single island endemics in each taxonomic group showed steeper slopes of the species–area relationship (SAR) compared to archipelago endemics indicating higher sensitivity to habitat loss which might increase sizes of ED. Conclusion: Despite differences in species’ generation times, plants and invertebrates showed delayed extinctions after habitat destruction in the Canary Islands. Our SAR approach suggests that a considerable number of Canary Island endemics will eventually become extinct in the future without further habitat loss. The case of the Canary archipelago is probably not unique. Hence, we interpret our results as a warning for island conservationists that the worst of the extinction crisis on oceanic islands might be yet to come. Conservation actions should focus on habitat restoration to attenuate or reverse current extinction processes. Universidad de Las Palmas de Gran Canaria Universidad de La Laguna

Aims: The 50th anniversary of the publication of the seminal book, The Theory of Island Biogeography, by Robert H. MacArthur and Edward O. Wilson, is a timely moment to review and identify key research foci that could advance island biology. Here, we take a collaborative horizon-scanning approach to identify 50 fundamental questions for the continued development of the field. Location: Worldwide. Methods: We adapted a well-established methodology of horizon scanning to identify priority research questions in island biology, and initiated it during the Island Biology 2016 conference held in the Azores. A multidisciplinary working group prepared an initial pool of 187 questions. A series of online surveys was then used to refine a list of the 50 top priority questions. The final shortlist was restricted to questions with a broad conceptual scope, and which should be answerable through achievable research approaches. Results: Questions were structured around four broad and partially overlapping island topics, including: (Macro)Ecology and Biogeography, (Macro)Evolution, Community Ecology, and Conservation and Management. These topics were then subdivided according to the following subject areas: global diversity patterns (five questions in total); island ontogeny and past climate change (4); island rules and syndromes (3); island biogeography theory (4); immigration–speciation–extinction dynamics (5); speciation and diversification (4); dispersal and colonization (3); community assembly (6); biotic interactions (2); global change (5); conservation and management policies (5); and invasive alien species (4). Main conclusions: Collectively, this cross-disciplinary set of topics covering the 50 fundamental questions has the potential to stimulate and guide future research in island biology. By covering fields ranging from biogeography, community ecology and evolution to global change, this horizon scan may help to foster the formation of interdisciplinary research networks, enhancing joint efforts to better understand the past, present and future of island biotas., B.C.E. was supported by Spanish grant CGL2013-42589-P awarded to B.C.E. by the MINECO and co-financed by FEDER, and Spanish grant S20141203_002597 awarded to B.C.E. by the Organismo Autónomo Parques Nacionales of the MAGRAMA.

Crop pollination by bees has long been recognized as an ecosystem service of huge economic value; a large number of food crops depend upon pollination. Features across landscapes that are important for pollination delivery include: nesting habitats, floral resource availability at foraging distance, and climate. The conditions for presence/absence of pollinators are therefore complex and rely upon a combination of biotic and abiotic factors. To date there has been no easily available method for landowners to determine the potential of pollination delivery across the land effectively and rapidly. In this paper we develop a method that uses freely available datasets to remotely estimate the relative provision of pollination service delivery provided by bees across Europe at a 300 m-pixel resolution. We then identify the potential pollination delivery and efficiency across Europe at country and regional level. This study illustrates an approach that obtains a first approximation for land managers to identify potential areas across landscapes to protect in order to enhance pollination service delivery. Norwegian Academy of Science and Letters

Question How are semi-natural ecosystems affected by goat grazing regime (heavy, light and long-term abandonment)? Location Anaga Rural Park, Tenerife Island, Canary Islands (Spain). Methods We evaluated plant species composition, diversity and structure (frequencies of functional groups based on growth form and bare ground) for three goat grazing regimes using 63 permanent point-quadrat transects. The effect of orientation (N vs S slope) was also analysed. Data were collected in the spring during each year from 2001 to 2005. Results Grazing regime affected the studied functional groups differently. The frequency of annual grasses was higher in the heavily grazed areas, shrubs decreased sharply from abandoned to heavily grazed areas, and shrub legumes appeared less abundant in the lightly grazed transects. An interaction between grazing regime and orientation affected some functional groups. Grazing led to higher plant diversity, and did not affect the frequency of bare ground or native and endemic species. There were no strong differences in species composition among the three grazing regimes. However, species composition in abandoned areas was characterized by a higher abundance of late-successional and endemic shrub species, while herbaceous species typical of pastures were more common in the grazed areas. Conclusions Grazing regimes noticeably affect the composition and structure of the vegetation of semi-natural ecosystems but do not result in a complete turnover in species composition. Goat grazing is beneficial for maintaining traditional open agroecosystems; however, controlling the grazing intensity can avoid negative effects on the vegetation, particularly the sharp reduction in shrub and palatable species. Some abandoned areas should be maintained to preserve grazing-sensitive endemic shrub species in these Canarian semi-natural ecosystems.

Macaronesia is a biogeographical region comprising five Atlantic Oceanic archipelagos: the Azores, Madeira, Selvagen (Savage Islands), Canaries and Cape Verde. It has strong affinities with the Atlantic coast of the Iberian Peninsula and the north-western fringes of Africa. This paper re-evaluates the biogeographical history and relationships of Macaronesia in the light of geological evidence, which suggests that large and high islands may have been continuously available in the region for very much longer than is indicated by the maximum surface area of the oldest current island (27 Ma) – possibly for as long as 60 million years. We review this literature, attempting a sequential reconstruction of Palaeo-Macaronesia from 60 Ma to the present. We consider the implications of these geological dynamics for our understanding of the history of colonization of the present islands of Macaronesia. We also evaluate the role of these archipelagos as stepping stones and as both repositories of palaeo-endemic forms and crucibles of neoendemic radiations of plant and animal groups. Our principal focus is on the laurel forest communities, long considered impoverished relicts of the Palaeotropical Tethyan flora. This account is therefore contextualized by reference to the long-term climatic and biogeographical history of Southern Europe and North Africa and by consideration of the implications of changes in land–sea configuration, climate and ocean circulation for Macaronesian biogeography. We go on to provide a synthesis of the more recent history of Macaronesian forests, which has involved a process of impoverishment of the native elements of the biota that has accelerated since human conquest of the islands. We comment briefly on these processes and on the contemporary status and varied conservation opportunities and threats facing these forests across the Macaronesian biogeographical region.

Past climate dynamics have helped shape the endemic ecosystems of Macaronesia. However, these insular ecosystems have since been modified following the arrival of human settlers, who had to adapt to the new environments and resources.

We provide the first fossil pollen and charcoal analysis from the island of Gran Canaria (Canary Islands). The pollen record obtained from Laguna de Valleseco (870 m a.s.l.) spans the late Holocene (c. 4500–1500 cal. years BP) and thereby captures the impact of human colonization. During the earliest period, pollen composition resembled contemporary thermophilous communities, with palms (Phoenix canariensis) and junipers (Juniperus cf. turbinata) being the dominant trees, suggesting that these elements were more widespread in the past. Vegetation in Valleseco began to change at around 2300 cal. years BP, 400 years before the earliest archaeological evidence of human presence in the island (c. 1900 cal. years BP). Our data show an increased frequency of fires at that time, coinciding with the decline of palms and the increase of grasses, indicating that humans were present and were transforming vegetation, thus showing that the demise of Gran Canaria’s forest began at an early point in the prehistoric occupation of the island. In the following centuries there were no signs of forest recovery. Pollen from cultivated cereals became significant, implying the introduction of agriculture in the site, by 1800 cal. years BP. The next shift in vegetation (c. 1600 cal. years BP) involved the decrease of grasses in favour of shrubs and trees like Morella faya, suggesting that agriculture was abandoned at the site.

Although the role that Pleistocene glacial cycles have played in shaping the present biota of oceanic islands world-wide has long been recognized, their geographical, biogeographical and ecological implications have not yet been fully incorporated within existing biogeographical models. Here we summarize the different types of impacts that glacial cycles may have had on oceanic islands, including cyclic changes in climate, shifts in marine currents and wind regimes and, especially, cycles of sea level change. The latter have affected geographical parameters such as island area, isolation and elevation. They have also influenced the configurations of archipelagos via island fusion and fission, and cycles of seamount emergence and submergence. We hypothesize that these sea level cycles have had significant impacts on the biogeographical processes shaping oceanic island biotas, influencing the rates and patterns of immigration and extinction and hence species richness. Here we provide a first step toward the development of a glacial-sensitive model of island biogeography, representing the tentative temporal evolution of those biogeographical parameters during the last glacial cycle. From this reasoning we attempt to derive predictions regarding the imprint of sea level cycles on genetic, demographic or biogeographical patterns within remote island biotas.

Vegetation history in the Canary Islands, one of the most biodiverse regions within Europe, has recently and for the first time, been the subject of palaeoecological studies. The interpretation of fossil records may be limited by several uncertainties regarding howwell the different vegetation types are represented in the pollen rain. In this study we address this key knowledge gap within Canarian vegetation science, taking the island of Tenerife as a model. Based on quantitative and qualitative data we analysed pollen–vegetation relationships to test whether different vegetation types can be discriminated by means of their pollen rain composition, to identify underand over-represented taxa, and to test the match between modern pollen rain and fossil pollen assemblages. We found clear differences in pollen composition and abundance among major Canarian vegetation types. We also identified good indicator taxa of the local occurrence of their source plants by their high fidelity and low dispersibility index scores. Extra-regional types (taxa without potential source plants in the Canary Islands) were not detected in our traps. However, several important floristic elements are either over-represented (Pinus, Morella and Ericaceae trees, Chenopodiaceae, Poaceae, Rumex and Urticaceae herbs and shrubs) or under-represented (Lauraceae trees, Fabaceae and Euphorbia shrubs). Results indicate that pollen composition is a good reflection of vegetation in Canarian ecosystems and can be used effectively to reconstruct past environments.

International audience; Key message The long-term effect of forest fires in the regeneration ofPinus canariensiswas studied. Forest fires had little long-term effects on seed production, seedling germination and seedling mortality. The characteristics of different forest stands across the island had influence in some of the regeneration parameters studied.ContextDespite the importance of forest regeneration dynamics after wildfires, little is known about its long-term evolution after a fire.AimsWe tested the effect of fire on the long-term regeneration dynamics of P. canariensis.MethodIn a forest fire chronosequence of five fire ages (time elapsed since the last fire) plus an unburned stand, we monitored seed production, seedling germination and mortality during 2 years.ResultsWe detected significant differences among forest stands in seed production, seedling density and mortality but not in germination and turnover. These differences were unrelated to fire age. Seed production was conditioned by the number of large adults and elevation, germination by diameter at breast height (DBH) and soil nitrogen content and mortality by DBH.ConclusionWe detected no long-term effect of fire on the regeneration of P. canariensis in natural pine forest; however, during the first years after fire, modification of nitrogen availability in soil can reduce germination. Stand conditions in natural pine forests appear to mainly control regeneration dynamics. The regeneration strategies and fire-resistance traits of this species have ensured its persistence in the long term.

As a working hypothesis, we examined evidence for the former presence of a climacic woodland of Juniperus cedrus above the pine forest in the high elevation area of Tenerife (Canary Islands), which would indicate that the current dominant vegetation (endemic Spartocytisus supranubius scrub) may not be pristine. The main causes of the great regression of this woodland were caused by human activities (timber harvesting, herbivory by goats, and fires). The main support for this hypothesis is the survival of a presumably relict seed dispersal system of the endangered endemic J. cedrus, which relies mainly on the wintering thrush Turdus torquatus. The fact that genetic factors are directly involved in the control of bird migration routes strongly supports the idea that this interaction could be remnant of an older system, probably more widespread in the past. To test this hypothesis, we propose that a paleoecological approach could reconstruct the vegetation dynamics in the Teide National Park (Tenerife) and the past presence of this seed disperser migratory thrush. The analysis of plant microfossils in sediments (e.g., pollen, spores, phytoliths, coprolites, and charcoal) would allow us to evaluate whether the current vegetation is the same as that which naturally existed in the past, and assess the impact of the anthropogenic and natural factors to which it has been subjected during history. The results of these analyses will be useful for future management policies and practices aimed at restoring the pristine landscape and biotic interactions of the Teide National Park. To our knowledge, the case presented in this contribution, based on the high dependence of the seed dispersal of an endemic tree (J. cedrus) on a migratory bird, is the only reported in the context of oceanic islands., Rumeu was funded by a Spanish National Research Council grant (CSIC: JAE-PRE). This study is framed within the projects CGL2010-18759 and PI2007/053 and financed by the Spanish Ministry of Science and Innovation and the Canary Islands Government, respectively; both of which were partially funded by the European Union. The Organismo Autónomo de Parques Nacionales (Canary Islands National Parks Council) also financed this project (051/2010).

Garajonay National Park in La Gomera (Canary Islands) contains one of the largest remnant areas of a forest formation once widespread throughout Europe and North Africa. Here, we aim to address the long-term dynamics (the last 9600 cal. years) of the monteverde forest (laurel forest and Morella-Erica heath) located close to the summit of the National Park (1487 m a.s.l.) and determine past environmental and human impacts. 2. We used palaeoecological (fossil pollen, microscopic and macroscopic charcoal) and multivariate ecological techniques to identify compositional change in the monteverde forest in relation to potential climatic and human influences, based on the analysis of a core site at 1250-m elevation. 3. The regional mid-Holocene change towards drier conditions was matched in this system by a fairly rapid shift in representation of key forest elements, with declines in Canarian palm tree (Phoenix canariensis), Canarian willow (Salix canariensis) and certain laurel forest taxa and an increase in representation of the Morella–Erica woody heath. 4. Charcoal data suggest that humans arrived on the island between about 3000 and 1800 years ago, a period of minimal vegetation change. Levels of burning over the last 800 years are among the lowest of the entire 9600 years. 5. Synthesis. A rapid climatic-induced shift of forest taxa occurred 5500 years ago, with a decrease in hygrophilous species in the pollen record. In contrast, we found no evidence of a significant response to human colonization. These findings support the idea that Garajonay National Park is protecting a truly ancient relict, comprising a largely natural rather than cultural legacy.

The outstanding nature of the Canary Islands has been recognized by European, national and regional administrations since the arrival of democracy in Spain. Forty‐five per cent of its emerged territory has been declared as Natural Protected Areas, four Canarian National Parks were included within the Spanish network, more than 200 endemics were listed in the Spanish catalogue of endangered species, and 450 species were listed in the Canarian catalogue of protected species. However, in recent years, political decisions have started dismantling this splendid conservation network, which impedes construction of large infrastructure, golf courses and resorts, despite the advice of the scientific community. Canarian nature is now facing two threats: delisting and downgrading of numerous endangered species, and transfer of the management of Canarian National Parks to the regional administration.

Número especial: Exotic Species in Forest Stands of the Canary Islands Apis mellifera L. is a generalist pollinator present in most of the Canary Islands. When foraging, honeybees transfer pollen grains to honey, and presence and abundance of pollen from different species can be interpreted as a sign of local flora, and a cue to spread of aliens. The relative use of alien vs native species by honeybees could influence island pollination mutualisms and/or favour alien species. Analyzing pollen content data from honey samples an approach can be made to the relative foraging intensity on different plant communities and identify the importance of alien plant species in nearby areas. Based on published information on pollen contents of honeys from beehives in La Palma, we made an indirect evaluation of the use of endemic, native and alien species by honeybees in two native forests of the island (evergreen laurel forest and Canarian pine forest). Some of the most pervasive alien plants in the Canary Islands were represented in these pollen samples. The most frequent species in pollen counts was Castanea sativa. Proportion of alien species’ pollen was significantly higher in the laurel forest, while the most visited group in the pine forest was that of endemics (p < 0.05). Specific composition of pollen samples analysed with Detrended Correspondence Analysis revealed (61.3 % variance explained) a pattern related to species distribution in each forest type. Pollen content has revealed the presence of alien species in forests of La Palma, some of them considered invasive. The laurel forest is the most threatened of both ecosystems, mainly affected by the proximity to urban areas and the presence of intersperse arboreal plantations. The overall prevalence of aliens in the evaluated pollen data suggests that honeybees are prone to exploit exotics, and that the selection of plant species by honeybees in this oceanic island is not random. This may have serious consequences for island pollination systems and favour the spread of some exotic species.

Aim We report the first analysis of the long-term ecology of Tenerife, in order to establish a pre-colonization base-line and to assess the effect of human activity and the role of climatic variation on vegetation during the Late Holocene. Location A former lake bed in the city of La Laguna (Tenerife, Canary Islands, Spain). Methods A sedimentary sequence of over 2 m was obtained from the former lake bed. Fossil pollen and microfossil charcoal concentrations were analysed. Radiocarbon dating of the sequence indicates that it spans approximately the last 4700 years. The pollen diagram was zoned using optimal splitting within psimpoll 4.25. Results Three pollen zones were differentiated: (1) in Zone L1 (c. 4700– 2900 cal. yr bp) a mixed forest was dominated by Quercus, Carpinus, Myrica and Pinus; (2) in Zone L2 (c. 2900–2000 cal. yr bp) the laurel forest taxa increased, while Pinus, Juniperus and Phoenix declined; and (3) Zone L3 (c. 2000– 400 cal. yr bp) was characterized by the decline of Carpinus and Quercus and the abundance of laurel forest taxa (e.g. Myrica). Neither Carpinus nor Quercus was hitherto considered to be native to the Canary Islands. Their decline started c. 2000 years ago, coinciding with microfossil charcoal evidence of increased burning and with archaeological evidence for the first human settlement on Tenerife. Main conclusions Between c. 4700 and 2000 cal. yr bp, the composition of the forest in the valley of La Laguna was very different from what it is at present. In particular, Quercus and Carpinus appear to have been significant components, alongside components of the present-day laurel forest, and the native pine (Pinus canariensis) forest and thermophilous woodland were also more prevalent in the region (but probably not within the lake basin itself) until 3000 cal. yr bp. The subsequent decline of Quercus and Carpinus led to the establishment of the present laurel forest in the region and a shift to more open vegetation types. These changes indicate that the aboriginal inhabitants of the islands, the Guanches, had a far more profound impact on the vegetation of Tenerife than hitherto realized.

The discovery and colonization of islands by humans has invariably resulted in their widespread ecological transformation. The small and isolated populations of many island taxa, and their evolution in the absence of humans and their introduced taxa, mean that they are particularly vulnerable to human activities. Consequently, even the most degraded islands are a focus for restoration, eradication, and monitoring programmes to protect the remaining endemic and/or relict populations. Here, we build a framework that incorporates an assessment of the degree of change from multiple baseline reference periods using long-term ecological data. The use of multiple reference points may provide information on both the variability of natural systems and responses to successive waves of cultural transformation of island ecosystems, involving, for example, the alteration of fire and grazing regimes and the introduction of non-native species. We provide exemplification of how such approaches can provide valuable information for biodiversity conservation managers of island ecosystems.

Human-mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non-native species. However, data on past changes in non-native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non-native species. We matched fossil pollen data with botanical status information (native, non-native), and quantified the timing, trajectories and magnitude of non-native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non-native plant taxa within the last 1000 years. Individual island trajectories are context-dependent and linked to island settlement histories. Our data show that non-native plant introductions have a longer and more dynamic history than is generally recognized, with critical implications for biodiversity baselines and invasion biology.