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opencc-zeroSep 2020View details →

Data from: Exotic species drive patterns of plant species diversity in 93 restored tallgrass prairies

<p>A primary goal of restoration ecology is to understand the factors that generate variability in species diversity and composition among restorations. Plant communities may assemble deterministically towards a common community type, or they may assemble stochastically, ending differently because of weather conditions during establishment, soil legacy effects, or exotic species propagule pressure. To test these alternative hypotheses, we sampled plant communities and soil at 93 randomly selected restored prairies distributed throughout Iowa, USA. Five remnant sites were sampled as a reference. We tested our hypotheses using multiple regressions and investigated the strength of direct and indirect effects on species diversity and richness using structural equation models. The prairie restorations were highly variable in their age, size, diversity, soil characteristics, and how they were managed post-seeding. The strongest predictor of plant species richness and diversity was the degree of invasion, as measured by the abundance of exotic species. Restorations planted with species-rich seed mixes had reduced exotic species abundance, which led indirectly to higher species richness of restorations. Sites with higher organic matter and a more linear shape had a direct positive effect on exotic abundance, which in turn decreased diversity. We found little support for deterministic assembly, and diversity did not increase with the age of planting. Our results indicate that restored prairie communities tend to assemble into states of high or low diversity, driven by invasion from exotic plant species. Management of exotic species is essential for maximizing species diversity in temperate grassland restorations.</p>

opencc-zeroDec 2013View details →

Data from: Shrubs as ecosystem engineers across an environmental gradient: effects on species richness and exotic plant invasion

Ecosystem-engineering plants modify the physical environment and can increase species diversity and exotic species invasion. At the individual level, the effects of ecosystem engineers on other plants often become more positive in stressful environments. In this study, we investigated whether the community-level effects of ecosystem engineers also become stronger in more stressful environments. Using comparative and experimental approaches, we assessed the ability of a native shrub (Ericameria ericoides) to act as an ecosystem engineer across a stress gradient in a coastal dune in northern California, USA. We found increased coarse organic matter and lower wind speeds within shrub patches. Growth of a dominant invasive grass (Bromus diandrus) was facilitated both by aboveground shrub biomass and by growing in soil taken from shrub patches. Experimental removal of shrubs negatively affected species most associated with shrubs and positively affected species most often found outside of shrubs. Counter to the stress-gradient hypothesis, the effects of shrubs on the physical environment and individual plant growth did not increase across the established stress gradient at this site. At the community level, shrub patches increased beta diversity, and contained greater rarified richness and exotic plant cover than shrub-free patches. Shrub effects on rarified richness increased with environmental stress, but effects on exotic cover and beta diversity did not. Our study provides evidence for the community-level effects of shrubs as ecosystem engineers in this system, but shows that these effects do not necessarily become stronger in more stressful environments.

opencc-zeroDec 2018View details →

Data from: Correlation of native and exotic species richness: a global meta-analysis finds no invasion paradox across scales

Support for the "biotic resistance hypothesis," that species-rich communities are more successful at resisting invasion by exotic species than are species-poor communities, has long been debated. It has been argued that native-exotic richness relationships (NERR) are negative at small spatial scales and positive at large scales, but evidence for the role of spatial scale on NERR has been contradictory. However, no formal quantitative synthesis has previously examined whether NERR is scale-dependent across multiple studies, and previous studies on NERR have not distinguished spatial grain and extent, which may drive very different ecological processes. We used a global systematic review and hierarchical mixed-effects meta-analysis to provide a comprehensive quantitative assessment of the patterns of NERR over a range of spatial grain sizes and spatial extents, based on 204 individual cases of observational (non-experimental) NERRs from 101 publications. We show that NERR was indeed highly scale-dependent across studies and increased with the log of grain size. However, mean NERR was not negative at any grain size, although there was high heterogeneity at small grain sizes. We found no clear patterns of NERR across different spatial extents, suggesting that extent plays a less important role in determining NERR than does grain, although there was a complex interaction between extent and grain size. Almost all studies on NERR were conducted in North America, western Europe, and a few other regions, with little information on tropical or Arctic regions. We did find that NERR increased northward in temperate regions and also varied with longitude. We discuss possible explanations for the patterns we found, and caution that our results do not show that invasive species are benign or have no negative consequences for biodiversity preservation. This study represents the first global quantitative analysis of scale-based NERR and casts doubt on the existence of an "invasion paradox" of negative NERR at small scales and positive correlations at large scales in non-experimental studies.

opencc-zeroDec 2014View details →

Data from: A basin-scale application of environmental DNA assessment for rare endemic species and closely related exotic species in rivers: a case study of giant salamanders in Japan

1. To prevent the invasion of exotic species causing a decline in an endangered endemic species, it is important to determine the distribution of both species at an early stage, when the density of the exotic species is still low, and to manage the invasion immediately. However, distinguishing between closely related species is difficult because they share similar characteristics. 2. The identification of DNA fragments sampled from a body of water (environmental DNA) has become a popular technique for rapidly determining the distribution of a target species. In this study, we analysed environmental DNA in water samples from 37 sites across the Katsura River basin in Japan. We used TaqMan real-time PCR to distinguish the Japanese giant salamander Andrias japonicus from the closely related Chinese giant salamander Andrias davidianus, which is known to invade Japanese rivers and hybridize with the Japanese species. 3. In environmental samples, we detected mtDNA of the endemic species at 25 sites and mtDNA of the exotic species at nine sites. The DNA detection sites were concentrated in the upstream region. The exotic species DNA was found beyond the limits of an earlier capturing survey. 4. Synthesis and applications. Using environmental DNA to monitor the two salamander species requires less time and effort than traditional surveys, so a wide-ranging survey can be conducted rapidly. Our results showed that performing three environmental DNA surveys for each site between autumn and winter is desirable for giant salamanders. Further collection of environmental DNA, in combination with conventional population surveys, will provide valuable information that can help protect rare endemic species in a variety of aquatic ecosystems and can help monitor the invasion of exotic species.

opencc-zeroDec 2019View details →

Does urbanization favor exotic bee species? Implications for the conservation of native bees in cities

A growing body of research indicates that cities can support diverse bee communities. However, urbanization may disproportionately benefit exotic bees, potentially to the detriment of native species. We examined the influence of urbanization on exotic and native bees using two datasets from Michigan, USA. We found that urbanization positively influenced exotic – but not native – bee abundance and richness, and that this association could not be explained by proximity to international ports of entry, prevalence of exotic flora, or urban warming. We found a negative relationship between native and exotic bee abundance at sites with high total bee abundance, suggesting that exotic bees may negatively affect native bee populations. These effects were not driven by the numerically dominant exotic honeybee, but rather by other exotic bees. Our findings complicate the emerging paradigm of cities as key sites for pollinator conservation.

opencc-zeroDec 2018View details →

Data from: Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats

Exotic species are a major threat to biodiversity and have modified native communities worldwide. Invasion processes have been extensively studied, but studies on species richness and beta diversity patterns of exotic and native species are rare. We investigate such patterns among exotic and native fish communities in upland and lowland rivers to explore their relationship with environmental drivers. Location: Northern Italy. Exotic and native fish beta diversity patterns were investigated separately in lowland and upland sites using Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD) analyses. To examine the main environmental variables affecting the LCBD, a Boosted Regression Trees (BRT) method was used. Community dispersion among and within stream orders was investigated with the PERMDISP test. In lowland sites, exotic species richness was higher than native species richness, especially in large rivers and drainage canals. An opposite trend was found in upland sites, where native species richness was higher than exotic species richness, especially in large rivers. No clear LCBD patterns were found along stream orders in the lowland, whereas higher stream orders in the upland showed the highest LCBD. Its patterns in upland and lowland sites were related with a number of factors, such as total suspended solids and total phosphorus. Community dispersion among stream orders did not show a relationship with environmental heterogeneity. SCBD values were positively correlated with species occupancy in the study area and native species showed higher SCBD values than exotic species only in the uplands. Main conclusions: Large rivers in the uplands are important in maintaining native fish diversity and should be protected against invasive fish. In contrast, most lowland rivers have suffered from biological homogenization. Some rare native species can show low contribution to beta diversity, but still need conservation actions due to their risk of local extinction.

opencc-zeroDec 2013View details →

Data from: Rapid genetic adaptation precedes the spread of an exotic plant species

Human activities have increasingly introduced plant species far outside their native ranges under environmental conditions that can strongly differ from those originally met. Therefore, before spreading, and potentially causing ecological and economical damage, non native species may rapidly evolve. Evidence of genetically based adaptation during the process of becoming invasive is very scant however, which is due to the lack of knowledge regarding the historical genetic makeup of the introduced populations and the lack of genomic resource. Capitalizing on the availability of old non-native herbarium specimens, we examined frequency shifts in genic SNPs of the Pyrenean Rocket (Sisymbrium austriacum subsp. chrysanthum), comparing the (i) native, (ii) currently spreading non-native, and (iii) historically introduced gene pool. Results show strong divergence in flowering time genes during the establishment phase, indicating that rapid genetic adaptation preceded the spread of this species and possibly assisted in overcoming environmental constraints.

FIGURE 2 in Phloeocharis subtilissima Mannerheim (Staphylinidae: Phloeo charinae) and Cephennium gallicum Ganglbauer (Scydmaenidae) new to North America: a case study in the introduction of exotic Coleoptera to the port of Halifax, with new records of other species

FIGURE 2: Phloeocharis subtilissima Mannerheim, Point Pleasant Park, Halifax, Nova Scotia, Canada. Living specimen in bark of red maple (Acer rubrum).

FIGURE 4 in Phloeocharis subtilissima Mannerheim (Staphylinidae: Phloeo charinae) and Cephennium gallicum Ganglbauer (Scydmaenidae) new to North America: a case study in the introduction of exotic Coleoptera to the port of Halifax, with new records of other species

FIGURE 4: Cephennium gallicum Ganglbauer, Point Pleasant Park, Halifax, Nova Scotia, Canada. Lateral habitus.

FIGURE 1 in Phloeocharis subtilissima Mannerheim (Staphylinidae: Phloeo charinae) and Cephennium gallicum Ganglbauer (Scydmaenidae) new to North America: a case study in the introduction of exotic Coleoptera to the port of Halifax, with new records of other species

FIGURE 1: Phloeocharis subtilissima Mannerheim, Point Pleasant Park, Halifax, Nova Scotia, Canada. Dorsal habitus.

FIGURE 3 in Phloeocharis subtilissima Mannerheim (Staphylinidae: Phloeo charinae) and Cephennium gallicum Ganglbauer (Scydmaenidae) new to North America: a case study in the introduction of exotic Coleoptera to the port of Halifax, with new records of other species

FIGURE 3: Cephennium gallicum Ganglbauer, Point Pleasant Park, Halifax, Nova Scotia, Canada. Dorsal habitus.

FIGURE 34 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 34. Tetranychus yusti McGregor, female. (a) Tarsus I; (b) Tarsi I, dorsal and ventral view, dashed line indicates level

FIGURE 30 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 30. Tetranychus schoenei McGregor, female. (a) Pretarsus IV, from specimen on type slide; (b) Hourglass-shaped pattern of dorsal striae between setae e and f; (c) Pregenital striae. Male. (d) Pretarsi I and II, from specimens on type slide; (e) Aedeagi from non-type and type specimen.

FIGURE 33 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 33. Tetranychus urticae Koch, female. (a) Pretarsus IV; (b) Tarsi I, dorsal and ventral view, dashed line indicates level of proximal duplex setae; (c) Diamond-shaped pattern of dorsal striae between setae e and f; (d) Pregenital striae; (e) Pregenital region, setae labelled. Male. (f) Pretarsus II; (g) Aedeagus.

FIGURE 29 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 29. Tetranychus rhagodiae Miller, female. (a) Pretarsus I; (b) Diamond-shaped pattern of dorsal striae between setae e and f; (c, d) Variation in pregenital striae. Male. (e) Aedeagus.

FIGURE 28 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 28. Tetranychus piercei McGregor, female. (a) Tarsus and pretarsus I; (b) Diamond-shaped pattern of dorsal striae between setae e and f; (c) Pregenital striae; (d) Ventral striae between setae 3a and 4a. Male. (e) Pretarsi I, II, III; (f) Aedeagus; (g) Aedeagi from different specimens.

FIGURE 25 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 25. Tetranychus mexicanus (McGregor), female. (a) Pretarsus I; (b) Hourglass pattern in dorsal striae between e and f; (c) Pregenital striae. Male. (d) Pretarsus I; (e) Pretarsus II; (f) Aedeagus.

FIGURE 24 in Identification of exotic pest and Australian native and naturalised species of Tetranychus (Acari: Tetranychidae)

FIGURE 24. Tetranychus mcdanieli McGregor, female. (a) Entirely transverse striae between setae e and f; (b) Pregenital