Abstract
Harvest can disrupt wildlife populations by removing adults with naturally high survival. This can reshape sociospatial structure, genetic composition, fitness, and potentially affect evolution. Genetic tools can detect changes in local, fine‐scale genetic structure (FGS) and assess the interplay between harvest‐caused social and FGS in populations. We used data on 1614 brown bears, Ursus arctos, genotyped with 16 microsatellites, to investigate whether harvest intensity (mean low: 0.13 from 1990 to 2005, mean high: 0.28 from 2006 to 2011) caused changes in FGS among matrilines (8 matrilines; 109 females ≥4 years of age), sex‐specific survival and putative dispersal distances, female spatial genetic autocorrelation, matriline persistence, and male mating patterns. Increased harvest decreased FGS of matrilines. Female dispersal distances decreased, and male reproductive success was redistributed more evenly. Adult males had lower survival during high harvest, suggesting that higher male turnover caused this redistribution and helped explain decreased structure among matrilines, despite shorter female dispersal distances. Adult female survival and survival probability of both mother and daughter were lower during high harvest, indicating that matriline persistence was also lower. Our findings indicate a crucial role of regulated harvest in shaping populations, decreasing differences among “groups,” even for solitary‐living species, and potentially altering the evolutionary trajectory of wild populations.
Highlights
Anthropogenic effects on ecosystems are widespread (Vitousek, 1997)
Harvest can disrupt population social structure (e.g., Esteban et al, 2015; Little et al, 1993), which is an important driver of genetic structure (e.g., Storz, 1999), by (a) removing adult females in matrilines and adult males that disproportionately contribute to reproduction (Archie et al, 2008; Turner et al, 2016) and/or (b) by altering spatial demography, including sex-specific natal dispersal and the distribution of mating success (Dieckmann et al, 1999; Ferreira da Silva et al, 2014; Harris et al, 2002)
We predicted that (a) high harvest intensity decreases fine-scale genetic structure (FGS), that is, the distribution of genotypes becomes more random, among females and matrilines; (b) survival for both sexes is lower for all ages during high harvest, for adults (≥4 years); (c) lower survival of mother–daughter pairs during high harvest; (d) an increase in the proportion of unique males siring offspring during high harvest; (e) changes in FGS are reflected in spatial configuration of related individuals on the landscape, that is, less clustering or weaker negative relationship between pairwise distances of home ranges for female kin during the high harvest; and (f) dispersal distances are shorter for both sexes during high harvest, as dispersing bears occupy nearby harvest-induced vacancies
Summary
Anthropogenic effects on ecosystems are widespread (Vitousek, 1997). Harvest, the offtake of wildlife by humans, is pervasive and critical to many societies, for example, for food acquisition and population management. Harvest can disrupt population social structure (e.g., Esteban et al, 2015; Little et al, 1993), which is an important driver of genetic structure (e.g., Storz, 1999), by (a) removing adult females in matrilines and adult males that disproportionately contribute to reproduction (Archie et al, 2008; Turner et al, 2016) and/or (b) by altering spatial demography, including sex-specific natal dispersal and the distribution of mating success (Dieckmann et al, 1999; Ferreira da Silva et al, 2014; Harris et al, 2002). We predicted that (a) high harvest intensity decreases FGS, that is, the distribution of genotypes becomes more random, among females and matrilines; (b) survival for both sexes is lower for all ages during high harvest, for adults (≥4 years); (c) lower survival of mother–daughter pairs during high harvest; (d) an increase in the proportion of unique males siring offspring during high harvest; (e) changes in FGS are reflected in spatial configuration of related individuals on the landscape, that is, less clustering or weaker negative relationship between pairwise distances of home ranges for female kin during the high harvest; and (f) dispersal distances are shorter for both sexes during high harvest, as dispersing bears occupy nearby harvest-induced vacancies
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