More than 50% of the world’s population currently lives in cities, yet cities can be home to significant biodiversity that provides important ecosystem services to urban populations. An international team of researchers, including Andrew J. Hamer, Senior Research Fellow at the Institute of Aquatic Ecology at the Centre for Ecological Research, has shown that urbanisation causes different changes in trait composition between animal groups through a systematic review of databases and publications on six terrestrial fauna groups (amphibians, bats, bees, birds, beetles and reptiles) in 379 cities on six continents. The study was published in Nature Communications.

Although urban environments cause significant habitat loss and alter the spatial structure of the landscape, it is crucial to conserve the remaining urban biodiversity and even increase the role of cities in reducing the current biodiversity extinction crisis. Understanding how different groups of animals respond through their functional traits to the impacts of urban environments worldwide is essential for developing effective strategies to promote biodiversity in urban environments.

Significant progress has been made in understanding the impacts of urbanisation on global biodiversity, there are still many gaps in research. Previous studies has focused geographically on major metropolitan areas in the northern hemisphere and Australia. However, the majority of the areas of greatest biodiversity value are in the tropics and the southern hemisphere, and these areas have been less investigated. Urban landscape structure has largely been characterised by negative indicators such as the proportion of impermeable surfaces, while biodiversity-enhancing indicators such as the proportion and spatial distribution of vegetation cover have received relatively less attention, particularly at the global level. Studies on urban biodiversity have so far mainly focused on plants and birds. Urbanisation also affects other species-rich and functionally important animal groups that have been little studied, such as insects, amphibians, bats and reptiles. Most studies on urban biodiversity continue to focus on taxonomic diversity, despite the growing importance of functional traits in the ecological literature.

In the Nature Communications study, six groups of terrestrial fauna (amphibians, bats, bees, birds, beetles and reptiles) from 379 cities on six continents were reviewed and shown that urbanisation causes taxon-specific changes in trait composition, with traits related to reproductive strategy showing the strongest response. The study results suggest that the impact of urbanisation on functional traits results in a set of four urban traits related to animal mobility and food preference, which can be classified into four types: mobile generalists, site specialists, central foragers and mobile specialists.

Mobile generalists includes taxa such as bats and carabid beetles are highly mobile species with more generalist diets and reproductive strategies that are better able to exploit available resources in urban environments. The urban trait syndrome associated with site specialists was characterised by reduced mobility, increased dietary specialism and a shift towards smaller clutch sizes. These traits are advantageous to species that are reliant on highly localised life cycles, such as amphibians and reptiles. Central place foragers establish a home base location from which they undertake daily movements to forage for additional resources. The taxa that displayed this urban trait syndrome were bees and birds. Mobile specialists are characterised by species that are able to meet their resource needs by being dietary specialists that are highly mobile and can move between spatially isolated food sources without having to return to a central place. Wetland birds can be regarded as mobile specialists, where their distribution is tightly linked to a specific resource (waterbodies), but they have the capacity to easily move between locations when resources fluctuate.

These findings are in contrast to the hypothesis that there is one single global ‘urban trait syndrome’ as a species response to urbanisation. The results therefore reassess previous ideas about ecological community dynamics and biotic homogenisation of urban ecosystems. It is crucial for the survival of different animal groups that conservation and urban development regulations and plans for cities and their environments take into account the different needs of different animal groups, as this may underpin the increasing role of cities in mitigating global biodiversity loss.

Lead photo: Julia Horanyi: An urban wetland that is habitat for species covered by all four urban trait syndromes

With the decisive participation of Eörs Szathmáry, Member of the HAS and Research Professor at the Institute of Evolution of the Centre for Ecological Research, an international team of researchers has achieved a major new breakthrough in the study of the origin of life. The paper was published in Nature Chemistry, one of the world’s leading chemistry journals.

The discipline of systems chemistry deals with the analysis and synthesis of various autocatalytic systems and is therefore closely related to the study of the origin of life, since it investigates systems that can be considered as a transition between chemical and biological evolution: more complex than simple molecules, but simpler than living cells.

Tibor Gánti described the theory of self-replicating microspheres as early as 1978. These still lacked genetic material, but concealed within their membranes an autocatalytic metabolic network of small molecules, isolated (compartmentalised) within their membranes. As the autocatalytic process takes place, the membrane-building material is also produced, leading to the division of the sphere. This system may appear to be a living cell, and although it lacks genetic material, this can only be verified experimentally. These microspheres can be considered as ‘infrabiological’ chemical systems, since they do not reach the level of biological organisation, but they exceed the complexity of normal chemical reactions.

Years ago, we started to think about the possibility of experimentally realising the process whereby the growth of a small molecule metabolic network leads to the growth of the compartments that enclose the network, to the effect that they can divide. Already Tibor Gánti has described that one of the most promising candidates for this system is the formose reaction, an autocatalytic sugar-producing reaction that consumes formaldehyde and involves the circular transformation and propagation of glycolaldehyde molecules. The reaction does not require enzymes.
The experiment on which the study is based was carried out in the biochemistry laboratory of the École Supérieure de Physique et de Chimie Industrielles (ESPCI) in Paris by Professor Andrew Griffiths and his colleagues. The experiment involved creating tiny water droplets in an oil medium that did not fuse and therefore acted as artificial cells. Some of the ‘cells’ were given glycolaldehyde as an autocatalyst (in addition to formaldehyde as a nutrient), others were not. In the former group, the formose reaction was triggered and, by osmosis, it sucked water away from compartments that did not contain glycolaldehyde. This allowed them to grow and to divide under external influence. Many researchers have suggested that before the emergence of regulated cell division, the initial cells divided in response to external influences such as turbulent flow.

The significance of this study is that we are the first in the world to show that the operation of a network of small-molecule autocatalytic reactions, without genetic material and enzymes, leads to the growth and division of compartments, i.e. the formation of new generations. This has never been demonstrated before, so the result is fundamental to the experimental verification of the principles of systems chemistry and points the way forward in the study of the origin of life.

About:

Szathmáry Eörs evolúcióbiológus, az MTA rendes tagja, az MTA Fenntartható Fejlődés Elnöki Bizottság elnöke. Kutatásai során az élet keletkezésétől kezdve az emberi nyelvkészség kialakulásáig számos evolúciós folyamatot vizsgált és modellezett. John Maynard Smithszel közösen írt könyvét, az Az evolúció nagy lépéseit a modern evolúcióbiológia alapműveként tartják számon.

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Researchers from the ELKH Centre for Ecological Research (CER) and Babeș-Bolyai University (BBE) in three recent papers have described the effects of twelve invasive plant species with different traits on vegetation (Fenesi et al. 2023), pollinator communities (Kovács-Hostyánszki et al. 2022), and the traits of pollinating insects (Szigeti et al. 2023). During their field studies they assessed and compared the plant and pollinator communities of invaded and semi-natural habitats in Hungary and Romania. In order to facilitate proper comparisons and conduct detailed exploration, the researchers employed uniform field methods while utilizing diverse ecological indicators, ranging from the height of indigenous vegetation, honeybee abundances, depth of flowers to tongue length of pollinator insects.

Bees and other pollinator species play an extremely important role in most terrestrial ecosystems, including agriculture. Increasingly, studies report the drastic decline of pollinating insects, one reason being the reduced availability of their food resources. The strong spread of invasive species is one of the five most important causes of biodiversity loss, that is why the Invasion Biology Division was established under the leadership of the Ecological Research Center within the National Laboratory for Health Security, where researchers investigate the complex effects of invasion. Where invasive plant species appear and are able to spread, they inundate and dominate the given area, reducing diversity and making habitats more homogeneous. In many cases, they also reduce the range of available flowers, thus helping some compatible pollinator species while displacing the food resources of others from the landscape. In general, it can be stated that the impacts of invasive plant species on native vegetation and pollinator insects are often varied and dependent on their specific traits.

Based on the research results, there is no universal effect of plant invasion, except for a few general patterns there are differences among invasive plant species in almost every ecological indicator studied. Perhaps the most important message is that as many invasive plant species and traits as there are, there can be a variety of effects on invaded plant-pollinator communities. The three publications highlight that the cover of invasive plant species strongly influences the composition, diversity, and height of the remaining native vegetation, among other factors. As the invasive plant species displaces native plants in a given area, fewer of the original or potential communities remain. Perennial invasive plant species have an even stronger negative impact on flower availability and pollinators than annual species. This is likely due to their stronger invasive capacity, dominance, different growth and flowering strategies, and presence in later successional stages of habitats. Timing is extremely important in plant-pollinator systems. Invaded areas are similar to crop fields such as rapeseed or sunflowers: during their blooming period, they provide significant amounts of food for the pollinating insects, while beyond of their flowering period, these areas are extremely poor in resources of pollinators. Where invasive plant species appear, they eventually become dominant. They cover the area with green vegetation mass for most of the year, but only bloom for a short period of time. As indicated by the studies, natural areas have more and more diverse resources along the year. The researchers also found important and interesting relations when comparing the traits of invasive flowers and the traits of wild bees. For example, the sites invaded by two invasive species with deep flowers had more long-tongued and also larger-bodied bees, while a species with shallow flowers had more smaller-bodied bees. This indicates a strong size determination between flowers and their pollinators, meaning that the invasion of a particular trait (such as deep flowers in invasive plants) affects the functional characteristics of the remaining pollinator community in the invaded area (i.e., only long-tongued pollinators that can feed on deep flowers will remain).

Proper nature conservation management of (semi)natural habitats and effective control of invasive plant species are important for the protection of pollinators, but some invasive plants can also provide valuable foraging resources for pollinator insects. Therefore, instead of uniformly eradicating all invasive species, it is recommended to consider the best approach on a case-by-case and location-specific basis, taking also into account the needs of protected pollinator insects. For example, efforts to combat plant invasion could incorporate the nutritional requirements of pollinators. Some of the costs associated with invasive plant eradication could be redirected towards providing alternative nutrition sources, such as sowing native seed mixes in or in the neighborhood of invaded areas. Overall, the factors and impacts important in the plant-pollinator systems are complex and interrelated, hence further detailed studies are needed to uncover the specific relationships between species and to develop effective conservation solutions.

Publications:

Fenesi, A., Botta-Dukát, Z., Miholcsa, Zs., Szigeti, V., Molnár, Cs., Sándor, D., Szabó, A., Kuhn, T., Kovács-Hostyánszki, A. (2023). No consistencies in abundance-impact relationships across herbaceous invasive species and ecological impact metrics. Journal of Ecology. DOI: 10.1111/1365-2745.14085

Kovács-Hostyánszki, A., Szigeti, V., Miholcsa, Zs., Sándor, D., Soltész, Z., Török, E., Fenesi, A. (2022). Threats and benefits of invasive alien plant species on pollinators. Basic and Applied Ecology, 64:89–102. DOI: 10.1016/j.baae.2022.07.003

Szigeti, V., Fenesi, A., Botta-Dukát, Z., Kuhlmann, M., Potts, S. G., Roberts, S., Soltész, Z., Török, E., Kovács-Hostyánszki, A. (2023). Trait-based effects of plant invasion on floral resources, hoverflies and bees. Insect Conservation and Diversity. DOI: 10.1111/icad.12640

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Over the past two centuries, in Hungary and globally, the area of natural and semi-natural forests shrunk dramatically, while at the same time some of the economic functions of forests have been taken over by tree plantations, which cover a significant area (3.8% of Europe’s forests but in Hungary in some region e.g. Kiskunság this proportion exceeds 80%). Plantations are intensively managed forests, mainly composed of one or two tree species, which mainly perform economic functions (e.g. timber and firewood production). There is a long-standing controversy about the evaluation of tree plantations, depending on whether the economic or the nature conservation values of the forest are regarded as a primary role. While tree plantations can also provide some important ecosystem services alongside the economic benefits of timber production, in these ‘forests’ taxonomic diversity decreases radically or the plantations become a hot spot for biological invasions.

A paper of the researchers of the University of Szeged and the Centre for Ecological Research, published in Forest Ecology and Management, represents a significant step forward in the more accurate ecological assessment and evaluation of Hungarian tree plantations. The sample area was the Kiskunság Sand Ridge, a lowland region in the center of the Pannonian biogeographic region between the rivers Danube and Tisza in Hungary, where semi-natural forests survived almost exclusively in the forest-steppe mosaics of protected areas, but tree plantations are widespread in the landscape. The analysis compared four types of forest habitat: near-natural poplar forest Junipero-Populetum albae and three types of tree plantation: native deciduous white poplar (Populus alba), the non-native deciduous black locust (Robinia pseudoacacia), and the non-native evergreen Austrian pine (Pinus nigra) plantation. The study assessed the diversity of the vegetation, not only in terms of species diversity, but also in terms of functional and phylogenetic diversity indicators, i.e., how diverse the vegetation is in each type in terms of plant traits (pollination type, seed dispersal, life form, flowering date, etc) and phylogenetic lineages. Each type of habitat was assessed from an ecological and conservation point of view based on the occurrence of protected, endemic and red-listed species, i.e. the rarest and most valuable species from a conservation point of view.

László Erdős, a research fellow at the Centre for Ecological Research and one of the lead authors of the paper, says that each forest type has a unique species composition, but semi-natural forests are the richest in native species, while tree plantations are dominated by weeds and non-native species. The semi-natural forest is also characterized by the frequent occurrence of native shrub species such as Berberis vulgaris, Ligustrum vulgare, and Rhamnus catharticus. In the case of tree plantations, shrubs disappear as a result of the forestry activities (mechanical site preparation and mechanical weed control) to protect the saplings. The planted tree species also have an impact on the forest floor, e.g. in Robinia pseudoacacia stands weed species that tolerate high nitrogen levels appear, or in pine forests, the deep layer of slowly decaying leaf litter results in a special species composition.
The analysis also showed that low taxonomic diversity in tree plantations does not necessarily imply low functional or phylogenetic diversity, as several different diversity indicators provide a more complex characterization of the plant diversity of a habitat. Among the tree plantations, native poplar plantation and pine forest were found to be more favorable habitats for plant diversity than black locust stands. Black locust was also the most degraded of the habitats studied in terms of naturalness indicators.

The study provides a more accurate assessment of the different types of tree plantations in the region and has important implications for forest management and conservation. From an ecological and conservation point of view, the remnants of semi-natural forest are much more valuable than any of the tree plantations, and therefore conservation and restoration programs should focus primarily on these areas. Of the tree plantations, the planting of native white poplar (Populus alba) should be preferred when further tree plantations are to be established. In the longer term, reducing the area of black locust and pine plantations is inevitable, and the establishment of a mosaic of grassland and forest, in keeping with the semi-arid climate of the Kiskunság, is appropriate for the forest-steppe region.

Publication:
Khanh Vu Ho, György Kröel-Dulay, Csaba Tölgyesi, Zoltán Bátori, Eszter Tanács, Miklós Kertész, Péter Török, László Erdős: Non-native tree plantations are weak substitutes for near-natural forests regarding plant diversity and ecological value Forest Ecology and Management, Volume 531. 2023.
https://doi.org/10.1016/j.foreco.2023.120789.

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