Quantifying the individual impact of artificial barriers in freshwaters: A standardized and absolute genetic index of fragmentation

Evolutionary Applications

Paz‐Vinas

et al. 2020

Self Cite

Rivers are fascinating ecosystems in which the eco‐evolutionary dynamics of organisms are constrained by particular features, and biologists have developed a wealth of knowledge about freshwater biodiversity patterns. Over the last 10 years, our group used a holistic approach to contribute to this knowledge by focusing on the causes and consequences of intraspecific diversity in rivers. We conducted empirical works on temperate permanent rivers from southern France, and we broadened the scope of our findings using experiments, meta‐analyses, and simulations. We demonstrated that intraspecific (genetic) diversity follows a spatial pattern (downstream increase in diversity) that is repeatable across taxa (from plants to vertebrates) and river systems. This pattern can result from interactive processes that we teased apart using appropriate simulation approaches. We further experimentally showed that intraspecific diversity matters for the functioning of river ecosystems. It indeed affects not only community dynamics, but also key ecosystem functions such as litter degradation. This means that losing intraspecific diversity in rivers can yield major ecological effects. Our work on the impact of multiple human stressors on intraspecific diversity revealed that—in the studied river systems—stocking of domestic (fish) strains strongly and consistently alters natural spatial patterns of diversity. It also highlighted the need for specific analytical tools to tease apart spurious from actual relationships in the wild. Finally, we developed original conservation strategies at the basin scale based on the systematic conservation planning framework that appeared pertinent for preserving intraspecific diversity in rivers. We identified several important research avenues that should further facilitate our understanding of patterns of local adaptation in rivers, the identification of processes sustaining intraspecific biodiversity–ecosystem function relationships, and the setting of reliable conservation plans.

Section: The Impacts Of Human Activities On Intraspecific Diversity Imentioning

confidence: 99%

Section: The Impacts Of Human Activities On Intraspecific Diversity Imentioning

confidence: 99%

A river runs through it: The causes, consequences, and management of intraspecific diversity in river networks

Blanchet

Evolutionary Applications

Paz‐Vinas

et al. 2020

Self Cite

“…We preferred this metric of differentiation over other metrics (e.g., Fst, Gst, Jost’s D, etc.) as it has been shown to be robust to variations in mutation rates and sample sizes [ 58 , 59 ].…”

Section: Methodsmentioning

confidence: 99%

Patterns of Epigenetic Diversity in Two Sympatric Fish Species: Genetic vs. Environmental Determinants

Fargeot

Loot

et al. 2021

Genes

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Epigenetic components are hypothesized to be sensitive to the environment, which should permit species to adapt to environmental changes. In wild populations, epigenetic variation should therefore be mainly driven by environmental variation. Here, we tested whether epigenetic variation (DNA methylation) observed in wild populations is related to their genetic background, and/or to the local environment. Focusing on two sympatric freshwater fish species (Gobio occitaniae and Phoxinus phoxinus), we tested the relationships between epigenetic differentiation, genetic differentiation (using microsatellite and single nucleotide polymorphism (SNP) markers), and environmental distances between sites. We identify positive relationships between pairwise genetic and epigenetic distances in both species. Moreover, epigenetic marks better discriminated populations than genetic markers, especially in G. occitaniae. In G. occitaniae, both pairwise epigenetic and genetic distances were significantly associated to environmental distances between sites. Nonetheless, when controlling for genetic differentiation, the link between epigenetic differentiation and environmental distances was not significant anymore, indicating a noncausal relationship. Our results suggest that fish epigenetic variation is mainly genetically determined and that the environment weakly contributed to epigenetic variation. We advocate the need to control for the genetic background of populations when inferring causal links between epigenetic variation and environmental heterogeneity in wild populations.

“…Sampling operations ‘Before’ and ‘After’ restoration were performed using electrofishing, until a maximum of 30 adult individuals of each species were captured on either side of obstacles. Fish were captured in the direct downstream and upstream vicinity of each obstacle (Prunier et al, 2020), starting from the downstream site to avoid accidental upstream to downstream movements of individuals. A piece of pelvic fin was sampled on all individuals and stored in 96% alcohol.…”

Section: Methodsmentioning

confidence: 99%

“…In this study, we implemented a “before-after genetic monitoring” of the restoration of 11 weirs in France using a recently developed genetic index of fragmentation (the F INDEX ; Prunier et al, 2020). The F INDEX provides, independently for each obstacle, an absolute and standardized estimate of (species-specific) genetic connectivity, while taking into account two confounding factors: the age of the obstacle and the size of populations on either side of the obstacle.…”

Section: Introductionmentioning

confidence: 99%

Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species

Loot

Veyssière

et al. 2021

Preprint

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Rivers are heavily fragmented by man-made instream barriers such as dams and weirs. This hyper-fragmentation is a major threat to freshwater biodiversity and restoration policies are now adopted worldwide to mitigate these impacts. However, there is surprisingly little feedback on the efficiency of barrier mitigation measures in restoring riverine connectivity, notably for non-migratory fish species. Here, we implemented a "before-after genetic monitoring" of the restoration of 11 weirs in France using a dedicated genetic index of fragmentation (the FINDEX), with a focus on five fish species from two genera. We found that most obstacles actually had a significant impact on connectivity before restoration, especially the highest and steepest ones, with an overall barrier effect of about 51% of the maximal theoretical impact. Most importantly, we demonstrated for the first time that mitigation measures such as dam removal or fish pass creation significantly and rapidly improved connectivity, with -for some barriers- a complete recovery of the genetic connectivity in less than twelve months. Our study provides a unique and strong proof-of-concept that barrier removal is an efficient strategy to restore riverine connectivity and that molecular tools can provide accurate measures of restoration efficiency within a few months.