Abstract
A quantitative analysis of wing variation in grasshoppers can help us to understand how environmental heterogeneity affects the phenotypic patterns of insects. In this study, geometric morphometric methods were used to measure the differences in wing shape and size of Trilophidia annulata among 39 geographical populations in China, and a regression analysis was applied to identify the major environmental factors contributing to the observed morphological variations. The results showed that the size of the forewing and hindwing were significantly different among populations; the shape of the forewing among populations can be divided into geographical groups, however hindwing shape are geographical overlapped, and populations cannot be divided into geographical groups. Environmental PCA and thin-plate spline analysis suggested that smaller individuals with shorter and blunter-tip forewings were mainly distributed in the lower latitudes and mountainous areas, where they have higher temperatures and more precipitation. Correspondingly, the larger-bodied grasshoppers, those that have longer forewings with a longer radial sector, are distributed in contrary circumstances. We conclude that the size variations in body, forewing and hindwing of T. annulata apparently follow the Bergmann clines. The importance of climatic variables in influencing morphological variation among populations, forewing shape of T. annulata varies along an environmental gradient.
Highlights
A quantitative analysis of wing variation in grasshoppers can help us to understand how environmental heterogeneity affects the phenotypic patterns of insects
The one-way ANOVA showed that there were significantly different (F(38,367) = 64.571, P < 0.001), a Tukey’s post-hoc HSD test results suggested that the 39 populations can be divided into 3 groups with significant difference (P < 0.001) (Fig. 1). Those body size range from 13.08 mm to 14.35 mm were mainly distributed in the south of 30° N, where the body size range from 14.35 mm to 17.07 mm were mainly distributed within region between 30° N and the south of Qinling www.nature.com/scientificreports/ Figure 2
When latitude is higher than 40° N, the body size of T. annulata fell below expectations
Summary
A quantitative analysis of wing variation in grasshoppers can help us to understand how environmental heterogeneity affects the phenotypic patterns of insects. A number of studies have shown that the body size of insects along environmental gradients fit Bergmann clines or converse-Bergmann clines, but other studies have suggested that Bergmann’s rule might not work in insects[16,17]. Numerous studies have focused on the factors influencing the size of adult insects, but little is known from the large geographical scale, intraspecific variations in body size and shape of individuals that lives in diverse environments. Some studies have shown that grasshoppers are larger in cooler areas with longer growing seasons, whereas smaller body sizes are observed in warmer areas with shorter growing seasons[32,33,34] These patterns of ecological variation are typical examples of Bergmann or converse-Bergmann clines. Among these characters, wing size and shape are commonly used as indicators of the environmental changing and stress[41,42]
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