Fish community responses to global changes in French streams: patterns and mechanisms
Lucie Kuczynski (1), Pierre Legendre (2) , Gaël Grenouillet (3)
1 UMR5174 EDB (Laboratoire Evolution et Diversité Biologique), CNRS, UPS, ENFA, 118 route de Narbonne, F-31062, Toulouse, France, UPS, UMR5174 EDB, Université de Toulouse 3, F-31062, Toulouse, France, lucie.kuczynski@univ-tlse3.fr
2 Département de sciences biologiques, Université de Montreal, C.P. 6128, succursale Centre-ville, Montreal, QC, H3C 3J7, Canada, pierre.legendre@umontreal.ca
3 UMR5174 EDB (Laboratoire Evolution et Diversité Biologique), CNRS, UPS, ENFA, 118 route de Narbonne, F-31062, Toulouse, France, UPS, UMR5174 EDB, Université de Toulouse 3, F-31062, Toulouse, France, gael.grenouillet@univ-tlse3.fr
Species’ distribution shifts in response to climate change have been documented for many taxa, and these shifts can result in community reorganization which can have considerable impacts on species interactions and lead to profound alterations of ecosystem functioning. However, there is ample evidence of idiosyncratic responses, which limits our ability to predict the consequences of range shifts at the community level. Thus, it is critical to evaluate how species assemblages are responding to on-going environmental changes, and to assess biodiversity changes from both a spatial and temporal perspective to understand underlying processes. Based on national monitoring data collected over the last decades in France, here we explore temporal changes in alpha and beta diversity of stream fish communities by comparing more than 300 resurveyed communities between an initial (1980 – 1993) and a contemporary period (2004 – 2012). We quantified for each community how its composition and its uniqueness have changed over time relative to the overall temporal change that other communities experienced. Finally, we identified the environmental drivers of these temporal biodiversity changes. Overall, we found a global homogenization of freshwater fish communities since the 80s. Our results showed that the changes in community structure were spatially structured dependent but mainly due to species losses. Finally, we demonstrated that these temporal changes were mainly driven by changes in rainfall, temperature seasonality and the relative abundance of non-native species over time, pointing to the importance of understanding the complex interplay of multiple environmental and biotic drivers in defining future patterns of freshwater biodiversity.