Do Harvest Refuges Buffer Kangaroos Against Evolutionary Responses to Selective Harvesting?

475

417

Human harvest of phenotypically desirable animals from wild populations imposes selection that can reduce the frequencies of those desirable phenotypes. Hunting and fishing contrast with agricultural and aquacultural practices in which the most desirable animals are typically bred with the specific goal of increasing the frequency of desirable phenotypes. We consider the potential effects of harvest on the genetics and sustainability of wild populations. We also consider how harvesting could affect the mating system and thereby modify sexual selection in a way that might affect recruitment. Determining whether phenotypic changes in harvested populations are due to evolution, rather than phenotypic plasticity or environmental variation, has been problematic. Nevertheless, it is likely that some undesirable changes observed over time in exploited populations (e.g., reduced body size, earlier sexual maturity, reduced antler size, etc.) are due to selection against desirable phenotypes-a process we call ''unnatural'' selection. Evolution brought about by human harvest might greatly increase the time required for over-harvested populations to recover once harvest is curtailed because harvesting often creates strong selection differentials, whereas curtailing harvest will often result in less intense selection in the opposing direction. We strongly encourage those responsible for managing harvested wild populations to take into account possible selective effects of harvest management and to implement monitoring programs to detect exploitation-induced selection before it seriously impacts viability.conservation ͉ genetic change ͉ human exploitation

Section: Discussionmentioning

confidence: 93%

Human-induced evolution caused by unnatural selection through harvest of wild animals

Allendorf

Hard

2009

475

417

“…There is accumulating evidence that adaptation to strong directional selection can contribute to the persistence of populations (23). Whereas the presence of genetic variation in populations needed for traits such as age at maturation is well established (24)(25)(26)(27), of emerging interest is the role of phenotypic plasticity in adaptive responses. If a particular form of phenotypic plasticity enhances an organism's probability of surviving directional selection at the population level, it may lead to an adaptive evolutionary response (28).…”

Section: Discussionmentioning

confidence: 99%

Life-history change in disease-ravaged Tasmanian devil populations

Jones

Cockburn

Hamede

et al. 2008

253

246

Changes in life history are expected when new sources of extrinsic mortality impact on natural populations. We report a new disease, devil facial tumor disease, causing an abrupt transition from iteroparity toward single breeding in the largest extant carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii), in which males can weigh as much as 14 kg and females 9 kg. This change in life history is associated with almost complete mortality of individuals from this infectious cancer past their first year of adult life. Devils have shown their capacity to respond to this diseaseinduced increased adult mortality with a 16-fold increase in the proportion of individuals exhibiting precocious sexual maturity. These patterns are documented in five populations where there are data from before and after disease arrival and subsequent population impacts. To our knowledge, this is the first known case of infectious disease leading to increased early reproduction in a mammal. The persistence of both this disease and the associated life-history changes pose questions about longer-term evolutionary responses and conservation prospects for this iconic species.carnivorous marsupial ͉ infectious cancer ͉ wildlife disease ͉ precocious breeding ͉ semelparity

“…phenotypic plasticity | eco-evolutionary dynamics | management | genetic adaptation | genetic variance H arvesting is usually selective, differentially targeting and removing members of a population based on their phenotypic attributes (1,2). Such selective harvesting induces a genetic response in life history traits when it renders some genotypes more likely than others to survive and reproduce (3,4).…”

mentioning

confidence: 99%

Roles of density-dependent growth and life history evolution in accounting for fisheries-induced trait changes

Eikeset

Dunlop

Heino

et al. 2016

The relative roles of density dependence and life history evolution in contributing to rapid fisheries-induced trait changes remain debated. In the 1930s, northeast Arctic cod (Gadus morhua), currently the world's largest cod stock, experienced a shift from a traditional spawning-ground fishery to an industrial trawl fishery with elevated exploitation in the stock's feeding grounds. Since then, age and length at maturation have declined dramatically, a trend paralleled in other exploited stocks worldwide. These trends can be explained by demographic truncation of the population's age structure, phenotypic plasticity in maturation arising through density-dependent growth, fisheries-induced evolution favoring faster-growing or earlier-maturing fish, or a combination of these processes. Here, we use a multitrait eco-evolutionary model to assess the capacity of these processes to reproduce 74 y of historical data on age and length at maturation in northeast Arctic cod, while mimicking the stock's historical harvesting regime. Our results show that model predictions critically depend on the assumed density dependence of growth: when this is weak, life history evolution might be necessary to prevent stock collapse, whereas when a stronger density dependence estimated from recent data is used, the role of evolution in explaining fisheries-induced trait changes is diminished. Our integrative analysis of density-dependent growth, multitrait evolution, and stock-specific time series data underscores the importance of jointly considering evolutionary and ecological processes, enabling a more comprehensive perspective on empirically observed stock dynamics than previous studies could provide.phenotypic plasticity | eco-evolutionary dynamics | management | genetic adaptation | genetic variance