Refining and defining riverscape genetics: How rivers influence population genetic structure

Abstract

Traditional analysis in population genetics evaluates differences among groups of individuals and, in some cases, considers the effects of distance or potential barriers to gene flow. Genetic variation of organisms in complex landscapes, seascapes, or riverine systems, however, may be shaped by many forces. Recent research has linked habitat heterogeneity and landscape or seascape configuration to genetic structure by integrating methods from landscape ecology, population genetics, and spatial statistics in approaches known as landscape or seascape genetics. However, functional differences between terrestrial or seascapes systems in comparison to riverscape topography (i.e., movement pathways for aquatic obligate species are constrained to river channels) make translating these approaches into freshwater analyses problematic. Studies that may be described as riverscape genetics (RG) have linked temperature, stream gradient, and confluences to genetic variability. Lack of consistency in methodology, however, has made comparisons across species and scales difficult. We provide a perspective on how RG could be used to provide a more comprehensive conceptual and applied understanding of connectivity and dispersal in freshwater systems. We describe four thematic areas of study representing current and future research opportunities and describe a basic workflow for conducting RG analysis. Although numerous methodological challenges remain, a RG approach can enhance our understanding of habitat heterogeneity in shaping gene flow and spatial genetic structure. These characteristics of populations are critical components for interpreting demographic and evolutionary consequences of habitat loss and fragmentation.

Temporal dynamics of migration‐linked genetic variation are driven by streamflows and riverscape permeability

“…Landscape features can shape both neutral genetic structure and the distribution of adaptive variation within a species (Davis, Epps, Flitcroft, & Banks, ; Grummer et al, ; Orsini, Andrew, & Eizaguirre, ). While landscape genetic studies in rivers increasingly consider adaptive variation (Brauer, Unmack, Smith, Bernatchez, & Beheregaray, ; Micheletti, Matala, Matala, & Narum, ; Vincent, Dionne, Kent, Lien, & Bernatchez, ), few studies have directly compared patterns of neutral genetic variation with patterns of variation at loci associated with adaptive phenotypic variation (but see Hand et al, ; Keller, Taverna, & Seehausen, ; O’Malley, Jacobson, Kurth, Dill, & Banks, ).…”

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

“…Faulks, Gilligan, & Beheregaray, ; Finn & Adler, ; Finn, Blouin, & Lytle, ; Fluker, Kuhajda, & Harris, ; Fluker, Kuhajda, Lang, & Harris, ; Kang, Ma, & He, ; Lecaudey, Schliewn, Osinov, Taylor, Bernatchez, Schliewn, & Osinov, ; Robinson, Simmons, Williams, & Moyer, ; Stobie, Oosthuizen, Cunningham, & Bloomer, ). Moreover, hypotheses that predict diversity patterns across riverine landscapes have been mostly developed with data on freshwater insects and fish (reviewed by Davis et al, ; Hughes et al, ). These hypotheses include the River Continuum Concept that predicts lower species diversity in headwaters compared to main stem populations (Vannote et al, ), the Mighty Headwaters Hypothesis that postulates headwater or tributary populations will harbour greater genetic uniqueness than main stem river segments (Finn, Bonada, Múrria, & Hughes, ), and the Stream Hierarchy Model that states populations will demonstrate a pattern of isolation by distance along a stream network path (Meffe & Vrijenhoek, ).…”

“…Many factors influence genetic diversity across a landscape including life history, physical dispersal barriers and anthropogenic activity. Compared to terrestrial or marine organisms, animals occupying fluvial ecosystems have gene-flow constraints associated with inherent hierarchical properties of drainage networks, unidirectional water flow and relatively limited lateral connectivity (Davis, Epps, Flitcroft, & Banks, 2018;Hughes, Schmidt, & Finn, 2009;Malmqvist, 2002;Vannote, Minshall, Cummins, Sedell, & Cushing, 1980). However, these fluvial characteristics have unequal influence on different organismal groups.…”

On the roles of landscape heterogeneity and environmental variation in determining population genomic structure in a dendritic system

“…Growing evidence suggests that most adaptive genomic responses to environmental variation are polygenic in nature (Bernatchez, ; Pritchard & Di Rienzo, ). For species inhabiting complex spatial environments, landscape structure is also expected to greatly impact patterns of demographic connectivity and genetic diversity (Davis, Epps, Flitcroft, & Banks, ; Thomaz, Christie, & Knowles, ). Following the emergence of the field of landscape genetics (Manel, Schwartz, Luikart, & Taberlet, ), significant research effort has been focused on understanding how environmental heterogeneity affects patterns of gene flow and spatial population structure (Manel & Holderegger, ).…”