Statistical models of invertebrate distribution on Macquarie Island: a tool to assess climate change and local human impacts

Sub-Antarctic islands are good model systems in which to study the ecological effects of human impacts, particularly global climate change and alien species. Invertebrates form a central component of these ecosystems. We conducted a stratified survey of 69 sites on sub-Antarctic Macquarie Island and used logistic regression models to describe the distribution of 14 abundant invertebrate species. We also developed a statistical model of windspeed based on topography. The distributions of individual species were described by different combinations of aspect, altitude and vegetation type. Ordination of sites based on species composition showed strong effects of altitude and vegetation on invertebrate assemblages. The species distribution models provide a tool for detecting, monitoring and predicting effects of climate change and alien species on biota and ecosystem processes. Accepted: 30 August 1998     

Climate change and biological invasions: evidence,expectations, and response options

A changing climate may directly or indirectly influence biological invasions by altering the likelihood of introduction or establishment, as well as modifying the geographic range, environmental impacts, economic costs or management of alien species. A comprehensive assessment of empirical and theoretical evidence identified how each of these processes is likely to be shaped by climate change for alien plants, animals and pathogens in terrestrial, freshwater and marine environments of Great Britain. The strongest contemporary evidence for the potential role of climate change in the establishment of new alien species is for terrestrial arthropods, as a result of their ectothermic physiology, often high dispersal rate and their strong association with trade as well as commensal relationships with human environments. By contrast, there is little empirical support for higher temperatures increasing the rate of alien plant establishment due to the stronger effects of residence time and propagule pressure. The magnitude of any direct climate effect on the number of new alien species will be small relative to human‐assisted introductions driven by socioeconomic factors. Casual alien species (sleepers) whose population persistence is limited by climate are expected to exhibit greater rates of establishment under climate change assuming that propagule pressure remains at least at current levels. Surveillance and management targeting sleeper pests and diseases may be the most cost‐effective option to reduce future impacts under climate change. Most established alien species will increase their distribution range in Great Britain over the next century. However, such range increases are very likely be the result of natural expansion of populations that have yet to reach equilibrium with their environment, rather than a direct consequence of climate change. To assess the potential realised range of alien species will require a spatially explicit approach that not only integrates bioclimatic suitability and population‐level demographic rates but also simulation of landscape‐level processes (e.g. dispersal, land‐use change, host/habitat distribution, non‐climatic edaphic constraints). In terms of invasive alien species that have known economic or biodiversity impacts, the taxa that are likely to be the most responsive are plant pathogens and insect pests of agricultural crops. However, the extent to which climate adaptation strategies lead to new crops, altered rotations, and different farming practices (e.g. irrigation, fertilization) will all shape the potential agricultural impacts of alien species. The greatest uncertainty in the effects of climate change on biological invasions exists with identifying the future character of new species introductions and predicting ecosystem impacts. Two complementary strategies may work under these conditions of high uncertainty: (i) prioritise ecosystems in terms of their perceived vulnerability to climate change and prevent ingress or expansion of alien species therein that may exacerbate problems; (ii) target those ecosystem already threatened by alien species and implement management to prevent the situation deteriorating under climate change.     

A new look at evolution in the Galápagos: evidence from the late Cenozoic marine molluscan fauna

Endemism is not as common in the marine invertebrate fauna of the Galápagos Islands region as in the adjacent terrestrial biota. Marine invertebrates in the Galápagos are largely cosmopolitan species from the Panamic, Indo-Pacific, Californian, or Peruvian faunal provinces. However, an endemic component is also present in the fauna. The observed pattern among marine invertebrate organisms can be accounted for by at least two processes: (1) genetic continuity between mainland and island populations mediated through planktonic larvae; and (2) lower rates of intrinsic evolutionary change. The evolutionary scenario standardly applied to terrestrial organisms in the Galápagos, namely, adaptive radiation and speciation in reproductive isolation from mainland source populations, does not apply to all marine invertebrates. Evidence in support of the alternative scenario for marine invertebrates comes from both published records of species occurring in the islands and recent studies of fossil-bearing deposits on several islands in the archipelago. Two misconceptions–considering the islands and sedimentary deposits to be older than now thought, and equating the rate of evolution of the terrestrial biota with the marine biota–can lead to an incorrect interpretation of evolution in the Galápagos Contrasts between marine invertebrate and terrestrial organisms serve to illustrate some fundamental differences which have important evolutionary implications. Some of these are: endemism; dispersal; taxonomic relationships; island definitions; rates of evolutionary change; and age of fossils. In terms of Darwin's evolutionary scenario, terrestrial organisms represent the paradigm and marine organisms represent the paradox.     

Human transformations of the Wadden Sea ecosystem through time: a synthesis

Todays Wadden Sea is a heavily human-altered ecosystem. Shaped by natural forces since its origin 7,500 years ago, humans gradually gained dominance in influencing ecosystem structure and functioning. Here, we reconstruct the timeline of human impacts and the history of ecological changes in the Wadden Sea. We then discuss the ecosystem and societal consequences of observed changes, and conclude with management implications. Human influences have intensified and multiplied over time. Large-scale habitat transformation over the last 1,000 years has eliminated diverse terrestrial, freshwater, brackish and marine habitats. Intensive exploitation of everything from oysters to whales has depleted most large predators and habitat-building species since medieval times. In the twentieth century, pollution, eutrophication, species invasions and, presumably, climate change have had marked impacts on the Wadden Sea flora and fauna. Yet habitat loss and overexploitation were the two main causes for the extinction or severe depletion of 144 species (~20% of total macrobiota). The loss of biodiversity, large predators, special habitats, filter and storage capacity, and degradation in water quality have led to a simplification and homogenisation of the food web structure and ecosystem functioning that has affected the Wadden Sea ecosystem and coastal societies alike. Recent conservation efforts have reversed some negative trends by enabling some birds and mammals to recover and by creating new economic options for society. The Wadden Sea history provides a unique long-term perspective on ecological change, new objectives for conservation, restoration and management, and an ecological baseline that allows us to envision a rich, productive and diverse Wadden Sea ecosystem and coastal society.     

The significance of the sub-Antarctic Kerguelen Islands for the assessment of the vulnerability of native communities to climate change,alien insect invasions and plant viruses

The suite of environments and anthropogenic modifications of sub-Antarctic islands provide key opportunities to improve our understanding of the potential consequences of climate change and biological species invasions on terrestrial ecosystems. The profound impact of human introduced invasive species on indigenous biota, and the facilitation of establishment as a result of changing thermal conditions, has been well documented on the French sub-Antarctic Kerguelen Islands (South Indian Ocean). The present study provides an overview of the vulnerability of sub-Antarctic terrestrial communities with respect to two interacting factors, namely climate change and alien insects. We present datasets assimilated by our teams on the Kerguelen Islands since 1974, coupled with a review of the literature, to evaluate the mechanism and impact of biological invasions in this region. First, we consider recent climatic trends of the Antarctic region, and its potential influence on the establishment, distribution and abundance of alien insects, using as examples one fly and one beetle species. Second, we consider to what extent limited gene pools may restrict alien species’ colonisations. Finally, we consider the vulnerability of native communities to aliens using the examples of one beetle, one fly, and five aphid species taking into consideration their additional impact as plant virus vectors. We conclude that the evidence assimilated from the sub-Antarctic islands can be applied to more complex temperate continental systems as well as further developing international guidelines to minimise the impact of alien species.     

Phenotypic plasticity mediates climate change responses among invasive and indigenous arthropods

Synergies between global change and biological invasion have been identified as a major potential threat to global biodiversity and human welfare. The global change-type drought characteristic of many temperate terrestrial ecosystems is especially significant because it will apparently favour invasive over indigenous species, adding to the burden of conservation and compromising ecosystem service delivery. However, the nature of and mechanisms underlying this synergy remain poorly explored. Here we show that in a temperate terrestrial ecosystem, invasive and indigenous springtail species differ in the form of their phenotypic plasticity such that warmer conditions promote survival of desiccation in the invasive species and reduce it in the indigenous ones. These differences are consistent with significant declines in the densities of indigenous species and little change in those of invasive species in a manipulative field experiment that mimicked climate change trends. We suggest that it is not so much the extent of phenotypic plasticity that distinguishes climate change responses among these invasive and indigenous species, as the form that this plasticity takes. Nonetheless, this differential physiological response provides support for the idea that in temperate terrestrial systems experiencing global change-type drought, invasive species may well be at an advantage relative to their indigenous counterparts.     

应用Maxent生态位模型预测淡水钩虾(甲壳纲,端足目)的分布(英文)

预测物种的适生区对于物种资源的评估、保护以及生物多样性的管理非常重要。由于全球气候变化和人类的过度开发,冷水性无脊椎动物的衰减速度比在陆地和海洋生活的无脊椎动物都要高。目前关于中国淡水钩虾分布方面的研究很少,本研究基于103个地表淡水钩虾的不同分布位点和广布种湖泊钩虾Gammarus lacustris 23个不同分布位点以及32个环境因子数据,使用生态位模型(Maxent)预测了淡水钩虾和湖泊钩虾在我国的适生分布区域。结果显示淡水钩虾非常适合分布在我国的一些偏远山区,如长白山、太行山、横断山、天山、昆仑山和祁连山,而青藏高原的东部、西部边缘地区和南部分布地区、尼泊尔、不丹和朝鲜半岛也是淡水钩虾的潜在适生区域,但淡水钩虾在我国华南、华中和华北的平原地区分布却很少,其在我国的潜在分布区与-10℃和5℃1月平均气温线间的区域相似。淡水钩虾是典型的狭温性物种,在不适宜温度条件下很难存活,这可能也是限制其扩散和存活的关键性因素。     

Climate change impacts on wildlife in a High Arctic archipelago – Svalbard,Norway

The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of ‘rain‐on‐snow’ events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore–predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long‐term (multidecadal) demographic, population‐ and ecosystem‐based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming.     

Insights from modeling studies on how climate change affects invasive alien species geography

Climate change and biological invasions are threatening biodiversity and ecosystem services worldwide. It has now been widely acknowledged that climate change will affect biological invasions. A large number of studies have investigated predicted shifts and other changes in the geographic ranges of invasive alien species related to climate change using modeling approaches. Yet these studies have provided contradictory evidence, and no consensus has been reached. We conducted a systematic review of 423 modeling case studies included in 71 publications that have examined the predicted effects of climate change on those species. We differentiate the approaches used in these studies and synthesize their main results. Our results reaffirm the major role of climate change as a driver of invasive alien species distribution in the future. We found biases in the literature both regarding the taxa, toward plants and invertebrates, and the areas of the planet investigated. Despite these biases, we found for the plants and vertebrates studied that climate change will more frequently contribute to a decrease in species range size than an increase in the overall area occupied. This is largely due to oceans preventing terrestrial invaders from spreading poleward. In contrast, we found that the ranges of invertebrates and pathogens studied are more likely to increase following climate change. An important caveat to these findings is that researchers have rarely considered the effects of climate change on transport, introduction success, or the resulting impacts. We recommend closing these research gaps, and propose additional avenues for future investigations, as well as opportunities and challenges for managing invasions under climate change.     

The influence of freshwater-lake subsidies on invertebrates occupying terrestrial vegetation

Studies investigating effects of aquatic-derived resource subsidies have often found large effects on terrestrial systems. Those studies have mostly been performed on effects of subsidies derived from oceanic and riverine systems, and very few have considered effects of subsidies from freshwater lakes. However, since lakes can produce large quantities of emergent aquatic insects that end up on nearby land, it is likely that also freshwater-lake subsidies influence terrestrial systems. We performed sweep-net collections of aquatic and terrestrial invertebrates at varying distances from the shore on vegetation of islands of varying size, in two freshwater lakes in northern Sweden, as well as on the surrounding mainland. We found that the amounts of aquatic insects on terrestrial vegetation decreased with distance from the shore, and that they were the most abundant on small islands, presumably because small islands have a higher perimeter-to-area ratio. Web-building spiders responded positively to the aquatic subsidy by being the most abundant on small islands and by showing a positive relationship with aquatic insect biomass. However, distance from the shore showed no effects on the spiders. Our results strongly support the view that terrestrial systems are subsidized by lakes, and indicate that freshwater-lake subsidies are important for terrestrial invertebrate community structure on adjacent land. Further, our study shows that ecosystems should be treated as interdependent, not as self-contained units, and may as such be important for an increased understanding of the nature and importance of resource flows across ecosystem boundaries.     

Invasive aliens on tropical East Asian islands

Tropical East Asia (TEA) has numerous islands, both continental and oceanic. This study uses information on invasive aliens in terrestrial habitats on these islands to test the generality of the continental-oceanic contrast in invasibility, assess the conservation impacts of invasive species, and suggest ways to mitigate these. The continental islands of Hong Kong and Singapore are worst-case scenarios for continental invasibility and alien species often dominate in chronically disturbed sites, but very few have successfully invaded closed forests, with the exception of birds in Hong Kong. On other, less densely populated, continental islands, closed-canopy forests appear to resist invasions by all taxa, with few known exceptions. Forests on oceanic islands isolated by <100 km during the last glacial maximum appear no more susceptible to plant and invertebrate invasions than those on continental islands, but invasions by mammals are widespread. Snake invasions may be under-recognized. The remote oceanic Ogasawara (Bonin) Islands, >1000 km from the nearest continent, have a native biota of largely tropical East Asian origin and are suffering from alien forest invasions across the taxonomic spectrum. These patterns of invasibility are consistent with the idea that alien invasion is facilitated by the absence of native species in the same functional group. Alien invasives are not yet a major conservation problem in TEA, except on remote islands, but their dominance on disturbed sites may slow or prevent recovery of native biodiversity. Strict quarantine is impractical in TEA, although some major introduction routes could be blocked. Management efforts should focus on early recognition and immediate control of potential problem species.     

Ion regulation in invertebrates: molecular and integrative aspects

The subject of ion regulation in invertebrates is discussed, using a variety of invertebrate model species and approaches that range from the whole-organism level to tissue, subcellular, and molecular levels to illustrate the future direction of the field. These organisms inhabit a variety of aquatic, freshwater, and terrestrial environments, showing specific adaptations to each environment. This overview discusses mechanisms of metal detoxification and the presence of Cl-ATPase in marine organisms to avoid excess intracellular Cl(-); Ca(2+) regulation and endocrine aspects of adaptations to transitional (semiterrestrial) environments; adaptations to Ca(2+)-poor freshwater, particularly the reabsorption of Ca(2+) through specific transporters found in the urine; and finally, ionoregulatory mechanisms for life on land, such as Ca(2+) conservation during molting in isopods and the presence of K(+) channels in insect Malpighian tubules. Convergent mechanisms for dealing with similar problems in dissimilar habitats are discussed, taking into consideration that invertebrates will continue to serve as model systems for the evolution of ionoregulation in different habitats.     

The distribution and economic losses of alien species invasion to China

Invasive alien species have become one of the most serious environmental issues in the world. Data of taxon, origin, pathway, and environmental impacts of invasive alien microorganisms, invertebrates, amphibians and reptiles, fish, birds, mammals, herbs, trees, and, marine organisms in terrestrial, aquatic, and marine ecosystems of China were analyzed during 2001 and 2003, based on literature retrieval and field survey. There were 283 invasive alien species in China, and the number of species of invasive alien microorganisms, aquatic plants, terrestrial plants, aquatic invertebrates, terrestrial invertebrates, amphibians and reptiles, fish, and mammals were 19, 18, 170, 25, 33, 3, 10, and 5, respectively. The proportion of invasive alien species originated from America, Europe, Asia, Africa, and Oceania were 55.1, 21.7, 9.9, 8.1, and 0.6%, respectively. Methods for estimation of direct economic losses to agriculture, forestry, stockbreeding, fishery, road and water transportation, storage, water conservancy, environment and public facilities, and human health were established. Methods for estimation of indirect economic losses caused by invasive alien species to service functions of forest ecosystems, agricultural ecosystems, grassland ecosystems, and wetland ecosystems were also established. The total economic losses caused by invasive alien species to China were to the time of USD 14.45 billion, with direct and indirect economic losses accounting for 16.59% and 83.41% of total economic losses, respectively.     

Alien Grazing: Indirect Effects of Muskrats on Invertebrates

Effects of alien herbivores on plants are quite well known, especially on oceanic islands. Much less is known about the indirect effects of alien herbivores. Via indirect effects indigenous organisms can become more vulnerable to other ecological factors. We studied the effect of dense muskrat population on aquatic invertebrates in patches, which were in different succession phases after grazing. The succession was divided into three phases:(i) open-water area, (ii) mixed floating and submerged vegetation, and (iii) undisturbed Equisetum stands. Intensive muskrat grazing affected especially the size distribution of invertebrates. The proportion of small invertebrates was greatest in clear-cut areas, whereas that of large invertebrates was greatest in the Equisetum-stands. According to activity traps, the clear-cut areas harboured good populations of small perch, which are known as invertebrate predators. The study showed that the indirect effects of alien herbivore can be considerable. In this case, they seemed to be mediated to invertebrates through the change in vegetative habitat structure. This change rendered invertebrates more vulnerable to fish predation.     

Tropical terrestrial invertebrates—Where to from here?

There are over one million described invertebrate species on Earth, the majority of which are likely to inhabit the highly biodiverse rain forests around the equator. These are some of the most vulnerable ecosystems on Earth due to the pressures of deforestation and climate change with many of their inhabitants at risk of extinction. Invertebrates play a major role in ecosystem functioning from decomposition and nutrient cycling to herbivory and pollination; however, while our understanding of these roles is improving, we are far from being able to predict the consequences of further deforestation, climate change, and biodiversity loss due to the lack of comparative data and the high proportion of species which remain to be discovered. As we move into an era of increased pressure on old-growth habitats and biodiversity, it is imperative that we understand how changes to invertebrate communities, and the extinction of species, affect ecosystems. Innovative and comprehensive methods that approach these issues are needed. Here, we highlight priorities for future tropical terrestrial invertebrate research such as the efficiency of sustainable land management, exploration of innovative methods for better understanding of invertebrate ecology and behavior, and quantifying the role of invertebrates in ecosystem functioning.     

Marine range shifts and species introductions: comparative spread rates and community impacts

Aim Shifts in species ranges are a predicted and realized effect of global climate change; however, few studies have addressed the rates and consequence of such shifts, particularly in marine systems. Given ecological similarities between shifting and introduced species, we examined how our understanding of range shifts may be informed by the more established study of non‐native species introductions. Location Marine systems world‐wide. Methods Database and citation searches were used to identify 129 marine species experiencing range shifts and to determine spread rates and impacts on recipient communities. Analyses of spread rates were based on studies for which post‐establishment spread was reported in linear distance. The sizes of the effects of community impacts of shifting species were compared with those of functionally similar introduced species having ecologically similar impacts. Results Our review and meta‐analyses revealed that: (1) 75% of the range shifts found through the database search were in the poleward direction, consistent with climate change scenarios, (2) spread rates of range shifts were lower than those of introductions, (3) shifting species spread over an order of magnitude faster in marine than in terrestrial systems, and (4) directions of community effects were largely negative and magnitudes were often similar for shifters and introduced species; however, this comparison was limited by few data for range‐shifting species. Main conclusions Although marine range shifts are likely to proceed more slowly than marine introductions, the community‐level effects could be as great, and in the same direction, as those of introduced species. Because it is well‐established that introduced species are a primary threat to global biodiversity, it follows that, just like introductions, range shifts have the potential to seriously affect biological systems. In addition, given that ranges shift faster in marine than terrestrial environments, marine communities might be affected faster than terrestrial ones as species shift with climate change. Regardless of habitat, consideration of range shifts in the context of invasion biology can improve our understanding of what to expect from climate change‐driven shifts as well as provide tools for formal assessment of risks to community structure and function.     

Simulating plant invasion dynamics in mountain ecosystems under global change scenarios

Across the globe, invasive alien species cause severe environmental changes, altering species composition and ecosystem functions. So far, mountain areas have mostly been spared from large‐scale invasions. However, climate change, land‐use abandonment, the development of tourism and the increasing ornamental trade will weaken the barriers to invasions in these systems. Understanding how alien species will react and how native communities will influence their success is thus of prime importance in a management perspective. Here, we used a spatially and temporally explicit simulation model to forecast invasion risks in a protected mountain area in the French Alps under future conditions. We combined scenarios of climate change, land‐use abandonment and tourism‐linked increases in propagule pressure to test if the spread of alien species in the region will increase in the future. We modelled already naturalized alien species and new ornamental plants, accounting for interactions among global change components, and also competition with the native vegetation. Our results show that propagule pressure and climate change will interact to increase overall species richness of both naturalized aliens and new ornamentals, as well as their upper elevational limits and regional range‐sizes. Under climate change, woody aliens are predicted to more than double in range‐size and herbaceous species to occupy up to 20% of the park area. In contrast, land‐use abandonment will open new invasion opportunities for woody aliens, but decrease invasion probability for naturalized and ornamental alien herbs as a consequence of colonization by native trees. This emphasizes the importance of interactions with the native vegetation either for facilitating or potentially for curbing invasions. Overall, our work highlights an additional and previously underestimated threat for the fragile mountain flora of the Alps already facing climate changes, land‐use transformations and overexploitation by tourism.     

The status and causes of alien species invasion in China

Data of classification, origin, pathway and environmental impacts of invasive alien micro-organisms, invertebrates, amphibians and reptiles, fish, birds, mammals, weeds, trees, and marine organisms in terrestrial, aquatic and marine ecosystems of China, were analyzed, based on literature retrieval, field survey and consultation. Some 283 invasive alien species were recorded in China, including 19 invasive alien micro-organisms, 18 aquatic plants, 170 terrestrial plants, 25 aquatic invertebrates, 33 terrestrial invertebrates, 3 amphibians and reptiles, 10 fish, and 5 mammals. Of the invasive alien species, 55.1% originated from North and South America, 21.7% from Europe, 9.9% from Asia, 8.1% from Africa and 0.6% from Oceania. Many institutions and individuals in China lack adequate knowledge of ecological and environmental consequences caused by invasive alien species, with some ignorance of the dangerous invasion in the introduction of alien species. For instance, 50.0% of invasive alien plants were intentionally introduced as pasture, feedingstuff, ornamental plants, textile plants, medicinal plants, vegetables, or lawn plants, 25% of alien invasive animals were intentionally introduced for cultivation, ornament, or biological control, In addition, more efforts are being made in the introduction of alien species, and little attention is paid on the management of introduced alien species, which may cause their escape into natural environment and potential threats to the environment. There were also gaps in quarantine system in China. All microorganisms were unintentionally introduced, through timber, seedling, flowerpot, or soil; 76.3% of alien invasive animals invaded through commodity or transportation facility because of the failure of quarantine. Therefore, quarantine measures should be strictly implemented; and meanwhile the intentional introduction of alien species should be strictly managed and a system of risk assessment should be implemented.     

Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea)

Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world''s 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.     

Taxonomic homogenization and differentiation across Southern Ocean Islands differ among insects and vascular plants

Aim To investigate taxonomic homogenization and/or differentiation of insect and vascular plant assemblages across the Southern Ocean Islands (SOI), and how they differ with changing spatial extent and taxonomic resolution. Location Twenty‐two islands located across the Southern Ocean, further subdivided into five island biogeographical provinces. These islands are used because comprehensive data on both indigenous and non‐indigenous insect and plant species are available. Methods An existing database was updated, using newly published species records, identifying the indigenous and non‐indigenous insect and vascular plant species recorded for each island. Homogenization and differentiation were measured using Jaccard’s index (JI) of similarity for assemblages across all islands on a pairwise basis, and for island pairs within each of the biogeographical provinces. The effects of taxonomic resolution (species, genus, family) and distance on levels of homogenization or differentiation were examined. To explore further the patterns of similarity among islands for each of the taxa and groupings (indigenous and non‐indigenous), islands were clustered based on JI similarity matrices and using group averaging. Results Across the SOI, insect assemblages have become homogenized (0.7% increase in similarity at species level) while plant assemblages have become differentiated at genus and species levels. Homogenization was recorded only when pairwise distances among islands exceeded 3000 km for insect assemblages, but distances had to exceed 10,000 km for plant assemblages. Widely distributed non‐indigenous plant species tend to have wider distributions across the SOI than do their insect counterparts, and this is also true of the indigenous species. Main conclusions Insect assemblages across the SOI have become homogenized as a consequence of the establishment of non‐indigenous species, while plant assemblages have become more differentiated. The likely reason is that indigenous plant assemblages are more similar across the SOI than are insect assemblages, which show greater regionalization. Thus, although a suite of widespread, typically European, weedy, non‐indigenous plant species has established on many islands, the outcome has largely been differentiation. Because further introductions of insects and vascular plants are probable as climates warm across the region, the patterns documented here are likely to change through time.