Habitat fragmentation has interactive effects on the population genetic diversity and individual behaviour of a freshwater salmonid fish

Abstract

Sufficient genetic diversity can aid populations to persist in dynamic and fragmented environments. Understanding which mechanisms regulate genetic diversity of riverine fish can therefore advance current conservation strategies. The aim of this study was to investigate how habitat fragmentation interacted with population genetic diversity and individual behaviour of freshwater fish in large river systems. We studied a population of the long-distance migratory, iteroparous freshwater salmonid European grayling (Thymallus thymallus) in south-eastern Norway. Genotyping (n = 527) and radio-tracking (n = 54) of adult fish throughout a 169-km river section revealed three major migration barriers limiting gene flow and depleting genetic diversity upstream. Individuals from upstream areas that had dispersed downstream of barriers showed different movement behaviour than local genotypes. No natal philopatry was found in a large unfragmented river section, in contrast to strong fidelity to spawning tributaries known for individuals overwintering in lakes. We conclude that (a) upstream sub-populations in fragmented rivers show less genetic variation, making it less likely for them to adapt to environmental changes; (b) fish with distinct genotypes in the same habitat can differ in their behaviour; (c) spawning site selection (natal philopatry) can differ between fish of the same species living in different habitats.Together this implies that habitat loss and fragmentation may differently affect individual fish of the same species if they live in different types or sections of habitat. Studying behaviour and genetic diversity of fish can unravel their complex ecology and help minimize human impact.

Genetic diversity, admixture, and hatchery influence in Brook Trout (Salvelinus fontinalis) throughout western New York State

“…Gene flow among populations can maintain or increase the level of genetic variation within the populations involved, as new alleles are added and new genotypic combinations are created. This association between genetic diversity and population‐level admixture has been documented in other salmonids (Gomez‐Uchida, Knight, & Ruzzante, ; Van Leeuwen, Dalen, Museth, Junge, & Vøllestad, ; Matthaeus, ; Wofford, Gresswell, & Banks, ) as well as in Brook Trout populations in other regions (Bruce & Wright, ; Kanno, Vokoun, & Letcher, ; Kelson et al, ).…”

Ecological and Evolutionary Consequences of Environmental Change and Management Actions for Migrating Fish

“…Naturally, obstacles are often harder to traverse in the upstream direction, while weirs and spillways may allow for some downstream dispersal. This unidirectional dispersal constricts gene flow in the upstream direction and reduces genetic diversity in the upstream direction (Gouskov et al, 2016;Van Leeuwen et al, 2018). Small populations upstream of dams, with no possibility for immigration or recolonization from downstream populations, may also be extirpated (Morita and Yamamoto, 2002).…”

“…Depending on the severity of the upstream and downstream barriers, movement becomes restricted and gene flow between fragments reduced. This can lead to population differentiation among fragments and manifest as local population structures between barriers (Van Leeuwen et al, 2018). Reductions in the number, size, and type of available habitats (Figure 4C vs.…”

Riverscape genetic variation, migration patterns, and morphological variation of the threatened Round Rocksnail, Leptoxis ampla

“…Galbraith, Zanatta, & Wilson, 2015;Inoue, Lang, & Berg, 2015;Inoue, Monroe, Elderkin, & Berg, 2014;Stoeckle et al, 2017), fish (e.g. Fluker et al, 2014a;Fluker, Kuhajda, & Harris, 2014b;Fluker et al, 2010;Prunier, Dubut, Loot, Tudesque, & Blanchet, 2017;Thomaz, Malabarba, & Knowles, 2017;Van Leeuwen, Dalen, Museth, Junge, & Vøllestad, 2018) and insects (e.g. Finn & Adler, 2006;Finn et al, 2007;Geismar et al, 2015;Múrria et al, 2017;Razeng et al, 2017).…”