Understanding How the Replacement of Native Fish Affects Ecosystem Multifunctionality Over Eight Decades

Biological invasions have been widely discussed and researched in ecology over recent decades, not only because of growing concern about their effects on native species and biodiversity conservation but also because of the substantial potential for invasive species expansion in the context of global change (Yang et al. 2022). Biological invasions are themselves major drivers of global change (Peller and Altermatt 2024) and, when combined with climate change, represent one of the greatest threats to ecosystems worldwide (IPBES 2023). They promote the ecological homogenization of communities and alter key ecosystem processes (IPBES 2023). Increasing evidence shows that the interaction between biological invasions and other environmental drivers is complex and can produce effects of varying magnitude and direction on ecosystem functioning (Hu et al. 2025; Rodrigues et al. 2024). This complexity arises because traditional, taxonomy-focused approaches often fail to capture the functional roles species play in ecological processes. A functional perspective, which considers the diversity of species' traits and evolutionary histories, is crucial for predicting how the replacement of native by non-native species reshapes ecosystems. In a landmark study published in Global Change Biology, Liang et al. (2025) analyze an eight-decade dataset from China's Lake Erhai to apply precisely this multidimensional approach, offering insights into the long-term interplay between invasion, biodiversity, and ecosystem multifunctionality. Several studies have addressed how invasive species affect community structure (IPBES 2023), primarily through competitive exclusion mechanisms associated with their higher resource-use efficiency and the absence of natural enemies (Theoharides and Dukes 2007). However, studies that explicitly evaluate how such community modifications influence ecosystem processes have only recently gained proper attention (e.g., Gallardo et al. 2024), and most remain restricted to specific species or geographic regions (Vilà and Hulme 2017). In freshwater ecosystems, investigations directly assessing the effects of native species replacement by non-native ones on ecosystem functioning are even rarer, despite biological invasions being considered the leading driver of biodiversity loss and the decline of ecosystem service provision (IPBES 2023). Liang et al. (2025) address this directly, asking not just how non-native fishes affect native fish diversity, but also how these changes influence ecosystem functioning. This study is a direct extension of a growing research focus by delving deeper into the mechanistic traits and phylogenetic relationships that underpin biodiversity patterns. Using an exceptional dataset spanning nearly 80 years from Lake Erhai, China, the authors simultaneously analyzed the taxonomic, functional, and phylogenetic diversity of native and non-native fish species, integrating these with metrics of productivity, decomposition, and overall ecosystem multifunctionality. Their results depict a clear scenario of ecological replacement: While the multidimensional diversity of non-native fishes increased steadily, that of native fishes declined sharply. Concurrently, both ecosystem productivity and multifunctionality increased, suggesting that biological invasions may initially enhance certain aspects of ecosystem functioning, though at the expense of eroding the functional diversity and integrity of native communities. In freshwater environments, the introduction of non-native species can differentially affect multiple biological groups, particularly consumers such as zooplankton and fish, directly influencing trophic structure and the strength of top-down and bottom-up processes (Gallardo et al. 2016). Under climate change scenarios, biological invasions may even increase consumer biomass, acting as a compensatory mechanism that weakens the top-down control of detritus decomposition and triggers cascading effects on freshwater ecosystem functioning (Rodrigues et al. 2024). The core findings of Liang et al. (2025) reveal an ecological swap: Over eight decades, the functional diversity of non-native fishes increased markedly, whereas that of native fishes declined by over 60%. This was accompanied by the extinction of six native species following the introduction of 11 non-natives. Despite this loss of native functional diversity, the ecosystem showed increased productivity and average multifunctionality. The models revealed a critical nuance: Non-native fish functional diversity had a hump-shaped relationship with ecosystem productivity, providing a benefit at low-to-moderate levels but becoming detrimental at higher levels. In contrast, native fish functional diversity was consistently negatively correlated with multifunctionality, a counterintuitive result that the authors attributed to the high functional redundancy and limited trait variability within the native assemblage, which was dominated by bottom-dwelling omnivores. Therefore, the potential of non-native species to support certain ecosystem processes appears to be context-dependent, emerging most clearly when native communities are functionally constrained. Liang et al. (2025) also demonstrated that environmental variables such as water level, transparency, and precipitation also modulated these relationships, emphasizing the combined influence of biotic and abiotic factors in determining freshwater ecosystem performance. Together, these results reveal that while non-native species can temporarily sustain or enhance certain ecological processes, they ultimately promote functional homogenization and long-term instability in aquatic ecosystems. Among these remarkable findings, Liang et al. (2025) identify a “convergence–divergence–convergence” (CDC) pattern in fish community assembly, reflecting dynamic shifts in ecological structuring mechanisms. Throughout the invasion process, there is an alternation between communities determined by environmental filters (convergence) and niche differentiation (divergence). The CDC framework offers a dynamic model for understanding how community assembly rules shift over the course of an invasion, moving beyond static snapshots. It provides insights into ecosystems functioning under human disturbance, highlighting the need for long-term functional monitoring to guide conservation and management policies in freshwater environments. The study also opens avenues for future research and presents caveats that must be considered. The positive, albeit context-dependent, role of non-native fishes in supporting ecosystem functions is a provocative finding. Future research should test the CDC framework in other ecosystems and through experimental manipulations to establish causality. Furthermore, the reliance on historical data, while invaluable, introduces inherent uncertainties. The authors rightly call for standardized, long-term monitoring to complement such retrospective analyses. Overall, Liang et al. (2025) offer a compelling demonstration of how biological invasions can simultaneously drive ecosystem processes and undermine community resilience, advancing our understanding of the long-term functional consequences of native species replacement. In conclusion, Liang et al. (2025) deliver a powerful demonstration that the legacy of biological invasions is written not only in the loss of native species but also in the fundamental restructuring of functional trait spaces and ecosystem processes. By integrating taxonomic, functional, and phylogenetic dimensions across an 80-year timeline, they move the field beyond simple narratives of invasion impact toward a more mechanistic and predictive understanding. Their work makes it clear that effective conservation in the Anthropocene requires managing not just for species richness but for the functional diversity and resilience of ecosystems in the face of ongoing change. The author declares no conflicts of interest. This article is a Invited Commentary by Liang et al., https://doi.org/10.1111/gcb.70501. The author has nothing to report.