The vascular flora of Mt Svilaja (Outer Dinarides, South Croatia)

Based on our own research carried out from 2013 to 2019 and literature data, this study presents for the first time a comprehensive floristic list of Mt Svilaja (max. 1508 m a.s.l.). It contains 1285 taxa classified within 502 genera and 109 families. Of these, 552 taxa are listed for the first time for Svilaja. Out of 733 taxa recorded previously, the presence of 128 taxa has not been confirmed. Poaceae (8.79%), Asteraceae and Fabaceae (8.72% each) had the highest number of taxa, with the largest number of taxa within the genera Trifolium (23 taxa), Carex (20) and Centaurea (17). Hemicryptophytes (43.35%) and therophytes (25.45%) prevailed, and Mediterranean (23.27%), southern European (20.83%) and Eurasian (17.43%) plant taxa dominated. Altogether, there were 76 endemics (5.91%), mostly of Illyrian-Adriatic origin, 34 endangered (CR, EN, VU) taxa (2.65%), and 155 strictly protected taxa according to Croatian law (12.06%). Among the endemics, the presence of Scabiosa delminiana Abadžić must be stressed. Mt Svilaja is characterized by rich orchid flora (51 taxa, 3.97%), and features Epipactis placentina Bongiorni & Grünanger, the only site found in Croatia that does. Although as many as 34 invasive taxa have been recorded, their presence is mostly limited to anthropogenic habitats.

Economic costs of biological invasions in terrestrial ecosystems in Russia

Terrestrial ecosystems, owing to the presence of key socio-economic sectors such as agriculture and forestry, may be particularly economically affected by biological invasions. The present study uses a subset of the recently developed database of global economic costs of biological invasions (InvaCost) to quantify the monetary costs of biological invasions in Russia, the largest country in the world that spans two continents. From 2007 up to 2019, invasions costed the Russian economy at least US$ 51.52 billion (RUB 1.38 trillion, n = 94 cost entries), with the vast majority of these costs based on predictions or extrapolations (US$ 50.86 billion; n = 87) and, therefore, not empirically observed. Most cost entries exhibited low geographic resolution, being split between European and Asian parts of Russia (US$ 44.17 billion; n = 72). Just US$ 7.35 billion (n = 22) was attributed to the European part solely and none to the Asian part. Invasion costs were documented for 72 species and particularly insects (37 species). The empirically-observed costs, summing up to US$ 660 million (n = 7), were reported only for four species: two insects Agrilus planipennis Fairmaire and Cydalima perspectalis (Walker) and two plants Ambrosia artemisiifolia L. and Heracleum sosnowskyi Manden. The vast majority of economic costs were related to resource damages and economic losses, with very little reported expenditures on managing invasions in terrestrial ecosystems. In turn, agriculture (US$ 37.42 billion; n = 68) and forestry (US$ 14.0 billion; n = 20) were the most impacted sectors. Overall, we report burgeoning economic costs of invasions in Russia and identify major knowledge gaps, for example, concerning specific habitat types (i.e. aquatic) and management expenditures, as well as for numerous known invasive taxa with no reported economic costs (i.e. vertebrates). Given this massive, largely underestimated economic burden of invasions in Russia, our work is a call for improved reporting of costs nationally and internationally.

Some Observations on Invasive Vascular Plant Species of the Eastern United States, New York to the Florida Keys

The objective of the present study was to compare the invasive vascular plant species at city, state, National Parks, and research preserves in New York, New Jersey, South Carolina and Florida, where the author has conducted research and published his findings in refereed journals. Sites with human activity have a high percent (<50%) of invasive species. Invasive taxa have increased at “protected” sites where human impact is minimal posing a further threat to native vegetation. The deliberate introduction of exotic taxa such as Callery Pear, Kudzu, Multiflora Rose, Norway Maple, Oriental Bittersweet, and more pose a threat to native taxa.

Weed vegetation of arable land in Slovakia: diversity and species composition

Arable fields are among the most widespread habitats in Slovakia, but recently, there have been no studies regarding species composition and structure of weed vegetation in these fields. Therefore, we studied the structure of arable weed vegetation and detected α- and β-diversity. The dataset of 507 phytosociological relevés in different crop types contains 407 plant taxa in 46 plant families. Native plants dominated over aliens, archaeophytes dominated over neophytes, and 14 plants belonged to invasive taxa. The most common species in the dataset were <em>Tripleurospermum perforatum</em>, <em>Cirsium arvense</em>, and <em>Viola arvensis</em>. Weeds were mostly therophytes, b- and a-euhemerobic, competitors, and ruderals, reproducing by seeds and pollinated by insects. The β-diversity of weed vegetation decreased with elevation and temperature and was higher in the Pannonicum than the Carpaticum region. The highest β-diversity was established in fodder+fallow fields, followed by that in cereals and root-crop fields, and the smallest diversity was found in stubble. Beta-diversity increased from spring to summer and slightly decreased again in fall. Detrended correspondence analysis indicated that the major compositional turnover of weed vegetation was related to light, temperature, moisture, and elevation. Weed vegetation constitutes an important habitat in the landscape that provides refuge to many threatened plants, and this vegetation has important functions in the agro-ecosystem food chain.

Checklist of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain)

This is an inventory of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain) updated to 2018, representing 1068 alien taxa in total. 554 (52.0%) out of them are casual and 514 (48.0%) are established. 87 taxa (8.1% of the total number and 16.8 % of those established) show an invasive behaviour. The geographic zone with more alien plants is the most anthropogenic maritime area. However, the differences among regions decrease when the degree of naturalization of taxa increases and the number of invaders is very similar in all sectors. Only 26.2% of the taxa are more or less abundant, while the rest are rare or they have vanished. The alien flora is represented by 115 families, 87 out of them include naturalised species. The most diverse genera are Opuntia (20 taxa), Amaranthus (18 taxa) and Solanum (15 taxa). Most of the alien plants have been introduced since the beginning of the twentieth century (70.7%), with a strong increase since 1970 (50.3% of the total number). Almost two thirds of alien taxa have their origin in Euro-Mediterranean area and America, while 24.6% come from other geographical areas. The taxa originated in cultivation represent 9.5%, whereas spontaneous hybrids only 1.2%. From the temporal point of view, the rate of Euro-Mediterranean taxa shows a progressive reduction parallel to an increase of those of other origins, which have reached 73.2% of introductions during the last 50 years. The most important way of introduction is gardening (58.0%), followed by agriculture and commerce, while forestry is marginal. Invasive taxa mainly come from gardening and trade, but the proportion of the latter that become invasive is higher (6.1% and 15.6%, respectively). Most of the established aliens are annual and perennial forbs, while other biological types are less represented. These two types are also dominant among the invasive alien species, although a notable increase of trees and climbers has been observed recently.

Development of alien and invasive taxa lists for regulation of biological invasions in South Africa

Background: Lists are fundamental for guiding policy and management of biological invasions. The process of developing regulatory lists of alien and invasive taxa should be based on scientific evidence through an objective, transparent and consistent process.Objectives: In this study, we review the development of the lists for the alien and invasive species regulations in terms of section 97(1) of the National Environmental Management: Biodiversity Act, 2004 (NEM:BA) (Act No. 10 of 2004).Method: Lists published in the National Government Gazette were compared and assessed for changes in the taxa listed and their status between 2009 and 2016. Minutes from expert workshops convened to inform the listing were reviewed. Relevant information such as the criteria for listing taxa was extracted from minutes of the workshops.Results: Three draft versions were produced and published in the Government Gazette for public comment before the final list was published in August 2014 and promulgated in October 2014. The list is to be reviewed regularly and additional species can be added, and the status of species can be changed as additional evidence of threat levels is available – and was even amended in May 2015. The various stakeholders involved in the listing process were academics, conservation experts, managers and the general public through an inclusive process which included participation workshops or through public comment. A scoring tool based on the likelihood of invasion versus the impact of invasion was recommended for evaluating the risk of a species, but was rarely used. A number of issues relating to conflicts and approaches for listing were faced during development of lists.Conclusion: We conclude with some recommendations for future refinements in the listing process, including improving transparency and participation as well as developing standardised approaches for listing.

Effects of invasive plant species on species diversity: implications on ruderal vegetation in Bratislava City, Slovakia, Central Europe

Invasive species pose one of the most serious global environmental threats. Our study aimed to examine the correlation between the proportion of invasive alien taxa and species diversity of ruderal vegetation in the urban ecosystem of Bratislava, located in Central Europe. Ruderal habitats serve as the means of spread of invasive species to seminatural and natural habitats. Twenty-six invasive taxa were recorded among the ruderal vegetation of Bratislava. The majority of the recorded invasive species were neophytes, which came from North America and represent the Asteraceae family. Half of them were introduced accidentally, whereas the remaining species were introduced deliberately. Correlation and regression analyses showed that the proportion of invasive taxa has a negative effect on the species diversity of all the analyzed syntaxa in the ruderal vegetation of Bratislava.

Dynamics of the species diversity and composition of the ruderal vegetation of Slovak and Czech cities

This study reports the results of the evaluation of changes in the species diversity and composition of ruderal vegetation of three Slovak and one Czech city over the time. The dataset of 1489 relevés from five ruderal syntaxa from the cities Bratislava, Malacky, Trnava and Brno was used. Data were from two different time periods, the older dataset from the years 1960–1982, the more recent dataset from the years 2005–2016. The statistical analysis revealed the decrease of Shannon–Wiener diversity index of all (native + alien) species in the majority of classes of ruderal vegetation of cities. The analysis of the changes in the Pielou’s measure of species evenness showed that in some of the classes and cities, the species evenness remained unchanged, in the other ones it decreased. The percentage of native species in the ruderal vegetation did not change over the time, but the percentage of invasive alien species in the majority of syntaxa and cities increased significantly. In total, 38 invasive taxa were recorded in the ruderal vegetation of cities. Most of them are neophytes, therophytes and belong to the family Asteraceae. The majority of invasive taxa were recorded in both time periods. Some of the invasive species, e.g. Fallopia japonica and Juncus tenuis were recorded only in the more recent time period. Our results contribute to the knowledge about biological invasions in the cities.

Stronger connectivity of the resident gut microbiome lends resistance to invading bacteria

Bacterial infection in the gut is often due to successful invasion of the host microbiome by an introduced pathogen. Ecological theory indicates that resident community members and their interactions should be strong determinants of whether an invading taxon can persist in a community. In the context of the gut microbiome, this suggests colonization resistance against newly introduced bacteria should depend on the instantaneous bacterial community composition within the gut and interactions between these constituent members. Here we develop a mathematical model of how metabolite-dependent biotic interactions between resident bacteria mediate invasion, and find that stronger biotic connectivity from metabolite cross-feeding and competition increases colonization resistance. We then introduce a statistical method for identifying invasive taxa in the human gut, and show empirically that greater connectivity of the resident gut microbiome is related to increased resistance to invading bacteria. Finally, we examined patient outcomes after fecal microbiota transplant (FMT) for recurring Clostridium difficile infection. Patients with lower connectivity of the gut microbiome after treatment were more likely to relapse, experiencing a later infection. Thus, simulation models and data from human subjects support the hypothesis that stronger interactions between bacteria in the gut repel invaders. These results demonstrate how ecological invasion theory can be applied to the gut microbiome, which might inform targeted microbiome manipulations and interventions. More broadly, this study provides evidence that low connectivity in gut microbial communities is a hallmark of community instability and susceptibility to invasion.