Living Earth Collaborative, Washington University in St. Louis, St. Louis, MO, USA.
Division of Natural Sciences, New College of Florida, Sarasota, FL, USA.
Am J Bot. 2022 Jul;109(7):1085-1096. doi: 10.1002/ajb2.16021. Epub 2022 Jun 28.
Although the balance between cross- and self-fertilization is driven by the environment, no long-term study has documented whether anthropogenic climate change is affecting reproductive strategy allocation in species with mixed mating systems. Here, we test whether the common blue violet (Viola sororia; Violaceae) has altered relative allocation to the production of potentially outcrossing flowers as the climate has changed throughout the 20th century.
Using herbarium records spanning from 1875 to 2015 from the central United States, we quantified production of obligately selfing cleistogamous (CL) flowers and potentially outcrossing chasmogamous (CH) flowers by V. sororia, coupled these records with historic temperature and precipitation data, and tested whether changes to the proportion of CL flowers correlate with temporal climate trends.
We find that V. sororia progressively produced lower proportions of CL flowers across the past century and in environments with lower mean annual temperature and higher total annual precipitation. We also find that both CL and CH flower phenology has advanced across this time period.
Our results suggest that V. sororia has responded to lower temperatures and greater water availability by shifting reproductive strategy allocation away from selfing and toward potential outcrossing. This provides the first long-term study of how climate change may affect relative allocation to potential outcrossing in species with mixed mating systems. By revealing that CL flowering is associated with low water availability and high temperature, our results suggest the production of obligately selfing flowers is favored in water limited environments.
尽管杂交和自交之间的平衡是由环境驱动的，但没有长期研究记录表明人为气候变化是否正在影响具有混合交配系统的物种的生殖策略分配。在这里，我们测试了普通蓝堇（Viola sororia；堇菜科）是否随着 20 世纪气候的变化而改变了潜在的异交花的生产相对分配。
使用 1875 年至 2015 年期间来自美国中部的标本记录，我们量化了强制性自交的闭花（CL）花和潜在异交的开花（CH）花的产生，将这些记录与历史温度和降水数据相结合，并测试了 CL 花的比例变化是否与时间气候趋势相关。
我们发现，在过去的一个世纪里，在平均年温度较低和总年降水量较高的环境中，V. sororia 逐渐产生的 CL 花比例较低。我们还发现，CL 和 CH 花的物候期都在这段时间内提前了。
我们的结果表明，V. sororia 通过将生殖策略分配从自交转向潜在的异交，对较低的温度和较高的水分可用性做出了反应。这提供了关于气候变化如何影响具有混合交配系统的物种潜在异交的相对分配的第一个长期研究。通过揭示 CL 开花与低水分可用性和高温有关，我们的结果表明，在水分有限的环境中，强制性自交花的产生更受青睐。
