Data from: Non-native species affect the long-term dynamics of native stream fish assemblages

Characterizing the temporal changes of biotic communities and
disentangling the importance of their driving mechanisms are central
themes in ecology and environmental management. Non-native species have
multiple adverse impacts on native communities and species. However, there
is a dearth of information on how non-natives influence the long-term
dynamics of native communities. In this study, we compared the role of
non-native species alongside various local and regional factors in the
long-term dynamics of stream fish assemblages in the catchment area of
Lake Balaton, Hungary, the largest lake in Central-Europe. Although, we
found no consistent trend in species re-ordering between native and
non-native species, native fish assemblages indicated significantly lower
temporal stability with increasing relative abundance of co-occurring
non-natives. Structural equation modelling revealed that assemblage
dynamic patterns were also determined by a habitat gradient influenced by
both natural and human-induced processes. Moreover, habitat degradation
and the presence of fishponds increased the relative abundance of
non-native species, further affecting native assemblages through indirect
interactions. Fish assemblage dynamics also exhibited a certain degree of
finer-scale spatial structure highlighting the need for tailored
management strategies for each stream. Non-metric multidimensional scaling
reinforced the destabilizing effect of non-native species but highlighted
that native fish assemblages could generally be described by
non-directional gradual or saltatory changes over time, regardless of the
relative abundance of non-natives. Our results thus revealed that the
studied native fish assemblages may possess some degree of resilience
against biological invasions. However, increasing temporal variability
induced by non-natives makes native assemblages more vulnerable to
environmental stochasticity threatening their long-term persistence. This
is especially worrying, since the frequency and intensity of environmental
disturbances are expected to rise in the future due to climate change and
increasing anthropogenic pressure on aquatic ecosystems.