Biological Invasions ( IF 2.9 ) Pub Date :
Abstract
Predicting changes in the abundance and distribution of introduced species over time is difficult, but clues regarding the underlying causes of these changes may come from long-term surveys. Resurveys conducted over large spatial scales, for example, can be used to discriminate between site-specific causes of decline and those that act at the population level. Here we used regional resurvey data to address changes in Argentine ant site occupancy in urban, agricultural, and natural environments in coastal southern California. We resurveyed 145 locations originally sampled 12–14 years ago and observed a slight decrease in Argentine ant site occupation, from 85 to 79% across all sites. At the majority of sites where apparent absences were recorded, however, the Argentine ant had merely retreated outside of the proscribed sampling area (a 25-m radius circle) and was still present within 80 m, on average, of the original sampling point. This finding thus suggests that the apparent absences observed most likely reflect contractions of the area occupied by polydomous supercolonies, possibly in response to local-scale changes in environmental conditions, as opposed to processes acting at larger spatial scales. We also conducted back-to-back annual resurveys (in 2018 and 2019) of all urban sampling points (n = 95) to quantify annual turnover in site occupancy. These resurveys revealed 2.4% site turnover with 97% (92/95) sites being classified as either presences (n = 85) or absences (n = 7) in both years. Our results support the findings of resurveys conducted in northern California, where Argentine ant distributions have slowly expanded over decadal time scales. Historical resurveys can provide insights into why populations of introduced species change over time and should incorporate an appreciation of how invader traits affect detectability.
中文翻译:
历史回顾表明,加利福尼亚南部沿海地区阿根廷蚂蚁遗址的使用率没有下降
摘要
很难预测引入物种随时间的变化,但是有关这些变化的根本原因的线索可能来自长期调查。例如,在较大的空间尺度上进行的调查可用于区分特定地点的下降原因和在人口水平上起作用的原因。在这里,我们使用区域调查数据来解决加利福尼亚南部沿海城市,农业和自然环境中阿根廷蚂蚁遗址的占用变化。我们重新调查了最初在12至14年前采样的145个位置,并观察到阿根廷蚂蚁站点的占用率从所有站点的85%下降到79%。但是,在大多数记录到明显缺勤的地点,阿根廷蚂蚁仅退到了规定的采样区域外(半径为25 m的圆圈),并且仍然存在于平均原始采样点80 m以内。因此,这一发现表明,观察到的明显缺失最有可能反映了由多态超殖民地占据的区域的收缩,这可能是由于环境条件的局部尺度变化所致,而不是在更大的空间尺度上起作用。我们还对所有城市采样点(n = 95)进行了背对背的年度重新调查(2018年和2019年),以量化场地占用率的年度营业额。这些调查显示,在这两年中,站点转换率为2.4%,其中97%(92/95)站点被分类为存在(n = 85)或不存在(n = 7)。我们的结果支持在加利福尼亚北部进行的重新调查的结果,在十年的时间尺度上,阿根廷的蚂蚁分布已逐渐扩大。历史回顾可以洞悉为什么引进物种的种群会随着时间而变化,并且应该结合入侵者特征如何影响可检测性的认识。