Genomic basis of fishing-associated selection varies with population density – pnas.org

Genomic basis of fishing-associated selection varies with population density – pnas.org

Significance

Fisheries-associated selection is recognized as one of the strongest potential human drivers of contemporary evolution in natural populations. The results of this study show that while simulated commercial fishing techniques consistently remove fish with traits associated with growth, metabolism, and social behavior, the specific genes under fishing selection differ depending on the density of the targeted population. This finding suggests that different fish populations of varying sizes will respond differently to fishing selection at the genetic level. Furthermore, as a population is fished over time, the genes under selection may change as the population diminishes. This could have repercussions on population resilience. This study highlights the importance of selection but also environmental and density effects on harvested fish populations.

Abstract

Fisheries induce one of the strongest anthropogenic selective pressures on natural populations, but the genetic effects of fishing remain unclear. Crucially, we lack knowledge of how capture-associated selection and its interaction with reductions in population density caused by fishing can potentially shift which genes are under selection. Using experimental fish reared at two densities and repeatedly harvested by simulated trawling, we show consistent phenotypic selection on growth, metabolism, and social behavior regardless of density. However, the specific genes under selection—mainly related to brain function and neurogenesis—varied with the population density. This interaction between direct fishing selection and density could fundamentally alter the genomic responses to harvest. The evolutionary consequences of fishing are therefore likely context dependent, possibly varying as exploited populations decline. These results highlight the need to consider environmental factors when predicting effects of human-induced selection and evolution.

The selective harvest of animals by humans is one of the most important contemporary pressures on natural populations (1, 2). Intensive commercial fishing has been demonstrated to alter life history traits (e.g., reduced body size and/or age and size at maturation) in ecologically and economically important populations (3–7). However, a major question persists about whether the observed changes stem from Darwinian evolution via selection on phenotypic traits and associated genotypes or result from human-induced environmental changes generating phenotypic plasticity (8–11). In addition, harvest-associated phenotypic plasticity may interact with the fishing selection on genotypes (Gene by Environment interaction, G×E) to alter evolutionary outcomes, but this possibility has been overlooked.

For selection by fishing to occur, there must be phenotypic variation among individuals with respect to their vulnerability to capture. Vulnerability is likely comprised of a suite of life history, morphological, physiological, and behavioral traits that interact to determine whether a fish will ultimately escape or be captured by a fishing gear. While size and maturation are well established to be selected by fishing (12, 13), emerging evidence shows that fishing may also drive selection on traits related to bioenergetics or social behavior that also vary widely within species (14–16). This is especially likely given that commercial fishing methods such as trawling directly exploit aspects of fish foraging, schooling, and escape behaviors to facilitate capture (14). If the traits under fishing selection possess a genetic basis, fishing could lead to direct evolution (8, 17). Recent research suggests that fisheries can induce a shift in the genomic variants of targeted populations (18–20). While …….

Source: https://www.pnas.org/content/118/51/e2020833118

Fishing