Graduate School of Science, Kyoto University, Kyoto, Japan.
General Education Division, Miyagi Gakuin Women's University, Sendai, Japan.
Glob Chang Biol. 2018 Dec;24(12):5622-5628. doi: 10.1111/gcb.14436. Epub 2018 Oct 4.
Recent climate warming has affected some life-history traits of insects, including voltinism and body size. The magnitude of changes in these traits may differ latitudinally within a species because of the differing lengths of season available for growth. The present study aims to estimate the change in voltinism of the lawn ground cricket, Polionemobius mikado (Shiraki) (Orthoptera: Trigonidiidae), over the last four decades by comparing the body size between adults collected from a wide range of latitudes in Japan in recent years (2015-2017) and those collected four decades ago (1969-1976). The body size of adults collected in recent years showed a latitudinal saw-tooth cline, in the same way as body size did four decades ago, and the cline shifted northward over the last four decades: In 2015-2017, the body size decreased slightly with increasing latitude from 31°N to 36°N, and then increased to 40°N, and again decreased from 40°N to 44°N. Comparison of the body size between recent years and four decades ago revealed that the body size has decreased significantly at the middle latitudes (36-40°N), suggesting that the proportion of smaller bivoltine individuals there has increased over the last four decades. The sum of effective temperatures for postdiapause embryonic development at around 36°N in recent years was comparable to that at 31-35°N four decades ago, at which P. mikado populations were bivoltine. Taken together, these findings suggested that the latitudinal range suitable for the bivoltine life cycle of P. mikado has expanded northward over the last four decades because of climate warming. This is the first report that shows that a decrease in body size can be caused by climate warming via an increase in voltinism.
近年来气候变暖影响了昆虫的一些生活史特征，包括世代交替和体型。由于生长季节的长短不同，同一物种在不同纬度的这些特征变化幅度可能不同。本研究旨在通过比较近年来（2015-2017 年）和四十年前（1969-1976 年）在日本广泛纬度采集的成虫体型，来估计草坪蟋蟀 Polionemobius mikado（Shiraki）（直翅目：Trigonidiidae）的世代交替变化。近年来采集的成虫体型表现出与四十年前相同的纬度锯齿状渐变，且在过去四十年中向北迁移：在 2015-2017 年，从 31°N 到 36°N ，成虫体型随着纬度的增加略有减小，然后在 40°N 增加，然后从 40°N 到 44°N 再次减小。近年来和四十年前的体型比较表明，在中纬度（36-40°N）体型显著减小，表明那里的两化性个体比例在过去四十年中有所增加。近年来，36°N 左右滞育后胚胎发育的有效温度总和与四十年前 31-35°N 时相当，当时 P. mikado 种群为两化性。综上所述，这些发现表明，由于气候变暖，适合 P. mikado 两化性生活周期的纬度范围向北扩展。这是第一个表明体型减小可能是由于气候变暖导致世代交替增加而引起的报告。
