Island Plant Research Articles

Research on base isolation design of nuclear island plant of a new-type metal-cooled fast reactor

This paper establishes a 3D finite element model of a new-type metal-cooled fast reactor (MCFR) nuclear island plant for applied research of base isolation technology, and the research includes the base isolation scheme for the split base layer structure, the selection from different types of isolation bearings, etc. According to the mechanical characteristics of different isolation bearings and rigidity distribution of the structure itself, the layout of isolation bearing scheme is carried out. Dynamic analysis of nuclear plan has been done based on ANSYS, and the optimal isolation scheme is determined by repeated trial calculation, isolation design schemes adjustment, acceleration and displacement of key nodes comparison. The results show that: applying base isolation design to the nuclear island plant, natural vibration period of the structure increases, acceleration response of the key nodes of the superstructure and displacement between the layers of the structure significantly decreases, seismic resistance of the nuclear island plant is improved significantly; isolation effect of the scheme with multiple types of isolation bearings is much better than that of the scheme with only rubber bearings.

Controls of plant diversity and composition on a desert archipelago.

AimWith the most robust floristic data set for any arid archipelago, we use statistical modeling to determine the underlying controls of plant diversity and species composition.LocationThe study was undertaken in the Midriff Islands of the Gulf of California, Mexico.MethodsUsing the area–diversity relationship we estimate the power coefficient z with generalized linear models (GLM). We tested eight predictors (area, human presence, habitat diversity, topography, distance to mainland, island type, precipitation, and seabird dynamics) using a step-wise process on the same GLM procedure. Plant species composition was assessed by conducting a non-standardized principal component analysis on a presence-absence matrix of the 476 (plant species) × 14 (islands). Finally, families were tested for over or under representation with a X2 analysis subjected to a Bonferroni correction.ResultsThe classic species-area model explained 85% of the variance in island plant diversity and yielded a slope (z) of 0.303 (±0.01). When the effect of area is removed, four additional factors were shown to account for observed variation; habitat diversity (34%), seabird dynamics (23%), island type (21%), topography (14%). Human presence and distance to mainland were not predictors of species richness. Species composition varies significantly with island area; small islands have a particular flora where certain families are overrepresented, such as Cactaceae, while the flora of larger islands is strongly dependent on the continental source.Main conclusionsThe factors that control diversity levels are expressions of geology, landscape heterogeneity, and land-sea connections. Species assemblages in small islands are governed by copious marine nutrients in the form of guano that depress species diversity. Distance to mainland and human presence hold no predictive power on diversity. The results show these islands to be isolated arid ecosystems with functioning ecological networks.

A new look at phenotypic disparity and diversification rates in island plant radiations.

This article is a Commentary on Nürk et al. 224: 518–531.

Prickly pairs: the proportion of spinescent species does not differ between islands and mainlands

AbstractAimsOrganisms on islands are thought to escape biotic pressure and lose defensive capabilities. However, broadscale, evidence-based tests of this idea are rare. In this study, we asked: (i) whether the proportion of spinescent plant species differed between islands and mainlands and (ii) whether the proportion of spinescent species increased with increasing island area and with decreasing island distance to mainland.MethodsWe compiled species lists for 18 island–mainland pairs around Australia. We classified 1129 plant species as spinescent or non-spinescent using published species descriptions.Important FindingsThere was no significant difference between the proportion of spinescent species found on islands and on mainlands. Proportions of spinescent species were not significantly related to island area or distance to mainland. Our results suggest that spinescence is just as important to island plants as it is to mainland plants, even for plants inhabiting small or distal islands. This is unexpected, given prevailing thought and previous work on island–mainland comparisons. Our study demonstrates the importance of testing well-accepted yet untested ideas.

Plant competition as a mechanism of invasion on islands: Revisiting the conclusions of Kuebbing and Nuñez (2016)

AbstractIdentifying the mechanisms underlying invasive plant establishment and native plant decline remains a central goal in ecology, particularly for biodiversity hotspots such as islands. We re‐analyzed a previously published meta‐dataset to test the prediction that neighbor effects are stronger on islands vs. continents because island plants are weaker competitors. Although we detected marginally stronger neighbor effects on islands than continents, this was due, at least in part, to stronger competition among native species. An absence of studies testing neighbor effects between native vs. invasive plants on islands prevents a rigorous test for competition effects on islands, highlighting an important knowledge gap.

Geese are overlooked dispersal vectors for vascular plants in archipelago environments

AbstractQuestionWe addressed the importance of gut‐mediated dispersal by greylag geese for vascular plants in archipelago environments and asked: (a) What proportion of the local species pool is dispersed by geese? (b) Which plant traits characterize species dispersed by geese? (c) Which plant communities are likely to benefit from endozoochory by geese?LocationThree Swedish Baltic archipelagos.MethodsGoose droppings were collected on 45 islands. Plants germinating from the droppings represent the endozoochorous species pool (ESP). On 108 islands, the presence of vascular plants was recorded in each habitat. These species represent the island species pool (ISP). Differences in functional traits between ESP and ISP were expressed as effect sizes and tested using meta‐regressions. Using indicator species analyses and indicator species for managed semi‐natural grasslands, we identified the primary habitats of the ESP.ResultsGeese dispersed viable diaspores of 97 plant species, which represents 22% of the ISP. Most ESP species were typical for small islands. Geese dispersed a higher proportion of graminoids and less woody plants, higher proportions of chamaephytes and therophytes and less phanerophytes; annuals and bi‐annuals were significantly overrepresented. On average, seed volume of the ESP was 95% smaller than that of the ISP. About 51% of all ESP species were dispersed in at least two archipelagos. Geese showed a bias towards species of rocky shore habitats.ConclusionGeese potentially disperse large amounts of diaspores of many terrestrial island plant species. Through their feeding behaviour, geese select species with certain suites of traits from the regional species pool. Plant dispersal by geese may benefit plants species of rocky shores, but species of formerly managed semi‐natural grasslands may also find refuge sites on epilittoral shores after goose‐mediated dispersal. The relative importance of geese as dispersal vectors may increase under on‐going land‐use changes and cessation of grazing networks.

Non-intrusive systematic study reveals mutualistic interactions between threatened island endemic species and points to more impactful conservation

Oceanic islands harbour a disproportionately large share of extinct and endangered birds worldwide and up to about 6,800 highly threatened plants, stressing the urgency for conservation efforts there. However, effective conservation action can only be as sound as the ecological understanding on which it is based. Knowledge about the ecology of threatened birds and plants can be relatively sketchy even in well-studied oceanic islands and this can potentially misdirect or erode conservation actions’ effectiveness. We used camera traps to document vertebrate flower visitors of a threatened, mono-specific endemic oceanic island plant (Roussea simplex) that produces much nectar and which was abundant until the 1930s before declining severely despite its presence mostly within protected areas. We determined proportions of native and alien flower visitors in four populations and characterised their ecological role (e.g. florivore, nectar robber, pollinator) through observations and exclusion experiments alongside experiments to determine seed sets by agamospermy, autogamy, geitonogamy and xenogamy. Five native and three alien vertebrate species visited flowers (N = 5,085 camera trap-hours), 96.6% of visits being from birds. Among endemics, 74–96% of visits were by the Mauritius Bulbul (Hypsipetes olivaceus), a threatened bird able to effect pollination contrary to the other endemic birds. Roussea simplex is primarily xenogamous, producing 2,657 ± 480 seeds, and seed set dropped markedly when the bird was excluded (861.8 ± 91.0 SE, Kruskal-Wallis χ2 = 14.2, p < 0.001). Natural seed set was very low (410.0 ± 85.3 SE) where the bird was locally extinct or very rare. Invasive alien rats (Rattus rattus) and long-tailed macaques (Macaca fascicularis) were important florivores or nectar robbers. Systematic non-intrusive study using camera traps combined with manipulative experiments revealed a mutualism between two relatively well-studied threatened endemic species as well as new threats from alien vertebrates acting as nectar robbers and florivores. Roussea simplex’s major decline within protected areas and its abundant and year round flowering and nectar production point to a major hitherto unrecorded drop in floral resource previously available to at least five endemic species, and particularly to its commonest flower visitor and principal pollinator, the threatened Mauritius Bulbul. These findings exemplify how systematic non-intrusive study of threatened species may radically change conservation managers’ priorities which in the current case should focus primarily on controlling alien rats and macaques and re-instating or reinforcing Bulbul-Roussea mutualism as each would be more impactful than addressing gecko-Roussea mutualism disruption by alien ants which so far was the only recorded threat thought to drive the rapid decline of Roussea simplex. Our study underscores that current conservation efforts should also pay particular attention to medium to longer-term changes in habitat or community composition which may not be obvious from merely considering extent and composition of current habitats.

Island woodiness underpins accelerated disparification in plant radiations.

Summary The evolution of secondary (insular) woodiness and the rapid disparification of plant growth forms associated with island radiations show intriguing parallels between oceanic islands and tropical alpine sky islands. However, the evolutionary significance of these phenomena remains poorly understood and the focus of debate.We explore the evolutionary dynamics of species diversification and trait disparification across evolutionary radiations in contrasting island systems compared with their nonisland relatives. We estimate rates of species diversification, growth form evolution and phenotypic space saturation for the classical oceanic island plant radiations – the Hawaiian silverswords and Macaronesian Echium – and the well‐studied sky island radiations of Lupinus and Hypericum in the Andes.We show that secondary woodiness is associated with dispersal to islands and with accelerated rates of species diversification, accelerated disparification of plant growth forms and occupancy of greater phenotypic trait space for island clades than their nonisland relatives, on both oceanic and sky islands.We conclude that secondary woodiness is a prerequisite that could act as a key innovation, manifest as the potential to occupy greater trait space, for plant radiations on island systems in general, further emphasizing the importance of combinations of clade‐specific traits and ecological opportunities in driving adaptive radiations.

Pleistocene extinctions as drivers of biogeographical patterns on the easternmost Canary Islands

AbstractSubtropical 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 (&lt;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.

The ethnobotany and biogeography of wild vegetables in the Adriatic islands

BackgroundArchipelagos of islands have played an important role in shaping some of the paradigms of biology, including the theory of the evolution of species. Later, their importance in biology was further emphasised by the theory of island biogeography, which contributed to a better understanding of the shaping of species richness not only on real islands, but on isolated habitat islands as well. Although ethnobotany is a well-established discipline, patterns of knowledge about plant uses in archipelagos have never been quantitatively analysed, and the whole concept has been only briefly mentioned in the ethnobiological context.The aim of our study was to record which taxa of wild vegetables have been consumed in the Adriatic islands and to establish if such variables as island size, population size, flora or its isolation are correlated with the number of wild vegetables used.MethodsWe interviewed 225 people (15 from each island).ResultsAltogether, the use of 89 species of wild vegetables has been recorded. The largest number of wild vegetables is eaten on the islands of Korčula, Vis and Šolta, and the lowest on Ugljan, Cres and Dugi Otok. The studied independent variables had a small and statistically not significant effect on the wild vegetable list length. The most visible effect was an increasing trend from north-west to south-east, overrunning the typical biogeographical island patterns. Moreover, one of the large and well-populated islands, Korčula, showed an ‘unusually’ high level of wild vegetable use. We hypothesise that the current use of so many species on this island has been maintained by the inhabitants’ awareness that they are the holders of relic knowledge, an awareness reiterated by ethnographic and popular publications, as well as a strong history of famine. The most interesting edible species used in the Adriatic islands are Bunium alpinum, Cytinus hypocystis (both mainly on Pašman), Lotus edulis (on Vis) and Posidonia oceanica (on Vis and Korčula).ConclusionsThe recorded relationships between the demographic and geographical features of the islands were statistically not significant. We assume that cultural and historical factors diversifying the use of plants in particular islands are stronger than the above-mentioned measurable variables.

An early evaluation of translocation actions for endangered plant species on Mediterranean islands

In situ conservation is widely considered a primary conservation strategy. Plant translocation, specifically, represents an important tool for reducing the extinction risk of threatened species. However, thus far, few documented translocations have been carried out in the Mediterranean islands. The Care-Mediflora project, carried out on six Mediterranean islands, tackles both short- and long-term needs for the insular endangered plants through in situ and ex situ conservation actions. The project approach is based on using ex situ activities as a tool to improve in situ conservation of threatened plant species. Fifty island plants (representing 45 taxa) were selected for translocations using common criteria. During the translocations, several approaches were used, which differed in site selection method, origin of genetic material, type of propagative material, planting method, and more. Although only preliminary data are available, some general lessons can be learned from the experience of the Care-Mediflora project. Among the factors restricting the implementation of translocations, limited financial resources appear to be the most important. Specific preliminary management actions, sometimes to be reiterated after translocation, increase the overall cost, but often are necessary for translocation success. Translocation using juvenile/reproductive plants produces better results over the short term, although seeds may provide good results over the long run (to be assessed in the future). Regardless, plant translocation success can only be detected over long periods; therefore, proper evaluation of plant translocations requires a long-term monitoring protocol. Care-Mediflora project represents the first attempt to combine the existing approaches in a common plant conservation strategy specifically focusing on the Mediterranean islands.

Generation Control System: Using Isochronous Load-Sharing Principles With Gas and Steam Turbine Generators

A liquefied natural gas facility in the United States is being expanded to allow the liquefaction of natural gas and exportation of liquefied natural gas while keeping intact its existing import facilities. This means it will add more loads and steam-based generation to its existing gas turbine generator (GTG ) portfolio. The upgraded system will feature six GTG s and two steam turbine generators (STGs) in an islanded plant with no grid connection. This article reveals the fundamentals of how the plant performs isochronous load sharing in an islanded power system with various makes and sizes of generators (steam and gas turbines) and details the decentralized generation control system interface methodology with automatic speed governors and voltage regulators. Also presented are some topics that are crucial for industrial power systems-particularly in islanded configurations-as well as the transient simulations performed in a controlled lab environment that analyze system stability and help finalize the generator modes of operation.

A hurricane alters pollinator relationships and natural selection on an introduced island plant

AbstractNovel relationships between the floral morphology of introduced plants and the trophic morphology of native pollinators have been hypothesized to cause strong natural selection on both parties, but evidence for such selection is rare. We capitalized on a natural disturbance to examine selection on an introduced plant,Heliconia wagneriana, on the island of Dominica, before and after Hurricane Maria. Prior to the hurricane, femaleAnthracothorax jugularishummingbirds, which have longer bills than males, were the main visitor toH. wagneriana, and directional selection on corolla length was insignificant. After the hurricane, shorter‐billed maleA. jugulariswere the main visitor toH. wagneriana. The absence of trait matching between a short‐billed pollinator and a long‐flowered plant resulted in directional selection for shorter flowers because males preferentially visited plants with shorter flowers. The amount of nectar removed by maleA. jugulariswas negatively associated with flower length, with flowers &gt;53 mm containing nearly five times the nectar than flowers &lt;53 mm. We estimate a roughly 75% decrease in the population size ofA. jugularis, and results suggest the heaviest mortality occurred among short‐billed male hummingbirds and larger‐bodied individuals of both sexes, which would have higher nectar requirements and the most difficulty obtaining nectar. Our results indicate that hurricanes may alter relationships between plants and pollinators and that lack of trait matching resulting from such disturbances may lead to selection on both plant and pollinator.

Mycorrhizal fungi influence global plant biogeography.

Island biogeography has traditionally focused primarily on abiotic drivers of colonization, extinction and speciation. However, establishment on islands could also be limited by biotic drivers, such as the absence of symbionts. Most plants, for example, form symbioses with mycorrhizal fungi, whose limited dispersal to islands could act as a colonization filter for plants. We tested this hypothesis using global-scale analyses of ~1.4 million plant occurrences, including ~200,000 plant species across ~1,100 regions. We find evidence for a mycorrhizal filter (that is, the filtering out of mycorrhizal plants on islands), with mycorrhizal associations less common among native island plants than native mainland plants. Furthermore, the proportion of native mycorrhizal plants in island floras decreased with isolation, possibly as a consequence of a decline in symbiont establishment. We also show that mycorrhizal plants contribute disproportionately to the classic latitudinal gradient of plant species diversity, with the proportion of mycorrhizal plants being highest near the equator and decreasing towards the poles. Anthropogenic pressure and land use alter these plant biogeographical patterns. Naturalized floras show a greater proportion of mycorrhizal plant species on islands than in mainland regions, as expected from the anthropogenic co-introduction of plants with their symbionts to islands and anthropogenic disturbance of symbionts in mainland regions. We identify the mycorrhizal association as an overlooked driver of global plant biogeographical patterns with implications for contemporary island biogeography and our understanding of plant invasions.

海岛植物不同演替阶段植物功能性状与环境因子的变化规律

PDF HTML阅读 XML下载 导出引用 引用提醒 海岛植物不同演替阶段植物功能性状与环境因子的变化规律 DOI: 10.5846/stxb201807051468 作者: 作者单位: 福建农林大学,福建农林大学,福建农林大学,云南大学,福建农林大学 作者简介: 通讯作者: 中图分类号: 基金项目: 福建省自然科学基金面上项目（2018J01699）；国家自然科学基金项目（31800401）；福建省教育厅科技项目（JAT170198） Summary of changes in plant functional traits and environmental factors in different successional stages of island plants Author: Affiliation: Fujian Agriculture and Forestry University,Fujian Agriculture and Forestry University,Fujian Agriculture and Forestry University,,Fujian Agriculture and Forestry University Fund Project: 省、部研究计划基金, 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植物功能性状与环境之间的关系是功能性状研究的重点，环境因子驱使植物功能性状发生变化，进而推动群落发生演替。以平潭岛4个不同演替阶段的森林植被（灌草丛、针叶林、针阔混交林、常绿阔叶林）为研究对象，结合不同群落演替阶段的物种特征和群落结构，分析海岛不同演替阶段茎、叶功能性状的变化规律，以及功能性状与环境因子的关系。结果表明：（1）随着演替的进行，土壤养分和水分逐渐增加，土壤pH逐渐下降。比叶面积（SLA）、叶片氮含量（LNC）、叶片磷含量（LPC）、茎氮含量（SNC）、茎磷含量（SPC）下降后上升，叶厚度（LT）、叶片碳含量（LCC）、茎碳含量（SCC）与之相反，叶干物质含量（LDMC）、茎组织密度（STD）逐渐上升。（2）冗余分析表明，演替早期植物主要分布在土壤pH、容重高的贫瘠环境，拥有较高SLA、SNC、SPC、LPC的性状组合；演替后期植物主要分布在土壤养分和水分高的肥沃环境，拥有较高的STD、LDMC、LCC、LNC的性状组合。其中，土壤有机质和全氮含量是影响海岛植物演替过程中功能性状变化的关键环境因子。研究海岛植物功能性状与环境之间的关系随演替的变化规律，探讨各演替阶段功能性状和环境特征，以及功能性状如何响应环境变化。旨在为今后选择合适的树种进行海岛植被修复和重建提供依据。 Abstract:The relationship between plant functional traits and environment is the focus of functional traits research. Environmental factors drive the changes in plant functional traits, which in turn promote community succession. Based on the forest vegetation of four different succession stages (shrub-grassland, coniferous forest, mixed wood, and broadleaf forest) in Pingtan Island, this study combined the species characteristics and community structure of different community successional stages. We analyzed the changes in stem and leaf functional traits in different succession stages of island plants. Moreover, we explored the relationship between plant functional traits and environmental factors. The results showed the following. (1) With progress in succession, soil nutrient and water content gradually increased and the soil pH gradually decreased. The specific leaf area (SLA), leaf nitrogen content (LNC), leaf phosphorus content (LPC), stem nitrogen content (SNC), and stem phosphorus content (SPC) decreased initially, and then increased, Meanwhile, the leaf thickness (LT), leaf carbon content (LCC), and stem carbon content (SCC) increased initially, and then decreased. The leaf dry matter content (LDMC) and stem tissue density (STD) gradually increased. (2) The redundancy analysis showed that the early succession plants were mainly distributed in barren environments with high soil pH and high bulk density, and they presented higher SLA, SNC, SPC, and LPC. Plants in the late succession stages were mainly distributed in fertile environments with high soil nutrient and water content, and they presented higher STD, LDMC, LCC, and LNC. Therefore, soil organic matter and total nitrogen are the important environmental factors that affect the functional traits of island plants succession. We studied the relationship between plant functional traits and environment along with the changes in succession, understood the functional traits and environmental characteristics of each succession stage, and revealed how plant functional traits adapted to the environmental changes. The study provides the basis for the selection of suitable tree species for island vegetation restoration and reconstruction in the future. 参考文献 相似文献 引证文献

Understanding the Indian mainland–island biogeography through plant dispersal mechanism

The plant–disperser relationship and its key predictors in Indian tropical archipelagos are understudied. East of the Indian mainland (the Eastern coast, EC) are the Andaman and Nicobar Islands (AN, about 1221 km away at the shortest distance), which exhibit a great plant diversity, with 848 unique species. West of the Indian mainland (the Western Ghats, WG) are another group of islands, the Lakshadweep Islands (LD, about 320 km away at the shortest distance), which exhibit less diversity (102 unique species) than do the AN. We compared these two mainland–island pairs (EC–AN, WG–LD), which exhibit different insular isolation conditions, to understand the plant dispersal mechanisms and their determining predictors (plant richness, geographic area, perimeter, elevation, and shortest distance). We found epizoochory (adherence to an animal surface), ornithochory (birds), and hydrochory (water) to be the dominant dispersers of both the pairs. Additionally, the plant dispersal in the WG–LD pair is predominantly driven by anemochory (wind), possibly denoting the effects of the northeasterly trade winds. The major role of biotic dispersers in the EC–AN pair may be explained as resulting from plant dispersal to more remote islands through biotic dispersers being more rapid and efficient. The plant commonality was found to be positively correlated with the plant richness, geographic area, and perimeter; whereas it was negatively correlated with the shortest distance and elevation of the selected mainland–island pairs. Both linear (R2 = 0.85) and non-linear (R2 = 0.95) regression with maximum accuracy found island plant richness, geographic area, and shortest distance to the nearest mainland pool to be the determinants in explaining plant-dispersal mechanisms. These predictors are important to maintain the habitat suitability and connectivity and thereby support more newly dispersed plants. The plant–disperser relationship (epizoochory, ornithochory, anemochory, and hydrochory) and the key predictors (plant richness, geographic area, and shortest distance) found in this study could be useful for conservation, planning, and monitoring of biodiversity.

Reduced Defenses and Increased Herbivore Preference of Island Chaparral Shrubs Compared to Mainland Relatives

The absence of herbivores from certain environments may select for plants that are less defended and more palatable compared to plants in similar environments that are exposed to herbivory. This potential loss of defenses becomes especially important when exotic herbivores are introduced to islands that historically lack such organisms, potentially resulting in negative effects on native island ecosystems. To test the hypothesis that island plants have reduced defensive traits, we measured structural defenses and palatability of 10 taxonomic pairs from contrasting island and mainland environments. Our study compares plants from Santa Catalina Island, California—which has a long history without large native herbivores followed by more recent human-caused introductions—to the adjacent southern California mainland where ungulate herbivores are native and common. Our results suggest that island plants have reduced structural defenses and are more preferred by herbivores compared to their mainland plant relatives. These patterns are likely driven by selection on plant traits in the unique and insular island environment. Reduced defenses and increased palatability of island plant species should be considered when developing management strategies for island ecosystems that historically lack native ungulate herbivores.

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

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. 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. 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. 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.

Yes We Can! Exciting Progress and Prospects for Controlling Invasives on Islands and Beyond

Eradication and maintenance management of island invasive species have long histories, and incremental improvements of existing technologies plus occasional novel approaches have led to more challenging targets and increased success rates in certain categories. Many nonnative mammals have been eradicated from islands, as have several nonnative birds, insects, and plants. Hundreds of rat populations have been eliminated, with a success rate over 80%, and islands over 10,000 ha are now feasible targets. Mouse eradication has proven more challenging, but aerial broadcast of anticoagulant toxins has led to increased success. Carnivore eradication—especially of feral housecats and foxes—has been frequently attempted with a recent success rate over 90%. Eradication of herbivores—primarily goats, rabbits, wild boar, and boar/pig hybrids—has been attempted almost 200 times, with a success rate over 90%. Trends in mammal eradication include more frequent attempts and higher success rates on larger islands and inhabited islands, as well as attempts targeting multiple invasive species. Documented conservation gains from island mammal eradications are numerous. For insects, about two-thirds of some 50 island attempts have succeeded, and most targeted agricultural pests. No summary statistics exist on island plant eradications, but several small infestations have been eradicated. Several insect and plant island invaders have been maintained at low densities by biological control, and plants have been controlled short of eradication by herbicides, often combined with physical or mechanical means. Failures in both eradication and maintenance management on islands often result from insufficient long-term commitment of resources. Excitement and controversy abound over the prospect that new techniques relying on molecular genetic tools—especially RNA-guided gene drives—may permit eradication or maintenance management of nonnative invaders in situations that have previously appeared extremely difficult or infeasible. Island populations of invertebrates, small mammals, and some plants are particularly propitious targets.

Retracing the Hawaiian silversword radiation despite phylogenetic, biogeographic, and paleogeographic uncertainty.

The Hawaiian silversword alliance (Asteraceae) is an iconic adaptive radiation. However, like many island plant lineages, no fossils have been assigned to the clade. As a result, the clade's age and diversification rate are not known precisely, making it difficult to test biogeographic hypotheses about the radiation. In lieu of fossils, paleogeographically structured biogeographic processes may inform species divergence times; for example, an island must first exist for a clade to radiate upon it. We date the silversword clade and test biogeographic hypotheses about its radiation across the Hawaiian Archipelago by modeling interactions between species relationships, molecular evolution, biogeographic scenarios, divergence times, and island origination times using the Bayesian phylogenetic framework, RevBayes. The ancestor of living silverswords most likely colonized the modern Hawaiian Islands once from the mainland approximately 5.1 Ma, with the most recent common ancestor of extant silversword lineages first appearing approximately 3.5 Ma. Applying an event-based test of the progression rule of island biogeography, we found strong evidence that the dispersal process favors old-to-young directionality, but strong evidence for diversification continuing unabated into later phases of island ontogeny, particularly for Kaua'i. This work serves as a general example for how diversification studies benefit from incorporating biogeographic and paleogeographic components.