Lehtinen Richard M, Carlson Brian M, Hamm Alyssa R, Riley Alexis G, Mullin Maria M, Gray Weston J
The College of Wooster Department of Biology Wooster OH USA.
Ecol Evol. 2020 Jan 16;10(3):1526-1538. doi: 10.1002/ece3.6006. eCollection 2020 Feb.
Heritable color polymorphisms have a long history of study in evolutionary biology, though they are less frequently examined today than in the past. These systems, where multiple discrete, visually identifiable color phenotypes co-occur in the same population, are valuable for tracking evolutionary change and ascertaining the relative importance of different evolutionary mechanisms. Here, we use a combination of citizen science data and field surveys in the Great Lakes region of North America to identify patterns of color morph frequencies in the eastern gray squirrel (). Using over 68,000 individual squirrel records from both large and small spatial scales, we identify the following patterns: (a) the melanistic (black) phenotype is often localized but nonetheless widespread throughout the Great Lakes region, occurring in all states and provinces sampled. (b) In Ohio, where intensive surveys were performed, there is a weak but significantly positive association between color morph frequency and geographic proximity of populations. Nonetheless, even nearby populations often had radically different frequencies of the melanistic morph, which ranged from 0% to 96%. These patterns were mosaic rather than clinal. (c) In the Wooster, Ohio population, which had over eight years of continuous data on color morph frequency representing nearly 40,000 records, we found that the frequency of the melanistic morph increased gradually over time on some survey routes but decreased or did not change over time on others. These differences were statistically significant and occurred at very small spatial scales (on the order of hundreds of meters). Together, these patterns are suggestive of genetic drift as an important mechanism of evolutionary change in this system. We argue that studies of color polymorphism are still quite valuable in advancing our understanding of fundamental evolutionary processes, especially when coupled with the growing availability of data from citizen science efforts.
可遗传的颜色多态性在进化生物学中的研究历史悠久，不过如今对它们的研究不如过去频繁。在这些系统中，多种离散的、视觉上可识别的颜色表型在同一群体中共存，对于追踪进化变化以及确定不同进化机制的相对重要性很有价值。在这里，我们结合北美五大湖地区的公民科学数据和实地调查，来确定东部灰松鼠（Sciurus carolinensis）颜色形态频率的模式。利用来自大小不同空间尺度的超过68000条松鼠个体记录，我们识别出以下模式：（a）黑化（黑色）表型通常呈局部性分布，但在五大湖地区仍广泛存在，在所采样的所有州和省份都有出现。（b）在进行了密集调查的俄亥俄州，颜色形态频率与种群的地理距离之间存在微弱但显著的正相关。尽管如此，即使是相邻的种群，黑化形态的频率也常常有很大差异，范围从0%到96%。这些模式是镶嵌式的而非渐变式的。（c）在俄亥俄州伍斯特的种群中，有超过八年关于颜色形态频率的连续数据，代表了近40000条记录，我们发现黑化形态的频率在一些调查路线上随时间逐渐增加，但在其他路线上随时间减少或没有变化。这些差异具有统计学意义，且发生在非常小的空间尺度上（在数百米的量级）。综合来看，这些模式表明遗传漂变是该系统进化变化的一个重要机制。我们认为，颜色多态性的研究对于推进我们对基本进化过程的理解仍然非常有价值，特别是当与公民科学工作中日益增多的数据相结合时。
