Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
PLoS One. 2023 Jul 13;18(7):e0288415. doi: 10.1371/journal.pone.0288415. eCollection 2023.
Allochronic speciation, where reproductive isolation between populations of a species is facilitated by a difference in reproductive timing, depends on abiotic factors such as seasonality and biotic factors such as diapause intensity. These factors are strongly influenced by latitudinal trends in climate, so we hypothesized that there is a relationship between latitude and divergence among populations separated by life history timing. Hyphantria cunea (the fall webworm), a lepidopteran defoliator with red and black colour morphs, is hypothesized to be experiencing an incipient allochronic speciation. However, given their broad geographic range, the strength of allochronic speciation may vary across latitude. We annotated >11,000 crowd-sourced observations of fall webworm to model geographic distribution, phenology, and differences in colour phenotype between morphs across North America. We found that red and black morph life history timing differs across North America, and the phenology of morphs diverges more in warmer climates at lower latitudes. We also found some evidence that the colour phenotype of morphs also diverges at lower latitudes, suggesting reduced gene flow between colour morphs. Our results demonstrate that seasonality in lower latitudes may increase the strength of allochronic speciation in insects, and that the strength of sympatric speciation can vary along a latitudinal gradient. This has implications for our understanding of broad-scale speciation events and trends in global biodiversity.
时间错配物种形成，即物种的种群之间通过生殖时间的差异而产生生殖隔离，取决于非生物因素（如季节性）和生物因素（如休眠强度）。这些因素受气候的纬度趋势的强烈影响，因此我们假设，通过生活史时间分隔的种群之间的分歧与纬度之间存在关系。秋粘虫（秋幕毛虫）是一种具有红色和黑色形态的鳞翅目食叶害虫，据推测正在经历初期的时间错配物种形成。然而，鉴于它们广泛的地理范围，时间错配物种形成的强度可能会因纬度而异。我们对超过 11000 个秋粘虫的众包观察结果进行注释，以建立北美地区的地理分布、物候学以及形态之间颜色表型差异的模型。我们发现，红色和黑色形态的秋粘虫生活史时间在整个北美洲存在差异，形态的物候学在较低纬度的温暖气候中差异更大。我们还发现了一些证据表明形态的颜色表型也在较低纬度上存在差异，这表明颜色形态之间的基因流减少。我们的研究结果表明，较低纬度的季节性可能会增加昆虫时间错配物种形成的强度，并且同域物种形成的强度可以沿着纬度梯度而变化。这对我们理解广泛的物种形成事件和全球生物多样性的趋势具有重要意义。
