Biological Invasions最新文献

Although the impacts of single-species invasions on resident communities have been widely studied, the ecological effects of co-invasion (simultaneous invasion by multiple alien species) remain largely unexplored. In this study, using an analytical framework, we investigate the individual and combined effects of two global plant invaders (Leucanthemum vulgare and Lupinus polyphyllus) on the aboveground vegetation (plant richness, diversity and biomass) and belowground soil variables (pH, salinity, electrical conductivity, total dissolved solids, organic carbon [OC], phosphorous, and potassium) of grassland communities in the Himalaya. We studied these ecological variables in comparable plots under the following four scenarios: both invaders absent (i.e. uninvaded), either of the two invaders present (i.e. single species invasion), and both invaders present (i.e., co-invasion). Our results show invasion effects vary with the invasion scenarios and the studied variables. The single species invasion plots had lower mean plant richness and diversity but higher mean soil OC than the uninvaded plots. The co-invasion plots had significantly increased mean plant biomass and soil OC, but had a non-significant effect on plant richness and diversity compared to the uninvaded plots. The overall combined effect of species’ co-invasion was additive in nature, but the effect varied significantly with choice of the response variable. We found synergistic effects of co-invasion on species richness and diversity, antagonistic effects on soil pH, and additive effects on the remaining response variables when compared with the predicted additive effect of the two invaders. Our findings suggest that further spread of L. polyphyllus will impact the resident plant community more severely when co-invading with L. vulgare than when invading alone, thereby lending support to the invasional meltdown hypothesis. Nevertheless, antagonistic and additive impacts for soil pH and other response variables respectively hint towards other alternate mechanisms at play. Overall, our study showcases a proof-of-concept to empirically estimate the additive, antagonistic and synergistic impacts of plant co-invasions, and also provides a model for designing co-invasion studies on other taxa/systems/scales elsewhere. Finally, based on the insights gained from this study, we highlight priority areas of future research in species’ co-invasions.

Ecosystems worldwide are increasingly being invaded by multiple species, and the rate of biological invasion is accelerating, leading to more interactions among invasive species. One such interaction that has received little attention is the phenomenon of ‘serial replacement’ or ‘over-invasion’, where an established invasive species is supplanted by a second invasive species. Understanding this interaction is important as controlling the second species could inadvertently lead to an increase in the abundance of the first species. We used a hierarchical state-space model to analyse changes in annual abundances (commercial catch-per-unit-effort) of three invasive fish species, tench (Tinca tinca), common carp (Cyprinus carpio) and redfin perch (Perca fluviatilis), in the Murray-Darling River system (MDRS), Australia between 1954–2002. Tench were present at low abundances until the mid-1970 s, before declining to the point of no commercial catch post-1989. This rapid decline coincided with a significant increase in carp abundance, suggesting that carp may have driven the tench decline through habitat modification (particularly the destruction of aquatic plants), consistent with findings from European studies that show the disappearance of tench from ponds with intensive carp farming. Redfin perch populations, were inferred to be much less impacted by the invading carp population. While carp were present in the MDRS for the duration of the study, the rapid increase in carp abundance in the early 1970 s coincided with the introduction of a specific genetic lineage—the “Boolarra strain”. Our analysis provides compelling evidence of serial replacement of long-established tench by invading common carp triggered by the introduction of a novel carp strain.

Hakea decurrens subsp. physocarpa is an invasive fire-adapted shrub of Australian origin that is quickly expanding in Portugal with potential impacts on fire behavior and fire regime. In this study we examined the effects of H. decurrens on fire hazard by assessing fire behavior indicators at the landscape scale, using a modeling and simulation approach. Six fuel models for H. decurrens were developed through fuel characterization and experimental fires. The fuel models correspond to combinations of developmental stages of H. decurrens populations (Early, Intermediate and Mature) and management (Standing and Slashed fuels). These combinations were used with three levels of H. decurrens invasion, corresponding to 25%, 50% and 75% of cover of the landscape, applied to five real landscapes in northern Portugal (replicates) under three fuel moisture conditions (Low, Medium and High), used as surrogates of weather severity. Fire behavior simulations were conducted with FlamMap software. The relationships between fire behavior indicators (flame length, rate of spread and burn probability) at the landscape level and the four factors tested were analyzed using Generalized Linear Mixed Models. Standing fuels were found to be more hazardous than slashed fuels. Fire-hazard increased with H. decurrens stand maturity and slash, regardless of moisture conditions. The results of this study indicate that H. decurrens expansion might negatively affect the fire regime in the north of Portugal. Our findings add to other known negative impacts of the species on native ecosystems, calling for the need to reinforce its control.

The invasive shrub, Russian olive (Elaeagnus augustifolia), is widely established within riparian areas across North America and eastern Europe. Limited information on its distribution and invasion dynamics in northern regions has hampered understanding and management efforts. Given this lack of spatial and ecological information we worked with local stakeholders and developed two main objectives: (1) map the distribution of Russian olive along the Powder River (Montana and Wyoming, United States) as of 2020 with field data and remote sensing; and (2) relate that distribution to environmental variables to understand its habitat suitability and community/invasion dynamics. Field data showed Russian olive has reached near equal canopy cover (18.3%) to native Plains cottonwood (Populus deltoides; 19.1%) and has a broader distribution. At the watershed scale, we modeled Russian olive distribution using field surveys, ocular sampling of aerial imagery, and spectral variables from Sentinel-2 MultiSpectral Instrument using a random forest model (RMSE = 15.42, R² = 0.64). A statistical model linking the resulting Russian olive percent cover detection map to environmental variables for the entire watershed indicated Russian olive cover increased with flow accumulation and decreased with elevation, and was associated with poorer soil types. We attribute the success of Russian olive to its broad habitat suitability combined with changing hydrologic conditions favoring it over natives. The maps of Russian olive cover along the Powder River and its main tributaries in northern Wyoming and southern Montana revealed regions of the watershed with high and low cover, which can guide landscape-scale management prioritization. This study provides a repeatable Russian olive detection method due to the use of Sentinel-2 imagery that is available worldwide and provides insight into Russian olive’s ecological relationships and success with relevance for management across areas with similar environmental conditions.

Invasive species’ plasticity and latitudinal spread have become an increasing matter of concern in rapidly changing climate. The brush-clawed shore crab (Hemigrapsus takanoi), native along northwestern Pacific shores, has established dense populations in northern European coasts. Detrimental effects in natura have been reported, such as displacement of native species and competition for shelter, rasing concerns regarding shellfish early life stages and food webs-posing a threat to wild stocks’ recruitment and aquaculture. The species has not yet been observed in southern European countries (e.g., Portugal), where niche habitats such as harbours, mudflats, and lagoons reach higher temperatures than the invaded northern range. The aims of this study were to determine H. takanoi potential to acclimate to a southern thermal range, assess thermal performance, and identify potential competitive advantages over the native shore crab Carcinus maenas. This was accomplished through individual exposure to one of three treatments, resembling a southern European thermal range (17 °C, 21 °C, or 25 °C), for 30 days. H. takanoi thrived in temperatures as high as 25 °C, a realistic thermal scenario in Óbidos Lagoon (the biggest Portuguese lagoon)—while the native shore crab C. maenas underperformed at that treatment, showing lower survival, growth, and feed intake than H. takanoi. These results suggest that H. takanoi may be able to colonise southern and warmer European locations and have higher plasticity than the native species already inhabiting areas close to its upper thermal limits. Under global warming scenarios, inferences of further latitudinal spread and increased invaded range may also be taken to the invaded northern European habitats.

Invasive species are one of the most significant factors affecting biodiversity. American mink (Neovison vison) was introduced to Hokkaido, Japan, and is known to compete with other medium-sized mammals and prey on freshwater fish. Therefore, it is important to understand their distribution and the types of environments they prefer. We developed an N. vison-specific environmental DNA (eDNA) detection assay to estimate their distribution. Applying this assay to water samples from 48 rivers in the Shiretoko Peninsula, the World Natural Heritage site in Hokkaido, N. vison-specific DNA was identified in 10 rivers. Including seven rivers from a previous study on N. vision distribution in the peninsula, the environmental characteristics of the 17 rivers with the potential establishment of N. vison populations were investigated using a generalized linear model. The evaluated environmental factors included eDNA concentrations of two salmonid species (Salvelinus curilus and Oncorhynchus masou, potential food resources for N. vison), the presence of salmon hatchery and release programs, land uses around the rivers, and river structures. While the estimated N. vison distribution did not show a clear association with the eDNA concentrations of the two salmonid species, it showed positive and significant associations with the salmon release programs (p = 0.031) and with the proportion of farmland (p = 0.034). These findings imply that human activities have the potential not only to cause the introduction of invasive species but also unintentionally to contribute to the establishment of such species in new environments.

Two tilapia species, Oreochromis aureus and Oreochromis niloticus, were introduced into Morocco in 2004 for fish farming. O. niloticus was subsequently introduced into the wild in several watersheds. During a fish survey at six locations, we observed other specimens of tilapia that appear to be more related to O. aureus. Partial sequences of COI and S7 genes and geometric morphometrics were used to assess the specific status of all the specimens. Out of 1691 specimens sampled, 159 COI and 153 S7 partial sequences were obtained and confirmed the presence of both species. O. aureus was present in part of Rabat-Salé-Kenitra region (the Nador Channel (NC), Al Kansra dam (AK) and Oued Sebou (OS)) while O. niloticus was found in the fish farm (AS), in the province of Rabat (Sidi Mohamed Ben Abdellah dam (BA)) and the region of Casablanca-Settat (Al Massira dam (AM)). A few hybrids were identified at AS and OS. Body shapes and sizes were assessed using geometric morphometrics with 18 landmarks and were found to differ significantly between O. aureus and O. niloticus. Both species exhibited significantly different allometric changes during their growth, but kept their morphological signature independently of their specific allometric changes during growth. Specimens from riverine environments (OS, NC) had a similar shape with an elongated body with a large head and eye, while individuals found in lacustrine environments (AK, AM and BM) had a larger body depth, small head and eye. Morphometrics also suggested that hybrids or sympatry could occur to a small extent in AS, OS and NC.

Recent collection efforts along the Brazilian coast revealed a Haliclona species preliminarily identified as a likely new species. However, sequencing of the 28S rRNA C-Region, a barcode marker in sponges, showed its high genetic similarity with a Haliclona sp. from Hawaiʻi (GenBank MW016137–MW016139). We applied an integrated morphological and molecular assessment, which allowed us to identify both Brazilian and Hawaiian specimens as H. (Reniera) laubenfelsi, a species with an Indo-Pacific distribution. We postulate this species to be exotic both in the Brazilian coast and in Hawaiʻi. Our evidence is based on the arrival of the species in Brazil after 2001, being first registered next to an international port. In turn, the species is distributed discontinuously in Hawaiʻi, being mainly restricted to sheltered bays and vicinities of ports, showing a predilection for anthropogenic substrates, which strengthen the hypothesis of its exotic origin. Recent collections in Hawaiʻi (2016–2018) failed to find this species in natural habitats, though it was an abundant pioneer species in Autonomous Reef Monitoring Structures. Its capacity to colonize artificial substrata may indicate either a cryptobenthic nature or an invasive potential. We highlight the need of monitoring its abundance, spatial distribution, and biotic interactions along the Brazilian coast to assess its potential environmental impacts. The full morphological description, and the molecular sequences we provided certainly will speed up the identification of this species, allowing to track its range extension.

Cities are increasingly recognised as important sites for biodiversity and essential for improving human-nature connections. However, urban areas are also hotspots for rats, which negatively impact biodiversity due to competition and depredation. Urban residents may undertake rat control on their properties, but the effectiveness of such volunteer initiatives for broader biodiversity outcomes has not been tested in urban environments. We conducted a comprehensive study inclusive of rat abundance, adult bird diversity, and bird breeding success. We monitored rat (Norway rat Rattus norvegicus; ship rat Rattus rattus) presence and modelled detection probabilities and occupancy in suburban residential backyards in Auckland, New Zealand. We also compared bird abundance and richness among backyards and recorded 140 nesting attempts from 15 bird species between September 2021 and February 2022. Despite rat control, rats were detected at some point in all backyards, though relative abundance was low, and fewer rats were detected in backyards with more frequent rat control. Higher bird abundance, and to a lesser extent richness, were associated with proximity to native vegetation patches and more frequent rat control. Overall fledging success was relatively high and predation by rats was relatively low compared to previous research. Nest survival was slightly higher for introduced bird species. Daily nest survival rate increased with nest height, proximity to native vegetation patches, and when rat detection rates decreased. Although the effect was small, frequent rat control within a backyard was associated with increased fledging success and increased bird species richness and abundance. Further research is required to explore the factors that interact with backyard rat control to improve local outcomes for birds. High levels of community participation in backyard rat control are required to improve neighbourhood-wide outcomes for birds.

Silver Carp (Hypophthalmichthys molitrix) populations have established and expanded throughout the lower Mississippi River basin (LMRB). Information pertaining to Silver Carp population mixing among rivers within the LMRB is lacking. Documented relations between Silver Carp otolith and river water barium (Ba) and strontium (Sr) microchemical signatures may enable estimation of origins of Silver Carp in the LMRB. Replicate water samples and otoliths from 308 Silver Carp were collected from the Cache, Arkansas, White, Yazoo, St. Francis, L’Anguille, and Mississippi rivers, and Merrisach Lake (situated along a canal connecting the lower reaches of the Arkansas and White rivers) within the LMRB. Water and carp otolith microchemical signatures exhibited consistent differences among water bodies. A classification and regression tree model exhibited 80% accuracy when assigning carp collected from the White, Arkansas, and Mississippi rivers based on fish-water microchemical signatures. Model accuracy decreased as smaller rivers were incorporated into models. Predicted natal origin based on otolith microchemical signatures suggested the White River (43%) and the lower Mississippi River (39%) were the likely origins for ~ 82% of the Silver Carp sampled. Despite the prevalence of adult Silver Carp within the Arkansas River system, fewer (18%) appeared to have originated there compared to the White and Mississippi rivers. Long-term water sampling and additional isotopic measurements may refine analyses to better determine the relative contributions of Silver Carp from the smaller river systems. Population mixing of Silver Carp among tributary rivers appears to be common within the LMRB, and removal efforts may benefit from evaluating the magnitude of fish movement and connectivity among rivers.