Two centuries for an almost complete community turnover from native to non‐native species in a riverine ecosystem

Abstract

Non‐native species introductions affect freshwater communities by changing community compositions, functional roles, trait occurrences and ecological niche spaces. Reconstructing such changes over long periods is difficult due to limited data availability. We collected information spanning 215 years on fish and selected macroinvertebrate groups (Mollusca and Crustacea) in the inner‐Florentine stretch of the Arno River (Italy) and associated water grid, to investigate temporal changes. We identified an almost complete turnover from native to non‐native fish (1800: 92% native; 2015: 94% non‐native species) and macroinvertebrate species (1800: 100% native; 2015: 70% non‐native species). Non‐native fish species were observed ~50 years earlier compared to macroinvertebrate species, indicating phased invasion processes. In contrast, α‐diversity of both communities increased significantly following a linear pattern. Separate analyses of changes in α‐diversities for native and non‐native species of both fish and macroinvertebrates were nonlinear. Functional richness and divergence of fish and macroinvertebrate communities decreased non‐significantly, as the loss of native species was compensated by non‐native species. Introductions of non‐native fish and macroinvertebrate species occurred outside the niche space of native species. Native and non‐native fish species exhibited greater overlap in niche space over time (62%–68%) and non‐native species eventually replaced native species. Native and non‐native macroinvertebrate niches overlapped to a lesser extent (15%–30%), with non‐natives occupying mostly unoccupied niche space. These temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in α‐diversity and species turnover. These changes are potentially driven by deteriorations in hydromorphology as indicated by alterations in trait modalities. Additionally, we identified that angling played a considerable role for fish introductions. Our results support previous findings that the community turnover from native to non‐native species can be facilitated by, for example, deteriorating environmental conditions and that variations in communities are multifaceted requiring more indicators than single metrics.

Economic costs of invasive alien species across Europe

“…Despite an increasing number of indicators and alarming reports on the rapid decline of biodiversity globally (Díaz et al 2020;Haubrock et al 2021b), efforts to halt biodiversity losses have remained insufficient (Hulme 2009;Scalera 2010;Rayment et al 2018). Notwithstanding the multiple signals of the rapid decline of natural capital worldwide, global economic resources allocated to prevent and mitigate such losses have not proven adequate to meet conservation management goals, or have been designated inefficiently (Murdoch et al 2007;Underwood et al 2008;Stokstad 2010;McCarthy et al 2012;Waldron et al 2013Waldron et al , 2017.…”

Seasonal variability in the diet of juvenile European catfish, Silurus glanis, in the Arno River (Italy) in Florence

“…Haubrock et al (2019) argued that the strong resource overlap with the co-occurring invasive species I. punctatus could be the reason the less competitive S. glanis juveniles shifted to other potential food sources. However, invasive, and potentially predatory species like Dikerogammarus villosus, Palaemon sp., or P. parva (the latter combined with A. alburnus as cyprinids) are highly abundant in the section of the Arno studied (Haubrock et al 2021a). Accordingly, we found that cyprinids comprised a considerable portion of the S. glanis diet.…”

“…While it is difficult to determine the reason for this, it was previously argued that major drivers could be either competition with I. punctatus or increasingly unsuitable environmental conditions (Haubrock et al 2020). While the Arno River is not the ideal environment to investigate this predator's impact on nearly absent native species (Haubrock et al 2021a), the present study indicated this species has a generalist diet that could impact multiple resource types. Based on the prey occurrences observed, it can also be argued that the diet of S. glanis, and therefore its feeding impact on the community of potential prey, can affect species beyond those previously identified as prey species such as cyprinids and crustaceans.…”

“…The ecological impacts of biological invasions can potentially challenge conservation efforts and management interventions (Hulme et al 2009, Cuthbert et al 2021. Freshwater ecosystems are particularly susceptible to increased introductions and the spread of non-native species (Poulin et al 2011) and are prone to be modified by them (Gallardo et al 2016, Haubrock et al 2021a). Indeed, the already complex ecological interactions among species are further complicated by interactions with novel invasive species in communities (Stellati et al 2019), but interactions among invasive species themselves also pose problems (Haubrock et al 2019).…”

Trophic structure of a pond community dominated by an invasive alien species: Insights from stomach content and stable isotope analyses

“…This is particularly true in freshwater ecosystems, which are vulnerable to biological invasions owing to the strong link of humans to water, the inconspicuousness of aquatic ecosystems (Rico‐Sánchez et al, 2020), and the high interconnectedness, and thus the dispersal ability, of freshwater species compared with terrestrial species (Selge, Fischer & van der Wal, 2011; Tricarico, Junqueira & Dudgeon, 2016). As a result, freshwater communities are often dominated by multiple invasive alien species (IAS) living in sympatry and interacting with each other (Gamradt & Kats, 1996; Kiesecker & Blaustein, 1998; Haubrock et al, 2020), and some of these may have facilitative effects (Crane et al, 2020).…”