Soil pH influences patterns of plant community composition after restoration with native‐based seed mixes

Reclamation of highly disturbed lands typically includes establishing fast‐growing, non‐native plants to achieve rapid ground cover for erosion control. Establishing native plant communities could achieve ecosystem functions beyond soil erosion, such as providing wildlife habitat. Pipelines, or other disturbed corridors through a landscape, present unique challenges for establishing native plant communities given the heterogeneity of soil environments and invasive plant propagule pressure. We created two structural equation models to address multiple related hypotheses about the influence of soil pH on plant community composition (current diversity and vegetative cover of the original restoration seed mix and background flora, and invasive plant density during mix establishment and current density) of a highly disturbed landscape corridor restored with native species. To test our hypotheses we conducted a plant survey on a gas pipeline crossing two state forests in the north‐central Appalachians that had been seeded with a native‐based mixture 8 years prior. Low soil pH was a strong predictor of density of the invasive annual plant, Microstegium vimineum, and had resulted in lower species diversity and cover of the seeded mix. Overall, our data provide evidence that native‐based grass and forb mixtures can establish and persist on a wide range of soil environments and thrive in competition with invasive plants in moderately acidic to neutral soils. Advancing knowledge on restoration methods using native species is essential to improving restoration practice norms to incorporate multifunctional ecological goals.     

Do soil inoculants accelerate dryland restoration? A simultaneous assessment of biocrusts and mycorrhizal fungi

Biological soil crusts (biocrusts) and arbuscular mycorrhizal (AM) fungi are communities of soil organisms often targeted to assist in the achievement of multiple ecological restoration goals. In drylands, benefits conferred from biocrust and AM fungal inoculation, such as improved native plant establishment and soil stabilization, have primarily been studied separately. However, comparisons between these two types of soil inoculants and investigations into potential synergies between them, particularly at the plant community scale, are needed to inform on‐the‐ground management practices in drylands. We conducted two full‐factorial experiments—one in greenhouse mesocosms and one in field plots—to test the effects of AM fungal inoculation, biocrust inoculation, and their interaction on multiple measures of dryland restoration success. Biocrust inoculation promoted soil stabilization and plant drought tolerance, but had mixed effects on native plant diversity (positive in greenhouse, neutral in field) and productivity (negative in greenhouse, neutral in field). In greenhouse mesocosms, biocrust inoculation reduced plant biomass, which was antagonistic to % root length colonized by AM fungi. Inoculation with native or commercial AM fungi did not influence plant establishment, drought tolerance, or soil stabilization in either study, and few synergistic effects of simultaneous inoculation of AM fungi and biocrusts were observed. These results suggest that, depending on the condition of existing soil communities, inoculation with AM fungi may not be necessary to promote dryland restoration goals, while inoculation with salvaged biocrust inoculation may be beneficial in some contexts.     

Examining the impact of a symbiotic lifestyle on the fecundity of the marine gastropod Crepidula plana

The marine gastropod Crepidula plana has an extensive latitudinal range along the eastern coast of the United States. It is usually found living within gastropod shells occupied by hermit crabs, although individuals can sometimes also be found living on rocks and on the exposed surfaces of shells. Our study sought to determine the extent to which residing inside periwinkle (Littorina littorea) shells occupied by the hermit crab Pagurus longicarpus at a study site in coastal Massachusetts compromises the fecundity of C. plana, through size limitation. The egg masses of symbiotic and free‐living females of C. plana included comparable numbers of egg capsules and embryos per female despite the smaller sizes of the symbionts; symbiotic females compensated for their smaller size by producing significantly more embryos per milligram of female body tissue than their free‐living counterparts. These data raise interesting questions about why—unlike its congener C. fornicata—C. plana has not yet become a successful invasive species.     

A trophic cascade initiated by an invasive vertebrate alters the structure of native reptile communities

Invasive vertebrates are frequently reported to have catastrophic effects on the populations of species which they directly impact. It follows then, that if invaders exert strong suppressive effects on some species then other species will indirectly benefit due to ecological release from interactions with directly impacted species. However, evidence that invasive vertebrates trigger such trophic cascades and alter community structure in terrestrial ecosystems remains rare. Here, we ask how the cane toad, a vertebrate invader that is toxic to many of Australia's vertebrate predators, influences lizard assemblages in a semi‐arid rangeland. In our study area, the density of cane toads is influenced by the availability of water accessible to toads. We compared an index of the abundance of sand goannas, a large predatory lizard that is susceptible to poisoning by cane toads and the abundances of four lizard families preyed upon by goannas (skinks, pygopods, agamid lizards and geckos) in areas where cane toads were common or rare. Consistent with the idea that suppression of sand goannas by cane toads initiates a trophic cascade, goanna activity was lower and small lizards were more abundant where toads were common. The hypothesis that suppression of sand goannas by cane toads triggers a trophic cascade was further supported by our findings that small terrestrial lizards that are frequently preyed upon by goannas were more affected by toad abundance than arboreal geckos, which are rarely consumed by goannas. Furthermore, the abundance of at least one genus of terrestrial skinks benefitted from allogenic ecosystem engineering by goannas where toads were rare. Overall, our study provides evidence that the invasion of ecosystems by non‐native species can have important effects on the structure and integrity of native communities extending beyond their often most obvious and frequently documented direct ecological effects.     

The impacts of warming and nitrogen addition on competitive ability of native and invasive populations of Plantago virginica

全球变化因子(如增温和氮沉降)可能会影响生物入侵,但是这些因子如何影响入侵物种的表现并进一步调节入侵物种与本地竞争者之间的相互作用仍不清楚。本文通过为期五个月的温室实验,研究了增温(开顶式增温箱,+0.62°C)和氮添加(4.2 g N m⁻²)对入侵物种北美 车前(Plantago virginica)原产地和入侵地种群与本地车前草(Plantago asiatica)竞争的影响。实验结果表明,在增温及其与氮添加处理(W × N) 的相互作用下,P. virginica的入侵种群(PV-In)和原产地种群(PV-Na)在与本地竞争者P. asiatica竞争时具有不同的生物量分配策略。其中,PV-Na在与P. asiatica竞争时增加了地下生物量,而PV-In增加了地上生物量。我们还发现,P. virginica对增温和氮添加比P. asiatica的反应更强 烈。增温显著降低了P. virginica的竞争能力,这表明P. virginica比P. asiatica对增温的响应更为敏感。同样,在竞争条件下,氮添加及 其和增温交互作用减少了PV-In地下生物量,但增加了PV-Na地上和总生物量。这些发现表明,P. virginica在入侵过程中改变了生物量分配 策略,PV-In展示出更具弹性的竞争能力以适应环境变化(特别是增温)。这些发现可能有助于我们预测气候变化下的植物入侵并制定相应的 管理策略。     

Incorporating physiology into species distribution models moderates the projected impact of warming on selected Mediterranean marine species

Species distribution models (SDMs) correlate species occurrences with environmental predictors, and can be used to forecast distributions under future climates. SDMs have been criticized for not explicitly including the physiological processes underlying the species response to the environment. Recently, new methods have been suggested to combine SDMs with physiological estimates of performance (physiology-SDMs). In this study, we compare SDM and physiology-SDM predictions for select marine species in the Mediterranean Sea, a region subjected to exceptionally rapid climate change. We focused on six species and created physiology-SDMs that incorporate physiological thermal performance curves from experimental data with species occurrence records. We then contrasted projections of SDMs and physiology-SDMs under future climate (year 2100) for the entire Mediterranean Sea, and particularly the ‘warm’ trailing edge in the Levant region. Across the Mediterranean, we found cross-validation model performance to be similar for regular SDMs and physiology-SDMs. However, we also show that for around half the species the physiology-SDMs substantially outperform regular SDM in the warm Levant. Moreover, for all species the uncertainty associated with the coefficients estimated from the physiology-SDMs were much lower than in the regular SDMs. Under future climate, we find that both SDMs and physiology-SDMs showed similar patterns, with species predicted to shift their distribution north-west in accordance with warming sea temperatures. However, for the physiology-SDMs predicted distributional changes are more moderate than those predicted by regular SDMs. We conclude, that while physiology-SDM predictions generally agree with the regular SDMs, incorporation of the physiological data led to less extreme range shift forecasts. The results suggest that climate-induced range shifts may be less drastic than previously predicted, and thus most species are unlikely to completely disappear with warming climate. Taken together, the findings emphasize that physiological experimental data can provide valuable supplemental information to predict range shifts of marine species.     

Impact of brood parasitism and predation on nest survival of the fan-tailed gerygone in New Caledonia

Predation and brood parasitism are common reasons for nesting failure in passerine species and the additive impact by invasive species is a major conservation concern, particularly on tropical islands. Recognising the relative contribution of the different components of nesting failure rates is important to understand co-evolutionary interactions within brood parasite–host systems. In the remote archipelago of New Caledonia, the fan-tailed gerygone Gerygone flavolateralis is the exclusive host of the brood-parasitic shining bronze-cuckoo Chalcites lucidus. Additionally, invasive rodents also possibly have an impact on breeding success. To estimate the impact of potential nest predators, we 1) video monitored nests to identify predators, 2) estimated the probability of predation based on nest visibility and predator abundance and 3) tested the possibility that the location of experimental nests and lack of odour cues decrease the predation by rodents. In addition, we estimated nest survival rates using data collected in different habitats over the course of eight breeding seasons. Nesting success of fan-tailed gerygones was relatively low and predation was the main cause of nesting failure. We recorded mainly predation by native birds, including the shining bronze-cuckoo, whereas predation by rats was rare. In open habitats predation by cuckoos was much lower than predation by other avian predators. Neither predator activity around nests nor nest visibility influenced the probability of predation. Experimental nests in more accessible locations and containing an odorous bait were more exposed to rodent predation. Apparently, the fan-tailed gerygone has either never been specifically vulnerable to predation by rats or has developed anti-predator adaptations.     

Intrinsic competition between two European egg parasitoids of the brown marmorated stink bug

Following the accidental introduction and spread of the invasive polyphagous agricultural pest Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), the two European egg parasitoids Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) have been investigated for inundative biological control. Since the competititve outcome between the two generalist parasitoids is difficult to predict, intrinsic competition was investigated with a time-course development study. Both species readily oviposited in H. halys eggs containing eggs and early instar larvae of the competitor, but oviposition decreased when eggs contained late instar larvae and pupae. Ooencyrtus telenomicida offspring emergence from multiparasitized eggs was significantly lower than that from rearing controls, independent of the order of parasitization. Anastatus bifasciatus offspring emergence was not influenced by the presence of O. telenomicida when it parasitized as the first species, but emergence was decreased after oviposition in eggs containing O. telenomicida larvae and pupae. There was no indication that O. telenomicida can act as a facultative hyperparasitoid of A. bifasciatus. These results suggest that A. bifasciatus is the superior intrinsic competitor and no or minor negative implications for A. bifasciatus are expected if released in combination with O. telenomicida.     

Single and combined effects of Drosophila suzukii and Drosophila melanogaster on sour rot development in viticulture

Sour rot is a disease complex that causes serious damage in viticulture. The common vinegar fly Drosophila melanogaster (Diptera: Drosophilidae) is associated with sour rot in overripe or otherwise damaged grapes. Drosophila suzukii (Diptera: Drosophilidae) is an invasive species, which is suspected to induce sour rot in previously undamaged grapes due to the flies' ability to infest healthy, undamaged soft fruits with its serrated ovipositor. As a consequence, infection of healthy grapes by D. suzukii may facilitate the colonization by D. melanogaster. We investigated the single and combined effects of D. suzukii and D. melanogaster on sour rot development by measuring volatile acidity under near-natural conditions in the vineyard, along with laboratory experiments under controlled climate. In 2017, the combined field and laboratory experiments suggested that the presence of D. suzukii and D. melanogaster increased the volatile acidity levels at a similar rate. In 2018, the field experiments showed an only marginal increase in sour rot development in treatments with both Drosophila species. Under more favourable laboratory conditions, the presence of D. suzukii, but not D. melanogaster triggered sour rot emergence. A facilitating effect of D. suzukii infestation for D. melanogaster was not detectable. These findings suggest that D. suzukii does in fact have the potential to trigger sour rot, but will probably rarely do so under field conditions in the vineyard, at least in the studied region. Instead, our study showed that D. melanogaster can have a similar impact on sour rot development as D. suzukii, emphasizing the need of comparative studies.     

经皮穿刺抽取大鼠脑脊液方法的改良

目的: 改进传统经皮穿刺抽取脑脊液的方法,提高采集大鼠脑脊液动物存活率。方法: 90只SD大鼠随机分为对照组、传统穿刺组和改良穿刺组(每组30只)。对照组不进行穿刺。传统穿刺组按反握抓持法进行穿刺取样。改良穿刺组采用左手固定大鼠头部,将其抬高至约135°,右手正握改良1 ml注射器,以枕骨隆突和第一颈椎为标志定位枕骨大孔,在枕骨大孔中心偏下平行进针,抽取脑脊液。分别于第1、4、7日抽取大鼠脑脊液,每次抽取记录取样时间、采集量、脑脊液性状,抽取后3 d观察大鼠存活情况,选取存活大鼠进行重复采样。结果: 传统经皮穿刺取样法采样成功率为63.33%,三次重复采样动物存活率为10%;改良经皮穿刺取样法采样成功率为86.67%,三次重复采样动物存活率为50%,相比传统采样有显著升高(P＜0.01)。结论: 改良经皮穿刺取样法操作简单,耗时少,成功率高。操作无需定位设备,单人可以完成。动物反复取样存活率高,方便进行脑脊液重复采样。