中国缺齿藓科新记录种——冻原丝瓜藓(新拟,Pohlia tundrae A. J. Shaw)

冻原丝瓜藓(Pohlia tundrae)在北美被首次描述,随后在欧洲中部、俄罗斯远东地区和西伯利亚西北部也相继报道。最近,作者在西藏林芝也发现了冻原丝瓜藓的分布。该文详细描述了冻原丝瓜藓的形态结构特征,提供了显微形态学照片,并对其生境、地理分布以及与相似种的形态学进行了比较讨论。凭证标本存放于中国农业大学标本馆(BAU)。     

Simulating the effects of climate change on the distribution of an invasive plant,using a high resolution,local scale,mechanistic approach: challenges and insights

The growing economic and ecological damage associated with biological invasions, which will likely be exacerbated by climate change, necessitates improved projections of invasive spread. Generally, potential changes in species distribution are investigated using climate envelope models; however, the reliability of such models has been questioned and they are not suitable for use at local scales. At this scale, mechanistic models are more appropriate. This paper discusses some key requirements for mechanistic models and utilises a newly developed model (PSS[gt]) that incorporates the influence of habitat type and related features (e.g., roads and rivers), as well as demographic processes and propagule dispersal dynamics, to model climate induced changes in the distribution of an invasive plant (Gunnera tinctoria) at a local scale. A new methodology is introduced, dynamic baseline benchmarking, which distinguishes climate‐induced alterations in species distributions from other potential drivers of change. Using this approach, it was concluded that climate change, based on IPCC and C4i projections, has the potential to increase the spread‐rate and intensity of G. tinctoria invasions. Increases in the number of individuals were primarily due to intensification of invasion in areas already invaded or in areas projected to be invaded in the dynamic baseline scenario. Temperature had the largest influence on changes in plant distributions. Water availability also had a large influence and introduced the most uncertainty in the projections. Additionally, due to the difficulties of parameterising models such as this, the process has been streamlined by utilising methods for estimating unknown variables and selecting only essential parameters.     

Plant‐parasitic nematodes as invasive species: characteristics,uncertainty and biosecurity implications

Few species of plant‐parasitic nematodes (PPN) are currently recognised as invasive but this is largely because of insufficient investigation and recognition. We compared the characteristics of PPN with those of invasive species generally, using the propagule pressure, abiotic and biotic factors (PAB) framework. Most PPN had many of the characteristics of invasive species and hence have the potential to become invasive. The most common characteristics included: adaptations for human mediated dispersal; multiple entry pathways; microscopic size; large number of propagules; high fecundity; many or cosmopolitan hosts; short lifecycle; ability to survive harsh or unfavourable conditions; ability to vary sex ratios; and ability to overcome host plant resistance. Information is lacking for many characteristics of many species and their impacts remain unquantified, which leaves some important unanswered questions and challenges for assessing PPN as invasive species. However many economically important PPN species have not been recognised as invasive, even when most of the known characteristics and data suggests they should be.     

Phylogeographic insights into the invasion history and secondary spread of the signal crayfish in Japan

Successful invasion by nonindigenous species is often attributed to high propagule pressure, yet some foreign species become widespread despite showing reduced genetic variation due to founder effects. The signal crayfish (Pacifastacus leniusculus) is one such example, where rapid spread across Japan in recent decades is believed to be the result of only three founding populations. To infer the history and explore the success of this remarkable crayfish invasion, we combined detailed phylogeographical and morphological analyses conducted in both the introduced and native ranges. We sequenced 16S mitochondrial DNA of signal crayfish from across the introduced range in Japan (537 samples, 20 sites) and the native range in western North America (700 samples, 50 sites). Because chela size is often related to aggressive behavior in crayfish, and hence, their invasion success, we also measured chela size of a subset of specimens in both introduced and native ranges. Genetic diversity of introduced signal crayfish populations was as high as that of the dominant phylogeographic group in the native range, suggesting high propagule pressure during invasion. More recently established crayfish populations in Japan that originated through secondary spread from one of the founding populations exhibit reduced genetic diversity relative to older populations, probably as a result of founder effects. However, these newer populations also show larger chela size, consistent with expectations of rapid adaptations or phenotypic responses during the invasion process. Introduced signal crayfish populations in Japan originate from multiple source populations from a wide geographic range in the native range of western North America. A combination of high genetic diversity, especially for older populations in the invasive range, and rapid adaptation to colonization, manifested as larger chela in recent invasions, likely contribute to invasion success of signal crayfish in Japan.     

Effects of climate change and horticultural use on the spread of naturalized alien garden plants in Europe

Climate warming is supposed to enlarge the area climatically suitable to the naturalization of alien garden plants in temperate regions. However, the effects of a changing climate on the spread of naturalized ornamentals have not been evaluated by spatially and temporarily explicit range modelling at larger scales so far. Here, we assess how climate change and the frequency of cultivation interactively determine the spread of 15 ornamental plants over the 21st century in Europe. We coupled species distribution modelling with simulations of demography and dispersal to predict range dynamics of these species in annual steps across a 250 × 250 m raster of the study area. Models were run under four scenarios of climate warming and six levels of cultivation intensity. Cultivation frequency was implemented as size of the area used for planting a species. Although the area climatically suitable to the 15 species increases, on average, the area predicted to be occupied by them in 2090 shrinks under two of the three climate change scenarios. This contradiction obviously arises from dispersal limitations that were pronounced although we assumed that cultivation is spatially adapting to the changing climate. Cultivation frequency had a much stronger effect on species spread than climate change, and this effect was non‐linear. The area occupied increased sharply from low to moderate levels of cultivation intensity, but levelled off afterwards. Our simulations suggest that climate warming will not necessarily foster the spread of alien garden plants in Europe over the next decades. However, climatically suitable areas do increase and hence an invasion debt is likely accumulating. Restricting cultivation of species can be effective in preventing species spread, irrespective of how the climate develops. However, for being successful, they depend on high levels of compliance to keep propagule pressure at a low level.     

The role of propagule pressure in the invasion success of bluegill sunfish, Lepomis macrochirus, in Japan

The bluegill sunfish, Lepomis macrochirus, is a widespread exotic species in Japan that is considered to have originated from 15 fish introduced from Guttenberg, Iowa, in 1960. Here, the genetic and phenotypic traits of Japanese populations were examined, together with 11 native populations of the USA using 10 microsatellite markers and six meristic traits. Phylogenetic analysis reconfirmed a single origin of Japanese populations, among which populations established in the 1960s were genetically close to Guttenberg population, keeping high genetic diversity comparable to the ancestral population. In contrast, genetic diversity of later-established populations significantly declined with genetic divergence from the ancestral population. Among the 1960s established populations, that from Lake Biwa showed a significant isolation-by-distance pattern with surrounding populations in which genetic bottlenecks increased with geographical distance from Lake Biwa. Although phenotypic divergence among populations was recognized in both neutral and adaptive traits, P(ST)-F(ST) comparisons showed that it is independent of neutral genetic divergence. Divergent selection was suggested in some populations from reservoirs with unstable habitats, while stabilizing selection was dominant. Accordingly, many Japanese populations of L. macrochirus appear to have derived from Lake Biwa population, expanding their distribution with population bottlenecks. Despite low propagule pressure, the invasion success of L. macrochirus is probably because of its drastic population growth in Lake Biwa shortly after its introduction, together with artificial transplantations. It not only enabled the avoidance of a loss in genetic diversity but also formed a major gene pool that supported local adaptation with high phenotypic plasticity.     

The risk of establishment of aquatic invasive species: joining invasibility and propagule pressure

Invasive species are increasingly becoming a policy priority. This has spurred researchers and managers to try to estimate the risk of invasion. Conceptually, invasions are dependent both on the receiving environment (invasibility) and on the ability to reach these new areas (propagule pressure). However, analyses of risk typically examine only one or the other. Here, we develop and apply a joint model of invasion risk that simultaneously incorporates invasibility and propagule pressure. We present arguments that the behaviour of these two elements of risk differs substantially--propagule pressure is a function of time, whereas invasibility is not--and therefore have different management implications. Further, we use the well-studied zebra mussel (Dreissena polymorpha) to contrast predictions made using the joint model to those made by separate invasibility and propagule pressure models. We show that predictions of invasion progress as well as of the long-term invasion pattern are strongly affected by using a joint model.     

Ancestral origins and invasion pathways in a globally invasive bird correlate with climate and influences from bird trade

Invasive species present a major threat to global biodiversity. Understanding genetic patterns and evolutionary processes that reinforce successful establishment is paramount for elucidating mechanisms underlying biological invasions. Among birds, the ring‐necked parakeet (Psittacula krameri) is one of the most successful invasive species, established in over 35 countries. However, little is known about the evolutionary genetic origins of this species and what population genetic signatures tell us about patterns of invasion. We reveal the ancestral origins of populations across the invasive range and explore the potential influence of climate and propagule pressure from the pet trade on observed genetic patterns. Ring‐necked parakeet samples representing the ancestral native range (n = 96) were collected from museum specimens, and modern samples from the invasive range (n = 855) were gathered from across Europe, Mauritius and Seychelles, and sequenced for two mitochondrial DNA markers comprising 868 bp of cytochrome b and control region, and genotyped at 10 microsatellite loci. Invasive populations comprise birds that originate predominantly from Pakistan and northern areas of India. Haplotypes associated with more northerly distribution limits in the ancestral native range were more prevalent in invasive populations in Europe, and the predominance of Asian haplotypes in Europe is consistent with the higher number of Asian birds transported by the pet trade outside the native range. Successful establishment of invasive species is likely to be underpinned by a combination of environmental and anthropogenic influences.