Fish community responses to global changes in French streams Patterns and mechanisms Aerial view of the Copper River Delta, Alaska Lucie Kuczynski1, Gaël Grenouillet1 and Pierre Legendre2 1 Laboratoire Évolution et Diversité Biologique – Toulouse, France 2 Département de Sciences Biologiques – Montréal, Canada lucie.kuczynski@hotmail.com

Aerial view of the Copper River Delta, Alaska

Different processes are shaping diversity… Abiotic conditions Ressources Climat Connectivity Perturbations Biotic interactions Predation/herbivory Parasitism Competition Symbiosis/Facilitation Mutualism Spatial structure Longitude Latitude Upstream/Downstream

Thus, diversity varies through space…

But also through time. Time 𝛼 diversity Space 𝛽 diversity

How does diversity change over time ? Change in 𝛼 diversity over time: Temporal 𝛽 diversity. Change in spatial 𝛽 diversity over time. 𝛼 diversity Space 𝛽 diversity

And, what are the drivers of these changes ? Time Change in 𝛼 diversity over time: Temporal 𝛽 diversity. Change in spatial 𝛽 diversity over time. 𝛼 diversity Space Abiotic conditions Biotic interactions Spatial structure 𝛽 diversity

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time.

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time. D 1 … N communities LCBD 1 … N communities

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 1 … N communities Y 1 … P species Period 2 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time. D 1 … N communities LCBD 1 … N communities ΔLCBD

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 1 … N communities Y 1 … P species Period 2 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time. D 1 … N communities LCBD 1 … N communities ΔLCBD

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 1 … N communities Y 1 … P species Period 2 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time. D 1 … N communities TBI 1 … N communities LCBD 1 … N communities ΔLCBD

Two new indices to quantify changes in diversity… 1 … N communities Y 1 … P species Period 1 1 … N communities Y 1 … P species Period 2 Local Contribution to Beta Diversity (LCBD): Uniqueness of a community in terms of structure. Temporal Beta Index (TBI): Change in community structure over time. D 1 … N communities TBI 1 … N communities = Losses 1 … N communities + Gains 1 … N communities LCBD 1 … N communities ΔLCBD

Stream fish communities as model…

Stream fish communities as model… Abundances for 64 species. 332 sampled communities. 2 time periods based on temperature anomalies.

Stream fish communities as model… Climate change (mean annual temperature, temperature seasonnality, total annual precipitations), Land use change (PCA axis), Fragmentation (number of dams), Change in relative abundances of non native species, Upstream – downstream gradient. Abundances for 64 species. 332 sampled communities. 2 time periods based on temperature anomalies.

In a context of climate change, …

… fish communities tend to homogenize... 𝛽cold = 0.852 and 𝛽warm = 0.842  Homogenization (pvalue < 0.001). No significant change in LCBD.

… by experiencing a great change in structure. 𝛽cold = 0.852 and 𝛽warm = 0.842  Homogenization (pvalue < 0.001). No significant change in LCBD. TBI = 0.62 ± 0.23

And this structure change is mainly due to population declines. 𝛽cold = 0.852 and 𝛽warm = 0.842  Homogenization (pvalue < 0.001). No significant change in LCBD. TBI = 0.62 ± 0.23 Losses = 65% versus Gains = 35%. Percentage of TBI due to losses

Overall, different drivers are implied for each observed change.

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality TBI + Upstream-Downstream

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality TBI + Upstream-Downstream Losses - Fragmentation

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality TBI + Upstream-Downstream Losses - Fragmentation

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality TBI + Upstream-Downstream Losses - Fragmentation Gains + Fragmentation - Change in Rainfall

Overall, different drivers are implied for each observed change. ΔLCBD + Change in Non native species + Change in Seasonality TBI + Upstream-Downstream Losses - Fragmentation Gains + Fragmentation - Change in Rainfall

To sum up… Change in Homogenization community structure No change in uniqueness

To sum up… Gains Change in Losses Homogenization community structure No change in uniqueness

Upstream – Downstream gradient To sum up… Gains Change in community structure Losses Homogenization Upstream – Downstream gradient No change in uniqueness

Upstream – Downstream gradient To sum up… Change in precipitations Gains Fragmentation Change in community structure Losses Homogenization Upstream – Downstream gradient Crowding effect. No change in uniqueness

Upstream – Downstream gradient To sum up… Change in precipitations Gains Fragmentation Change in community structure Losses Homogenization Change in relative abundances of non native species Upstream – Downstream gradient No change in uniqueness

To sum up… Change in precipitations Gains Fragmentation Change in community structure Losses Homogenization Change in relative abundances of non native species Upstream – Downstream gradient This differenciation could turn quickly in homogenization as non native species spread. No change in uniqueness Change in temperature seasonality

Thank you for your attention! If you have any questions …