Non-native plant drives the spatial dynamics of its herbivores: the case of black locust (Robinia pseudoacacia) in Europe

Non-native plants typically benefit from enemy release following their naturalization in non-native habitats. However, over time, herbivorous insects specializing on such plants may invade from the native range and thereby diminish the benefits of enemy release that these plants may experience. In this study, we compare rates of invasion spread across Europe of three North American insect folivores: the Lepidoptera leaf miners Macrosaccus robiniella and Parectopa robiniella, and the gall midge Obolodiplosis robiniae, that specialize on Robinia pseudoacacia. This tree species is one of the most widespread non-native trees in Europe. We find that spread rates vary among the three species and that some of this variation can be explained by differences in their life history traits. We also report that geographical variation in spread rates are influenced by distribution of Robinia pseudoacacia, human population and temperature, though Robinia pseudoacacia occurrence had the greatest influence. The importance of host tree occurrence on invasion speed can be explained by the general importance of hosts on the population growth and spread of invading species.

Multiscale Modelling of De Novo Anaerobic Granulation

A multiscale mathematical model is presented to describe de novo granulation, and the evolution of multispecies granular biofilms, in a continuously fed bioreactor. The granule is modelled as a spherical free boundary domain with radial symmetry. The equation governing the free boundary is derived from global mass balance considerations and takes into account the growth of sessile biomass as well as exchange fluxes with the bulk liquid. Starting from a vanishing initial value, the expansion of the free boundary is initiated by the attachment process, which depends on the microbial species concentrations within the bulk liquid and their specific attachment velocity. Nonlinear hyperbolic PDEs model the growth of the sessile microbial species, while quasi-linear parabolic PDEs govern the dynamics of substrates and invading species within the granular biofilm. Nonlinear ODEs govern the evolution of soluble substrates and planktonic biomass within the bulk liquid. The model is applied to an anaerobic, granular-based bioreactor system, and solved numerically to test its qualitative behaviour and explore the main aspects of de novo anaerobic granulation: ecology, biomass distribution, relative abundance, dimensional evolution of the granules and soluble substrates, and planktonic biomass dynamics within the bioreactor. The numerical results confirm that the model accurately describes the ecology and the concentrically layered structure of anaerobic granules observed experimentally, and that it can predict the effects on the process of significant factors, such as influent wastewater composition; granulation properties of planktonic biomass; biomass density; detachment intensity; and number of granules.

Strange invaders increase disturbance and promote generalists in an evolving food web

The patterns of diet specialization in food webs determine community structure, stability, and function. While specialists are often thought to evolve due to greater efficiency, generalists should have an advantage in systems with high levels of variability. Here we test the generalist-disturbance hypothesis using a dynamic, evolutionary food web model. Species occur along a body size axis with three traits (body size, feeding center, feeding range) that evolve independently and determine interaction strengths. Communities are assembled via ecological and evolutionary processes, where species biomass and persistence are driven by a bioenergetics model. New species are introduced either as mutants similar to parent species in the community or as invaders, with dissimilar traits. We introduced variation into communities by increasing the dissimilarity of invading species across simulations. We found that strange invaders increased the variability of communities which increased both the degree of generalism and the relative persistence of generalist species, indicating that invasion disturbance promotes the evolution of generalist species in food webs.

Trophic relationships among fourteen native and non-native fish species in the Shatt Al-Arab River, Iraq

The present study objectified to evaluate the trophic relationships among 14 fish species (10 natives and 4 non-natives) in the Shatt Al-Arab River, considering the trophic niche breadth and the diet overlaps of the species. The food items in the stomach of each species are determined by adopting the index of relative importance (IRI). The dietary analysis revealed a total of 12 types of major food items consumed (which represent >10% IRI). Two species (Oreochromis aureus and Cptodon zillii) were herbivores consumed mostly macrophytes, algae and diatoms. Four species (Planiliza abu, P. klunzengeri, P. subviridis and Osteomugil speigleri) were herbivores mainly fed on diatoms, macrophytes, detritus and algae. Three species (Carasobarbus luteus, Carassius auratus and Cyprinus carpio) were omnivores mostly consumed macrophytes, detritus, diatoms and algae. Two species (Tenualosa illisha and Nematalosa nasus) were filter feeders fed largely on zooplankton, algae, detritus and macrophytes. Three species (Acanthopagrus arabicus, Johnius belangerii and J. dussumeiri) were carnivores mainly preyed on shrimps, crabs and fish. Levin’s index diet breadth analyses divided the studied fish species into three categories; two species with high specialization, five species with low specialization, and seven species with generalization feeders. The dietary composition of fish species exhibited 62 diet overlaps as indicated by the Jaccard index, eight of them high, 36 moderate and 18 low overlaps. Only J. dussumeiri and J. belangerii have no diet overlap with other species. Overall, the study demonstrates that most trophic overlaps between species were moderate, but high degree overlap was between the native species (C. luteus) and invading species (C. auratus) and therefore strengthen earlier conclusions regarding interspecific competition between these two species.

Változó éghajlat, változó környezet, változó kórokozók. Meddig tart a járványok kora?

Összefoglaló. Az eddigi összes világjárványt olyan zoonotikus kórokozók, vírusok vagy baktériumok okozták, amelyek könnyen tudnak emberről emberre is terjedni. Minden egyes felbukkanó fertőzés egészségügyi, társadalmi és gazdasági költségeket von maga után. Az országhatárok nem tudják hatékonyan korlátozni a betegségek terjedését. Az eddigi trendek alapján jóval több mint félmillióféle, zömmel teljesen ismeretlen vírus lehet képes embereket megfertőzni. Az ember által letarolt vagy urbanizált területeken olyan állatfajok lesznek dominánsok, amelyek kifejezetten jó kórokozó-fenntartók. A hangsúlyt mostantól kezdve a megelőzésére kell helyezni, melynek a feltételei végrehajtható tervek formájában adottak. A hatékony megelőzés költséges, de jóval olcsóbb, mint egy világjárvány gazdasági következményeit viselni. Summary. So far, all pandemics have been caused by zoonotic pathogens, viruses or bacteria that could easily spread from human to human. Emerging infectious diseases entail huge costs for the health system, as well as for society and economy in general. Experience tells us that national borders are insufficient to prohibit the spread of infectious diseases. Extrapolation from current trends suggests that the number of largely unknown virus species able to infect humans is well over half a million. Overall, we seem to lack knowledge about 90% of the pathogens of the world. A striking experience is that pathogens can jump hosts based on their standing genetic variation and phenotypic plasticity. Mutations tend to follow later and lead to evolutionary finetuning of the pathogenic lifecycle. Human activity has contributed a great deal to the current dangerous rise of emerging infectious diseases. Climate change induces migration, biological invasions, and a higher incidence of the encounter of species with potential pathogens. Invading species tend to disrupt local ecosystems, resulting in lower biodiversity and higher susceptibility to disease of the remaining endemic species as well as the agriculturally important, domestic plant and animal populations. Habitats devastated by human activity as well urban areas will be dominated by species (such as rodents) that can harbour several potential and actual pathogens. Urbanization is a major risk factor for several reasons, including the elevated temperature in cities that contributes to the increase in pathogen survival during winter and the high population density and consequential contact rate of the local human population. Globalization adds to the security hazard posed by pathogens. From now on, emphasis should be put on the prevention of pandemics, for which we have executable plans. One such plan is the DAMA protocol (Document, Assess, Monitor, Act). We must document the occurrence of potential pathogens in candidate host species. Then we assess the threat level associated with identified potential pathogens, followed by a systematic monitoring of the most dangerous pathogens, looking for early signs of potential outbreaks. Action means advice by experts on possible preventive measures by experts and their evaluation and execution by decision makers. Similar ecological diagnostics seem possible for biological invasions in general. Efficient prevention is costly, but considerably less so than bearing the economic consequences of pandemics by (re-)emerging infectious diseases.

ZOOPLANKTON OF THE NORTH-EASTERN PART OF THE BLACK SEA OFF THE COAST OF TAMAN IN THE SUMMER-AUTUMN PERIOD 2018–2019

The taxonomic composition and quantitative characteristics of zooplankton in the northeastern part of the Black Sea near the Taman coast in the summer-autumn period of 2018–2019 were studied. Zooplankton was represented mainly by eurythermic and thermophilic forms. All the discovered species and taxa are currently typical of the Black Sea, including the invading species: copepods Acartia tonsa, Oithona davisae, and combtails Mnemiopsis leidyi, Beroe ovata. The average number of zooplankton in 2018 ranged from 2.7–15.9 thousand copies/m3, the biomass – 0.02–0.14 g/m3; its indicators in 2019; they were lower, respectively, 2.0–5.6 thousand copies/m3 and 0.02–0.07 g/m3. These indicators were within the values recorded earlier, in 2013–2014. A significant part of the coastal zooplankton is meroplankton, which accounted for 5–69% of the population and 4–47% its biomass. O. davisae dominated amoung copepods. This speciest was leading in numbers in both years except June 2019. Despite the similarity of the taxonomic composition of zooplankton, the dominant species in terms of biomass differed by month in two years.

Negative indirect effects of hurricanes on recruitment of range-expanding mangroves

Disturbances often have positive, direct effects on invasions by dispersing propagules or creating environmental conditions that favor invasive species. However, disturbances that alter interactions between resident and invading species could also affect invasion success. In northeast Florida, the black mangrove Avicennia germinans is expanding into salt marshes, where it interacts with the dead litter (wrack) of the native marsh cordgrass Spartina alterniflora. From 2015-2017, we performed monthly surveys before and after 2 hurricanes in 3 marsh microhabitats (bare sediment, vegetation, wrack) to quantify mangrove propagule and seedling densities. Wrack increased propagule retention up to 10 times relative to other microhabitats. Hurricanes did not directly harm mangrove propagules or seedlings. However, storm surge relocated wrack to upland environments, which indirectly inhibited mangroves by temporarily disrupting the facilitative effects of wrack on propagule recruitment and exposing intertidal bare patches that decreased propagule retention and seedling establishment. Wrack remained absent from intertidal areas for 1-3 mo. Because hurricane season overlaps with propagule recruitment, hurricane timing and wrack return time to intertidal areas influence the degree that hurricanes disrupt wrack-mangrove interactions. We demonstrate that large-scale disturbances can negatively and indirectly affect invader recruitment by altering interactions with resident species.

Presence of a resident species aids invader evolution

Phytoplankton populations are intrinsically large and genetically variable, and interactions between species in these populations shape their physiological and evolutionary responses. Yet, evolutionary responses of microbial organisms in novel environments are investigated almost exclusively through the lens of species colonising new environments on their own, and invasion studies are often of short duration. Although exceptions exist, neither type of study usually measures ecologically relevant traits beyond growth rates. Here, we experimentally evolved populations of fresh- and seawater phytoplankton as monocultures (the green algae Chlamydomonas moewusii and Ostreococcus tauri, each colonising a novel, unoccupied salinity) and co-cultures (invading a novel salinity occupied by a resident species) for 200 generations. Colonisers and invaders differed in extinction risks, phenotypes (e.g. size, primary production rates) and strength of local adaptation: invaders had systematically lower extinction rates and broader salinity and temperature preferences than colonisers – regardless of the environment that the invader originated from. We emphasise that the presence of a locally adapted species has the potential to alter the invading species’ eco-evolutionary trajectories in a replicable way across environments of differing quality, and that the evolution of small cell size and high ROS tolerance may explain high invader fitness. To predict phytoplankton responses in a changing world, such interspecific relationships need to be accounted for.