Predicting the potential geographic distribution of Bactrocera bryoniae and Bactrocera neohumeralis(Diptera: Tephritidae) in China using MaxEnt ecological niche modeling

Bactrocera bryoniae and Bactrocera neohumeralis are highly destructive and major biosecurity/quarantine pests of fruit and vegetable in the tropical and subtropical regions in the South Pacific and Australia.Although these pests have not established in China,precautions must be taken due to their highly destructive nature.Thus,we predicted the potential geographic distribution of B.bryoniae and B.neohumeralis across the world and in particular China by ecological niche modeling of the Maximum Entropy(Max Ent)model with the occurrence records of these two species.Bactrocera bryoniae and B.neohumeralis exhibit similar potential geographic distribution ranges across the world and in China,and each species was predicted to be able to distribute to over 20%of the globe.Globally,the potential geographic distribution ranges for these two fruit fly species included southern Asia,the central and the southeast coast of Africa,southern North America,northern and central South America,and Australia.While within China,most of the southern Yangtze River area was found suitable for these species.Notably,southern China was considered to have the highest risk of B.bryoniae and B.neohumeralis invasions.Our study identifies the regions at high risk for potential establishment of B.bryoniae and B.neohumeralis in the world and in particular China,and informs the development of inspection and biosecurity/quarantine measures to prevent and control their invasions.

Genetic analysis and ecological niche modeling delimit species boundary of the Przewalski’s scorpion(Scorpiones: Buthidae) in arid Asian inland

Reliable delimitation of venomous scorpions is not only consequential to toxicological studies but also instructive to conservation and exploration of these important medical resources.In the present study,we delimited species boundary for the the Przewalski’s scorpion from arid northwest China through a combined approach employing phylogenetic analysis,ecological niche modeling and morphological comparison.Our results indicate that the Przewalski’s scorpion represent an independent taxonomic unit and should be recognized as full species rank,Mesobuthus przewalskii stat.nov.This species and the Chinese scorpion M.martensii represent the eastern members of the M.caucasicus species group which manifests a trans-Central Asia distribution across the Tianshan Mountains range.We also discussed the likely geographic barrier and climatic boundary that demarcate distributional range of the the Przewalski’s scorpion.

Ecological Niche Modelling Reveals the Peculiarities of Ecological Disjunction Between Two Sympatric Racerunners in Kazakhstan:Eremias lineolata(Nikolsky,1897)and Eremias scripta(Strauch,1867)

The ecological-niche models for two sympatric species,Eremias lineolata(Nikolsky,1897)and Eremias scripta(Strauch,1867),reveal evidence of spatial and temporal disjunction in the actual niches of both species.Eremias lineolata demonstrates a wide range of adaptations and,at the same time,has a greater need for winter precipitation and minimal temperature than E.scripta.Possible explanations for the thermal diversity of both species are provided.Thermal variables(monthly temperatures,monthly solar radiation,etc.)are traditionally important for ectotherm animals.Interestingly,as many as half of the key variables in both species are related to different aspects of environmental water balance(precipitation,air humidity,vapor pressure).There are several ways in which moisture may impact the lizard’s life cycle.Soil humidity is related to soil temperature and may be important during winter hibernation.In summer,soil humidity may support successful embryogenesis.Precipitation during the warm months is a key factor in maintaining the moisture content of the soil.In winter,snow cover provides a better thermal balance of the soil’s top layers where winter shelters are housed.Ecological niche modeling(ENM)is an interdisciplinary approach combining the geographical,climatic,ecological,and biological aspects of the wellbeing of species.This interdisciplinary approach lifts biological studies onto a new,integrative level,providing a comprehensive view on species biology and answering the questions that might not be answered if the traditional methods for studying animals were used alone.

Elevation transition of aquatic insects closely matches a thermal feature in the Yungas of Northwestern Argentina

Temperature is a key factor that shapes the distribution of organisms.Having knowledge about how species respond to temperature is relevant to devise strategies for addressing the impacts of climate change.Aquatic insects are particularly vulnerable to climate change,yet there is still much to learn about their ecology and distribution.In the Yungas ecoregion of Northwestern Argentina,cold-and warm-adapted species of the orders Ephemeroptera,Plecoptera,and Trichoptera(EPT)are segregated by elevation.We modeled the ecological niche of South American EPT species in this region using available data and projected their potential distribution in geographic space.Species were grouped based on their ecogeographic similarity,and we analyzed their replacement pattern along elevation gradients,focusing on the ecotone where opposing thermal preferences converge.Along this interface,we identified critical points where the combined incidence of cold and warm assemblages maximizes,indicating a significant transition zone.We found that the Montane Cloud Forest holds the interface,with a particularly greater suitability at its lower boundary.The main axis of the interface runs in a N-S direction and falls between 14°C-16°C mean annual isotherms.The probability of a particular location within a basin being classified as part of the interface increases as Kira’s warmth index approaches a score around 150.Understanding the interface is critical for defining the thermal limits of species distribution and designing biomonitoring programs.Changes in the location of thermal constants related to mountainous ecotones may cause vertical displacement of aquatic insects and vegetation communities.We have recognized significant temperature thresholds that serve as indicators of suitability for the interface.As global warming is anticipated to shift these indicators,we suggest using them to monitor the imprints of climate change on mountain ecosystems.

Evolution of biogeographic disjunction between eastern Asia and North America in Chamaecyparis:Insights from ecological niche models

The disjunct distribution of plants between eastern Asia(EA) and North America(NA) is one of the most well-known biogeographic patterns. However, the formation and historical process of this pattern have been long debated. Chamaecyparis is a good model to test previous hypotheses about the formation of this disjunct pattern as it contains six species disjunctly distributed in EA, western North America(WNA)and eastern North America(ENA). In this study, we applied ecological niche models to test the formation of the disjunct pattern of Chamaecyparis. The model calibrated with the EA species was able to predict the distribution of eastern NA species well, but not the western NA species. Furthermore, the eastern Asian species were shown to have higher niche overlap with the eastern North American species. The EA species were also shown to share more similar habitats with ENA species than with WNA species in the genus. Chamaecyparis species in WNA experienced a significant niche shift compared with congeneric species. Chamaecyparis had a low number of suitable regions in Europe and the middle and western NA during the Last Glacial Maximum(LGM) period, and became extinct in the former region whereas it retains residual distribution in the latter. The extirpations in western NA and Europe in response to the late Neogene and Quaternary climatic cooling and the more similar habitats between ENA and EA ultimately shaped the current intercontinental disjunct distribution of Chamaecyparis. Both current hypotheses may be also jointly applied to explain more eastern Asian and eastern North American disjunctions observed today.

Analysis of genetic diversity and prediction of Larix species distribution in the Qinghai–Tibet Plateau,China

Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values.However,the lack of genetic diversity background and related research hinders the development of conservation strategies.In this study,genetic diversity and distribution of fi ve Larix species were investigated.Using 19 polymorphic microsatellite markers to study 272 representative individuals from 13 populations,the results show low genetic diversity at the population level,with variation explained mainly by diff erentiation among populations.The Larix populations were classifi ed into two clades,one formed by eight populations,including three of the species in this study,L.kongboensis,L.speciosa,and L.potaninii var.australis.The other clade consists of fi ve populations,including the other two species in this study,L.griffi thii and L.himalaica.Genetic distance of the species was aff ected by geographical isolation and genetic diversity was mainly aff ected by altitude.The area suitable for Larix spp.decreased during the Last Glacial Maximum compared to the current distribution according to the niche model,but should increase in future climate scenarios(2050s),expanding westward along the Himalayas.These results provide an important scientifi c basis for the development of conservation strategies and further the sustainable utilization of Larix resources in the Qinghai-Tibet Plateau.

Modelling the probability of presence of Aedes aegypti and Aedes albopictus in Iran until 2070

Objective:To determine the suitable ecological habitats of Aedes(Ae.)aegypti and Ae.albopictus in Iran due to climate change by the 2070s.Methods:All data relating to the spatial distribution of Ae.aegypti and Ae.albopictus worldwide,which indicated the geographical coordinates of the collection sites of these mosquitoes,were extracted from online scientific websites and entered into an Excel file.The effect of climatic and environmental variables on these mosquitoes was evaluated using the MaxEnt model in the current and future climatic conditions in the 2030s,2050s,and 2070s.Results:The most suitable areas for the establishment of Ae.aegypti are located in the southern and northern coastal areas of Iran,based on the model outputs.The modelling result for suitable ecological niches of Ae.albopictus shows that in the current climatic conditions,the southern half of Iran from east to west,and parts of the northern coasts are prone to the presence of this species.In the future,some regions,such as Gilan and Golestan provinces,will have more potential to exist/establish Ae.albopictus.Also,according to the different climate change scenarios,suitable habitats for this species will gradually change to the northwest and west of the country.The temperature of the wettest season of the year(Bio8)and average annual temperature(Bio1)were the most effective factors in predicting the model for Ae.aegypti and Ae.albopictus,respectively.Conclusions:It is required to focus on entomological studies using different collection methods in the vulnerable areas of Iran.The future modelling results can also be used for long-term planning to prevent the entry and establishment of these invasive Aedes vectors in the country.

Predicting the Potential Invasion Hotspots of Chromolaena odorata under Current and Future Climate Change Scenarios in Heterogeneous Ecological Landscapes of Mizoram,India

Recent trends in globalization,human mobility surge and global trade aggravated the expansion of alien species introduction leading to invasion by alien plants compounded by climate change.The ability to predict the spread of invasive species within the context of climate change holds significance for accurately identifying vulnerable regions and formulating strategies to contain their wide proliferation and invasion.Anthropogenic activities and recent climate change scenarios increased the risk of Chromolaena odorata invasion and habitat expansion in Mizoram.To forecast its current distribution and habitat suitability amidst climatic alterations in Mizoram,a MaxEnt-driven habitat suitability model was deployed using the default parameters.The resultant model exhibited that the current spatial range of C.odorata occupies 15.37%of geographical areas deemed suitable for varying degrees of invasion.Projections for 2050 and 2070 anticipated an expansion of suitable habitats up to 34.37%of the geographical area of Mizoram,specifically under RCP 2.6 in 2070 in comparison with its present distribution.Currently,the distributional range of C.odorata in Mizoram spans from lower(450 m)to mid elevational ranges up to 1700 meters,with limited presence at higher altitudes.However,the habitat suitability model extrapolates that climate changes will elevate the invasion risk posed by C.odorata across Mizoram,particularly in the North-Western and Central regions.The projection of further territorial expansion and an upward shift in altitudinal range in the future underscores the urgency of instating robust management measures to pre-empt the impact of C.odorata invasion.This study recommends the imperative nature of effective C.odorata management,particularly during the initial stages of invasion.

Mobilizing and integrating big data in studies of spatial and phylogenetic patterns of biodiversity

The current global challenges that threaten biodiversity are immense and rapidly growing.These biodiversity challenges demand approaches that meld bioinformatics,large-scale phylogeny reconstruction,use of digitized specimen data,and complex post-tree analyses(e.g.niche modeling,niche diversification,and other ecological analyses).Recent developments in phylogenetics coupled with emerging cyberinfrastructure and new data sources provide unparalleled opportunities for mobilizing and integrating massive amounts of biological data,driving the discovery of complex patterns and new hypotheses for further study.These developments are not trivial in that biodiversity data on the global scale now being collected and analyzed are inherently complex.The ongoing integration and maturation of biodiversity tools discussed here is transforming biodiversity science,enabling what we broadly term"next-generation"investigations in systematics,ecology,and evolution(i.e.,"biodiversity science").New training that integrates domain knowledge in biodiversity and data science skills is also needed to accelerate research in these areas.Integrative biodiversity science is crucial to the future of global biodiversity.We cannot simply react to continued threats to biodiversity,but via the use of an integrative,multifaceted,big data approach,researchers can now make biodiversity projections to provide crucial data not only for scientists,but also for the public,land managers,policy makers,urban planners,and agriculture.

Mapping the habitat suitability of Ottelia species in Africa

Understanding the influence of environmental covariates on plant distribution is critical,especially for aquatic plant species.Climate change is likely to alter the distribution of aquatic species.However,knowledge of this change on the burden of aquatic macroorganisms is often fraught with difficulty.Ottelia,a model genus for studying the evolution of the aquatic family Hydrocharitaceae,is mainly distributed in slow-flowing creeks,rivers,or lakes throughout pantropical regions in the world.Due to recent rapid climate changes,natural Ottelia populations have declined significantly.By modeling the effects of climate change on the distribution of Ottelia species and assessing the degree of niche similarity,we sought to identify high suitability regions and help formulate conservation strategies.The models use known background points to determine how environmental covariates vary spatially and produce continental maps of the distribution of the Ottelia species in Africa.Additionally,we estimated the possible influences of the optimistic and extreme pessimistic representative concentration pathways scenarios RCP 4.5 and RCP 8.5 for the 2050s.Our results show that the distinct distribution patterns of studied Ottelia species were influenced by topography(elevation)and climate(e.g.,mean temperature of driest quarter,annual precipitation,and precipitation of the driest month).While there is a lack of accord in defining the limiting factors for the distribution of Ottelia species,it is clear that water-temperature conditions have promising effects when kept within optimal ranges.We also note that climate change will impact Ottelia by accelerating fragmentation and habitat loss.The assessment of niche overlap revealed that Ottelia cylindrica and O.verdickii had slightly more similar niches than the other Ottelia species.The present findings identify the need to enhance conservation efforts to safeguard natural Ottelia populations and provide a theoretical basis for the distribution of various Ottelia species in Africa.

An evaluation of central Iran’s protected areas under different climate change scenarios (A Case on Markazi and Hamedan provinces)

Global climate change poses a new challenge for species and can even push some species toward an extinction vortex. The most affected organisms are those with narrow tolerance to the climatic factors but many large mammals such as ungulates with a wider ecological niche are also being affected indirectly. Our research mainly used wild sheep in central Iran as a model species to explore how the suitable habitats will change under different climatic scenarios and to determine if current borders of protected areas will adequately protect habitat requirements. To create habitat models we used animal-vehicle collision points as an input for species presence data. We ran habitat models using Max Ent modeling approach under different climatic scenarios of the past, present and future(under the climatic scenarios for minimum(RCP2.6) and maximum(RCP8.5) CO2 concentration trajectories). We tried to estimate the overlap and the width of the ecological niche using relevant metrics. In order to analyze the effectiveness of the protected areas, suitable maps were concerted to binary maps using True Skill Statistic(TSS) threshold and measured the similarity of the binary maps for each scenario using Kappa index. In order to assess the competence of the present protected areas boundary in covering the distribution of species, two different scenarios were employed, which are ensemble scenario 1: an ensemble of the binary maps of the species distribution in Mid-Holocene, present, and RCP2.6;and ensemble scenario 2: an ensemble of binary suitability maps in Mid-Holocene, present, and RCP8.5. Then, the borders of modeled habitats with the boundaries of 23 existing protected areas in two central provinces in Iran were compared. The predicted species distribution under scenario 1(RCP2.6) was mostly similar to its current distribution(Kappa = 0.53) while the output model under scenario 2(RCP8.5) indicated a decline in the species distribution range. Under the first ensemble scenario, current borders of the protected areas in Hamedan province showed better efficiency to cover the model species distribution range. Analyzing Max Ent spatial models under the second climatic scenario suggested that protected areas in both Markazi and Hamedan provinces will not cover "high suitability" areas in the future. Modeling the efficiency of the current protected areas under predicted future climatic scenarios can help the related authorities to plan conservation activities more efficiently.

Comparative multi-locus assessment of modern Asian newts(Cynops, Paramesotriton, and Pachytriton:Salamandridae) in southern China suggests a shared biogeographic history

Evolutionary biologists are always interested in deciphering the geographic context of diversification,therefore they introduced the concept of comparative phylogeography, which helps to identify common mechanisms that contribute to shared genetic structures among organisms from the same region.Here, we used multi-locus genetic data along with environmental data to investigate shared phylogeographic patterns among three Asianendemic newt genera, Cynops, Paramesotriton and Pachytriton, which occurred in montane/submontane streams or ponds in southern China. Our 222samples from 78 localities covered the entire range of the three genera and represented the largest dataset of this group to date. We reconstructed matrilineal genealogies from two protein-coding,mitochondrial genes, and gene network from two nuclear genes. We also estimated divergence times of major cladogenetic events and used occurrence data to evaluate niche difference and similarity between lineages. Our results revealed a common basal split in all three genera that corresponds to the separation of two geographic terrains of southern China.Those ancient divergence occurred during middle to late Miocene and likely correlate with paleoclimatic fluctuations caused by the uplift of the Qinghai-Xizang (Tibet) Plateau (QTP).Particularly,the strengthening and weakening of Asian summer monsoons during the Miocene may have profoundly impacted southern China and led to repeatedly vicariance in those newts.However,despite differences in realized niches between lineages,there is no evidence for divergence of fundamental niches.Preservation of old newt matriline lineages in mountains of southern China suggests that the region acts as both museums and cradles of speciation.Based on those results,we advocate a multi-pronged protection strategy for newts in the three genera.

A look into the past, present and future potential distributions of Talinopsis frutescens, a North American endemic lineage closely related to Cactaceae

Talinopsis frutescens(Anacampserotaceae,a family that is close related to Cactaceae)is a succulent species endemic to North America.The aim of this study was to explore,using Ecological Niche Modeling(ENM),changes in potential distribution ranges considering different climate scenarios:past conditions during the Last Inter Glacial(LIG)and the Last Glacial Maximum(LGM),the present and projections for 2070(RCP 2.6 to 8.5).A pattern of contraction is observed during the LIG,which agrees with other studies focused in species from arid environments.This pattern was followed by a migration towards the south during the LGM and a possible recent expansion to the north as is observed in the present scenario.All future projections show the same contraction and fragmentation patterns,resulting in three discontinuous areas:the northern part of the Chihuahuan Desert,the southern-central part of the Mexican Plateau,and the smallest one in the Tehuacán-Cuicatlán Valley.Our projections for future scenarios agree with other studies and support that global climate change tends to alter the current distribution of arid environment species.

Effects of climate changes on distribution of Eremanthus erythropappus and E.incanus(Asteraceae)in Brazil

Phylogeographic patterns of endemic species are critical keys to understand its adaptation to future climate change.Herein,based on chloroplast DNA,we analyzed the genetic diversity of two endemic and endangered tree species from the Brazilian savanna and Atlantic forest(Eremanthus erythropappus and Eremanthus incanus).We also applied the climate-based ecological niche modeling(ENM)to evaluate the impact of the Quaternary climate(last glacial maximum*21 kyr BP(thousand years before present)and Mid-Holocene*6 kyr BP)on the current haplotype distribution.Moreover,we modeled the potential effect of future climate change on the species distribution in 2070 for the most optimistic and pessimistic scenarios.One primer/enzyme combination(SFM/HinfI)revealed polymorphism with very low haplotype diversity,showing only three different haplotypes.The haplotype 1 has very low frequency and it was classified as the oldest,diverging from six mutations from the haplotypes 2 and 3.The E.erythropappus populations are structured and differ genetically according to the areas of occurrence.In general,the populations located in the north region are genetically different from those located in the center-south.No genetic structuring was observed for E.incanus.The ENM revealed a large distribution during the past and a severe decrease in geographic distribution of E.erythropappus and E.incanus from the LGM until present and predicts a drastic decline in suitable areas in the future.This reduction may homogenize the genetic diversity and compromise a relevant role of these species on infiltration of groundwater.

Potential distribution of a montane rodent (Cricetidae, Handleyomys chapmani) through time in Mexico: the importance of occurrence data

Ecological Niche Modeling uses the geographic coordinates of species presence records as the primary input to estimate potential geographic distributions.It is little known whether carrying out rigorous data pre-processing is necessary before building niche models to be transferred to different time period.Here we compared the current,past,and future potential distributions projected by niche models built from two different databases,an open-access database and a database compiled ad hoc,for Handleyomys chapmani,a rodent closely associated with montane cloud forests in Mexico.The models predicted different spatial patterns of climatic suitability for the three periods examined.Based on our current knowledge of cloud forest species in Mexico,the distributions predicted by the model built from the ad hoc database are more ecologically realistic than those obtained from the open-access database.The models built using the open-access database were particularly inaccurate at the limits of the geographic range,predicting larger,more diffuse distributions for the three periods.We conclude that pre-processing occurrence data is crucial for mountain species,as the number of localities and even minor inaccuracies in the geographic coordinates can translate into very different climatic conditions due to abrupt altitudinal changes.Finally,the predicted shifts in the potential distribution of H.chapmani over time indicate that this species is highly susceptible to climate change.

Spatial distribution and impacts of climate change on Milicia excelsa in Benin,West Africa

African teak(Milicia excelsa(Welw.)C.C.Berg)is an endangered multi-use species.Understanding the impact of climate change on the distribution of this species may improve the ability to anticipate or recognize its decline or expansion and to take appropriate conservation measures if necessary.Ecological niche modeling was projected in geographical space to study the current and future distribution of M.excelsa in Bénin.MaxEnt was used to estimate the potential geographic distribution of the species under two Representative Concentration Pathways(RCP).Miroc 5 summaries and two RCP 4.5 and RCP 8.5 scenarios were used as predictor variables for projections of the geographic potential of this species.The performance of the model was assessed by the area under the curve(AUC),true skill statistics(TSS)and partial receiver operating characteristics(Partial ROC).From the results,M.excelsa was more a secondary species in the Guinean climatic zone and part of the Sudanian-Guinean and Sudanian climatic zone.The projections show a signifi cant decrease in suitable habitats for the species from the two RCP scenarios.Only a part of the Guinean climatic zone remained suitable and few protected areas will conserve in situ M.excelsa.For the sustainable conservation of M.excelsa,it is essential to strengthen the protection of sacred forests located in the Guinean climatic zone.

Effect of climate change on spatial distribution of scorpions of significant public health importance in Iran

Objective:To establish a spatial geo-database for scorpions in Iran,and to identify the suitable ecological niches for the most dangerous scorpion species under different climate change scenarios.Methods:The spatial distribution of six poisonous scorpion species of Iran were modeled:Hemiscorpius lepturus,Androctonus crassicauda,Mesobuthus eupeus,Hottentotta saulcyi,Hottentotta zagrosensis,and Odontobuthus(O.)doriae,under RCP2.6 and RCP8.5 climate change scenarios.The Max Ent ecological niche model was used to predict climate suitability for these scorpion species in the 2030 s and 2050 s,and the data were compared with environmental suitability under the current bioclimatic data.Results:A total of 73 species and subspecies of scorpions belonging to 19 genera in Iran were recorded.Khuzestan Province has the highest species diversity with 34 species and subspecies.The most poisonous scorpion species of Iran are scattered in the semi-arid climates,at an altitudinal range between 11 m and 2954 m above sea level.It is projected that O.doriae,Androctonus crassicauda and Mesobuthus eupeus species would be widely distributed in most parts of the country,whereas the most suitable ecological niches for the other species would be limited to the west and/or southwestern part of Iran.Conclusions:Although the environmental suitability for all the species would change under the two climate change scenarios,the change would be more significant for O.doriae under RCP8.5 in the 2050 s.These findings can be used as basis for future studies in the areas with the highest environmental suitability for the most dangerous scorpion species to fill the gaps in the ecology of scorpion species in these areas.

Using remotely sensed and climate data to predict the current and potential future geographic distribution of a bird at multiple scales: the case of Agelastes meleagrides, a western African forest endemic

Background:Understanding geographic distributions of species is a crucial step in spatial planning for biodiversity conservation, particularly as regards changes in response to global climate change.This information is especially important for species of global conservation concern that are susceptible to the effects of habitat loss and climate change. In this study, we used ecological niche modeling to assess the current and future geographic distributional potential of White.breasted Guineafowl (Agelastes meleagrides)(Vulnerable) across West Africa. Methods:We used primary occurrence data obtained from the Global Biodiversity Information Facility and national parks in Liberia and Sierra Leone, and two independent environmental datasets (Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index at 250 m spatial resolution, and Worldclim climate data at 2.5' spatial resolution for two representative concentration pathway emissions scenarios and 27 general circulation models for 2050) to build ecological niche models in Maxent. Results: From the projections, White.breasted Guineafowl showed a broader potential distribution across the region compared to the current IUCN range estimate for the species. Suitable areas were concentrated in the Gola rainforests in northwestern Liberia and southeastern Sierra Leone, the Tai.Sapo corridor in southeastern Liberia and southwestern Cote d'lvoire, and the Nimba Mountains in northern Liberia, southeastern Guinea, and northwestern Cote d'lvoire.Future climate.driven projections anticipated minimal range shifts in response to climate change. Conclusions: By combining remotely sensed data and climatic data, our results suggest that forest cover, rather than climate is the major driver of the species' current distribution. Thus, conservation efforts should prioritize forest protection and mitigation of other anthropogenic threats (e.g.hunting pressure) affecting the species.

Species abundance distribution models of Toona ciliata communities in Hubei Province,China

The study of plant species abundance distribution(SAD)in natural communities is of considerable importance to understand the processes and ecological rules of community assembly.With the distribution of tree,shrub and herb layers of eight natural communities of Toona ciliata as research targets,three diff erent ecological niche models were used:broken stick model,overlapping niche model and niche preemption model,as well as three statistical models:log-series distribution model,log-normal distribution model and Weibull distribution model,to fi t SAD of the diff erent vegetation layers based on data collected.Goodness-of-fi t was compared with Chi square test,Kolmogorov–Smirnov(K–S)test and Akaike Information Criterion(AIC).The results show:(1)based on the criteria of the lowest AIC value,Chi square value and K–S value with no signifi cant diff erence(p>0.05)between theoretic and observed SADs.The suitability and goodness-of-fi t of the broken stick model was the best of three ecological niche models.The log-series distribution model did not accept the fi tted results of most vegetation layers and had the lowest goodness-of-fi t.The Weibull distribution model had the best goodness-of-fi t for SADs.Overall,the statistical SADs performed better than the ecological ones.(2)T.ciliata was the dominant species in all the communities;species richness and diversity of herbs were the highest of the vegetation layers,while the diversities of the tree layers were slightly higher than the shrub layers;there were fewer common species and more rare species in the eight communities.The herb layers had the highest community evenness,followed by the shrub and the tree layers.Due to the complexity and habitat diversity of the diff erent T.ciliata communities,comprehensive analyses of a variety of SADs and tests for optimal models together with management,are practical steps to enhance understanding of ecological processes and mechanisms of T.ciliata communities,to detect disturbances,and to facilitate biodiversity and species conservation.

The Potential Geographic Distribution of Radopholus similis in China

The burrowing nematode （Radopholus similis） is one of the main quarantine pests in China, and the risk of invasion posed by this nematode is becoming more and more serious with regard to the international trade being intensified day by day. It is urgent to analyse the potential geographic distribution of R. similis in China. Genetic algorithm for rule-set prediction modeling system （GARP） and maximum entropy （MAXENT）, the two niche models which have been widely used to predict the potential geographic distribution of alien species, were used to predict the distribution of R. similis in China. We also presented a model comparison of the results by both threshold-dependent and threshold-independent evaluations. It has been shown that the two niche models could be used to predict the potential distribution of R. similis reliably. The potential distribution of R. similis should be constricted within the south of China, such as Hainan, Guangdong, Guangxi, Fujian, Yunnan provinces, and Taiwan of China. The MAXENT gives a better prediction than that of GARP. R. similis can be introduced to China by flowers and nursery stock＇s international shipping. The predicted results indicate that R. similis can occur in south coastal area of China and Yunnan Province, which are the main flower and nursery stock＇s import-export areas in China. Consequently, a strong quarantine program is needed at the ports of such areas to prevent the pest from being introduced to China.