Department of Integrative Biology, University of South Florida, Tampa, FL 33620, USA.
Integr Comp Biol. 2013 Aug;53(2):351-8. doi: 10.1093/icb/ict007. Epub 2013 Mar 27.
The spread of invasive species presents a genetic paradox: how do individuals overcome the genetic barriers associated with introductions (e.g., bottlenecks and founder effects) to become adapted to the new environment? In addition to genetic diversity, epigenetic variation also contributes to phenotypic variation and could influence the spread of an introduced species in novel environments. This may occur through two different (non-mutually exclusive) mechanisms. Individuals may benefit from existing (and heritable) epigenetic diversity or de novo epigenetic marks may increase in response to the new environment; both mechanisms might increase flexibility in new environments. Although epigenetic changes in invasive plants have been described, no data yet exist on the epigenetic changes throughout a range expansion of a vertebrate. Here, we used methylation sensitive-amplified fragment length polymorphism to explore genome-wide patterns of methylation in an expanding population of house sparrows (Passer domesticus). House sparrows were introduced to Kenya in the 1950s and have significant phenotypic variation dependent on the time since colonization. We found that Kenyan house sparrows had high levels of variation in methylation across the genome. Interestingly, there was a significant, potentially compensatory relationship between epigenetic and genetic diversity: epigenetic diversity was negatively correlated with genetic diversity and positively correlated with inbreeding across the range expansion. Thus, methylation may increase phenotypic variation and/or plasticity in response to new environments and therefore be an important source of inter-individual variation for adaptation in these environments, particularly over the short timescales over which invasions occur.
个体如何克服与引入相关的遗传障碍（如瓶颈和奠基者效应），从而适应新环境？除了遗传多样性外，表观遗传变异也有助于表型变异，并可能影响引入物种在新环境中的传播。这可能通过两种不同的（非互斥）机制发生。个体可能受益于现有的（可遗传的）表观遗传多样性，或者新环境中可能会增加新的表观遗传标记；这两种机制都可能增加新环境中的灵活性。尽管已经描述了入侵植物中的表观遗传变化，但在脊椎动物的范围扩展过程中，还没有关于表观遗传变化的数据。在这里，我们使用甲基化敏感扩增片段长度多态性（methylation sensitive-amplified fragment length polymorphism）来探索扩展种群中麻雀（Passer domesticus）的全基因组甲基化模式。麻雀于 20 世纪 50 年代被引入肯尼亚，其表型变异与殖民时间密切相关。我们发现，肯尼亚麻雀的全基因组甲基化水平存在高度变异。有趣的是，表观遗传多样性与遗传多样性之间存在显著的、潜在的补偿关系：表观遗传多样性与遗传多样性呈负相关，与范围扩展过程中的近交呈正相关。因此，甲基化可能会增加对新环境的表型变异和/或可塑性，从而成为这些环境中适应的重要个体间变异来源，尤其是在入侵发生的短时间尺度内。
