Environmental niche patterns of native and non-native fishes within an invaded African river system

To test ecological niche theory, this study investigated the spatial patterns and the environmental niches of native and non-native fishes within the invaded Great Fish River system, South Africa. For the native fishes, there were contrasting environmental niche breadths that varied from being small to being large and overlapped for most species, except minnows that were restricted to headwater tributaries. In addition, there was high niche overlap in habitat association among fishes with similar distribution. It was therefore inferred that habitat filtering-driven spatial organisation was important in explaining native species distribution patterns. In comparison, most non-native fishes were found to have broad environmental niches and these fishes showed high tolerance to environmental conditions, which generally supported the niche opportunity hypothesis. The proliferation of multiple non-native fishes in the mainstem section suggest that they form a functional assemblage that is probably facilitated by the anthropogenic modification of flow regimes through inter-basin water transfer. Based on the distribution patterns observed in the study, it was inferred that there was a likelihood of negative interactions between native and non-native fishes. Such effects are likely to be exacerbated by altered flow regime that was likely to have negative implications for native ichthyofauna.     

Invasiveness of plants is predicted by size and fecundity in the native range

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Behavioural interactions between the introduced plague minnow Gambusia holbrooki and the vulnerable native Australian ornate rainbowfish Rhadinocentrus ornatus,under experimental conditions

The impact of the plague minnow Gambusia holbrooki on the ornate rainbowfish Rhadinocentrus ornatus was investigated by comparing the behavioural response and microhabitat preferences of populations of R. ornatus collected from locations that are sympatric and allopatric with G. holbrooki. Rhadinocentrus ornatus populations from sympatric areas exhibited a significantly higher frequency of intraspecific chases, spent significantly more time at an intermediate depth and were nipped significantly less often by G. holbrooki compared to the allopatric R. ornatus populations. The frequency of intraspecific chases by all R. ornatus populations were greatest immediately following G. holbrooki exposure and increased further with repeated exposure. Activity levels were also significantly higher in the presence of G. holbrooki. Gambusia holbrooki and the allopatric R. ornatus populations showed very similar microhabitat preferences, whereas the preferences for the sympatric R. ornatus populations have shifted to facilitate cohabitation with G. holbrooki. The results suggest that sympatric populations of R. ornatus have evolved or developed behavioural responses to G. holbrooki through niche and character shifts. The implications are discussed in relation to the conservation management of R. ornatus and other threatened species.     

Potential for biological control of native competing vegetation using native herbivores

1 The use of native natural enemies to combat native pests has received proportionately less consideration than other viable approaches to biological control. Successful attempts at augmentation, conservation, preservation, and enhancement of the effectiveness of natural enemies have been limited. 2 However, this approach to biological control should be re-examined, placing emphasis on intentional manipulation of population dynamics to encourage the natural tendencies of populations to grow in the absence (or during the delay in resurgence) of certain regulating forces. 3 We discuss theoretical and empirical evidence that suggests native herbivorous insects have the potential to be manipulated successfully as biological control agents for native competing vegetation.     

Predicting plant invasiveness from native range size: clues from the Kashmir Himalaya

Aims In view of the growing interest in modelling the potential spread of invasive species, prediction of plant invasiveness on the basis of native range size holds considerable promise. Our objective was to use a simple model to evaluate whether a wider native range predisposes plant species to become invasive in non-native regions and to easily identify potential invaders on this basis. The Kashmir Himalayan alien flora, of which a large proportion is native to Europe, was used to test this model.Methods The Kashmir Himalayan alien flora comprises 436 species of vascular plants at different stages of invasion. We focussed on plant species at two critical invasion stages (sensu Colautti and MacIsaac 2004), i.e. Stage II (species that are just at the earliest phase of introduction) and Stage V (species that are widespread and dominant in the invaded region and are thus considered invasive). We used the territorial distribution in Europe (number of countries) as a surrogate for the native range size of plants of European origin.Important findings Using a subset of 88 species, for which information on the native European range was available, we showed that a large proportion (68%) of Stage II species growing in the Kashmir Valley had a relatively restricted European range (present in ≤20 countries); on the other hand, 77% of Stage V species had an extensive native range (present in>20 countries). We consequently hypothesized that 14 Kashmir Himalayan Stage II species of European origin that are distributed in>20 European countries are at risk of becoming future invaders in Kashmir. On the other hand, those Kashmir Himalayan Stage II species of European origin distributed in ≤20 European countries are less likely to become invasive. Although this analysis is quite simple, the data suggest that a wider native range is a good predictor of plant invasiveness and could be used as a simple and low-cost early warning tool in predicting potential invasive species.     

In situ adaptation and ecological release facilitate the occupied niche expansion of a non‐native Madagascan day gecko in Florida

AimTo investigate whether the frequently advocated climate‐matching species distribution modeling approach could predict the well‐characterized colonization of Florida by the Madagascar giant day gecko Phelsuma grandis.LocationMadagascar and Florida, USA.MethodsTo determine the climatic conditions associated with the native range of P. grandis, we used native‐range presence‐only records and Bioclim climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence‐only data and projected it onto Madagascar. We constructed a third model using native‐range presences for both P. grandis and the closely related parapatric species P. kochi.ResultsDespite performing well within the native range, our Madagascar Bioclim model failed to identify suitable climatic habitat currently occupied by P. grandis in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by P. kochi. The model built using the combined P. kochi/P. grandis dataset modestly improved the prediction of the range of P. grandis in Florida, thereby implying competitive exclusion of P. grandis by P. kochi from habitat within the former''s fundamental niche. These findings thus suggest ecological release of P. grandis in Florida. However, because ecological release cannot fully explain the divergent occupied niches of P. grandis in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida.Main conclusionsOur models suggest that the discrepancy between the predicted and observed range of P. grandis in Florida is attributable to either in situ adaptation by P. grandis within Florida, or a combination of such in situ adaptation and competition with P. kochi in Madagascar. Our study demonstrates that climate‐matching species distribution models can severely underpredict the establishment risk posed by non‐native herpetofauna.     

Temporal and sociocultural effects of human colonisation on native biodiversity: filtering and rates of adaptation

Modern human societies have negatively impacted native species richness and their adaptive capacity on every continent, in clearly contrasting ways. We propose a general model to explain how the sequence, duration and type of colonising society alter native species richness patterns through changes in evolutionary pressures. These changes cause different ‘filtering effects' on native species, while simultaneously altering the capacity of surviving species to adapt to further anthropogenic pressures. This framework may better explain the observed native species extinction rates and extirpation legacies following human colonisation events, as well as better predict future patterns of human impact on biodiversity.     

The distribution of range sizes of native and alien plants in four European countries and the effects of residence time

Aim Do the statistical distributions of range sizes of native and alien species differ? If so, is this because of residence time effects? And can such effects indicate an average time to a maximum? Location Ireland, Britain, Germany and the Czech Republic. Methods The data are presence or absence of higher plants in mapping units of 100 km² (Ireland and Britain) or c. 130 km² (Germany and the Czech Republic) in areas varying from 79 to 357 thousand km². Logit transforms of range sizes so defined were tested for normality, and examined by ANOVA, and by loess, ordinary least square (OLS) and reduced major axis regressions. Results Current range sizes, in logits, are near normally distributed. Those of native plants are larger than those of naturalized neophytes (plants introduced since 1500 ad ) and much larger than those of casual neophytes. Archaeophytes (introduced earlier) have range sizes slightly larger than natives, except in Ireland. Residence time, the time since an invasive species arrived in the wild at a certain place, affects range sizes. The relationships of the range of naturalized neophytes to residence time are effectively straight in all four places, showing no significant curvature or asymptote back to 1500, though there are few records between 1500 and 1800. The relationships have an r² of only about 10%. Both OLS regressions and reduced major axes can be used to estimate the time it takes for the range of a naturalized neophyte to reach a maximum. Main conclusions Established neophytes have smaller range size distributions than natives probably because many have not yet reached their maximum. We estimate it takes at least 150 years, possibly twice that, on average, for the maximum to be reached in areas of the order of 10⁵ km². Policy needs to allow for the variation in rates of spread and particularly the long time needed to fill ranges. Most naturalized neophytes are still expanding their ranges in Europe.     

How policies constrain native seed supply for restoration in Brazil

Large‐scale ecological restoration programs across the world involve a voluminous demand for native seeds of diverse native plant species. In this article, we explore how institutional systems have operated and impacted native seed supply in Brazil. Native seed supply for restoration is essentially a community‐based activity which faces broad barriers to operating within regulations because of requirements for excessive and costly technical documentation, scarcity of seed laboratories, and lack of instructions for native seed quality testing. Although decentralized seed networks have stimulated arrangements for local organizations to promote seed supply, policies constrain the development of local capacities and the ongoing sustainability of these organizations. These conditions have resulted in a vast network of informal collectors and producers who are largely “invisible” and unknown to the regulatory authorities. Policies have decentralized responsibilities from the state without devolving decision‐making power to the multiple stakeholders engaged in policy elaboration. The policies maintain the centralized regulation of native seed supply. After examining Brazilian seed networks' experiences and conducting discussions with stakeholders and experts, we suggest adapting the current regulations to more local level contexts, encompassing the following strategies: (1) ensuring native seed origin and identity; (2) relaxation of the laboratory accreditation process for native seed quality assurance; (3) fostering seed markets for restoration; (4) research to provide technological innovation; (5) supporting local, diverse, and small seed‐based businesses.     

A trait-based approach across the native and invaded range to understand plant invasiveness and community impact

Alien plant species invasiveness and impact on diversity (i.e. species richness and composition) can be driven by the altered competitive interactions experienced by the invader in its invaded range compared to its native range. Trait-based competition effects on invasiveness can be mediated through size-asymmetric competition, i.e. a trait suit of the invader that drives competitive dominance, and through ‘niche differences', i.e. trait differentiation and thus minimized competition between invader and the invaded community. In terms of invasion impact, size-asymmetric competition is expected to result in competitive exclusion of co-occurring subordinate species, whereas ‘niche differences' might result in competitive exclusion of the most functionally similar co-occurring species. Although observational work does not allow the full disentanglement of both trait-based effects, it does allow to verify the occurrence of expected theoretical trait patters. In this study, we explored the trait-based competition effects on invasiveness and diversity impact for Rosa rugosa in both its invaded range in Belgium and its native range in Japan, based on seven functional traits across 100 vegetation plots. Following the predictions for enhanced invasiveness, we found much lower functional overlap between R. rugosa and the co-occurring species in the invaded range compared to the native range. This likely also explains the absence of diversity impact in its native range. Despite the absence of changes in species richness in the invaded range, the invader did strongly impact species composition of invaded communities. This impact occurred through strong shade tolerance responses, suggesting size-asymmetric competition effects and cover loss of co-occurring dominant species, next to exclusion of co-occurring species most functionally similar to the invader; suggesting niche difference effects. In conclusion, this case-study illustrates how exploring functional trait patterns across a species native and invaded range can help in understanding how trait-based competition processes can affect invasiveness and community impact.     

Explaining invasiveness from the extent of native range: new insights from plant atlases and herbarium specimens

Aim

We tested the relationship between the extent of the native range and the success (number of occurrences) in the introduced range of European vascular plant species naturalized in the province of Québec (Canada). We hypothesized that the performance of models linking native range size and species invasiveness can be improved if residence time and climate tolerance are taken into account.

Methods

The extent of the native range (Europe, Asia) was estimated using plant atlases. The number of occurrences in the introduced range (Québec) was estimated using the number of herbarium specimens stored in herbaria. Herbarium specimens were also used to obtain residence time. Plant hardiness was used as an indicator of the suitability of a species to the climate of the introduced range. Multiple linear regression models, corrected to take into account phylogenetic biases, were used to calculate correlations between the extent of the native range and the number of occurrences in the introduced range.

Results

The larger the native distribution area in Eurasia, the greater the number of occurrences (herbarium specimens) in Québec. The shorter the residence time and the less hardy the plant, the fewer the number of occurrences. In all models tested, the phylogenetic structure explained a significant proportion of the variance, but its influence decreased as the number of species or area studied (Europe versus Eurasia) increased.

Main conclusions

The extent of the native range is a good explanatory variable for the invasion success of vascular plants, especially once other factors (residence time, climate tolerance, phylogeny) are taken into account. Thus, a model using these variables could be used by environmental managers to flag species warranting further investigation. With the emergence of online databases, gathering the required information is becoming easier and cheaper. As online databases continue to improve and new analytical tools are developed, this approach will become even more powerful.

     

Analysis of Streptomyces coelicolor membrane proteome using two-dimensional native/native and native/sodium dodecyl sulfate gel electrophoresis

Analysis of the oligomeric state of a protein may provide insights into its physiological functions. Because membrane proteins are considered to be the workhorses of energy generation and polypeptide and nutrient transportation, in this study we characterized the membrane-associated proteome of Streptomyces coelicolor by two-dimensional (2D) blue native/sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), high-resolution clear native/native PAGE, and native/SDS–PAGE. A total of 77 proteins were identified, and 20 proteins belonging to 15 complexes were characterized. Moreover, the resolution of high-resolution clear native/SDS–PAGE is much higher than that of blue native/SDS–PAGE. OBP (SCO5477) and BldKB (SCO5113) were identified as the main protein spots from the membrane fractions of S. coelicolor M145, suggesting that these two proteins are involved in extracellular peptide transportation. These two transporters exhibited multiple oligomeric states in the native PAGE system, which may suggest their multiple physiological functions in the development of S. coelicolor.     

红火蚁入侵草坪过程中蚂蚁类群变动趋势

观察研究了红火蚁入侵草坪之后蚂蚁群落结构的变动趋势。对各处理区在不同时期的蚂蚁优势种进行了分析,结果表明,与对照区相比红火蚁入侵后各处理区的蚂蚁优势种发生了明显改变,红火蚁替代了原来的优势蚂蚁种类,并在数量上占主导地位,而且各处理区的蚂蚁类群多样性、均匀度降低,优势度明显增大。通过分析红火蚁入侵过程中各处理区的蚂蚁类群相似性,表明轻度发生区与对照区的蚂蚁类群相似性系数q一直处在0.25-0.50之间,为中等不相似;中度发生区与对照区的蚂蚁类群相似性系数q一直处在0.075-0.444之间,为中等不相似或极不相似;重度发生区与对照区的蚂蚁类群相似性系数q一直处在0.0-0.222之间,为极不相似,这也说明了不同的红火蚁危害程度对本地蚂蚁类群结构的影响是不同的,红火蚁种群数量越大,对本地蚂蚁类群的影响也越大,排挤或取代它们所需要的时间也越短。     

入侵植物藿香蓟与常见伴生杂草的生态位特征

基于传统生态位理论的生物入侵机制假说认为外来种和土著种生态位的差异是决定入侵成功与否和危害程度的关键。藿香蓟(Ageratum conyzoides L.)是一种在我国南方快速蔓延的恶性入侵种。为了了解藿香蓟与其他杂草在群落中的生态关系,探究造成藿香蓟成功入侵的可能机制及危害,在浙西南的丽水市开展了杂草群落调查,计算了藿香蓟和16种常见本地杂草的生态位宽度、生态位重叠和种间相关系数,并对主要物种进行典范对应分析(CCA)排序。结果表明(1)藿香蓟与常见本地杂草间的生态位重叠度显著高于本地杂草间的生态位重叠度,这与藿香蓟具有最大的生态位宽度有关;(2)藿香蓟与常见本地杂草的Pianka生态位重叠指数介于0.04-0.296之间,重叠度处于中下水平;(3)常见本地杂草对于藿香蓟的n-维超体积生态位重叠值显著高于藿香蓟对于常见本地杂草的n-维超体积生态位重叠值;(4)藿香蓟在CCA排序图上处于较中心的位置,说明其具有较高的中生性;不仅如此,外来杂草和本地杂草在排序图上充分混杂,说明外来种相对于本地种并无明显特化;(5)群落中大多数常见杂草间未出现显著种间负相关,仅7个种对显著正相关,大多数种对不相关。总的来说,丽水农村的杂草群落稳定较差,资源相对充足,种间生态位重叠较低,本地植物对于藿香蓟的竞争阻抗较小,加上藿香蓟本身较大的生态位宽度,导致了藿香蓟在本地区广泛而严重的入侵。     

Seventy years of stream‐fish collections reveal invasions and native range contractions in an Appalachian (USA) watershed

Aim

Knowledge of expanding and contracting ranges is critical for monitoring invasions and assessing conservation status, yet reliable data on distributional trends are lacking for most freshwater species. We developed a quantitative technique to detect the sign (expansion or contraction) and functional form of range‐size changes for freshwater species based on collections data, while accounting for possible biases due to variable collection effort. We applied this technique to quantify stream‐fish range expansions and contractions in a highly invaded river system.

Location

Upper and middle New River (UMNR) basin, Appalachian Mountains, USA.

Methods

We compiled a 77‐year stream‐fish collections dataset partitioned into ten time periods. To account for variable collection effort among time periods, we aggregated the collections into 100 watersheds and expressed a species’ range size as detections per watershed (HUC) sampled (DPHS). We regressed DPHS against time by species and used an information‐theoretic approach to compare linear and nonlinear functional forms fitted to the data points and to classify each species as spreader, stable or decliner.

Results

We analysed changes in range size for 74 UMNR fishes, including 35 native and 39 established introduced species. We classified the majority (51%) of introduced species as spreaders, compared to 31% of natives. An exponential functional form fits best for 84% of spreaders. Three natives were among the most rapid spreaders. All four decliners were New River natives.

Main conclusions

Our DPHS‐based approach facilitated quantitative analyses of distributional trends for stream fishes based on collections data. Partitioning the dataset into multiple time periods allowed us to distinguish long‐term trends from population fluctuations and to examine nonlinear forms of spread. Our framework sets the stage for further study of drivers of stream‐fish invasions and declines in the UMNR and is widely transferable to other freshwater taxa and geographic regions.