Nguyen Hoa Q, Andersen Desiree K, Kim Yuseob, Jang Yikweon
Interdisciplinary Program of EcoCreative, Ewha Womans University, Seoul, Republic of Korea.
Department of Life Sciences, Ewha Womans University, Seoul, Republic of Korea.
PeerJ. 2018 Jan 12;6:e4238. doi: 10.7717/peerj.4238. eCollection 2018.
Urban heat island (UHI) effect, the ubiquitous consequence of urbanization, is considered to play a major role in population expansion of numerous insects. and are the most abundant cicada species in the Korean Peninsula, where their population densities are higher in urban than in rural areas. We predicted a positive relationship between the UHI intensities and population densities of these two cicada species in metropolitan Seoul.
To test this prediction, enumeration surveys of cicada exuviae densities were conducted in 36 localities located within and in the vicinity of metropolitan Seoul. Samples were collected in two consecutive periods from July to August 2015. The abundance of each species was estimated by two resource-weighted densities, one based on the total geographic area, and the other on the total number of trees. Multiple linear regression analyses were performed to identify factors critical for the prevalence of cicada species in the urban habitat.
and were major constituents of cicada species composition collected across all localities. Minimum temperature and sampling period were significant factors contributing to the variation in densities of both species, whereas other environmental factors related to urbanization were not significant. More cicada exuviae were collected in the second rather than in the first samplings, which matched the phenological pattern of cicadas in metropolitan Seoul. Cicada population densities increased measurably with the increase in temperature. Age of residential complex also exhibited a significantly positive correlation to densities, but not to densities.
Effects of temperature on cicada densities have been discerned from other environmental factors, as cicada densities increased measurably in tandem with elevated temperature. Several mechanisms may contribute to the abundance of cicadas in urban environments, such as higher fecundity of females, lower mortality rate of instars, decline in host plant quality, and local adaptation of organisms, but none of them were tested in the current study.
In sum, results of the enumeration surveys of cicada exuviae support the hypothesis that the UHI effect underlies the population expansion of cicadas in metropolitan Seoul. Nevertheless, the underlying mechanisms for this remain untested.
城市热岛（UHI）效应是城市化普遍存在的结果，被认为在众多昆虫的种群扩张中起主要作用。黑蚱蝉和蒙古寒蝉是朝鲜半岛最常见的蝉种，在城市地区它们的种群密度高于农村地区。我们预测首尔大都市区这两种蝉的城市热岛强度与种群密度之间存在正相关关系。
为验证这一预测，在首尔大都市区及其附近的36个地点进行了蝉蜕密度的计数调查。样本于2015年7月至8月连续两个时期采集。通过两种资源加权密度估计每种蝉的丰度，一种基于总地理面积，另一种基于树木总数。进行多元线性回归分析以确定城市栖息地中对蝉种流行至关重要的因素。
黑蚱蝉和蒙古寒蝉是所有地点采集的蝉种组成的主要成分。最低温度和采样时期是导致两种蝉密度变化的重要因素，而其他与城市化相关的环境因素并不显著。第二次采样比第一次采样收集到更多的蝉蜕，这与首尔大都市区蝉的物候模式相符。蝉的种群密度随着温度升高而显著增加。住宅小区的年限也与黑蚱蝉密度呈显著正相关，但与蒙古寒蝉密度无关。
温度对蝉密度的影响已与其他环境因素区分开来，因为随着温度升高，蝉密度显著增加。有几种机制可能导致城市环境中蝉的数量增加，例如雌性繁殖力更高、若虫死亡率更低、寄主植物质量下降以及生物的局部适应性，但在本研究中均未进行测试。
总之，蝉蜕计数调查结果支持以下假设：城市热岛效应是首尔大都市区蝉种群扩张的基础。然而，其潜在机制仍未得到验证。
