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1.
Models predict that community invasibility generally declines with species diversity, a prediction confirmed by small‐scale experiments. Large‐scale observations and experiments, however, find that diverse communities tend to be more heavily invaded than simple communities. One hypothesis states that large‐scale environmental heterogeneity, which similarly influences native and invasive species, can cause a positive correlation between diversity and invasibility, overriding the local negative effects of diversity on invasibility. We tested this hypothesis using aquatic microbial communities consisting of protists and rotifers consuming bacteria and nanoflagellates. We constructed a productivity gradient to simulate large‐scale environmental heterogeneity, started communities with the same number of species along this gradient, and subjected equilibrial communities to invasion by non‐resident consumer species. Both invaders and most resident species increased their abundances with resource enrichment, resulting in a positive correlation between diversity and invasibility. Intraspecific interference competition within resident species and the positive effect of enrichment on the number of available resources probably accounted for the higher invasibility with enrichment. Our results provide direct experimental evidence that environmental heterogeneity in productivity can cause a positive diversity–invasibility relationship. 相似文献
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Investigations on non-native organisms have become an important task of modern ecology throughout the world. The major objective of this study was to identify the characteristics and habitats of non-native plant species in Korean cities in order to derive conclusions on the success of biological invaders. The city of Chonju in southwest Korea was selected as a representative investigation area. All wild-growing vascular plants were recorded in the city on a total of 106 sample plots located in representative land-use types and within various distances of the city center. Frequency, origin, life forms, and plant families of non-native species were analyzed. Additionally, the percentage of non-native species along a gradient from the city center to the outskirts was investigated. We found that most common non-native species of the flora of Chonju are: (i) native to the Northern hemisphere; (ii) belong to the annuals; (iii) belong to the plant families of the Compositae or Leguminosae; and (iv) they perform best on sites that are continuously disturbed by human impact. In conclusion, non-native species play a significant role in enhancing biological diversity in urban areas. 相似文献
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Marcel Rejmánek Brian J. Huntley Johannes J. Le Roux David M. Richardson 《African Journal of Ecology》2017,55(1):56-69
Angola is one of the most neglected African countries in terms of botanical research, in respect of both native and naturalized species. We conducted a rapid assessment of invasive plant species in western Angola during August 2014. In thirteen primary vegetation types, we recorded populations of 44 naturalized plant species, nineteen of which are conclusively invasive (spreading far from introduction sites). Dense invasive populations of Chromolaena odorata, Inga vera and Opuntia stricta pose the greatest environmental and economic threats. Some species with known taxonomic and/or biogeographic uncertainties (e.g. Chromolaena odorata and Ageratina adenophora) or which lacked key characteristics for identification such as flowers during our survey (e.g. Eucalyptus spp.) were subjected to DNA barcoding for comparisons with available genetic data from other studies. This approach allowed us to confirm the identity of taxonomically challenging taxa such as Inga vera, Opuntia stricta and Prosopis chilensis, to conclusively differentiate Chromolaena odorata from Ageratina adenophora, and identify the subspecific identity of Acacia saligna. Canonical correspondence analysis was used to assess the presence and abundance of invasive plant species with respect to the major abiotic factors and vegetation types. Three fairly distinct groups of species emerge from this analysis: (i) species of dry lowland habitats (Calotropis gigantea, Leucaena leucocephala and Opuntia stricta); (ii) species of relatively wet habitats at mid elevations (Ageratum conyzoides, Bidens pilosa, Cardiospermum grandiflorum, Chromolaena odorata, Solanum mauritianum and Tithonia diversifolia); and (iii) upland species (Ageratina adenophora, Galinsoga parviflora and Tagetes minuta). Several invasive species that are widespread in other tropical and subtropical African countries are currently either missing (e.g. many Australian Acacia species, Azolla filiculoides, Broussonetia papyrifera, Clidemia hirta, Parthenium hysterophorus, Rubus rosaefolius, Salvinia molesta), have only very localized populations in Angola (e.g. Lantana camara, Prosopis chilensis) or exist only as planted individuals (e.g. Acacia mearnsii and A. saligna subsp. saligna). 相似文献
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Miguel Baltazar‐Soares Filipa Paiva Yiyong Chen Aibin Zhan Elizabeta Briski 《Ecology and evolution》2017,7(19):7687-7698
Biological invasions are worldwide phenomena that have reached alarming levels among aquatic species. There are key challenges to understand the factors behind invasion propensity of non‐native populations in invasion biology. Interestingly, interpretations cannot be expanded to higher taxonomic levels due to the fact that in the same genus, there are species that are notorious invaders and those that never spread outside their native range. Such variation in invasion propensity offers the possibility to explore, at fine‐scale taxonomic level, the existence of specific characteristics that might predict the variability in invasion success. In this work, we explored this possibility from a molecular perspective. The objective was to provide a better understanding of the genetic diversity distribution in the native range of species that exhibit contrasting invasive propensities. For this purpose, we used a total of 784 sequences of the cytochrome c oxidase subunit I of mitochondrial DNA (mtDNA‐COI) collected from seven Gammaroidea, a superfamily of Amphipoda that includes species that are both successful invaders (Gammarus tigrinus, Pontogammarus maeoticus, and Obesogammarus crassus) and strictly restricted to their native regions (Gammarus locusta, Gammarus salinus, Gammarus zaddachi, and Gammarus oceanicus). Despite that genetic diversity did not differ between invasive and non‐invasive species, we observed that populations of non‐invasive species showed a higher degree of genetic differentiation. Furthermore, we found that both geographic and evolutionary distances might explain genetic differentiation in both non‐native and native ranges. This suggests that the lack of population genetic structure may facilitate the distribution of mutations that despite arising in the native range may be beneficial in invasive ranges. The fact that evolutionary distances explained genetic differentiation more often than geographic distances points toward that deep lineage divergence holds an important role in the distribution of neutral genetic diversity. 相似文献
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Pennisetum setaceum (Poaceae) is a perennial bunch grass that invaded the United States during the 20th century and is highly invasive in Hawaii, moderately invasive in Arizona, and not yet invasive in southern California. Pennisetum setaceum is apomictic, a condition that is normally associated with low genetic variation within populations, but even moderate levels of genetic variation among populations could account for differences in invasiveness. To determine whether genetic factors are causing the variable invasion success, we used Inter‐Simple Sequence Repeat markers (ISSRs) to examine genetic variation in populations from the three areas. Screening of 16 primers revealed no genetic variation within any population or between any geographical areas, a pattern consistent with complete apomixis. Variation in invasion success appears unrelated to genetic differences among populations. Differences in the seasonal timing of rainfall among the regions may be the cause of variable invasiveness of fountain grass. Alternatively, differences in timing of introduction or duration of lag phase may have limited invasiveness in Arizona and southern California. 相似文献
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The Global Invasive Species Database, GISD, comprises 27 species of the most significant invasive alien insects in the world (through November, 2005), 6 of which are originally native to China, 11 are established in China, and 10 have a potential invasion threat to China. This paper discusses these species in terms of distribution, harmfulness and dispersal ways, and finds that: (i) Information regarding invasive insects in the GISD remains inadequate. Such harmful invasive species as Opogona sacchari (Bojer), Oracella acuta (Lobdell), and Dendroctonus valens LeConte are not included. (ii) Ten species of invasive insects, particularly Lasius neglectus Van Loon and Linepithema humile (Mayr) which become established in areas near China, have the potential to become established in China. (iii) Special attention should be paid to species from Asia and the Americas because of their greater likelihood of becoming established in China. Finally, some management strategies including legislation, quarantine, early warning, prevention and control are suggested. 相似文献
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Riparian habitats are particularly susceptible to invasion by non‐native plants. At present, attempts to build consensus as to what the primary drivers of plant invasion in riparian ecosystems might be is hindered by the absence of common standards for data collected on plant species (e.g. occurrence, or relative abundance). Mimulus guttatus L., a non‐native riparian plant species, was used as a model to determine how environmental drivers influence two aspects of invasibility: species occurrence and abundance (assessed in relation to three variables number of patches, patch area and number of stems per patch). Mimulus occurrence and abundance, together with 20 environmental variables, were surveyed in almost 700 contiguous 50‐m‐long riverbank segments within a catchment in north‐east Scotland. More than half of the segments had been colonized by Mimulus. Occurrence and number of patches responded to similar environmental gradients, particularly bare sediment, boulders, high soil moisture, short‐statured ruderal communities, and open canopies, and tended to be highest downstream where the river was widest. In contrast to occurrence and patch number, patch area and stem number per patch were higher in the upper reaches of the catchment and were positively associated with low tree canopy and vegetation dominated by light‐demanding species and smaller‐statured species. Patch area and stem number per patch were also positively related to grazing. This study has highlighted the importance of assessing more than one measure of invasion success (occurrence or patch number and either patch area or stem number per patch), as they are each determined by a different suite of environmental variables. Abiotic factors, such as sediment availability and presence of boulders, appeared to be the major determinants of occurrence and patch number, whereas biotic factors, such as interspecific competition and grazing, were more important ecological determinants underlying area and stem number per patch. 相似文献
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Abstract. Alien invasions typically reduce species richness of habitats, but few studies have examined their effects on species turnover, the difference in species composition between localities. Agropyron cristatum (L.) Gaertn. (crested wheat grass) has been planted on 6–10 million ha of North American prairie, and is invading native prairie. We studied the invasion of A. cristatum into native prairie by measuring species composition along a gradient from maximum to minimum A. cristatum abundance. As A. cristatum increased, the abundance of most common native species decreased, but one appeared to be unaffected (Bouteloua gracilis (H.B.K.) Lag.), and another (Poa sandbergii Vasey) increased. The effect of A. cristatum on species turnover was investigated by examining species–area curves for areas from 0.5 m2 to 8.0 m2. Species diversity was reduced by 35% at high A. cristatum abundances at all areas. A. cristatum reduced the intercept of the species–area curve, but not the slope, suggesting that A. cristatum affected species turnover proportionally in all areas and habitats. This unusual result may indicate a homogeneous environment where species are distributed randomly. A. cristatum produced almost twice as many seeds as all native grasses combined. The number of seeds collected of native grasses and A. cristatum was highly correlated with the number of seed heads immediately nearby, but not with transect position. This suggests most seeds were dispersed over distances less than 5 m. In sum, the invasion of native prairie by A. cristatum might be related to high rates of seed production, and has the effect of decreasing species turnover by reducing the intercept of the species–area curve. 相似文献
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Most introduced species apparently have little impact on native biodiversity, but the proliferation of human vectors that transport species worldwide increases the probability of a region being affected by high-impact invaders – i.e. those that cause severe declines in native species populations. Our study determined whether the number of high-impact invaders can be predicted from the total number of invaders in an area, after controlling for species–area effects. These two variables are positively correlated in a set of 16 invaded freshwater and marine systems from around the world. The relationship is a simple linear function; there is no evidence of synergistic or antagonistic effects of invaders across systems. A similar relationship is found for introduced freshwater fishes across 149 regions. In both data sets, high-impact invaders comprise approximately 10% of the total number of invaders. Although the mechanism driving this correlation is likely a sampling effect, it is not simply the proportional sampling of a constant number of repeat-offenders; in most cases, an invader is not reported to have strong impacts on native species in the majority of regions it invades. These findings link vector activity and the negative impacts of introduced species on biodiversity, and thus justify management efforts to reduce invasion rates even where numerous invasions have already occurred. 相似文献
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Patricio Javier Pereyra 《Austral ecology》2016,41(5):519-528
Invasion science has not been developed without controversies. Two questions that are still unsolved are: what is an invasive species?, and are invasive species an inherent conservation problem? These questions have led to discussions about effects versus origins. In contrast to the definitional problems, a unified framework describing invasion as a step‐by‐step process has been widely accepted. I conducted a bibliographic search with two separate databases searching for (i) evidence of less use of controversial terms over time; (ii) how many articles defined ‘invasive species’; (iii) the criteria used to define a species as invasive; and (iv) in which stage of the invasion continuum were species labelled as invasive located. My results show that controversial terms are widely used, that authors rarely define ‘invasive species’ and, often, it is very complicated to determine which criterion they used. In addition, only a fraction of the species labelled as invasive could be classified as such according to the unified framework of invasion stages. This is not a merely semantic issue, because invasive is a strong and value‐laden term that is used to guide environmental agendas. The uncritical use of a key concept could hamper research, complicate communication among peers and produce mixed results. 相似文献
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- 1 We provide an updated distribution and dispersal rate of the introduced European rabbit Oryctolagus cuniculus in Argentina.
- 2 According to our results this invasive species is currently colonizing parts of Mendoza and Neuquén Provinces, where rivers are very important in the spread of the rabbits, especially in unfavourable areas. The maximun rate of dispersal registered in this study was 9 km/year.
- 3 Some information was obtained to indicate that the presence of this exotic species threatens agriculture, livestock, forestry, and natural ecosystems of the Patagonia region.
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Abstract There is a tendency for both scientists and lay people to regard invading alien species as inherently ‘bad’ and native species as inherently ‘good.’ Past invasions occurred commonly without human assistance. They rarely caused large, lasting decreases in species richness or ecological damage. Current invasions provide opportunities for scientific study. They are unintentional, uncontrolled experiments, which can provide insights into attributes of successful colonists, relationships with native species, and impacts on the structure and function of ecological systems. 相似文献
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- Biological invasions are a major driver of biodiversity loss, but no study has described the scope of threats to bats (Chiroptera) by invasive species.
- We reviewed the literature for negative effects of invasive species to bats and summarised threats according to four categories: predation, disease, competition, and indirect interactions. We identified threats of 37 invasive species to 40 bat species. Ten bat species were threatened by more than one invasion pathway.
- About 38 percent of cases are speculative and 18 percent circumstantial, many attributed to overlapping ranges, and most accounts do not quantify effects needed to forecast bat population impacts.
- Evidence of cat predation is frequently cited, constituting the greatest incidence of observational data. Other direct and indirect impacts were documented from goats, dogs, brown tree snake, rainbow lorikeet, rose‐ringed parakeet, yellow crazy ant, giant centipede, palm, burdock, avian cholera, and white‐nose syndrome. Circumstantial evidence suggests impacts by rats, stoats, coqui frog, common wolf snake, little fire ant, kudzu, and Lantana camara. Other impacts by giant centipede, yellow crazy ant, cats, goats, rats, and avian cholera are speculative, as are those from pigs, deer, white eye, common starling, house sparrow, rock dove, barn and little owls, brush‐tailed possum, honeybee, wasp, phytophagous insects, tamarisk, Cinnamomum verum, and Tabebuia pallida.
- Over 60 percent of bat species reviewed are island‐dwelling, corresponding with evidence indicating that most extinctions occur on islands and invasive species’ impacts are worse for island than mainland populations.
- Although appreciable bat population reductions owing to invasive species are often unproven, invasions are likely to exacerbate effects of other vulnerabilities. Multiple invaders and synergistic interactions may ultimately lead to species losses.
- Managers should exercise the precautionary principle by taking action against non‐native species when first detected, even if new species do not appear to be detrimental.
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Abstract. The common waxbill Estrilda astrild was first introduced to Portugal from Africa in 1964, and has spread across much of the country and into Spain. We modelled the expansion of the common waxbill on a 20 × 20 km UTM grid in 4‐year periods from 1964 to 1999. The time variation of the square root of the occupied area shows that this expansion process is stabilizing in Portugal, and reasons for this are discussed. Several methods used to model biological expansions are not appropriate for the present case, because little quantitative data are available on the species ecology and because this expansion has been spatially heterogeneous. Instead, colonization on a grid was modelled as a function of several biophysical and spatio‐temporal variables through the fitting of a multivariate autologistic equation. This approach allows examination of the underlying factors affecting the colonization process. In the case of the common waxbill it was associated positively with its occurrence in adjacent cells, and affected negatively by altitude and higher levels of solar radiation. 相似文献
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Nancy K. Gillis Linda J. Walters Flavio C. Fernandes Eric A. Hoffman 《Diversity & distributions》2009,15(5):784-795
Aim Levels of genetic diversity can be used to determine haplotype frequency, population size and patterns of invasive species distribution. In this study, we sought to investigate the genetic structure of the invasive marine mussel Mytella charruana and compare variation from invasive populations with variation found within three native populations.
Location Invaded areas in the USA (Florida, Georgia); native areas in Ecuador, Colombia and Brazil.
Methods We sequenced 722 bp of the mitochondrial COI gene from 83 M. charruana samples from four invasive populations (USA) and 71 samples from two natural populations (Ecuador, Columbia). In addition, we sequenced 31 individuals of a congeneric species, Mytella guyanensis , from Salvador, Brazil. We constructed the phylogenetic relationship among all haplotypes and compared diversity measures among all populations.
Results We found significantly higher levels of nucleotide diversity in invasive populations than in native populations, although the number of haplotypes was greater in the native populations. Moreover, mismatch distribution analyses resulted in a pattern indicative of population admixture for the invasive populations. Conversely, mismatch distributions of native populations resulted in a pattern indicative of populations in static equilibrium.
Main conclusion Our data present compelling evidence that the M. charruana invasion resulted from admixture of at least two populations, which combined to form higher levels of genetic diversity in invasive populations. Moreover, our data suggest that one of these populations originated from the Caribbean coast of South America. Overall, this study provides an analysis of genetic diversity within invasive populations and explores how that diversity may be influenced by the genetic structure of native populations and how mass dispersal may lead to invasion success. 相似文献
Location Invaded areas in the USA (Florida, Georgia); native areas in Ecuador, Colombia and Brazil.
Methods We sequenced 722 bp of the mitochondrial COI gene from 83 M. charruana samples from four invasive populations (USA) and 71 samples from two natural populations (Ecuador, Columbia). In addition, we sequenced 31 individuals of a congeneric species, Mytella guyanensis , from Salvador, Brazil. We constructed the phylogenetic relationship among all haplotypes and compared diversity measures among all populations.
Results We found significantly higher levels of nucleotide diversity in invasive populations than in native populations, although the number of haplotypes was greater in the native populations. Moreover, mismatch distribution analyses resulted in a pattern indicative of population admixture for the invasive populations. Conversely, mismatch distributions of native populations resulted in a pattern indicative of populations in static equilibrium.
Main conclusion Our data present compelling evidence that the M. charruana invasion resulted from admixture of at least two populations, which combined to form higher levels of genetic diversity in invasive populations. Moreover, our data suggest that one of these populations originated from the Caribbean coast of South America. Overall, this study provides an analysis of genetic diversity within invasive populations and explores how that diversity may be influenced by the genetic structure of native populations and how mass dispersal may lead to invasion success. 相似文献
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