A climate change context for the decline of a foundation tree species in south-western Australia: insights from phylogeography and species distribution modelling

Background and Aims A worldwide increase in tree decline and mortality has been linked to climate change and, where these represent foundation species, this can have important implications for ecosystem functions. This study tests a combined approach of phylogeographic analysis and species distribution modelling to provide a climate change context for an observed decline in crown health and an increase in mortality in Eucalyptus wandoo, an endemic tree of south-western Australia.Methods Phylogeographic analyses were undertaken using restriction fragment length polymorphism analysis of chloroplast DNA in 26 populations across the species distribution. Parsimony analysis of haplotype relationships was conducted, a haplotype network was prepared, and haplotype and nucleotide diversity were calculated. Species distribution modelling was undertaken using Maxent models based on extant species occurrences and projected to climate models of the last glacial maximum (LGM).Key Results A structured pattern of diversity was identified, with the presence of two groups that followed a climatic gradient from mesic to semi-arid regions. Most populations were represented by a single haplotype, but many haplotypes were shared among populations, with some having widespread distributions. A putative refugial area with high haplotype diversity was identified at the centre of the species distribution. Species distribution modelling showed high climatic suitability at the LGM and high climatic stability in the central region where higher genetic diversity was found, and low suitability elsewhere, consistent with a pattern of range contraction.Conclusions Combination of phylogeography and paleo-distribution modelling can provide an evolutionary context for climate-driven tree decline, as both can be used to cross-validate evidence for refugia and contraction under harsh climatic conditions. This approach identified a central refugial area in the test species E. wandoo, with more recent expansion into peripheral areas from where it had contracted at the LGM. This signature of contraction from lower rainfall areas is consistent with current observations of decline on the semi-arid margin of the range, and indicates low capacity to tolerate forecast climatic change. Identification of a paleo-historical context for current tree decline enables conservation interventions to focus on maintaining genetic diversity, which provides the evolutionary potential for adaptation to climate change.     

Local climatic adaptation in a widespread microorganism

Exploring the ability of organisms to locally adapt is critical for determining the outcome of rapid climate changes, yet few studies have addressed this question in microorganisms. We investigated the role of a heterogeneous climate on adaptation of North American populations of the wild yeast Saccharomyces paradoxus. We found abundant among-strain variation for fitness components across a range of temperatures, but this variation was only partially explained by climatic variation in the distribution area. Most of fitness variation was explained by the divergence of genetically distinct groups, distributed along a north–south cline, suggesting that these groups have adapted to distinct climatic conditions. Within-group fitness components were correlated with climatic conditions, illustrating that even ubiquitous microorganisms locally adapt and harbour standing genetic variation for climate-related traits. Our results suggest that global climatic changes could lead to adaptation to new conditions within groups, or changes in their geographical distributions.     

Biogeography and macroecology of phorid flies that attack fire ants in south-eastern Brazil and Argentina

Aim Saevissima group fire ants, Solenopsis richteri and S. invicta, have become serious pests when introduced from Argentina and Brazil to other continents. In South America, Solenopsis are distributed across a great variety of habitats and climates. In North America, S. invicta, introduced free of phorids, now ranges from coast to coast in the south. Success in introducing particular Pseudacteon as agents for the biological control of fire ants has varied across climatic zones. We aimed at assembling all the information about fire ant phorids from Argentina and Brazil, to estimate their richness and geographical ranges, to perform a climatic analysis for these distributions, to define groups and climate‐based communities, and to test and elucidate Rapoport's biogeographical rule. Location Argentina and Brazil (South America). Methods From field and museum collections and historical records, we developed a database of fire ant‐specific phorids throughout their known geographical range. A total of 123 sites with values for 15 climatic variables were mapped between 10° and 38° SL and between 35° and 65° C WL for the presence/absence of phorids. We calculated species richness across all sites combined, and for each phytogeographical region, using rarefaction curves, and ICE and Mmean estimators. We calculated mid‐latitudinal points, geographical ranges and areas for each species. The correlation between mid‐latitudinal point and ranges/areas was tested against a null model generated from the randomization of the raw distributional data. We used several types of multivariate analyses to distinguish groups of phorids by phytogeographical regions, hosts and climate, to find gradients of climate throughout the studied area, to define phorid communities in terms of their relationships with gradients of climate, and to test a mechanism for Rapoport's rule. Results Richness estimations using ICE and Mmean estimators were similar or higher than the observed values depending on the phytogeographical region. Cluster multivariate analyses based on climatic, phytogeographic and host data revealed distinct groupings of Pseudacton. The ‘cerrado’ group was confined to tropical savanna areas. A more ‘widespread’ group included ‘Chaco’ and ‘Maritime’ subgroups defined by their respective association with extreme temperatures or precipitation. Ordination multivariate analyses showed (1) two climatic gradients throughout the study area: one of temperature and the other of precipitation, and (2) that climatic variables significantly explained the observed assemblages of phorids. Positive and negative signs of the eigenvalues from the main axes of a canonical correspondence analysis allowed us to define eight communities whose geographical distribution resembled that of phytogeographical regions. We found a significant and positive correlation between geographical areas and mid latitudinal points, and furthermore, the Mantel test based on climatic variables suggested a mechanism for Rapoport's rule applying in the case of Pseudacteon. Main conclusions Pseudacteon species with greater mid‐latitudinal points occupy broader geographical areas and confront more stressful environmental conditions. Because the composition of Pseudacteon communities is largely determined by climatic variables, the correspondence between climates at sites of origin vs. sites of release should be an important consideration in choosing specific phorids for biocontrol efforts.     

内蒙古主要植被类型与气候因子关系的研究

利用地理信息系统工具,以最新的植被类型图为依据,在统计、建模和空间模拟区域气候因子的基础上,对内蒙古主要植被类型与气候的关系进行了分析,并获得适宜的气候范围.结果表明,内蒙古植被空间分布表现出明显的规律性.一方面,随着距离海洋的远近变化,无论是地带性植被,还是山地垂直带、沙地及低湿地植被,从东向西均反映出地带分异,水分对于这种东西向更替更为重要.另一方面,热量的差异导致纬向上的变化.此外,热量成为大兴安岭东西两麓发育的林缘草甸、草原、灌丛和低湿地等植被类型空间分布的主导因素.     

Environmental constraints at the edge of a species distribution, the Eurasian badger (Meles meles L.): a biogeographic approach

Aim This paper describes the distribution pattern (occurrence) of badgers (Meles meles L. 1758) in a Mediterranean mountain area of central Spain, in relation to landscape characteristics and climatic data. We test the fit of the badger occurrence pattern to the niche hypothesis predictions. Location We sampled twenty-four survey plots randomly distributed in the mountains of central Spain (Sierra de Guadarrama, Madrid): ten in the north and fourteen in the south slopes. All habitat types and climatic conditions typical of central Spain can be found. Methods The ocurrence of badgers in the plots were recorded through an exhaustive search of setts and latrines in four different (and evenly spaced) points in each plot. The index of occurrence was made by dividing the number of positive points (badger presence) by the total number of points sampled (four in all plots). Landscape patterns (% type of habitat in each plot) were obtained from detailed maps and climate data from meteorological stations placed in the plot. We analyse the contribution of landscape variables and climate data to explain the differences in badger occurrence through Pearson correlations and fixed one-way ANCOVA with climatic data as fixed factor, vegetation cover as covariates and badger occurrence as response variable. Additionally, we use an one-way ANOVA to check the differences in occurrence between north and south plots with the location of each plot as fixed factor. Results The results indicate that the badger is more abundant in rainy areas of the mountains, and in open landscapes vegetated by ash-tree forests than in closed landscapes vegetated by holm oak forests. In addition, the species is more abundant in the northern plots than in the southern ones. Northern plots were homogeneous areas characterized by their open landscape and wet climate, while southern plots were characterized by their dry climate and closed landscapes. In addition, climate (measured as summer rain) is more determinant than habitat type (holm oak cover) to explain the pattern of badger occurrence. Main conclusions Overall, we consider that the typical Mediterranean landscapes are poor habitats for badgers due to changes in the environmental conditions associated with concomitant changes in food resources. These data support the niche hypothesis to explain the changes in abundance or occurrence close to the edge of the distribution of species, and in particular, in Palearctic species in the Mediterranean area.     

气候变化下千金榆在我国潜在分布区预测

气候变化严重影响植物的地理分布格局,植物分布对气候变化响应的区域差异性也将为引种和保存提供重要的指导.本研究基于ArcGIS与MaxEnt模型,利用176个千金榆地理信息和13个气候变量,对当前和未来的生态位进行重建.结果表明:模型模拟当代潜在分布区可信度极高,测试集与训练集AUC值分别为0.973和0.957.主要核心适宜区集中在秦岭、长白山及其各自的邻近区域,其他为零星的“岛屿”式分布.贵州、江西、云南、福建等地未发现千金榆的分布,但存在一定的适宜分布区.随着未来气候变暖,千金榆生态适宜区明显增加,主要表现为“向高海拔地区收缩”、“北扩”和“东扩”.但核心适宜区略有减少,具体表现为“南缩”、“中稳”和“北扩”.千金榆的分布对气候变暖的响应存在明显的区域性,在东部江苏、安徽等地,因其独特的地理位置与气候环境,该地区开始成为千金榆生态适宜区;在较低纬度的南方,原有的低海拔地区可能不再适宜千金榆生存;中部秦岭地区气候为南北的渐变区,有较强的缓冲能力,气候变暖对其分布区影响不大;较高纬度的长白山地区及其邻近区域愈发适宜千金榆生存.     

The roles of climatic factors in spatial patterns of alien invasive plants from America into China

The roles of climatic factors in plant invasions have drawn intense attention in the past. America was one of the major donors of the invasive plants in China. In this study, we investigated the roles of climatic factors in plant invasions from America into China through Akaike’s information criterion model analysis in terms of specific geographical origins, respectively. From south to north, decreasing trends of species diversity were observed on the plants from Central-South America and Mexico, while the greatest alien species diversity in mid-Chinese latitudes was observed on the invaders from North America; For the invaders from Central-South America and Mexico, climatic factors explained most of the spatial variations, while for those from North America, the roles of the climatic factors were weak. The role of the climatic factors in plant invasions may, in some extent, depend on the ecological characters inherited form the geographical origins and their accommodation to the climate of the invaded regions. If the invasive plants were introduced into the region with similar environment to their area of origin, the role of the climatic factors may be shadowed by other factors. However, for the invaders whom were introduced into the regions vastly different from their areas of origin, climatic barriers may be responsible for most of the spatial variations. The invasive plants from Central-South America and Mexico may have strong potential to invade regions at higher latitude in China in the scenario of global warming, while for the invaders from North America, the impacts of global warming may be shadowed by other factors.     

内蒙古主要植被类型与气候因子关系的研究

利用地理信息系统工具,以最新的植被类型图为依据,在统计、建模和空间模拟区域气候因子的基础上,对内蒙古主要植被类型与气候的关系进行了分析,并获得适宜的气候范围。结果表明,内蒙古植被空间分布表现出明显的规律性。一方面,随着距离海洋的远近变化,无论是地带性植被,还是山地垂直带、沙地及低湿地植被,从东向西均反映出地带分异,水分对于这种东西向更替更为重要。另一方面,热量的差异导致纬向上的变化。此外,热量成为     

Macroenvironmental factors as ultimate determinants of distribution of common toad and natterjack toad in the south of Spain

We have analysed the relations between the distribution areas of Bufo bufo and Bufo calamita in the south of the Iberian Peninsula. In order to characterise the localities where the species were found, we used 24 environmental variables, and we tested their influence on the distribution of both species by nonparametric methods. By means of logistic regression we calculated the odds of finding one or other species in a locality. The environmental parameters that increase the probability of presence of each species and of both species together are related with the climatic stability and with the climatic subregions. Bufo bufo is more likely to be found in areas where the climate is more predictable, probably because in these areas it may exert its competitive superiority over B. calamita . In zones with very low climatic stability B. calamita is more likely to be found than B. bufo , probably because B. bufo lacks the ability to adapt to unpredictable conditions. In areas with intermediate climatic predictability B. bufo is present, but it would be prevented from removing B. calamita , and so the odds of finding each species are equilibrated. In these areas there would be a balance between the superior competitiveness of B. bufo and the higher adaptability of B. calamita . With the same logistic equation we characterise the typical habitats of each species, and also the environments shared by both species.     

The potential geographical distribution of the Old World screw-worm fly, Chrysomya bezziana

The potential geographical distribution and relative abundance of the Old World screw-worm fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) as determined by climate, was assessed using CLIMEX, a computer program for matching climates. CLIMEX describes the relative growth and persistence of animal populations in relation to climate. The observed global distribution of C.bezziana was compared with the potential distribution predicted by CLIMEX. The differences in the two distributions indicate the areas at risk of colonization, with particular reference to Australia and the Americas. According to the model, the potential area of permanent colonization in Australia extends south to the mid-coast of New South Wales. Comparison of areas suitable for permanent establishment with the potential summer distribution indicates that large additional areas, carrying most of the continent's livestock, could be colonized in the summer months. Seasonal population growth indices are presented for three ports in Australia at which screw-worm fly specimens have been collected by quarantine authorities. They indicate the relative risk associated with introductions at different places in different seasons and so provide valuable planning information for quarantine authorities. The CLIMEX predictions for C.bezziana in North America are shown to be similar to the recorded distribution limits of the New World screw-worm fly, Cochliomyia hominivorax (Coquerel). The fly could also colonize South America, as far south as southern Brazil and midway through Argentina.     

Ecological correlates between cladocerans and their endoparasites from permanent and rain pools: patterns in community composition and diversity

Water fleas (Cladocera) constitute a major component in freshwater food webs, with important ecosystem-level consequences. Their abundance and richness are strongly influenced by their ecology and coevolution with numerous endoparasites. We investigated how parasitism shapes cladoceran community structure and diversity. We surveyed 204 freshwater permanent and rain pools in Israel, identified all cladoceran specimens and screened them for infection. Daphniid species richness in this survey was lower than in previous surveys and the distribution pattern of the species was different, most likely due to local extinction and habitat loss. We recorded a total of 21 taxa of endoparasites, of which 13 are most likely species not yet described. Variation in parasite richness among hosts and sites could not be attributed to differences in host body size and behavioral feeding strategies. We extend the known host range and geographic distribution of eight parasites from Europe and North America (between latitudes 40° and 70°) to much southern areas (latitudes 31° and 32°) and to different climate zones (arid and semi-arid areas). In many infected populations we found co-occurrence of at least two endoparasites, and in most of these cases Daphnia individuals were found to be infected by several endoparasite species simultaneously. Such multiple infections may have important consequences for community structure as well as host?Cparasite coevolution.     

Common Distribution Patterns of Marsupials Related to Physiographical Diversity in Venezuela

The aim of this study is to identify significant biotic regions (groups of areas with similar biotas) and biotic elements (groups of taxa with similar distributions) for the marsupial fauna in a part of northern South America using physiographical areas as Operational Geographical Units (OGUs). We considered Venezuela a good model to elucidate this issue because of its high diversity in landscapes and the relatively vast amount of information available on the geographical distribution of marsupial species. Based on the presence-absence of 33 species in 15 physiographical sub-regions (OGUs) we identified Operational Biogeographical Units (OBUs) and chorotypes using a quantitative analysis that tested statistical significance of the resulting groups. Altitudinal and/or climatic trends in the OBUs and chorotypes were studied using a redundancy analysis. The classification method revealed four OBUs. Strong biotic boundaries separated: i) the xerophytic zone of the Continental coast (OBU I); ii) the sub-regions north of the Orinoco River (OBU III and IV); and those south to the river (OBU II). Eleven chorotypes were identified, four of which included a single species with a restricted geographic distribution. As for the other chorotypes, three main common distribution patterns have been inferred: i) species from the Llanos and/or distributed south of the Orinoco River; ii) species exclusively from the Andes; and iii) species that either occur exclusively north of the Orinoco River or that show a wide distribution throughout Venezuela. Mean altitude, evapotranspiration and precipitation of the driest month, and temperature range allowed us to characterize environmentally most of the OBUs and chorotypes obtained.     

Modelling chestnut biogeography for American chestnut restoration

Aim Chestnuts (Castanea spp.) are ecologically and economically important species. We studied the general biology, distribution and climatic limits of seven chestnut species from around the world. We provided climatic matching of Asiatic species to North America to assist the range‐wide restoration of American chestnut [C. dentata (Marsh.) Borkh.] by incorporating blight‐resistant genes from Asiatic species. Location North America, Europe and East Asia. Methods General chestnut biology was reviewed on the basis of published literature and field observations. Chestnut distributions were established using published range maps and literature. Climatic constraints were analysed for the northern and southern distribution limits and the entire range for each species using principal component analysis (PCA) of fourteen bioclimatic variables. Climatic envelope matching was performed for three Chinese species using Maxent modelling to predict corresponding suitable climate zones for those species in North America. Results Chestnuts are primarily distributed in the warm‐temperate and subtropical zones in the northern hemisphere. PCA results revealed that thermal gradient was the primary control of chestnut distribution. Climatic spaces of different species overlap with one another to different degrees, but strong similarities are shown especially between Chinese species and American species. Climatic envelope matching suggested that large areas in eastern North America have a favourable climate for Chinese species. Main conclusions The general biological traits and climatic limits of the seven chestnut species are very similar. The predictions of Chinese species climatic range corresponded with most of the historical American chestnut range. Thus, a regionally adapted, blight‐resistant, introgressed hybrid American chestnut appears feasible if a sufficiently diverse array of Chinese chestnut germplasm is used as a source of blight resistance. Our study provided a between‐continent climate matching approach to facilitate the range‐wide species restoration, which can be readily applied in planning the restoration of other threatened or endangered species.     

Primary Productivity and Precipitation-Use Efficiency in Temperate Grassland in the Loess Plateau of China

Clarifying spatial variations in aboveground net primary productivity (ANPP) and precipitation-use efficiency (PUE) of grasslands is critical for effective prediction of the response of terrestrial ecosystem carbon and water cycle to future climate change. Though the combination use of remote sensing products and in situ ANPP measurements, we quantified the effects of climatic [mean annual precipitation (MAP) and precipitation seasonal distribution (PSD)], biotic [leaf area index (LAI)] and abiotic [slope gradient, aspect, soil water storage (SWS) and other soil physical properties] factors on the spatial variations in ANPP and PUE across different grassland types (i.e., meadow steppe, typical steppe and desert steppe) in the Loess Plateau. Based on the study, ANPP increased exponentially with MAP for the entire temperate grassland; suggesting that PUE increased with increasing MAP. Also PSD had a significant effect on ANPP and PUE; where more even PSD favored higher ANPP and PUE. Then MAP, more than PSD, explained spatial variations in typical steppe and desert steppe. However, PSD was the dominant driving factor of spatial variations in ANPP of meadow steppe. This suggested that in terms of spatial variations in ANPP of meadow steppe, change in PSD due to climate change was more important than that in total annual precipitation. LAI explained 78% of spatial PUE in the entire Loess Plateau temperate grassland. As such, LAI was the primary driving factor of spatial variations in PUE. Although the effect of SWS on ANPP and PUE was significant, it was nonetheless less than that of precipitation and vegetation. We therefore concluded that changes in vegetation structure and consequently in LAI and/or altered pattern of seasonal distribution of rainfall due to global climate change could significantly influence ecosystem carbon and water cycle in temperate grasslands.     

Community organization and species richness of ants (Hymenoptera/Formicidae) in Mongolia along an ecological gradient from steppe to Gobi desert

Aim Ants (Hymenoptera/Formicidae) have strong influences on ecosystems especially in arid regions. However, little is known about ants of the vast steppe and desert regions of Central Asia. Here we provide the first comprehensive study of ant communities in Mongolia, conducted along a north‐to‐south gradient in climate. We examined ants’ distribution patterns, assessed the impact of climatic parameters on community structure and species diversity and investigated the influence of the corresponding communities of plants. Location Mongolia (Central Asia). Methods We observed 31,956 ants at seed baits at 11 study sites along a transect from steppe to Gobi desert for which we attained meteorological data (mean yearly precipitation: 197 to 84 mm). Extra sampling was conducted at sugar and protein baits and by the inspection of different microhabitats. Vegetation patterns of each plot were recorded. Statistical evaluation comprised ordination and correlation. Results We observed 15 species of ants at seed baits. Three faunal complexes of ants could be distinguished by detrended correspondence analysis (DCA): (1) in steppe baits were dominated by Formica‐ and Myrmica‐species, (2) in semi desert we found mostly species of Tetramorium, Myrmica, Proformica, Plagiolepis, and Leptothorax, and (3) in desert Cataglyphis aenescens and Messor aciculatus dominated, and Lasius was exclusively found there. Another 11 rare ant species were sampled by hand and at sugar baits. Altogether five ant species were new to the Mongolian fauna: Cardiocondyla koshewnikovi, Myrmica koreana, Myrmica pisarskii, Polyergus nigerrimus, and Proformica kaszabi. Assignment of taxa to functional groups showed that in steppe cold climate specialists dominated, in semi desert we found mainly opportunists, and in desert hot climate specialists. Several functional groups know from arid zones in other parts of the world were missing. In desert certain species were highly dominant. First DCA scores of ant‐ and plant‐communities were highly correlated with each other and with climatic parameters. While plant species diversity was positively correlated with increasing northern latitude, ant diversity and ant species richness were not correlated with latitude and responded neither to precipitation, nor to any other climatic parameter. Semi desert was a transition zone between steppe and desert, with high species richness. Ant genus composition of the ecotone overlapped with both other regions. However, beta diversity between pairs of plots within this zone was low, indicating a small‐scale mosaic pattern. Main conclusions The ant communities in the Mongolian steppe and desert zones were strongly influenced by low temperatures and differed in many aspects from the ant fauna in other arid ecosystems, especially in terms of species richness, diversity of feeding guilds, and richness of functional groups.     

西南地区红花龙胆分布格局模拟与气候变化影响评价

应用最大熵(MaxEnt)模型,基于230条分布记录及33个气候因子数据,模拟全新世中期(约6000年前)、当前时期(1950—2000年)和未来(2050s、2070s)气候条件下,红花龙胆西南地区的潜在分布范围;结合多元统计分析和ArcGIS空间分析,筛选影响物种分布的关键气候因子,探讨不同分布区对气候变化的敏感性.结果表明: 模型训练集AUC值为0.942,验证集AUC值为0.849,表明模型预测的准确性较高.5个气候因子(7月最高气温、8月最低气温、昼夜温差与年温差比值、7月最低气温和6月最低气温)对模型贡献最大,累计贡献率达59.9%.随未来气候变化,红花龙胆适生区将呈现先减少后增加的变化趋势,在RCP 8.5情景下,至2070s阶段,西南地区红花龙胆适宜生境总面积与当前气候条件相比减少15.0%,但云南境内适生区和高适生区面积较当前分别增加32.8%和32.7%.红花龙胆适宜生长于温暖、湿润的气候条件下,气候变暖明显影响着适宜生境的面积和范围,尤其低海拔分布区对气候变化较敏感,适宜生境退缩严重,而高海拔地区由于降水、温度条件的改善适宜生境有所增加.随着全球气候的变化,未来西南地区红花龙胆主要分布区可能向西迁移,并向更高海拔扩张.     

Bioclimatic constraints to Andean cat distribution: a modelling application for rare species

Aim To identify the bioclimatic niche of the endangered Andean cat (Leopardus jacobita), one of the rarest and least known felids in the world, by developing a species distribution model. Location South America, High Andes and Patagonian steppe. Peru, Bolivia, Chile, Argentina. Methods We used 108 Andean cat records to build the models, and 27 to test them, applying the Maxent algorithm to sets of uncorrelated bioclimatic variables from global databases, including elevation. We based our biogeographical interpretations on the examination of the predicted geographic range, the modelled response curves and latitudinal variations in climatic variables associated with the locality data. Results Simple bioclimatic models for Andean cats were highly predictive with only 3–4 explanatory variables. The climatic niche of the species was defined by extreme diurnal variations in temperature, cold minimum and moderate maximum temperatures, and aridity, characteristic not only of the Andean highlands but also of the Patagonian steppe. Argentina had the highest representation of suitable climates, and Chile the lowest. The most favourable conditions were centrally located and spanned across international boundaries. Discontinuities in suitable climatic conditions coincided with three biogeographical barriers associated with climatic or topographic transitions. Main conclusions Simple bioclimatic models can produce useful predictions of suitable climatic conditions for rare species, including major biogeographical constraints. In our study case, these constraints are also known to affect the distribution of other Andean species and the genetic structure of Andean cat populations. We recommend surveys of areas with suitable climates and no Andean cat records, including the corridor connecting two core populations. The inclusion of landscape variables at finer scales, crucially the distribution of Andean cat prey, would contribute to refine our predictions for conservation applications.     

First record of the freshwater snail Pseudosuccinea columella (Gastropoda: Lymnaeidae) in southern Pampas (Argentina) and assessment of future spread

ABSTRACT

The freshwater snail Pseudosuccinea columella was recorded for the first time in Argentina more than 60 years ago. Since then its distribution in the wild has been restricted to the northeastern provinces. Here we record the presence of P. columella in southern Pampas for the first time, extending its distribution more than 500?km southwards. The climatic suitability of this and other areas of South America for its establishment and spread was analysed using habitat modelling software. Hitherto its spread within and between watercourses in southern Pampas has been very limited, probably through a combination of low climatic suitability, recent introduction and low connectivity of the drainage basins. The suitability of other areas where it has been recently recorded indicates a moderate risk of further spread in central and northwestern Argentina and in coastal areas of the Pacific rim of South America (southern Perú and northern Chile). The recent spread of P. columella in the wild in Argentina may be the result of an increase in the trade in aquarium plants or of the evolution of a new lineage with different ecological capabilities.     

Invasion hotspots for non‐native plants in Australia under current and future climates

We apply the concept of biodiversity hotspot analysis (the identification of biogeographical regions of high species diversity) to identify invasion hotspots – areas of potentially suitable climate for multiple non‐native plant species – in Australia under current and future climates. We used the species distribution model Maxent to model climate suitability surfaces for 72 taxa, recognized as ‘Weeds of National Significance’ (WoNS) in Australia, under current and projected climate for 2020 and 2050. Current climate suitability layers were summed across all 72 species, and we observed two regions of high climatic suitability corresponding to the top 25th percentile of combined climatic suitability values across Australia. We defined these as potential invasion hotspots. Areas of climatic suitability equivalent to the hotspot regions were identified in the composite maps for 2020 and 2050, to track spatial changes in the hotspots over the two time steps. Two potential invasion hotspot regions were identified under current and projected climates: the south west corner of Western Australia (SW), and south eastern Australia (SE). Herbarium data confirmed the presence of 73% and 99% of those species predicted to be in each hotspot respectively, suggesting that the SE has greater invasion potential. The area of both hotspots was predicted to retract southward and towards the coast under future climate scenarios, reducing in size by 81% (SW) and 71% (SE) by 2050. This reduction was driven by the dominance of southern temperate invasive plant species in the WoNS list (47 of the 72), of which 44 were predicted to experience reductions in their bioclimatic range by 2050. While climate is likely to become less suitable for the majority of WoNS in the future, potential invasion hotspots based on climate suitability are likely to remain in the far south of eastern Australia, and in the far south west of Western Australia by 2050.