Biological Invasions最新文献

Invasive species can have complex direct and indirect impacts on ecosystems. The impacts of invasive prey species on native prey can be difficult to observe if the latter migrate seasonally, and when the interaction is indirect. We hypothesize that invasive lagomorphs and snow dynamics indirectly drive predation risk for guanaco by puma. We employed camera-trapping data collected over multiple years and seasons in an altitudinal gradient in the Andes of Central Chile. We predicted a high spatial and temporal association between puma and lagomorph detections, given these prey species comprise most of puma diet in the area. We also expected a higher spatiotemporal association between guanaco and puma detections towards higher snow cover in the study area, because of downward altitudinal migration of the ungulate. We obtained 4863 mammalian detections. Our data shows that the detection of puma was positively associated with hare capture rate year-round. In addition, puma detection was positively associated with the interaction of snow cover and guanaco capture rate. Puma temporal activity strongly overlapped with hare, whereas puma apparently increased diurnal activity with an increase in guanaco capture rate. Predation risk for guanaco increased when snow cover was higher and decreased when guanaco migrated to higher altitudes during dryer months. We conclude it is of conservation concern that lagomorphs may be subsidizing pumas and modifying patterns of consumptive and non-consumptive effects of the predator on native prey populations.

Estimates of the cost of damage caused by invasive alien speices and the money spent addressing biological invasions are needed to guide policy and management. Here, we quantify the known monetary costs of biological invasions to South Africa, using data from the InvaCost database, literature searches, and stakeholders. The Department of Forestry, Fisheries and the Environment, and agencies directly funded by them, provided most of the information on money spent, with very little information was available from other government agencies and the private sector. There was also very little information on the monetary costs due to the impacts of invasions. Between 1960 and 2023, ZAR9.6 billion (adjusted to 2022 values) was spent managing biological invasions in South Africa. This is only 4% of the money predicted as being necessary for management, which amounted to ZAR231.8 billion in 2022 values. There is uncertainty in the obtained estimates due to a paucity of information on both impacts and management costs. A few key points emerged from our analysis: the cost of damage caused by invasions far exceeds expenditure on control; the amount spent on control is much less than what is predicted to be needed; almost all management has focussed on a few invasive plant species; and there are large gaps in information that reduce the confidence in our estimates. Transparent cost reporting, strategic public–private collaborations, standardised impact metrics, and reliable assessments of management effectiveness are needed to enable South Africa to more effectively account for and prioritise investments.

The aquarium pet trade is one of the leading pathways for the introduction of invasive species into natural ecosystems. In 2018, we surveyed pet shops across South Africa to obtain a checklist of ornamental fish species in the aquarium pet shop trade and to assess their invasion potential using sourced data (e.g., natural environment, native range, introduction status, impact status and climatic zone). We evaluated selected common aquarium fish species with high invasion potential according to previous invasion history. We highlighted the need for the development of a management strategy for the aquarium pet trade in South Africa. We identified 312 fish species belonging to 77 families and 182 genera. Most pet shops were in Gauteng Province (n = 38), with few in Limpopo Province (n = 3). Gauteng had the highest number of fish species (n = 271), while North West Province had the lowest number (n = 95). Pet shops were dominated by freshwater species (68%), followed by marine species (22%), while the origin of 30 species (10%) was transitional aquatic ecosystems. Most freshwater taxa were native to South America and Asia, while most marine species were from the Pacific and Indo-Pacific Oceans. Most (88%) species were tropical, 10% subtropical, and 1% temperate. Several (n = 28) species had more than 50% frequency of occurrence, representing the most popular ornamental fishes. Several (n = 13) species are invasive in South Africa and other parts of the world. The system of importation of ornamental fish in South Africa is not clear. Although there is a recommendation that these importations must be regulated according to the whitelist and blacklist in South Africa, it is not clear how this is implemented in practice. We demonstrated a high risk of alien fish species introduction in South Africa through the aquarium pet shop trade.

Conflicting hypotheses regarding the factors underlying the invasibility of plant species persist, as portrayed by Darwin’s naturalization conundrum. This is particularly critical in arid and semiarid ecosystems, for which understanding remains elusive. We test how similarities between exotic and native plants in the Brazilian semiarid Caatinga affect the invasion stage and distribution of invasive species. We estimate diversity fields for exotic species, representing the composition of native species that co-occur with each exotic species and calculated phylogenetic metrics of the distance of focal species to its field. We also assess whether changes in stage from exotic to naturalized and from naturalized to invasive are influenced by phylogenetic relatedness and functional traits. We also test whether the observed phylogenetic distance values of the invasive species differ from those expected by chance. Finally, we analyze whether there are functional similarities between the stages of exotic species and native plants. Plants that are phylogenetically closer to the more frequent native species of the Caatinga are more likely to become naturalized and invasive. Among invasive species with a significant pattern of phylogenetic relatedness, those that are closer to native species are more prevalent. Naturalized and invasive plants are shorter and have smaller leaves and seeds than native plants. The observed functional differences suggest that naturalized and invasive species adopt strategies similar to those of competitive native plants, such as seed bank formation and dense populations.

Mitigating exotic species invasions requires reliable information on abundance and source-sink dynamics to evaluate effectiveness of control efforts. Despite being present in the southeastern United States for centuries, wild pigs (Sus scrofa) continue to invade new areas, including the Sam D. Hamilton Noxubee National Wildlife Refuge (NNWR) in Mississippi, a forested landscape with an emerging wild pig population. Considering the early stage of invasion, we designed and implemented a non-invasive hair sampling technique to estimate abundance and relatedness of wild pigs within the NNWR. Following 8-week sampling periods in 2021 (n = 160 samples) and 2022 (n = 159 samples), we identified 38 and 26 unique individuals, respectively, although recapture rates were too low to yield precise abundance estimates. We also identified low heterozygosity indicating high relatedness among our population which likely reflected lack of barrier features to gene flow and/or a limited number of external source populations. Finally, we observed positive trends in viable samples collected relative to sampling week, suggesting more optimal sampling period(s) may exist (e.g., autumn). We also acknowledge that use of grain in more accessible areas rather than our remote approach using scent-only attractants may increase hair snare attractiveness and wild pig encounters, while permitting increased sampling frequency. Collectively, these modifications (i.e., altered season, bait type, and access) provide viable pathways to increase precision for abundance estimates. When used concomitantly with ongoing monitoring and control efforts, non-invasive hair sampling will contribute to a more holistic understanding of this exotic species and better inform management actions.

Seed predation by rodents can act as a recruitment barrier during community assembly, limiting the establishment of exotic species. Predation rates of exotic seeds may depend on their attractiveness, determined by their traits, and how different they are from natives. Additionally, at the naturalization stage of the invasion process, exotic seeds may escape post-dispersal predation because they are rare in the community. To test these ideas, we assessed granivory in a Patagonian forest, where two species with contrasting seed sizes are naturalized. Rubus idaeus seeds are of similar size of natives, whereas Prunus cerasus seeds are four times larger. The relative abundance of their seeds within the landscape is low compared to native seeds. Throughout the fruiting season, we offered seeds from all species present in the community (native and exotics), whenever they were available in the landscape. To consider the effects of vegetation structure on rodent foraging behavior, we offered seeds in areas with and without understory cover. We found a hump-shaped relationship between predation rates and seed size. Consequently, rodents strongly avoided large exotic Prunus seeds, but removed Rubus seeds at similar rates to natives. Contrary to our expectations, seed abundance did not affect predation, and hence, rarity did not confer an advantage to exotic seeds. The presence of shrub cover increased 2.3 times the removal rates compared to open areas. We suggest that the dissimilarity in seed size compared to native species and the presence of shrub cover influenced predation pressure on exotic species within our community.

Oregon ash (Fraxinus latifolia Benth.) wetlands and riparian forests are an important economic, cultural, and ecological resource in the Pacific Northwest, USA, and are threatened by the invasive insect, emerald ash borer (Agrilus planipennis Fairmmaire) (EAB). Following the discovery of EAB in Forest Grove, Oregon in June of 2022, it is predicted that EAB-induced ash mortality will alter vegetation communities and modify hydrology of wetlands and streams in the Pacific Northwest. Of primary concern is an increase in solar loading of already degraded waterways and wetlands that support Endangered Species Act-listed salmonids and other cold-water species following canopy dieback of Oregon ash. Our study, which began before the first detection of EAB on the West Coast, models potential impacts of EAB-mediated Oregon ash canopy loss to temperature-related water quality on two waterways in the vicinity of Portland, Oregon. Our results indicate a significant increase in solar loading with likely negative impacts to Endangered Species Act-listed salmonids, other aquatic wildlife, and associated habitat. We forecast greater impacts to these resources outside our study scope and include considerations for entities with water quality-related regulatory obligations.

Invasive plants along transportation corridors can significantly threaten ecosystems and biodiversity if they spread beyond anthropogenic environments. Rapid evolution may increase the ability of invading plant populations to establish in resident plant communities over time, posing a challenge to invasion risk assessment. We tested for adaptive differentiation in Dittrichia graveolens (stinkwort), an invasive species of ruderal habitat in California that is increasingly spreading away from roadsides into more established vegetation. We collected seeds from eight pairs of vegetated sites and their nearest (presumed progenitor) roadside population. We assessed differentiation between populations in roadside and vegetated habitat for germination behavior and for response to competition in a greenhouse experiment. We also tested for increased performance in vegetated habitat with a grassland field experiment including a neighbor removal treatment. Germination rates were slightly reduced in seeds from vegetated sites, which may indicate lower seed viability. Otherwise, plants did not show consistent differences between the two habitat types. Competition strongly reduced performance of D. graveolens in both the greenhouse and in the field, but plants originating from vegetated sites did not show enhanced competitive ability. Our findings show no evidence of adaptive differentiation between D. graveolens populations from roadside and vegetated habitats to date, suggesting that invasiveness in grasslands has not been enhanced by rapid evolution in the 40 + years since this species was introduced to California. Evolutionary constraints or potentially high levels of gene flow at this small scale may limit adaptation to novel habitats along roadsides.

Forests provide crucial ecosystem services and are increasingly threatened by invasive plant species. The spread of these invasive species has affected biodiversity and has become a trending topic due to its impact on both endemic species and biodiversity. Therefore, it is imperative to implement conservation measures to protect native species such as mapping and monitoring invasive plant species in the forest realm. Mapping understory herb invasive plant species within forest categories is challenging, for example species such as Ageratum conyzoides and Cassia tora do not occur in distinct clusters, making them difficult to distinguish from the surrounding forest. In this paper, phenology plays a vital role for analysing the separability of both inter and intra-species discrimination to examine temporal curves for different vegetation indices that affect plant growth during the green and senescence periods. Machine learning algorithms, including regression tree-based algorithms, decision tree-based algorithms, and probabilistic algorithms, were used to determine the most effective algorithm for pixel-based classification. Support Vector Machine (SVM) classifier was the most effective method, with an overall accuracy of this classifier was calculated as 90.28% and a kappa of 0.88. The findings indicate that machine learning algorithms remain effective for pixel-based classification of understory invasive plant species from forest class. Thus, this study shows a technical method to distinguish invasive plant species from forest class which can help forest managers to locate invasion sites to eradicate them and conserve native biodiversity.

Non-native deer are becoming increasingly common in peri-urban landscapes, where they pose a risk to the health and wellbeing of people. Professional vehicle-based shooting is commonly used to control deer populations in these complex landscapes, but the effectiveness and cost of this method have seldom been evaluated. We analyzed the effectiveness and cost of using professional vehicle-based shooting to reduce the abundance and impacts of non-native rusa deer (Cervus timorensis) in a peri-urban landscape in Wollongong, eastern Australia, during 2011–2021. We incorporated the results from an independent monitoring program into a Bayesian joint-likelihood framework to model spatio-temporal changes in rusa deer abundance. Finally, we used our findings to assess the effect of the management program on the number of complaints from the residents. After eleven years and the removal of 4701 rusa deer from Wollongong LGA (712 km²), deer abundance did not change in 74.7% of the area, decreased in 19.4% of the area (mostly in and around the sites where the professional shooting occurred), and increased in 5.9% of the area. Shooting was most cost-effective during winter when the longer hours of darkness meant that shooters could visit more sites. In contrast to deer abundance, the probability of residents complaining about deer increased in space and time. Our study shows that professional vehicle-based shooting can locally reduce the abundance of invasive deer in a peri-urban landscape, providing that sufficient control effort is expended. We suggest that shooting effort is currently too thinly spread across this peri-urban landscape, and that concentrating shooting effort on the areas of greatest deer abundance and resident complaints might be a more cost-effective strategy for managing invasive deer in peri-urban landscapes.