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Towards global dominance of invasive alien plants in freshwater ecosystems: the dawn of the Exocene?

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Rossano Bolpagni at Università di Parma
Rossano Bolpagni
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Abstract and Figures

The global and seemingly unstoppable spread of invasive alien plants emerges as one of the main topics of current science. This is due to the multiple repercussions of invasive plants on biodiversity and ecosystem functioning, plus huge consequences on human existence. In freshwaters, lots of invaders are extremely competitive by virtue of their idiosyncratic reproductive and adaptive strategies. As “inland islands”, freshwaters seem particularly prone to changes when invaded, such as reorganisation of food webs and biotic interactions. Together, these events are self-reinforcing, implying hardly reversible hysteric phenomena. The intention of this paper is to point out: invasion pathways, driving factors, invasion mechanisms, and noticeable effects mediated by plant invaders in freshwaters through an extensive knowledge review. The growing evidence suggests the dawn of a new epochal phase: a globally alien-dominated “bio-historical horizon”, tentatively called “Exocene”, where invaders play predominant roles that drive freshwaters functioning and successional unexpected stages. In the context of invasion science, Exocene reinforces the need for an ecosystem-based perspective to properly understand the implications of plant invaders in freshwaters. Seven challenging issues emerge to be addressed to better outline the global paths of biodiversity and functioning between biomes when faced with biological invasion.
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INVASIVE SPECIES III Opinion Paper
Towards global dominance of invasive alien plants
in freshwater ecosystems: the dawn of the Exocene?
Rossano Bolpagni
Received: 13 May 2020 / Revised: 9 December 2020 / Accepted: 14 December 2020 / Published online: 18 January 2021
The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature 2021
Abstract The global and seemingly unstoppable
spread of invasive alien plants emerges as one of the
main topics of current science. This is due to the
multiple repercussions of invasive plants on biodiver-
sity and ecosystem functioning, plus huge conse-
quences on human existence. In freshwaters, lots of
invaders are extremely competitive by virtue of their
idiosyncratic reproductive and adaptive strategies. As
‘‘inland islands’’, freshwaters seem particularly prone
to changes when invaded, such as reorganisation of
food webs and biotic interactions. Together, these
events are self-reinforcing, implying hardly reversible
hysteric phenomena. The intention of this paper is to
point out: invasion pathways, driving factors, invasion
mechanisms, and noticeable effects mediated by plant
invaders in freshwaters through an extensive knowl-
edge review. The growing evidence suggests the dawn
of a new epochal phase: a globally alien-dominated
‘‘bio-historical horizon’’, tentatively called ‘‘Ex-
ocene’’, where invaders play predominant roles that
drive freshwaters functioning and successional unex-
pected stages. In the context of invasion science,
Exocene reinforces the need for an ecosystem-based
perspective to properly understand the implications of
plant invaders in freshwaters. Seven challenging
issues emerge to be addressed to better outline the
global paths of biodiversity and functioning between
biomes when faced with biological invasion.
Keywords Exotic plant species Inland aquatic
habitats Evolutionary processes Invasions
Impacts Biotic interactions Regime shifts
Ecosystem engineers
Introduction
In the last few decades, a growing bulk of literature has
been focussed on adverse impacts of invasive alien
species (IAS) on ecosystems and humans (Lockwood
et al., 2007; Rai & Singh, 2020). IAS have occupied
the phylogenetic and functional space within the range
formed by native species by bridging existing empty
gaps or excluding natives (Loiola et al. 2018; Dalle
Fratte et al. 2019). Overall, IAS tend to disrupt the
functional links among native species by supporting a
progressive multidimensional impoverishment of
Guest editors: Katya E. Kovalenko, Fernando M. Pelicice,
Lee B. Kats, Jonne Kotta & Sidinei M. Thomaz / Aquatic
Invasive Species III
Supplementary information The online version of this
article (https://doi.org/10.1007/s10750-020-04490-w) contains
supplementary material, which is available to authorized users.
R. Bolpagni (&)
Department of Chemistry, Life Sciences and
Environmental Sustainability, University of Parma,
Parma, Italy
e-mail: rossano.bolpagni@unipr.it
123
Hydrobiologia (2021) 848:2259–2279
https://doi.org/10.1007/s10750-020-04490-w(0123456789().,-volV)(0123456789().,-volV)
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... The expansion of alien invasive plants is occurring globally and seems like an unstoppable wave, affecting many, if not all, natural ecosystems [1]. Of these, freshwater ecosystems are among the most vulnerable to alien invasive species [2]. When invaded, the body of water and the surrounding land are particularly susceptible to drastic changes in community composition, structure, and biotic interactions [3]. ...
... Thus, the occurrence of alien invasive species within island water bodies becomes especially relevant. Nevertheless, even though alien invasive species are acknowledged as drivers of biodiversity loss, studies on the pathways, drivers, mechanisms, and effects of alien invasive species are relatively scarce for island water bodies [2]. ...
... The successful colonization and establishment of alien invasive plants depend on different factors: first, invasion pathways; second, driving factors that provide invasion opportunity windows; third, ecological mechanisms that promote a successful invasion. Finally, combining these factors determines the effects of invasive species in natural com-munities [2]. Next, we describe the possible invasion pathways, invasion drivers, invasion mechanisms, and invasion effects of the alien potentially invasive species found in the lagoons. ...
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... In the field of natural science, for example, interdisciplinarity will facilitate multiple-taxa research and cross-ecosystem studies, enabling the recognition of new species interactions, novel human-wildlife connections, and providing guidance for environmental managers. Microbiological, physiological, behavioral, and functional aspects of biological invasions remain poorly investigated (e.g., Amalfitano et al. 2015, Nuñez et al. 2015, Bolpagni 2021, and more space in the agenda of the field should be found ( figure 3 ). This would provide greater understanding of the invasion mechanisms involved in different contexts, further supporting both biological conservation and rewilding management. ...
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Identifying areas susceptible to invasion by an alien species is a strategy of prevention. We used national herbaria and global databases to assess the invasion trends of the two aquatic invasive species Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis in Italy. We defined the invasion status with invasion curves and predicted potentially suitable areas with Species Distribution Models based on WorldClim variables and the human footprint index. Low seasonal variation in temperature and precipitation, temperature ≥ 20 °C in the driest period of the year and low precipitation in the coldest period are the bioclimatic factors that most account for the potential distribution of the two species. The human footprint has a lower relative importance than bioclimatic variables. All Italian peninsula appears as a suitable bioclimatic environment for the invasion of the two Ludwigia species, with over 90% of areas with high suitability lying below 600 m altitude. Only mountain regions and the islands appear less suitable. The agricultural land at the foothill of the Appennine in the Mediterranean region is the most vulnerable to the invasion. Considering the trend of the invasion curves, which have been sharply rising for the latest decades, there are reasons to expect that the alien Ludwigia species will continue their expansion, if no timely and effective actions are taken. Informative campaigns, accurate monitoring and prompt management are fundamental preventive tools in areas predicted as vulnerable to invasion by this study.
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... Indeed, including intraspecific trait variability in ecological studies can capture more information that can better describe the tolerance of these species (Puglielli et al. 2024). While macrophytes are facing a rapid and dramatic decline worldwide due to direct anthropic pressure, climate change, and habitat degradation (O'Hare et al. 2018), many macrophyte species are spreading worldwide and represent some of the most invasive species, causing negative effects on ecosystems and nuisance to human activities (Strayer 2010;Hussner et al. 2017;Bolpagni 2021). Therefore, integrating the ecological and functional niche can provide information on resource-use strategies and functional adaptation (Luk acs et al. 2017), and thus reveal possible mechanistic explanations for their decline, migration, or invasive behavior. ...
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... 15 Alternanthera philoxeroides is one of the abundant plant species found in Bellandur Lake and recognised as invasive in the European Union Concern (EU Regulation 1143/2014). 16 Currently, there is limited understanding regarding endophytic bacterial isolates present in A. philoxeroides plants. It is uncertain whether the endophytic bacteria found in A. philoxeroides, can promote plant growth as well as be utilized to facilitate the heavy metal absorbance and degradation of dyes. ...
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Invasive alien plants are a major threat to biodiversity and they contribute to the unfavourable conservation status of habitats of interest to the European Community. In order to favour implementation of European Union Regulation no. 1143/2014 on invasive alien species, the Italian Society of Vegetation Science carried out a large survey led by a task force of 49 contributors with expertise in vegetation across all the Italian administrative regions. The survey summed up the knowledge on impact mechanisms of invasive alien plants in Italy and their outcomes on plant communities and the EU habitats of Community Interest, in accordance with Directive no. 92/43/EEC. The survey covered 241 alien plant species reported as having deleterious ecological impacts. The data collected illustrate the current state of the art, highlight the main gaps in knowledge, and suggest topics to be further investigated. In particular, the survey underlined competition as being the main mechanism of ecological impact on plant communities and Natura 2000 habitats. Of the 241 species, only Ailanthus altissima was found to exert an ecological impact on plant communities and Natura 2000 habitats in all Italian regions; while a further 20 species impact up to ten out of the 20 Italian administrative regions. Our data indicate that 84 out of 132 Natura 2000 Habitats (64%) are subjected to some degree of impact by invasive alien plants. Freshwater habitats and natural and semi-natural grassland formations were impacted by the highest number of alien species, followed by coastal sand dunes and inland dunes, and forests. Although not exhaustive, this research is the first example of nationwide evaluation of the ecological impacts of invasive alien plants on plant communities and Natura 2000 Habitats.
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