Data: Implementing a rapid geographic range expansion - the role of behavior changes

It is generally thought that behavioral flexibility, the ability to change behavior when circumstances change, plays an important role in the ability of species to rapidly expand their geographic range. Great-tailed grackles (Quiscalus mexicanus) are a social, polygamous species that is rapidly expanding its geographic range by settling in new areas and habitats. They are behaviorally flexible and highly associated with human-modified environments, eating a variety of human foods in addition to foraging on insects and on the ground for other natural food items. They offer an opportunity to assess the role of behavior change over the course of their expansion. We compared behavior in wild-caught grackles from two populations across their range (an older population in the middle of the northern expansion front: Tempe, Arizona, and a more recent population on the northern edge of the expansion front: Woodland, California) to investigate whether certain behaviors (flexibility, innovativeness, exploration, and persistence) have higher averages and variances in the newer or older population. We found that grackles in the edge population had a higher flexibility variance (measured by reversal learning) and a higher persistence average (they participated in a larger proportion of trials), and that there were no population differences in average levels of flexibility, innovativeness (number of loci solved on a multiaccess box), or exploration (latency to approach a novel environment). Our results elucidated that individuals differentially expressing a particular behavior in an edge population could facilitate the rapid geographic range expansion of great-tailed grackles, and we found no support for the importance of several traits that were hypothesized to be involved in such an expansion. Our findings highlight the value of population studies and of breaking down cognitive concepts into direct measures of individual abilities to better understand how species might adapt to novel circumstances.

普遍认为，行为灵活性（behavioral flexibility）——即环境变化时改变行为的能力——在物种快速扩张其地理分布范围的能力中发挥着重要作用。大尾拟八哥（Great-tailed grackles, Quiscalus mexicanus）是一种群居的一夫多妻制物种，通过定居于新区域和栖息地快速扩张其地理分布范围。它们具有行为灵活性，且高度适应人类改造的环境；除捕食昆虫和在地面搜寻其他天然食物外，还摄食多种人类食物。这为评估其扩张过程中行为变化的作用提供了机会。我们比较了来自其分布范围内两个种群的野生捕获拟八哥的行为：一个是位于北部扩张前沿中部的较古老种群（亚利桑那州坦佩市），另一个是位于北部扩张前沿边缘的较新种群（加利福尼亚州伍德兰市），以探究某些行为（灵活性、创新性（innovativeness）、探索性（exploration）和持久性（persistence））在较新种群或较古老种群中是否具有更高的平均值和方差。结果发现，边缘种群的拟八哥具有更高的灵活性方差（通过反转学习（reversal learning）测量）和更高的持久性平均值（它们参与了更大比例的试验）；而在灵活性平均值、创新性（通过多通道箱（multiaccess box）解决的位点数量）或探索性（接近新环境的潜伏期（latency to approach a novel environment））方面，两个种群无显著差异。我们的结果阐明，边缘种群中特定行为表达存在差异的个体可能促进大尾拟八哥的快速地理分布扩张，且未发现有证据支持若干被假设参与此类扩张的性状的重要性。本研究结果强调了种群研究的价值，以及将认知概念分解为个体能力的直接测量指标以更好地理解物种如何适应新环境的意义。