Is the sky the limit? On the expansion threshold of a species' range

More than 100 years after Grigg’s influential analysis of species’ borders, the causes of limits to species’ ranges still represent a puzzle that has never been understood with clarity. The topic has become especially important recently as many scientists have become interested in the potential for species’ ranges to shift in response to climate change—and yet nearly all of those studies fail to recognise or incorporate evolutionary genetics in a way that relates to theoretical developments. I show that range margins can be understood based on just two measurable parameters: (i) the fitness cost of dispersal—a measure of environmental heterogeneity—and (ii) the strength of genetic drift, which reduces genetic diversity. Together, these two parameters define an ‘expansion threshold’: adaptation fails when genetic drift reduces genetic diversity below that required for adaptation to a heterogeneous environment. When the key parameters drop below this expansion threshold locally, a sharp r...

在格里格（Grigg）对物种边界开展具有影响力的分析研究一百多年后，物种分布范围受限的成因仍是一个至今尚未被清晰阐明的谜题。近年来，随着众多科学家开始关注物种分布范围因气候变化而发生迁移的潜在可能性，这一议题的重要性愈发凸显——但几乎所有相关研究都未能以契合理论发展的方式，认知或纳入进化遗传学相关内容。本研究表明，物种分布范围边界的成因仅可通过两个可测量参数予以阐明：其一为扩散适合度成本（fitness cost of dispersal）——一种衡量环境异质性（environmental heterogeneity）的指标；其二为遗传漂变（genetic drift）的强度，该过程会降低遗传多样性。这两个参数共同定义了一个“扩张阈值”：当遗传漂变将遗传多样性降低至无法适应异质性环境所需的水平时，物种便无法实现扩张。当关键参数在局部区域低于该扩张阈值时，便会出现急剧的（原文未完整）