A preliminary assessment of the response of a native reptile assemblage to spot‐spraying invasive Bitou Bush with glyphosate herbicide

During recent work examining the effects of Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) invasion on native reptile assemblages in coastal heathland vegetation in Eastern Australia, unplanned spot‐spraying of glyphosate occurred at some of our experimental sites invaded by Bitou Bush. We used this unexpected herbicide application as an opportunity to provide a preliminary assessment of the short‐term impacts on reptiles of glyphosate spot‐spraying of Bitou Bush. Using an M‐BARCI design, we compared reptile assemblages among uninvaded (reference) sites, invaded (control) sites and invaded and sprayed (impact) sites before and after spraying. We found no significant short‐term (7 – 10 months) differences in reptile abundance, species richness or assemblage composition among invaded, uninvaded and sprayed sites before and after glyphosate application. We cautiously interpret our results to generate a preliminary finding that spot‐spraying of Bitou Bush with glyphosate appears not to have a deleterious effect on reptile assemblages at seven and ten months following herbicide application. While we would not recommend basing management decisions on the outcomes of our study alone, we suggest that our findings can be used to assist in the development of strategic analyses of glyphosate impacts on native flora and fauna.     

Epidermal fatty acid‐binding protein protects nerve growth factor‐differentiated PC12 cells from lipotoxic injury

Epidermal fatty acid‐binding protein (E‐FABP/FABP5/DA11) binds and transport long‐chain fatty acids in the cytoplasm and may play a protecting role during neuronal injury. We examined whether E‐FABP protects nerve growth factor‐differentiated PC12 cells (NGFDPC12 cells) from lipotoxic injury observed after palmitic acid (C16:0; PAM) overload. NGFDPC12 cells cultures treated with PAM/bovine serum albumin at 0.3 mM/0.15 mM show PAM‐induced lipotoxicity (PAM‐LTx) and apoptosis. The apoptosis was preceded by a cellular accumulation of reactive oxygen species (ROS) and higher levels of E‐FABP. Antioxidants MCI‐186 and N‐acetyl cysteine prevented E‐FABP's induction in expression by PAM‐LTx, while tert‐butyl hydroperoxide increased ROS and E‐FABP expression. Non‐metabolized methyl ester of PAM, methyl palmitic acid (mPAM), failed to increase cellular ROS, E‐FABP gene expression, or trigger apoptosis. Treatment of NGFDPC12 cultures with siE‐FABP showed reduced E‐FABP levels correlating with higher accumulation of ROS and cell death after exposure to PAM. In contrast, increasing E‐FABP cellular levels by pre‐loading the cells with recombinant E‐FABP diminished the PAM‐induced ROS and cell death. Finally, agonists for PPARβ (GW0742) or PPARγ (GW1929) increased E‐FABP expression and enhanced the resistance of NGFDPC12 cells to PAM‐LTx. We conclude that E‐FABP protects NGFDPC12 cells from lipotoxic injury through mechanisms that involve reduction of ROS.

     

Species‐Specific PCR‐Based Assay for Identification and Detection of Phomopsis (Diaporthe) azadirachtae Causing Die‐Back Disease in Azadirachta indica

Die‐back disease caused by Phomopsis (Diaporthe) azadirachtae is the devastating disease of Azadirachta indica. Accurate identification of P. azadirachtae is always problematic due to morphological plasticity and delayed appearance of conidia. A species‐specific PCR‐based assay was developed for rapid and reliable identification of P. azadirachtae by designing a species‐specific primer‐targeting ITS region of P. azadirachtae isolates. The assay was validated with DNA isolated from different Phomopsis species and other fungal isolates. The PCR assay amplified 313‐bp product from all the isolates of P. azadirachtae and not from any other Phomopsis species or any genera indicating its specificity. The assay successfully detected the pathogen DNA in naturally and artificially infected neem seeds and twigs indicating its applicability in seed quarantine and seed health testing. The sensitivity of the assay was 100 fg when genomic DNA of all isolates was analysed. The PCR‐based assay was 92% effective in comparison with seed plating technique in detecting the pathogen. This is the first report on the development of species‐specific PCR assay for identification and detection of P. azadirachtae. Thus, PCR‐based assay developed is very specific, rapid, confirmatory and sensitive tool for detection of pathogen P. azadirachtae at early stages.     

Oviposition preference and larval development of the invasive moth Cydalima perspectalis on five European box‐tree varieties

The box‐tree pyralid Cydalima perspectalis (Walker 1859) (Lepidoptera: Pyralidae), native to Eastern Asia, is a newly introduced species causing severe damage to box‐trees (Buxus sp.) in private and public gardens as well as in semi‐natural box‐tree forests in Central Europe. It is so far not known whether different box‐tree subspecies (or varieties) are similarly affected by this invasive moth. In a choice experiment offering branches of five different box‐tree varieties as oviposition sites, we found a preference of female moths for laying their egg clusters on the variety ‘Rotundifolia’, while other varieties were less frequently considered. The preference for ‘Rotundifolia’, the variety with the largest leaves in the tests, remained when intervariety differences in foliar area (mean leaf size × number of leaves) were taken into account. Feeding larvae on leaves of either of the five box‐tree varieties revealed a significant effect of the seasonal generation of C. perspectalis on the growth rate of individuals but no influence of the box‐tree variety. Larvae from the spring generation show the highest growth rate, those from the summer generation a moderate and those from the autumn generation the lowest growth rate. The moths used in the experiments may belong to the 10th to 12th generation present in Europe. The time elapsed since their introduction may be too short for an optimal adaptation to the partly novel diet encountered by the invasive moth.     

Ditches as species‐rich secondary habitats and refuge for meadow species in agricultural marsh grasslands

Questions

Can drainage ditches in agricultural marsh grassland provide a suitable habitat for the persistence of fen meadow species? How does the ditch margin vegetation develop as a function of regular dredging? Is ornithologically oriented management also beneficial for plant biodiversity?

Location

Riparian marshes, Eider‐Treene‐Sorge lowland, Schleswig‐Holstein, Germany.

Methods

We performed vegetation surveys of drainage ditches along with their water body, slope and margin structures annually for 3 years. The data were analysed with respect to date and means of ditch dredging. In addition, we recorded vegetation of the surrounding agricultural grassland, measured nutrient status of the soil and the water body and sampled seed bank of the ditch slopes. We used ANOVA and multivariate methods to describe the development of the ditch vegetation and the persistence of target meadow species.

Results

Vegetation re‐development of ditch margins proceeds quite rapidly after disturbance from dredging. Dominance of mudbank species was observed only in the first year, followed by an increase of reed species and reduction of phytodiversity. Target species of wet meadow communities reach highest abundance in the second and third year and build a significant seed bank before being suppressed by reeds.

Conclusions

In heavily eutrophicated, intensively used marsh grassland, regularly disturbed ditch margins are important secondary habitats for pioneer and subdominant wetland species, which have nearly disappeared in a larger area. Current management cycles of ditch dredging every 3–4 years comply with the successional development, allowing the mudbank and wet meadow species to persist in the vegetation and seed bank. In contrast to the frequency, the form of dredging (ditch profile), which is crucial for bird protection, plays a minor role for plants. We recommend moderate disturbance (mowing of ditch margins) to suppress strong competitors in the years between dredging for additional support to target plant species.     

Ectomycorrhizal fungal richness declines towards the host species’ range edge

Plant range boundaries are generally considered to reflect abiotic conditions; however, a rise in negative or decline in positive species interactions at range margins may contribute to these stable boundaries. While evidence suggests that pollinator mutualisms may decline near range boundaries, little is known about other important plant mutualisms, including microbial root symbionts. Here, we used molecular methods to characterize root‐associated fungal communities in populations of two related temperate tree species from across the species’ range in the eastern United States. We found that ectomycorrhizal fungal richness on plant roots declined with distance from the centre of the host species range. These patterns were not evident in nonmycorrhizal fungal communities on roots nor in fungal communities in bulk soil. Climatic and soil chemical variables could not explain these biogeographic patterns, although these abiotic gradients affected other components of the bulk soil and rhizosphere fungal community. Depauperate ectomycorrhizal fungal communities may represent an underappreciated challenge to marginal tree populations, especially as rapid climate change pushes these populations outside their current climate niche.     

Species‐specific differences in water uptake depth of mature temperate trees vary with water availability in the soil

• Temperate tree species differ in their physiological sensitivity to declining soil moisture and drought. Although species‐specific responses to drought have often been suggested to be the result of different water uptake depths, empirical evidence for such a mechanism is scarce.
• Here we test if differences in water uptake depths can explain previously observed species‐specific physiological responses of temperate trees to drought and if the water uptake depth of different species varies in response to declining soil moisture. For this purpose, we employed stable oxygen and hydrogen isotopes of soil and xylem water that we collected over the course of three growing seasons in a mature temperate forest in Switzerland.
• Our data show that all investigated species utilise water from shallow soil layers during times of sufficient soil water supply. However, Fraxinus excelsior, Fagus sylvatica and Acer pseudoplatanus were able to shift their water uptake to deeper soil layers when soil water availability decreased in the topsoil. In contrast, Picea abies, was not able to shift its water uptake to deeper soil layers.
• We conclude from our data that more drought‐resistant tree species are able to shift their water uptake to deeper soil layers when water availability in the topsoil is becoming scarce. In addition, we were able to show that water uptake depth of temperate tree species is a trait with high plasticity that needs to be characterised across a range of environmental conditions.

     

Development characteristics of the box‐tree moth Cydalima perspectalis and its potential distribution in Europe

The box‐tree moth Cydalima perspectalis (Walker) is an invasive pest causing severe damage to box trees (Buxus spp.). It is native to Japan, Korea and China, but established populations have been recorded in a number of locations across Europe since 2007 and the spread of the insect continues. The developmental investigations suggest that larvae overwinter mainly in their 3rd instar in Europe and that diapause is induced by a day length of about 13.5 h. One and a half to 2 months in the cold are necessary to terminate diapause. Threshold temperatures for development and number of degree‐days to complete a generation are slightly different from those calculated in previous studies in Japan. A bioclimatic (CLIMEX^®) model for C. perspectalis in Europe was developed, based on climate, ecological and developmental parameters from the literature and new field and laboratory studies on diapause termination, thermal requirements and phenology. The model was then validated with actual distribution records and phenology data. The current distribution and life history of C. perspectalis in Europe were consistent with the predicted distribution. The climate model suggests that C. perspectalis is likely to continue its spread across Europe, except for Northern Fenno‐Scandinavia, Northern Scotland and high mountain regions. The northern distribution of C. perspectalis is expected to be limited by a number of degree‐days above the temperature threshold insufficient to complete a generation, whereas its southern range is limited by the absence of a cold period necessary to resume diapause. The model predicts relatively high Ecoclimatic Indices throughout most of Europe, suggesting that the insect has the potential of becoming a pest in most of its predicted range. However, damage is likely to be higher in Southern and Central Europe where the moth is able to complete at least two generations per year.     

Predator–prey interactions in a ladybeetle–aphid system depend on spatial scale

The outcome of species interactions may manifest differently at different spatial scales; therefore, our interpretation of observed interactions will depend on the scale at which observations are made. For example, in ladybeetle–aphid systems, the results from small‐scale cage experiments usually cannot be extrapolated to landscape‐scale field observations. To understand how ladybeetle–aphid interactions change across spatial scales, we evaluated predator–prey interactions in an experimental system. The experimental habitat consisted of 81 potted plants and was manipulated to facilitate analysis across four spatial scales. We also simulated a spatially explicit metacommunity model parallel to the experiment. In the experiment, we found that the negative effect of ladybeetles on aphids decreased with increasing spatial scales. This pattern can be explained by ladybeetles strongly suppressing aphids at small scales, but not colonizing distant patches fast enough to suppress aphids at larger scales. In the experiment, the positive effects of aphids on ladybeetles were strongest at three‐plant scale. In a model scenario where predators did not have demographic dynamics, we found, consistent with the experiment, that both the effects of ladybeetles on aphids and the effects of aphids on ladybeetles decreased with increasing spatial scales. These patterns suggest that dispersal was the primary cause of ladybeetle population dynamics in our experiment: aphids increased ladybeetle numbers at smaller scales because ladybeetles stayed in a patch longer and performed area‐restricted searches after encountering aphids; these behaviors did not affect ladybeetle numbers at larger spatial scales. The parallel experimental and model results illustrate how predator–prey interactions can change across spatial scales, suggesting that our interpretation of observed predator–prey dynamics would differ if observations were made at different scales. This study demonstrates how studying ecological interactions at a range of scales can help link the results of small‐scale ecological experiments to landscape‐scale ecological problems.     

Stream invertebrate diversity reduces with invasion of river banks by non‐native plants

相似文献   

Reproductive interference by male Drosophila subobscura on female D. persimilis: A laboratory experiment

While females often reject courtship attempts by heterospecific males, reproductive interference by harassment from such males can nonetheless occur, potentially reducing female fitness. Such effects may be profound following a range expansion, when males from a new species may suddenly encounter (and perhaps even become abundant relative to) females of related native species. Drosophila subobscura recently invaded North America and may impact native species through reproductive interference and other processes. We test for the potential for reproductive interference by D. subobscura males on D. persimilis females in the laboratory. D. subobscura males aggressively copulated with D. persimilis females, including many females that exhibit rejection behaviors. Despite females attempting to dismount the males, the heterospecific copulations are on average longer than conspecific copulations, and females exhibit some reluctance to remate with conspecific males following this harassment. Females confined with both conspecific and heterospecific males produce fewer adult progeny than those with either conspecific males only or with conspecific males and distantly related D. simulans males that do not engage in female harassment. Overall, our results illustrate how reproductive interference by an invasive species can have negative effects on resident natural populations.     

An invasive tree facilitates the persistence of native rodents on an over‐grazed floodplain in tropical Australia

In an ecosystem under simultaneous threat from multiple alien species, one invader may buffer the impact of another. Our surveys on a remote floodplain in the Kimberley region of north western Australia show that invasive chinee apple trees (Ziziphus mauritiana) provide critical refuge habitat for native rodents (pale field rats, Rattus tunneyi). Feral horses (Equus caballus) have trampled most of the remaining floodplain, but are excluded from the area around each chinee apple tree by thorny foliage. Although chinee apple trees constituted <10% of trees along our transects, they represented >50% of trees that harboured rat burrows. The mean number of burrows under each chinee apple tree was twice as high as under most other tree species, and we trapped more than seven times as many rats under chinee apple trees as under other types of trees. The extensive burrow systems under chinee apple trees contained female as well as male rats, whereas we only captured males around the smaller burrow systems under other tree species. Our data suggest that this invasive tree plays a critical role in the persistence of pale field rat populations in this degraded ecosystem, and that managers should maintain these trees (despite their alien origins) at least until feral horses have been removed.     

The impact of Broussonetia papyrifera (L.) vent. on community characteristics in the forest and forest–savannah transition ecosystems of Ghana

Following its introduction in the late 1960s, Broussonetia papyrifera L. Vent. Moraceae (paper mulberry) has emerged as a major exotic invasive species in Ghana's forest ecosystems. This study was carried out to assess the effects of B. papyrifera invasion on community composition in forest and forest–savannah transition ecosystems. Comparative and removal experiments were conducted in paired B. papyrifera invaded versus uninvaded plots. In the comparative assessment, species composition was found to be similar in both invaded and uninvaded plots. However, relative per cent cover of resident species and guilds including Chromolaena odorata, indigenous broadleaves and indigenous grasses were significantly lower in invaded plots. Seven months after B. papyrifera was experimentally removed from invaded stands, cover by indigenous broadleaves increased by 35%, as against only 5% in control plots at the forest site. However, at the transition site, the increase in per cent cover of indigenous broadleaves (18%) was not significantly different from control (2.5%) plots. We conclude that B. papyrifera has the capacity to reduce the abundance of indigenous broadleaf species, although its removal is more likely to favour regeneration in a forest than a forest–savannah transition ecosystem.     

Efficacy of Acibenzolar‐S‐Methyl and β‐Aminobutyric Acid for Control of Downy Mildew in Greenhouse Grown Basil and Peroxidase Activity in Response to Treatment with these Compounds

Downy mildew, caused by the oomycete pathogen Peronospora belbahrii, is a devastating foliar disease of basil in the United States and worldwide. Currently there are very few chemistries or organic choices registered to control this disease. In this study, two systemic acquired resistance (SAR) inducers, acibenzolar‐S‐methyl (ASM) and β‐aminobutyric acid (BABA), were evaluated for their in vitro effects on the pathogen, for their potential to control basil downy mildew in greenhouses, and for changes in peroxidase activity in basil plants treated with these two SAR inducers. No significant inhibition of sporangial germination was detected in water agar amended with ASM at concentrations lower than 100 mg/l or with BABA at concentrations lower than 500 mg/l. Efficacy of ASM and BABA in greenhouses varied depending on the rate, method and timing of application. The area under the disease progress curve (AUDPC) of disease severity was significantly reduced compared to the non‐treated control when ASM was sprayed (in all experiments) or drenched (in one out of two experiments) pre‐, or pre‐ + post‐inoculation at rates of 25–400 mg/l. Three weekly post‐inoculation sprays of ASM at the rate of 50 mg/l reduced AUDPC by 93.0 and 47.2% when started 3 and 7 days after inoculation (DAI), respectively. The AUDPC of disease severity was also significantly reduced when BABA was sprayed pre‐ + post‐inoculation at rates of 125–500 mg/l. According to the prediction using a log‐logistic function, 50% maximum disease protection was achieved at a concentration of 27.5 mg/l of ASM. Basil plants treated with these two SAR inducers and challenged with the pathogen showed significantly higher peroxidase activity than the non‐treated control at 8 DAI. Temporally, the highest activity of peroxidase was detected at 8 DAI, decreased at 15 DAI and waned further at 23 DAI.     

Early events in speciation: Cryptic species of Drosophila aldrichi

Understanding the earliest events in speciation remains a major challenge in evolutionary biology. Thus identifying species whose populations are beginning to diverge can provide useful systems to study the process of speciation. Drosophila aldrichi, a cactophilic fruit fly species with a broad distribution in North America, has long been assumed to be a single species owing to its morphological uniformity. While previous reports either of genetic divergence or reproductive isolation among different D. aldrichi strains have hinted at the existence of cryptic species, the evolutionary relationships of this species across its range have not been thoroughly investigated. Here we show that D. aldrichi actually is paraphyletic with respect to its closest relative, Drosophila wheeleri, and that divergent D. aldrichi lineages show complete hybrid male sterility when crossed. Our data support the interpretation that there are at least two species of D. aldrichi, making these flies particularly attractive for studies of speciation in an ecological and geographical context.