Introduction

General description

Project description

Sampling methods

Geographic coverage

Taxonomic coverage

Traits coverage

Temporal coverage

Collection data

Usage licence

Data resources

Additional information

Results

At the national scale, Global Moran's I test indicated a significantly clustered pattern in the number of alien plant species (Z = 56.54, p < 0.001) and of species occurrences (Z > 1.96, p < 0.05) per UTM 5 km × 5 km grid cell, thus suggesting a strong bias in the distribution of alien plant species. Moreover, results of the Getis Ord Gi* spatial statistic revealed several hotspots of recorded alien plant species. We observed high clusters of records in cities and surroundings with the highest sampling effort recorded in Arad City (mean Z = 7.10) (1) and Timisoara (mean Z = 5.04) (4) in western Romania, Constanta (mean Z = 6.29) (2) in eastern Romania, Giurgiu (mean Z = 6.24) (3) and Bucharest (mean Z = 5.00) (5) in southern Romania. Moreover, there are several smaller hotspots in Cluj and Alba-Iulia Counties (in the central part of Romania), in Botosani and Iasi Counties (the north-eastern part of Romania) and around the Cities of Oradea (in the western part of Romania) and Sulina (south-eastern Romania) (Fig. 1).

Figure 1.  

Hotspots of alien plant species survey in Romania (in red) suggesting a significantly clustered pattern in the number of alien plant species occurrences per UTM 5 km × 5 km grid cell. The numbered statistically significant hotspots are: 1 Arad City, 2 Constanta City, 3 Giurgiu City, 4 Timisoara City, 5 Bucharest City.

Species richness aggregated at a 5 km × 5 km grid ranged from 3 to 123 species. The highest number of alien plant species was recorded in the western part of the country and around cities, namely Oradea and surrounding areas with 123 species per grid cell, followed by Arad with 72 species per grid cell, Timisoara with 55 species per grid cell, in the eastern part of the country, Braila with 51 species per grid cell, Tulcea with 50 species per grid cell and Bucharest in the southern part of the country with 59 species per grid cell. Most of the grid cells with high alien plant species richness recorded are concentrated in particular regions of Romania, i.e. the western part (e.g. Timisoara and Arad Counties), the eastern (e.g. Iasi, Neamt and Vrancea Counties), south-eastern (e.g. Braila, Tulcea and Constanta Counties) and the southern part of Romania (e.g. Bucharest), suggesting a distribution of alien plant species around urban centres and traffic routes (Fig. 2). Grid cells with low richness values are mostly distributed in the southern and northern parts of the country, reflecting an undersampling of alien plant species.

Figure 2.  

Alien plant species richness in Romania (UTM 5 km × 5 km grid resolution).

When represented at a lower spatial resolution (50 km × 50 km), alien plant species richness ranged from 23 to 145 species per grid cell (Fig. 3). The same patterns can be observed on the map: higher species richness in the western and eastern part of the country and around major cities and the capital (e.g. Oradea, Timisoara, Arad, Iasi, Tulcea, Bucharest) and lower alien plant species richness in the southern and northern parts of Romania.

Figure 3.  

Alien plant species richness in Romania (UTM 50 km × 50 km grid resolution).

Conclusion

The distribution of data collected suggests a correlation between the presence of transportation infrastructure and the occurrence of alien species (Mortensen et al. 2017, Rauschert et al. 2017), as most of the 5 km × 5 km grid cells in which alien plant species were recorded are crossed by, or have roads with high traffic volumes nearby (e.g. European routes E85, E81 and E60) or the cities with the highest number of alien plant species are located close to the borders (i.e. Oradea, Arad, Timisoara, Iasi, Braila, Oradea, Tulcea, Constanta). However, it is important to note that this distribution might be influenced by biases, as the in situ observations relied on the accessibility of the sample plots. This hypothesis serves as a a starting point for future research studies. A similar study by Lemke et al. (2018) demonstrated that traffic volume significantly affected dispersal distances and the lateral deposition of seeds of Ambrosia artemisiifolia on roadsides in Germany. The same invasive alien plant species with a highly allergenic effect on human health was repeatedly reported in Romania, being proposed as a species of interest for Romania and included in the Action plan on the pathways of invasive alien species (Ministerul Mediului, Apelor si Padurilor 2022).

Presently, of the 41 plant species of EU concern, four are already established in Romania and widespread: Ailanthus altissima, Asclepias syriaca, Elodea nuttallii and Impatiens glandulifera. The presence of Humulus scandens was also confirmed in several regions (e.g. southern and southwest, central and northwest parts of the country). Heracleum sosnowskyi and Ludwigia peploides are confirmed in one location for each species. The presence of Cabomba caroliniana and Myriophyllum aquaticum in Romania is not confirmed.

Amongst the 396 alien plant species inventoried in this study, seven species are proposed as species of interest for Romania (i.e. Ambrosia artemisiifolia, Ambrosia tenuifolia, Ambrosia trifida, Cyclachaena xanthiifolia, Phytolacca americana, Phytolacca acinosa and Verbesina encelioides) according to the Article 12(1) of Regulation 1143/2014 of the European Union (EU), where Member States may establish a national list of invasive alien species of interest to a Member State (European Union 2014). The seven alien plant species were selected, based on their significant impact on both human health, such as allergenic pollen and agriculture, particularly in terms of seed production (Lommen et al. 2017, Kumar Rai and Singh 2020). Three of them are also included in the Action plan on the pathways of invasive alien species (i.e. Ambrosia artemisiifolia, Ambrosia trifida and Phytolacca americana). This indicates that these species are considered to have a significant impact and require special measures for their management.

When comparing with the dataset published by Sirbu et al. (2022) by overlaying the spatially corresponding databases using GIS, the new distribution database shows a more reduced survey bias (Fig. 1). This suggests that our database included in this article reflect better the distribution of alien species and the pathways of introduction. Sirbu et al. (2022) indicate hotspots of invasive alien plant species near major academic and research facilities, concluding that the data collection was opportunistic rather than systematic (see literature records only, grid cells in yellow, Fig. 4). This finding validates the earlier mentioned studies, with this phenomenon attributed to the botanist effect (Moerman and Estabrook 2006). The globalisation era brought the spotlight upon transport networks, which are considered the frontline in the prevention of biological invasions (Hulme et al. 2009). Our results showed that most of the 5 km × 5 km cells in which alien plant species were recorded are crossed by important roads (high volumes of traffic roads, see field activity records only, grid cells in red, Fig. 4). This outcome endorses the prior studies acknowledging the role of transport infrastructures in the dispersal of alien plant species (Rauschert et al. 2017).

Figure 4.  

Alien plant species records in Romania, resulting from joining Sirbu et al. (2022) review of literature (1778-2018) and our field survey (2019-2022) at UTM 5 km × 5 km grid resolution.

In the field inventory-based database, we noted limited coverage of the northern and southern parts of Romania, facts also noticed by Sirbu et al. (2022) in the literature-based database. We also observed that high species richness matches the hotspots of sampling efforts, validating the finding that sampling in our survey was directly correlated with alien plant species diversity and ease of access (Fig. 4). The analysis revealed that high species richness was observed in the same areas mentioned by Sirbu et. al (2002) in his study (e.g. western, eastern, central and south-eastern parts of the country, as well as near major cities such as Arad, Timisoara, Oradea, Bucharest, Constanta and Iasi), indicating that urban environments frequently serve as entry points for alien species (Botham et al. 2009) (see records from field activity and literature, grid cells in green, Fig. 4). Thus, referencing bias in sampling serves to acknowledge the potential limitations in the comprehensiveness and representativeness of the collected data, despite efforts to achieve national coverage.

Data on the impact of alien plant species in Romania is still lacking and further studies are necessary. There is also a crucial need for coordinated institutional initiatives to enhance the effectiveness of alien species management at both national and local levels. Such efforts should encompass raising awareness and public engagement, harmonising legislation and enhancing the capacity of public institutions for invasive species management.

Acknowledgements

Author contributions

References

Anastasiu P, Negrean G (2005)
Alien plants in Romania (1)
.
Analele stiintifice ale Universitatiii Alexandru Ioan Cuza din Iasi
51
:
87
‑
96
.
Anastasiu P, Negrean G (2009)
Neophytes in Romania
. In: Rákosy L, Momeu L (Eds)
Neobiota din România
.
Presa Universitară Clujeană
Anastasiu P, Rozylowicz L, Skolka M, Preda C, Memedemin D, Cogǎlniceanu D (2016)
Scientific reports 1. State of the art of alien species in South-Eastern Europe. Country reports: Alien species in Romania
.
ESENIAS
.
Anastasiu P, Preda C, Bănăduc D, Cogălniceanu D (2017)
Alien species of EU concern in Romania
.
Transylvanian Review of Systematical and Ecological Research
19
(
3
):
93
‑
106
. https://doi.org/10.1515/trser-2017-0024
Botham MS, Rothery P, Hulme PE, Hill MO, Preston CD, Roy DB (2009)
Do urban areas act as foci for the spread of alien plant species? An assessment of temporal trends in the UK
.
Diversity and Distributions
15
(
2
):
338
‑
345
. https://doi.org/10.1111/j.1472-4642.2008.00539.x
Brundu G, Costello KE, Maggs G, Montagnani C, Nunes AL, Pergl J, Peyton J, Robertson P, Roy H, Scalera R, Smith K, Solarz W, Tricarico E, Valkenburg J (2022)
An introduction to the invasive alien species of Union concern
.
Publications Office of the European Union
.
CBD (2022)
COP 15: Kunming-Montreal Global Biodiversity Framework. Montreal, Canada
.
Convention on Biological Diversity
. URL: https://www.cbd.int/gbf/
Ciocarlan V (2009)
Flora ilustrata a Romaniei. Pteridophyta et Spermatophyta
.
Editura Ceres
,
Bucuresti
,
1142
pp.
Dihoru G (2004)
Invasive plants in Romania’s flora
.
Analele Universităţii din Craiova
9
(
45
):
73
‑
82
.
European Commission (2020)
EU Biodiversity Strategy for 2030. Bringing nature back into our lives. Communication From The Commission To The European Parliament, The Council, The European Economic And Social Committee And The Committee Of The Regions
.
European Commission
. URL: https://ec.europa.eu/research/environment/index.cfm?pg=nbs
European Commission (2022)
Commission Implementing Regulation (EU) 2022/1203 of 12 July 2022 amending Implementing Regulation (EU) 2016/1141 to update the list of invasive alien species of Union concern
. URL: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32022R1203
European Union (2014)
Regulation (EU) No 1143/2014 of the European Parliament and of the Council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species
.
Official Journal of the European Union
. URL: https://eur-lex.europa.eu/eli/reg/2014/1143/oj
Fortin M, Dale M (2005)
Spatial analysis: A guide for ecologists
.
Cambridge University Press
,
Cambridge
,
365
pp. https://doi.org/10.1017/CBO9780511542039
GBIF Secretariat (2023)
GBIF backbone taxonomy. Checklist dataset
.
GBIF
URL: https://doi.org/10.15468/39omei
Graham C, Hijmans R (2006)
A comparison of methods for mapping species ranges and species richness
.
Global Ecology and Biogeography
15
(
6
):
578
‑
587
. https://doi.org/10.1111/j.1466-8238.2006.00257.x
Haubrock P, Cuthbert R, Sundermann A, Diagne C, Golivets M, Courchamp F (2021)
Economic costs of invasive species in Germany
.
NeoBiota
67
:
225
‑
246
. https://doi.org/10.3897/neobiota.67.59502
Hulme P, Roy D, Cunha T, Larsson T (2009)
A pan-European inventory of alien species: Rationale, implementation and implications for managing biological invasions
.
Handbook of Alien Species in Europe
1
‑
14
. https://doi.org/10.1007/978-1-4020-8280-1_1
Keller RP, Geist J, Jeschke JM, Kühn L (2011)
Invasive species in Europe: Ecology, status, and policy
.
Environmental Sciences Europe
23
(
1
). https://doi.org/10.1186/2190-4715-23-23
Kumar Rai P, Singh JS (2020)
Invasive alien plant species: Their impact on environment, ecosystem services and human health
.
Ecological Indicators
111
https://doi.org/10.1016/j.ecolind.2019.106020
Latombe G, Pyšek P, Jeschke J, Blackburn T, Bacher S, Capinha C, Costello M, Fernández M, Gregory R, Hobern D, Hui C, Jetz W, Kumschick S, McGrannachan C, Pergl J, Roy H, Scalera R, Squires Z, Wilson JU, Winter M, Genovesi P, McGeoch M (2017)
A vision for global monitoring of biological invasions
.
Biological Conservation
213
:
295
‑
308
. https://doi.org/10.1016/j.biocon.2016.06.013
Lemke A, Kowarik I, von der Lippe M (2018)
How traffic facilitates population expansion of invasive species along roads: The case of common ragweed in Germany
.
Journal of Applied Ecology
56
(
2
):
413
‑
422
. https://doi.org/10.1111/1365-2664.13287
Lommen SE, Hallmann C, Jongejans E, Chauvel B, Leitsch-Vitalos M, Aleksanyan A, Tóth P, Preda C, Šćepanović M, Onen H, Tokarska-Guzik B, Anastasiu P, Dorner Z, Fenesi A, Karrer G, Nagy K, Pinke G, Tiborcz V, Zagyvai G, Zalai M, Kazinczi G, Leskovšek R, Stešević D, Fried G, Kalatozishvili L, Lemke A, Müller-Schärer H (2017)
Explaining variability in the production of seed and allergenic pollen by invasive Ambrosia artemisiifolia across Europe
.
Biological Invasions
20
(
6
):
1475
‑
1491
. https://doi.org/10.1007/s10530-017-1640-9
Ministerul Mediului, Apelor si Padurilor (2022)
Ordin nr. 3008 din 17 noiembrie 2022 al ministrului mediului, apelor si pădurilor privind aprobarea Planului national de actiune pentru abordarea căilor de introducere prioritare a speciilor alogene invazive din România, în cadrul proiectului "Managementul adecvat al speciilor alogene invazive din România, în conformitate cu Regulamentul (UE) nr. 1.143/2014, referitor la prevenirea si gestionarea introducerii si răspândirii speciilor alogene invazive" finantat prin Programul operational Infrastructura mare 2014-2020
.
Guvernul Romaniei
. URL: https://www.cdep.ro/pls/legis/legis_pck.htp_act?ida=190254
Moerman D, Estabrook G (2006)
The botanist effect: counties with maximal species richness tend to be home to universities and botanists
.
Journal of Biogeography
33
(
11
):
1969
‑
1974
. https://doi.org/10.1111/j.1365-2699.2006.01549.x
Mortensen D, Rauschert EJ, Nord A, Jones B (2017)
Forest roads facilitate the spread of invasive plants
.
Invasive Plant Science and Management
2
(
3
):
191
‑
199
. https://doi.org/10.1614/ipsm-08-125.1
Ord JK, Getis A (2010)
Local spatial autocorrelation statistics: Distributional issues and an application
.
Geographical Analysis
27
(
4
):
286
‑
306
. https://doi.org/10.1111/j.1538-4632.1995.tb00912.x
Pyšek P, Hulme P, Simberloff D, Bacher S, Blackburn T, Carlton J, Dawson W, Essl F, Foxcroft L, Genovesi P, Jeschke J, Kühn I, Liebhold A, Mandrak N, Meyerson L, Pauchard A, Pergl J, Roy H, Seebens H, van Kleunen M, Vilà M, Wingfield M, Richardson D (2020)
Scientists' warning on invasive alien species
.
Biological Reviews
95
(
6
):
1511
‑
1534
. https://doi.org/10.1111/brv.12627
Rauschert EJ, Mortensen D, Bloser S (2017)
Human-mediated dispersal via rural road maintenance can move invasive propagules
.
Biological Invasions
19
(
7
):
2047
‑
2058
. https://doi.org/10.1007/s10530-017-1416-2
Rey V, Ianos I, Groza O, Patroescu M (Eds) (2007)
Reclus Atlas de la Roumanie. Nouvelle éd
.
CNRS-Libergéo - La Documentation Française
,
Paris
,
208
pp.
Roy HE, Pauchard A, Stoett P, Renard T, Bacher. S, Galil BS, Hulme PE, Ikeda T, Sankaran K, McGeoch MA, Meyerson LA, Nuñez MA, Ordonez A, Rahlao SJ, Schwindt E, Seebens H, Sheppard AW, Vandvik. V (2023)
Intergovernmental science-policy platform on biodiversity and ecosystem services
.
IPBES Invasive Alien Species Assessment: Summary for Policymakers (Version 3). Zenodo
. https://doi.org/10.1007/978-94-017-9499-2_10
Rozylowicz L, Nita A, Manolache S, Popescu V, Hartel T (2019)
Navigating protected areas networks for improving diffusion of conservation practices
.
Journal of Environmental Management
230
:
413
‑
421
. https://doi.org/10.1016/j.jenvman.2018.09.088
Seebens H, Blackburn T, Dyer E, Genovesi P, Hulme P, Jeschke J, Pagad S, Pyšek P, Winter M, Arianoutsou M, Bacher S, Blasius B, Brundu G, Capinha C, Celesti-Grapow L, Dawson W, Dullinger S, Fuentes N, Jäger H, Kartesz J, Kenis M, Kreft H, Kühn I, Lenzner B, Liebhold A, Mosena A, Moser D, Nishino M, Pearman D, Pergl J, Rabitsch W, Rojas-Sandoval J, Roques A, Rorke S, Rossinelli S, Roy H, Scalera R, Schindler S, Štajerová K, Tokarska-Guzik B, van Kleunen M, Walker K, Weigelt P, Yamanaka T, Essl F (2017)
No saturation in the accumulation of alien species worldwide
.
Nature Communications
8
(
1
). https://doi.org/10.1038/ncomms14435
Seebens H, Bacher S, Blackburn T, Capinha C, Dawson W, Dullinger S, Genovesi P, Hulme P, van Kleunen M, Kühn I, Jeschke J, Lenzner B, Liebhold A, Pattison Z, Pergl J, Pyšek P, Winter M, Essl F (2020)
Projecting the continental accumulation of alien species through to 2050
.
Global Change Biology
27
(
5
):
970
‑
982
. https://doi.org/10.1111/gcb.15333
Sirbu C, Oprea A (2011)
Plante adventive în flora României
.
Editura Ion Ionescu de la Brad
,
Iasi
.
Sirbu C, Anastasiu P, Urziceanu M, Camen-Comănescu P, Sîrbu I, Popa A, Ioja C, Gavrilidis A, Oprea A (2021)
Invasive alien plant species in Romania of European Union concern
.
Environmental & Socio-economic Studies
9
(
4
):
32
‑
44
. https://doi.org/10.2478/environ-2021-0023
Sirbu C, Miu I, Gavrilidis A, Gradinaru S, Niculae I, Preda C, Oprea A, Urziceanu M, Camen-Comanescu P, Nagoda E, Sirbu I, Memedemin D, Anastasiu P (2022)
Distribution and pathways of introduction of invasive alien plant species in Romania
.
NeoBiota
75
:
1
‑
21
. https://doi.org/10.3897/neobiota.75.84684
Sirbu MI, Anastasiu P, Urziceanu M, Sesan TE (2021)
First ascertainable record of Ludwigia peploides from Romania
.
Contribuţii Botanice
56
:
13
‑
27
. https://doi.org/10.24193/contrib.bot.56.2
Universitatea din Bucuresti, Ministerul Mediului, Apelor si Padurilor (2023)
Managementul adecvat al speciilor invazive din România, în conformitate cu Regulamentul UE 1143/2014 referitor la prevenirea și gestionarea introducerii și răspândirii speciilor alogene invazive
. https://invazive.ccmesi.ro/. Accessed on: 2023-12-14.
Urziceanu M, Rozylowicz L, Stefanescu DM, Anastasiu P (2024)
Monitoring plant diversity in wind farm areas: An approach to early detection of alien plant species
.
Conservation Science and Practice
6
(
4
). https://doi.org/10.1111/csp2.13109
Zenni RD, Essl F, García-Berthou E, McDermott S (2021)
The economic costs of biological invasions around the world
.
NeoBiota
67
:
1
‑
9
. https://doi.org/10.3897/neobiota.67.69971

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