Data from: Domestication and fitness in the wild. a multivariate view

Domesticated species continually escaping and interbreeding with wild relatives impose a migration load on wild populations. As domesticated stocks become increasingly different as a result of artificial and natural selection in captivity, fitness of escapees in the wild is expected to decline, reducing the effective rate of migration into wild populations. Recent theory suggest that this may alleviate and eventually eliminate the resulting migration load. I develop a multivariate model of trait and wild fitness evolution resulting from the joint effects of artificial and natural selection in the captive environment. Initially, the evolutionary trajectory is dominated by the effects of artificial selection causing a fast initial decline in fitness of escapees in the wild. In later phases, through the counteracting effects of correlational multivariate natural selection in captivity, the mean phenotype is pushed in directions of weak stabilizing selection, allowing a sustained response in the trait subject to artificial selection. Provided that there is some alignment between the adaptive landscapes in the wild and in captivity, these phases are associated with slower rates of decline in wild fitness of the domesticated stock, suggesting that detrimental effects on wild populations are likely to remain a concern in the foreseeable future.

驯化物种持续逃逸并与野生近缘种杂交，会对野生种群施加迁移负荷（migration load）。由于圈养环境中的人工选择与自然选择作用，驯化种群的遗传分化程度不断加剧，逃逸个体在野生环境中的适合度预计会随之下降，进而降低迁入野生种群的有效迁移速率。最新理论研究表明，这一过程或可缓解并最终消除由此产生的迁移负荷。本研究构建了一个多变量模型（multivariate model），用以刻画圈养环境中人工选择与自然选择共同作用下，性状与野生适合度的演化过程。演化初期，进化轨迹主要受人工选择主导，导致逃逸个体的野生适合度快速下降。演化后期，圈养环境中的相关多变量自然选择会产生抵消效应，将平均表型推向弱稳定选择（stabilizing selection）的方向，使得受人工选择作用的性状能够持续产生演化响应。若野生与圈养环境的适应景观（adaptive landscape）存在一定程度的契合，上述演化阶段会伴随驯化种群逃逸个体的野生适合度下降速率放缓，这意味着对野生种群的负面影响在可预见的未来仍将是一个值得关注的问题。