Biological Invasions最新文献

Among reptiles, turtles are the most frequently traded species and often released in the wild once they become unwanted as pets. The common snapping turtle Chelydra serpentina and the alligator snapping turtle Macrochelys temminckii are freshwater turtles native to North America. Although their trade is regulated in some countries, they have been introduced worldwide as pets. While C. serpentina has established some self-sustaining populations outside its native range, there are no such reports for M. temminckii. However, there are increasing records from the wild for both species, yet a thorough assessment of the potential climatic suitability, observed impacts, and potential invasiveness of these two species has never been performed. To fill this critical gap, we combined species distribution models under current and future climatic scenarios, standardized scoring impact systems (EICAT(+) and SEICAT), and invasiveness risk-screening (AS-ISK). Our results show current and future climatic suitability for both species outside their native range, especially for C. serpentina. In their native ranges, our models predicted a future increase in climatic suitability for C. serpentina, but a decrease for M. temminckii, raising potential concerns for the conservation of this latter species. Only C. serpentina could be assessed for its impacts, being attributed a minor impact score. The invasiveness risk screening attributed a medium risk to C. serpentina and a low risk to M. temminckii. In any case, our results suggest that data collection outside both species’ native ranges is necessary to monitor the status of these as non-native species, identifying eventual reproductions in the wild and early detecting incipient invasions.

Many theories have been created to explain the mechanisms driving species coexistence. They are mainly based on biotic interactions and abiotic factors, which are being constantly affected by human activities. In invaded communities, novel ecological interactions among organisms are created and native and non-native species have to coexist. This coexistence can be supported by different interactions (both positive and negative) and, in some cases, can be followed by negative impacts on the spatial distribution of native species. We aimed to assess the role of the functional differences and species status influencing co-occurrence patterns between native and non-native species at the Upper Paraná River floodplain, Southern Brazil. We estimated the co-occurrence between pairs of native and non-native species and their functional dissimilarity using morphological traits. We found a positive relationship between co-occurrence and functional dissimilarity between species: more similar native and non-native species tended to co-occur less. The co-occurrence was also related to species status: it was higher between pairs of native species than between pairs of native and non-native species. Niche differentiation may play an important role in driving the observed co-occurrence patterns at small spatial scales. However, this can lead to a limitation on the space use of species and modifications in the taxonomic and functional diversity of the native community. Although we recognize that species coexistence may be driven by several factors, we show here that the co-occurrence patterns of native and non-native species were affected by their functional dissimilarity.

The freshwater zooplankton of New Zealand-Aotearoa are species-poor with only two indigenous Daphnia species: D. thomsoni, and D. tewaipounamu. Over the last two decades, two species of invasive non-indigenous Daphnia, D. pulicaria/pulex and D. galeata, have become well established in many lakes in New Zealand-Aotearoa and their distribution appears to be rapidly increasing. We report the current distribution of these two invasive species in approximately 300 lakes throughout New Zealand-Aotearoa and test the hypothesis that the distribution and establishment of these invaders is more closely related to human access to a lake than to any environmental attributes of a lake’s water or biota and consider potential implications of our findings for lake management. Boosted regression tree analysis identified total nitrogen and distance from the coast (D. pulicaria) and annual lake temperature (D. galeata) as key variables explaining current distributions. Inclusion of spatial autocorrelation overwhelmed other explanatory variables, highlighting the greater likelihood of spread from known source locations. Proximity to a road was an important predictor for D. pulicaria, and when tested separately both invasive Daphnia occurred significantly more often in lakes within 200 m of a road. Critically, D. galeata’s realised niche completely envelopes D. thomsoni’s, which could force the native species to become extinct through competitive exclusion. These results suggest that the spread of D. pulicaria and D. galeata to lakes where they do not yet occur is unlikely to be prevented unless public access to these waterways is denied or strictly controlled.

Intraspecific variation in functional traits between native and introduced plant species may underlie resilience and invasiveness of introduced species. We explored if observed phenotypic variation of Iris pseudacorus L. between populations in the native vs. introduced ranges results from genetic differentiation and/or phenotypic plasticity. Seeds were collected from populations along estuarine stress gradients within populations in both Guadalquivir Estuary (Andalusia, Spain) and San Francisco Bay-Delta Estuary (California, USA). Genetic analysis was performed on leaf tissue from plants in each seed donor population. Germinants (n = 48: 6 plants × 4 populations × 2 ranges) were grown for 12 months in a common garden experiment (CGE). We then evaluated 25 traits including growth, biomass allocation, morphological and biochemical responses. Geographic range explained relative intraspecific trait variation segregating native from introduced phenotypes. Native plants had lower specific leaf area (− 34%) and carbohydrate concentrations in rhizomes (− 63%) than introduced plants, providing evidence of genetic differentiation. Higher genetic diversity and 27% higher phenotypic variation (CGE) of native vs. introduced plants indicated longer-term adaptive processes in the native range. Genetic distance of introduced populations (field) increased along with their phenotypic distance (CGE), suggesting rapid genetic differentiation. Phenotypic plasticity also explained some observed inter-range differences under field conditions not expressed by plants in the CGE. Management of the introduced I. pseudacorus populations should be established urgently since they represent novel genotypes with key functional traits that can support invasiveness through increased competitive ability and physiological stress tolerances to sea level rise.

Humans and wildlife experience complex interactions in urban ecosystems, favoring the presence of commensal species, among which invasive species are particularly successful. Rodents are the main vertebrate group introduced to oceanic islands, where the invasion process and dispersal patterns strongly influence their evolutionary and genetic patterns. We evaluated the house mouse Mus musculus and the black rat Rattus rattus on Cozumel Island, Mexico. We assessed genetic diversity and structure, connectivity, gene flow, relatedness and bottleneck signals based on microsatellite loci. Our genetic findings suggest that introduction of individuals of different geographic sources to the island promotes high allelic diversity and the effective establishment of migrants. We identified a clear genetic structure and low connectivity for the two species, tightly linked with anthropogenic and urban features. Notably, we found that the genetic structure of the house mouse sampled within the city of San Miguel Cozumel is associated with the historical human population growth pulses accompanying the urbanization of the city. At the fine-scale genetic level, the main urban drivers of connectivity of the house mouse were both the impervious land surfaces, i.e. the urban landscape, and the informal commerce across the city (a proxy of resources availability). Chances of a secondary invasion to natural environments have been relatively low, which is crucial for the endemic taxa of the island. Nonetheless, improving urban planning to regulate future expansions of San Miguel Cozumel is of the outmost importance to prevent these invasive species to disperse further.

Conservation translocations are widely used to recover threatened species, but can pose risks to recipient ecosystems, particularly in the case of conservation introductions. Because of limited data and uncertainty, risk assessments for such projects often rely on extrapolated evidence and expert opinion, further complicating decision making. The Environmental Impact Classification for Alien Taxa (EICAT) serves to classify the realised impacts of invasive species. We developed a protocol combining EICAT and formal expert elicitation to predict these impacts. We applied our protocol to the extinct-in-the-wild sihek (Guam kingfisher; Todiramphus cinnamominus), for which introduction outside the known historical range is being considered. We elicited from multiple experts probability estimates of impact levels across four impact mechanisms and five candidate release sites. We aggregated estimates using simulation-based and Bayesian approaches, with and without accounting for expert confidence. Experts generally agreed that sihek introduction might impact the recipient ecosystem through predation, competition, and disease, although they disagreed about the likely impact levels. Releases to Palmyra Atoll were considered to pose the lowest risk across candidate sites, so this site was selected for further detailed ecological assessments and risk mitigation efforts. EICAT, with its standardized impact mechanisms and definitions, helped reduce the linguistic uncertainty and subjectivity common to expert-based assessments. Expressing judgments as probabilities allowed us to evaluate uncertainty transparently and to assess the weight of expert confidence on the overall risk estimation. Formal quantitative elicitation and aggregation then allowed a transparent evaluation of results, facilitating communication with stakeholders and decision-makers.

An unidentified ant species was discovered in the heart of New York City in 2011, which garnered national headlines and created the memorable nickname “ManhattAnt.” New York City is one of the oldest and largest cities in North America and has been the site of introduction for some of North America’s most damaging invasive pests. Nevertheless, there has been little follow up research on the ManhattAnt since its discovery, and it has yet to be formally identified. Here we use genetic and morphological approaches to confirm the identity of the ManhattAnt and characterize its introduced range and colony structure. Results from genetic analyses placed the ManhattAnt within the Lasius emarginatus species complex, and morphological comparisons ruled out closely related species to identify the ManhattAnt as the European ant L. emarginatus with 93–99% certainty depending on the nest sample. Since its initial discovery in the region, the ManhattAnt has become one of the most common ants in New York City and has spread at a rate of 2 km/yr into New Jersey and onto Long Island. Based on the climate it inhabits within its native range, L. emarginatus could expand to cover much of the eastern United states from Massachusetts to Georgia. Although many successful invasive ants display supercoloniality with little aggression between neighboring nests, we found no evidence that L. emarginatus colonies in New York City are supercolonial. Continued monitoring of L. emarginatus is warranted, as it has been increasingly reported as an indoor pest and is known to form mutualisms with honeydew producing pests of street trees.

The Gila topminnow (Poeciliopsis occidentalis) has undergone population recovery actions since being extirpated from much of its historical range in the United States of America (USA) prior to the 1970s. However, it returned to the Santa Cruz River in 2015 independently of these actions, which prompted concerns that a non-native Poeciliopsis lineage had been introduced from Mexico. Some Gila topminnow populations in Mexico are sympatric with P. monacha-occidentalis, which is an exclusively female taxon that originated from historical hybridization between P. occidentalis and headwater livebearer (P. monacha). This hybrid taxon reproduces through hybridogenesis, which is a unique mode of sexual reproduction in which half of one parent’s genome is inherited without recombination. This unique property was leveraged to identify hybridogens among 868 individuals from Arizona, USA using common genetic markers (i.e., nuclear microsatellite and mitochondrial sequence data). We described methods for P. monacha-occidentalis identification and conducted population genetic analysis of Santa Cruz River P. occidentalis populations to infer their possible origins. We concluded that human-mediated introduction was the most probable explanation for the current Santa Cruz River P. occidentalis and P. monacha-occidentalis presence. Contemporary diversity may be explained by four introduction events. Population ancestry estimates indicate that P. monacha-occidentalis may have hybridized with two P. occidentalis lineages in the Santa Cruz River. Variable prevalence of P. monacha-occidentalis was noted in two river sections, but the conservation implications of this hybridization are unclear. Public education, targeted removal of P. monacha-occidentalis, and genetic monitoring could mitigate future introductions and potential negative impacts.

Common milkweed (Asclepias syriaca L.) is a widespread invasive alien forb in dry sandy habitats of Central Europe. It adversely affects native plant and animal communities, but its ecosystem-level effects, particularly on hydrology, are little known. Since milkweed has an extensive, deep root system and large, broad leaves, we assumed a negative effect on the soil moisture content of the hosting ecosystem. Following the before-after control-impact protocol, we first compared the soil moisture content of the top 120 cm of the soil under seven milkweed stands to that of non-invaded reference sites. We then treated half of the stands by mechanically removing all aboveground milkweed biomass and repeated the comparative soil moisture measurements. We found that milkweed stands had significantly drier soils than reference grasslands during the growing season, but the soil under milkweed stands recharged to the level of the references in autumn and winter. However, the amount of moisture needed for this recharge was lost from deeper percolation to groundwater. Milkweed treatment prevented the depletion of moisture during the growing season, saving 21.6 l m⁻² of water on average. Treatment did not affect non-milkweed plant biomass, thus, moisture patterns could fully be attributed to the milkweed stands. Our results reinforce the importance of milkweed suppression in invaded grasslands, as, besides enabling the recovery of the native grassland ecosystem, it promotes groundwater recharge, which is particularly important in the dry regions of Central Europe, currently facing severe aridification due to climate change and unfavourable land use trends.

Sphagneticola trilobata, originally from the tropical regions of the Americas, has successfully invaded the subtropical regions of southern China and displays a tendency to spread towards colder northern regions. The accumulation of anthocyanins in stems under low temperature conditions exhibits strong cold tolerance, and therefore may be one mechanism supporting the northward spread of the species. However, the role and synthesis mechanism of anthocyanins in the stems of S. trilobata when confronted with low temperature stress are still unclear. Field experiments have shown that compared to in summer, the stems of S. trilobata significantly accumulated anthocyanins to cope with winter. Further short-term low-temperature treatments (0 °C) were conducted on red and green stems of S. trilobata, and the results showed that the red stems exhibited lower levels of reactive oxygen species, membrane damage, and chlorophyll fluorescence changes compared to the green stems. In an indoor low-temperature control experiment, it was observed that S. trilobata exhibited significant accumulation of callus in the periderm of its stems compared to S. calendulacea, which subsequently resulted in increased levels of sucrose, glucose, and fructose contents. Furthermore, there was a significantly induced higher levels of abscisic acid and cytokinin in S. trilobata stems under low temperatures. Under the joint regulation of these carbohydrates and hormones, the key structural genes associated with anthocyanins synthesis pathway in S. trilobata stems were more strongly induced compared to S. calendulacea. The upregulation of CHS, CHI, F3H, and DFR gene expression levels in S. trilobata was higher than that of native species, which directly leads to the accumulation of more anthocyanins in the epidermis of the stem of S. trilobata, thereby reducing the degree of oxidative stress and maintaining normal growth under low temperature. In summary, anthocyanins play an important light filtering role in the response of S. trilobatas stem to low temperature stress, which is one of the important mechanisms for its successful invasion into southern China. In the context of global climate change, we need to increase our vigilance against further invasion of S. trilobata into colder inland regions such as temperate regions. This research holds significant theoretical and practical implications for the prevention and control of S. trilobata invasion.