Head: prof. RNDr. Petr Pyšek, CSc.

People ׀ Projects ׀ Publications

Research topics

• Factors determining naturalization and spread of alien species
• The role of species traits in plant invasions
• Invasiveness of alien plant species and invasibility of habitats
• Developing schemes for standardized scoring of impacts of invasive plants and animals
• Global database of naturalized alien plants (GloNAF)
• Case studies of invasive species

Selected recent results

1/ Small genome size supports the naturalization of plants but constrains their invasive spread

By testing the effects of genome size and ploidy levels on plant naturalization and invasion, using ~11,000 species, we found that large genome constrains naturalization but favours invasion. A small genome is an advantage during naturalization, being linked to traits favouring adaptation to local conditions, but for invasive spread, traits associated with a large holoploid genome, where the impact of polyploidy may act, facilitate long-distance dispersal and competition with other species.

• Pyšek P., Lučanová M., Dawson W., Essl F., Kreft H., Leitch I., Lenzner B.., Meyerson L. A., Pergl J., van Kleunen M., Weigelt P., Winter M. & Guo W.-Y. 2023: Small genome size and variation in ploidy levels support the naturalization of vascular plants but constrain their invasive spread. New Phytologist 239, 2389 – 2403. doi:10.1111/NPH.19135

Small genome supports successful naturalization but constrains invasion where plants with large genome are most successful.

 

2/ Evolutionary imbalance and plant invasions

Humans cause global biotic redistribution, translocate species and provide them with opportunities to establish populations beyond their native ranges. Species originating from certain global regions, however, are disproportionately represented among naturalized aliens. The evolutionary imbalance hypothesis posits that differences in absolute fitness among biogeographic divisions determine outcomes when biotas mix. By using data from native and alien distributions for nearly the entire global seed plant flora, we found that successful aliens tend to originate from large, biodiverse regions that support abundant populations and where species evolve against a diverse backdrop of competitors and enemies. We also reveal that these same native distribution characteristics are shared among the plants that humans select for cultivation and economic use. In addition to influencing species’ innate potentials as invaders, we therefore suggest that evolutionary imbalance shapes plants’ relationships with humans, impacting which species are translocated beyond their native distributions.

• Fristoe T. S., Bleilevens J., Kinlock N. L., Yang Q., Zhang Z., Dawson W., Essl F., Kreft H., Pergl J., Pyšek P., Weigelt P., Dufour-Dror J.-M., Sennikov A. N., Wasowicz P., Westergaard K. B. & van Kleunen M. 2023: Evolutionary imbalance, climate and human history jointly shape the global biogeography of alien plants. Nature Ecology and Evolution 7, 1633 – 1644. doi:1038/s41559-023-02172-z

 

Global naturalization success of plant species originating from different continents.

 

3/ Elevated compositional change in plant assemblages linked to invasion

Invasions by alien species contribute to biodiversity change, but the extent to which they are associated with the reshaping of ecological communities is not well understood. One possible mechanism is that assemblages where alien species are found exhibit elevated temporal turnover. To test this, we used BioTIME database and compared those assemblages in which alien species are either present or absent and computed the compositional dissimilarity between consecutive censuses. We found that, although alien species are typically rare in invaded assemblages, their presence is associated with an increase in the average rate of compositional change. These differences in compositional change between invaded and uninvaded assemblages are not linked to differences in species richness but rather to species replacement (turnover). Rapid compositional restructuring of assemblages is a major contributor to biodiversity change, and as such, our results suggest a role for alien species in bringing this about.

• Kortz A. R., Moyes F., Pivello V. R., Pyšek P., Dornelas M., Visconti P. & Magurran A. E. 2023: Elevated compositional change in plant assemblages linked to invasion. Proceedings of the Royal Society B-Biological Sciences 290, 1 – 6. doi:1098/rspb.2022.2450

Jaccard dissimilarity between time steps in assemblages with alien species (triangles) and without aliens (circles) for both all evaluated periods and for a subset of assemblages sampled between 2000 and 2016.

 

4/ Catalogue of alien flora of the Czech Republic

The third edition of the complete catalogue of the alien flora of the Czech Republic, which follows the 2002 and 2012 editions, has been updated by incorporating new data collected over the last decade and reassessing the current status of taxa based on improved taxonomic and ecological knowledge. We list 1576 taxa alien to this country, of which 1084 are casual, 417 naturalized and 75 are invasive. Compared to the 2012 edition, there is an increase by 122 taxa. The contribution of alien taxa to the Czech flora is 37.8% if all aliens are considered or 16.2% if all naturalized taxa (including invasives), which are a permanent part of the flora, are included. Most alien plants originate from the Mediterranean region (618 taxa, i.e. 31.5%), other parts of Europe (380 taxa, 19.4%), other parts of Asia (290 taxa, 14.1%) and North America (262, 13.4%). Maps based on the cumulative record of alien species occurrence over the past 50 years, expressed as the proportion of the entire flora, show that alien species are relatively more prevalent in lowlands and large urban agglomerations. In a European comparison, the Czech Republic is currently a moderately invaded country.

• Pyšek P., Sádlo J., Chrtek J. Jr., Chytrý M., Kaplan Z., Pergl J., Pokorná A., Axmanová I., Čuda J., Doležal J., Dřevojan P., Hejda M., Kočár P., Kortz A., Lososová Z., Lustyk P., Skálová H., Štajerová K., Večeřa M., Vítková M., Wild J. & Danihelka J. (2022) Catalogue of alien plants of the Czech Republic (3rd edition): species richness, status, distributions, habitats, regional invasion levels, introduction pathways and impacts. Preslia 94: 477–577, doi: 10.23855/preslia.2022.447

 

Hotspots and coldsponts of alien species relative occurrence in the Czech Republic.

 

5/ Factors determining the plant diversity of South-African savanna

To identify factors that drive plant species richness in South-African savanna, we sampled plant communities across habitats differing in water availability, disturbance, and bedrock, using the Kruger National Park as a model system. We predicted that large herbivores would utilise seasonal rivers’ habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness.

• Hejda M., Čuda J., Pyšková K., Zambatis G., Foxcroft L. C., MacFadyen S., Storch D., Tropek R. & Pyšek P. (2022) Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna. Scientific Reports 12: 338, doi: 10.1038/s41598-021-02870-3

The sampled habitats in the Kruger National Park. Left column: (A) perennial river, (B) seasonal river, and (C) a dry crest. Right column: Elephants at a perennial plot in rainy (D) and dry season (E), and at a seasonal river (F).

 

6/ Naturalized alien floras still carry the legacy of European colonialism

The redistribution of alien species across the globe accelerated with the start of European colonialism. European powers were responsible for the deliberate and accidental transportation, introduction and establishment of alien species throughout their occupied territories and the metropolitan state. Here, we show that these activities left a lasting imprint on the global distribution of alien plants. Specifically, we investigated how four European empires (British, Spanish, Portuguese and Dutch) structured current alien floras worldwide. We found that compositional similarity is higher than expected among regions that once were occupied by the same empire. Further, we provide strong evidence that floristic similarity between regions occupied by the same empire increases with the time a region was occupied. Network analysis suggests that historically more economically or strategically important regions have more similar alien floras across regions occupied by an empire. Overall, we find that European colonial history is still detectable in alien floras worldwide.

• Lenzner B., Latombe G., Schertler A., Seebens H., Yang Q., Winter M., Weigelt P., van Kleunen M., Pyšek P., Pergl J., Kreft H., Dawson W., Dullinger S. & Essl F. (2022) Naturalized alien floras still carry the legacy of European colonialism. Nature Ecology and Evolution 6: 1723–1732, doi: 10.1038/s41559-022-01865-1

Increase over time in the number of colonies occupied by European colonial powers (left) and the relationship between the current number of naturalized plant species in a former colony and time of its colonization (right).

 

7/ Persistent soil seed banks promote invasiveness in plants

With globalization facilitating the movement of plants beyond their native range, preventing potentially harmful introductions requires knowledge of what drives the successful establishment and spread of alien plants. We examined global-scale relationships between naturalization and invasion success, soil seed bank properties (type and densities) and key species traits (seed mass, seed dormancy and life form) for 2350 species of angiosperms. Naturalization and invasiveness were strongly associated with the ability to form persistent seed banks but relatively weakly with seed bank densities and other traits. Our findings suggest that seed bank persistence is a trait that better captures the ability to become naturalized and invasive compared to seed traits more widely available in trait databases. Knowledge of seed persistence can contribute to our ability to predict global naturalization and invasiveness and to identify potentially invasive flowering plants before they are introduced.

• Gioria M., Carta A., Baskin C. C., Dawson W., Essl F., Kreft H., Pergl J., van Kleunen M., Weigelt P., Winter M. & Pyšek P. 2021: Persistent soil seed banks promote naturalisation and invasiveness in flowering plants. Ecology Letters 24, 1655 – 1667. doi:10.1111/ele.13783

Global naturalization incidence and extent of alien plants in relation to seed bank properties.

 

8/ Comparing impacts of native and invasive dominants on species diversity of plant communities

Invasive alien plants are known to reduce the diversity of recipient communities, but there is an ongoing debate on whether or not native dominant species have similar effects. To answer this question, we compared invasive dominant species of plant communities in central Europe with native species that dominate uninvaded communities in that region. The results showed that both native and invasive dominants can reduce the diversity of vegetation. In total, 17 dominants (nine native and eight invasive) significantly reduced community species richness, with Reynoutria ×bohemica, Calamagrostis epigejos, Phalaris arundinacea and Urtica dioica having the strongest effect. To conserve biodiversity, measures should be adopted to mitigate not only the impacts of invasive species but also those of native dominants, spreading in the current landscape; this would be best achieved by promoting traditional management and land-use.

• Hejda M., Sádlo J., Kutlvašr J., Petřík P., Vítková M., Vojík M., Pyšek P. & Pergl J. 2021: Impact of invasive and native dominants on species richness and diversity of plant communities. Preslia 93, 181 – 201. doi:10.23855/preslia.2021.181

Comparison of the impact of native and invasive dominants on species diversity of plant communities. The longer the bar the stronger the negative impact.

 

9/ Latitudinal patterns of plant invasions

Using the native and alien plant distribution data from 801 regions (including islands), we compared invasion levels (i.e. alien richness/total richness) in the Northern and Southern Hemispheres and across continental regions and islands around the globe. We show declining richness with increasing latitude, but the patterns differ among mainland and islands. Invasion levels decrease towards higher latitudes on islands but in continental regions, we found a unimodal pattern on each hemisphere. We identified significantly greater invasion levels on islands than in continental regions. Our findings identified latitudes with invasion hotspots where management is urgently needed, and latitudes with many areas of low invasions but high conservation potential where prevention of future invasions should be the priority.

• Guo Q., Cade B. S., Dawson W., Essl F., Kreft H., Pergl J., van Kleunen M., Weigelt P., Winter M. & Pyšek P. 2021: Latitudinal patterns of alien plant invasions. Journal of Biogeography 48, 253 – 262. doi:10.1111/jbi.13943

Comparative global patterns of plant invasion levels (alien richness/overall species richness) across latitudes and hemispheres when both islands and continental regions around the globe are combined.

 

10/ Phylogenetic relatedness mediates persistence of seeds in soil

Using a global seed bank database (GloSSBank) comprising data for 2,350 angiosperms, we examined whether soil seed bank type (transient vs. persistent) and density are determined by phylogenetic relatedness. We found a significant phylogenetic signal in seed bank type and density, providing evidence that the ability to form persistent seed banks is not randomly distributed across the phylogeny. The ability to persist in the soil was phylogenetically correlated with the production of dormant and smaller seeds, but seed mass and seed dormancy per se were poor predictors of seed persistence. Interestingly, habitat-related variables (mainly disturbance and canopy openness) but not climate significantly affect the ability of seed plants to form persistent seed banks. Our study is the first to show that phylogenetic relatedness plays an important role in explaining seed bank properties in angiosperms and how these properties relate to early life-history traits, climate and habitat-related variables. These findings represent important insights into plant behaviour in unpredictable environments and how seed plants might respond to global environmental changes.

• Gioria M., Pyšek P., Baskin C. C. & Carta A. (2020) Phylogenetic relatedness mediates persistence and density of soil seed banks. Journal of Ecology 108: 2121–2131. doi: 10.1111/1365-2745.13437

 

11/ Socioeconomic factors in biological invasions: which plants we cultivate and how we chose them?

To analyse how human cultivation habits contribute to naturalization success, we combined global databases on economic uses and naturalization success of the world’s seed plants. We found that naturalization likelihood is 18 times higher for plants with economic value than for noneconomic plants. Naturalization success is highest for plants grown as animal food or for environmental uses (e.g. ornamentals) and increases with number of uses. Taxa from the Northern Hemisphere are over-represented among economic plants, and economic plants from Asia have the greatest naturalization success. Phylogenetic patterns in the naturalized flora partly result from phylogenetic patterns in the plants that humans choose to cultivate (van Kleunen et al. 2020). Which plants and animals are selected for cultivation and captivity, though, is partly determined by species charisma, defined as a set of characteristics, and the perception thereof, that affect people’s attitudes and behaviours toward a species. We show that such charisma can influence all stages of the invasion process, from introduction patterns to management actions by influencing public support or contributing to social conflicts (Jaric et al. 2020).

Horticultural trade is one of the most important drivers of plant invasions. Photo: Foto M. Vilà

• van Kleunen M., Xu X., Yang Q., Maurel N., Zhang Z., Dawson W., Essl F., Kreft H., Pergl J., Pyšek P., Weigelt P., Moser D., Lenzner B. & Fristoe T. (2020): Economic use of plants is key to unravelling their naturalization success. – Nature Communications 11: 3201. doi: 10.1038/s41467-020-16982-3
• Jarić I., Courchamp F., Correia R. A., Crowley S. L., Essl F., Fischer A., González-Moreno P., Kalinkat G., Lambin X., Lenzner B., Meinard Y., Mill A., Musseau C., Novoa A., Pergl J., Pyšek P., Pyšková K., Robertson P., von Schmalensee M., Shackleton R. T., Stefansson R. A., Štajerová K., Veríssimo D. & Jeschke J. M. (2020): The role of species charisma in biological invasions. – Frontiers in Ecology and the Environment 18: 345–353 (doi: 10.1002/fee.2195). doi: 10.1002/fee.2195

 

12/ Mycorrhizal fungi and other symbionts as drivers of plant geography and implications for invasions

Mycorrhizal associations are less common among native island plants than native mainland plants, but naturalized floras show a greater proportion of mycorrhizal plant species on islands than in mainland regions. Mycorrhizal plant species are more likely to naturalize than non-mycorrhizal plants, and species with facultative mycorrhizal associations are more successful than those with obligate mycorrhizal associations. Mycorrhizae are an overlooked driver of global plant biogeographical patterns.

Naturalized floras show a greater proportion of mycorrhizal plant species on islands than in mainland regions, as expected from the anthropogenic co-introduction of plants with their symbionts to islands and anthropogenic disturbance of symbionts in mainland regions. Taken from Delavaux et al., Nature Ecology and Evolution 2019.

• Delavaux C. S., Weigelt P., Dawson W., Duchicela J., Ess F., van Kleunen M., König C., Pergl J., Pyšek P., Stein A., Winter M., Schultz P., Kreft H. & Bever J. D. (2019) Mycorrhizal fungi influence global plant geography. Nature Ecology and Evolution 3: 424–429. doi: 10.1038/s41559-019-0823-4
• Pyšek P., Guo W.-Y., Štajerová K., Moora M., Bueno C. G., Dawson W., Essl F., Gerz M., Kreft H., Pergl J., van Kleunen M., Weigelt P., Winter M. & Zobel M. (2019) Facultative mycorrhizal associations promote plant naturalization worldwide. Ecosphere 10: e02937. doi: 10.1002/ecs2.2937
• Warrington S., Ellis A., Novoa A., Wandrag E. M., Hulme P. E., Duncan R. P., Valentine A. & Le Roux J. J. 2019. Cointroductions of Australian acacias and their rhizobial mutualists in the Southern Hemisphere. Journal of Biogeography 46: 1519-1531. doi: 10.1111/jbi.13602

 

13/ Changes in species richness in the Anthropocene: from global inventories to theoretical concepts

The first global analysis of the effects of biogeographic factors, the physical environment and socioeconomy on the richness of naturalized and invasive alien plants revealed that socioeconomic factors were more important in explaining invasion than naturalization (1). The analysis was based on publicly released Global Naturalized Alien Flora (GloNAF) database, including 13,939 naturalized taxa and their distribution in 1,029 regions of the world, including 381 islands (2). To contribute to the global data on plant invasions we also developed global inventories of two functional groups, terrestrial alien ferns (3) and tall stature naturalized grasses (4). A separate analysis revealed that North and South America might face contrasting challenges in terms of potential threats to biodiversity posed by alien plant species, because of the different past and present dynamics of invasions and predictions of future development. In North America and South America additions of naturalized species to the native flora from other continents make up 6.9 and 1.4 %, respectively (5). As a theoretical concept we argue that it is important to distinguish species for which human-induced environmental changes are important indirect drivers of range expansion into new regions and that such species will become an essential feature for biodiversity management and science in the Anthropocene. We propose the term neonative for these taxa (6).

Dynamics over time of new species introductions to North and South America. (A, left panel) cumulative numbers of species, (B, right panel), numbers recorded as per year. Taken from Pyšek et al., Global Ecology and Biogeography 2019

• 1. Essl F., Dawson W., Kreft H., Pergl J., Pyšek P., van Kleunen M., Weigelt P. et al. (2019) Drivers of the relative richness of naturalized and invasive plant species on the Earth. AoB Plants 11: plz051. doi: 10.1093/aobpla/plz051
• 2. van Kleunen M., Pyšek P., Dawson W., Essl F., Kreft H., Pergl J., Weigelt P. et al. (2019) The Global Naturalized Alien Flora (GloNAF) database. – Ecology 100: e02542. doi: 10.1002/ecy.2542
• 3. Jones E. J., Kraaij T., Fritz H. & Moodley D. 2019. A global assessment of terrestrial alien ferns (Polypodiophyta): species’ traits as drivers of naturalisation and invasion. Biological Invasions 21:861-873. doi: 10.1007/s10530-018-1866-1
• 4. Canavan S., Meyerson L. A., Packer J. G., Pyšek P., Maurel N., Lozano V., Richardson D. M., Brundu G., Canavan K., Cicatelli A., Čuda J., Dawson W., Essl F., Guarino F., Guo W-Y, van Kleunen M., Kreft H., Lambertini C., Pergl J., Skálová H., Soreng R. J., Visser V., Vorontsova M. S., Weigelt P., Winter M. & Wilson J. R. U. 2019. Tall-statured grasses: a useful functional group for invasion science. Biological Invasions 21: 37-58.doi: 10.1007/s10530-018-1815-z
• 5. Pyšek P., Dawson W., Essl F., Kreft H., Pergl J., Seebens H., van Kleunen M., Weigelt P. & Winter M. (2019): Contrasting patterns of naturalized plant richness in Americas: numbers are higher in the North but expected to rise sharply in the South. Global Ecology and Biogeography 28: 779–783. doi: 10.1111/geb.12891
• 6. Essl F., Dullinger S., Genovesi P., Hulme P. E., Jeschke J., Katsanevakis S., Kühn I., Lenzner B., Pauchard A., Pyšek P., Rabitsch W., Richardson D. M., Seebens H., van Kleunen M., van der Putten W., Vilà M. & Bacher S. (2019) A conceptual framework for range-expanding species that track human-induced environmental change. BioScience 69: 908–919. doi: 10.1093/biosci/biz101