Harvest-induced evolution: insights from aquatic and terrestrial systems

Abstract

Commercial and recreational harvests create selection pressures for fitness-related phenotypic traits that are partly under genetic control. Consequently, harvesting can drive evolution in targeted traits. However, the quantification of harvest-induced evolutionary life history and phenotypic changes is challenging, because both density-dependent feedback and environmental changes may also affect these changes through phenotypic plasticity. Here, we synthesize current knowledge and uncertainties on six key points: (i) whether or not harvest-induced evolution is happening, (ii) whether or not it is beneficial, (iii) how it shapes biological systems, (iv) how it could be avoided, (v) its importance relative to other drivers of phenotypic changes, and (vi) whether or not it should be explicitly accounted for in management. We do this by reviewing findings from aquatic systems exposed to fishing and terrestrial systems targeted by hunting. Evidence from aquatic systems emphasizes evolutionary effects on age and size at maturity, while in terrestrial systems changes are seen in weapon size and date of parturition. We suggest that while harvest-induced evolution is likely to occur and negatively affect populations, the rate of evolutionary changes and their ecological implications can be managed efficiently by simply reducing harvest intensity.This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'.

Keywords: contemporary evolution; eco-evolutionary dynamics; fisheries; hunting; life histories; selection.

Figure 1.

Examples of life-history trends in marine and terrestrial harvested populations. Fisheries: age at maturity of Atlantic cod ((a) Gadus morhua; unit 3PS) [4] and American plaice ((b) Hippoglossoides platessoides; unit 2J3 K) [5], plotted against the year the cohort was born. Hunting: changes in age-adjusted deviations from average horn length (c) and breeding value (d) for horn length in cohorts of bighorn sheep (Ovis canadensis) at Ram Mountain, Alberta, Canada [6]. End of harvesting of the population is indicated by the dashed vertical line. Cohort-specific horn growth during the second and third year of life of Stone's sheep (O. dalli) males (e) from the heavily harvested Peace area (dashed line) and lightly harvested Skeena area (solid line) of northern British Columbia, Canada [7].