Geographic Variation in Body Size and Sexual Size Dimorphism of a Seed‐Feeding Beetle
Geographic Variation in Body Size and Sexual Size Dimorphism of a Seed‐Feeding Beetle
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DOI：
10.1086/520118
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发表时间：
2007-07
期刊：
影响因子：
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通讯作者：
R. Stillwell;Geoffrey E. Morse-Geoffrey E.-Morse-2286197598;Charles W. Fox
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文献类型：
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作者：
R. Stillwell;Geoffrey E. Morse-Geoffrey E.-Morse-2286197598;Charles W. Fox
许多动物的身体大小随纬度而变化：身体大小在高纬度地区较大（伯格曼规则）或在高纬度地区较小（伯格曼规则的匡威）。然而，这些模式背后的原因知之甚少。此外，研究很少探讨性别大小二态性如何随纬度而变化。在这里，我们调查的地理变化的身体大小和性别大小二型性的种子喂养甲虫定子limbatus，收集从95个地点沿着38°的纬度范围。我们检查了14个变量，以测试是否在环境因素中的倾斜足以解释身体大小的地理模式。结果表明，在不同的生长发育阶段，S. limbatus随纬度变化很大;甲虫较小，但在较低纬度的二型性更强。身体大小与平均温度梯度无关，与普遍接受的假设，即倾斜是由纬度梯度的温度。相反，我们发现，三个因素足以解释身体大小的渐变：寄主植物种子大小的渐变，水分（湿度），季节性（湿度，降水和温度的变化）。我们还发现，在性别大小二型性的渐变部分是由水分梯度解释，虽然水分本身是不足以解释的渐变。其他生态或环境变量必然会导致对雄性和雌性体型的选择差异。我们的研究的主要影响是，性别不同的倾斜变化的大小在身体大小，创造纬度变化的性别大小二型性，和倾斜的种子甲虫的身体大小的变化可能会受到影响，在主机种子大小，水的可用性和季节性。
Body size of many animals varies with latitude: body size is either larger at higher latitudes (Bergmann’s rule) or smaller at higher latitudes (converse Bergmann’s rule). However, the causes underlying these patterns are poorly understood. Also, studies rarely explore how sexual size dimorphism varies with latitude. Here we investigate geographic variation in body size and sexual size dimorphism of the seed‐feeding beetle Stator limbatus, collected from 95 locations along a 38° range in latitude. We examine 14 variables to test whether clines in environmental factors are adequate to explain geographic patterns of body size. We found that body size and sexual size dimorphism of S. limbatus varied considerably with latitude; beetles were smaller but more dimorphic at lower latitudes. Body size was not correlated with a gradient in mean temperature, contrary to the commonly accepted hypothesis that clines are produced by latitudinal gradients in temperature. Instead, we found that three factors were adequate to explain the cline in body size: clinal variation in host plant seed size, moisture (humidity), and seasonality (variance in humidity, precipitation, and temperature). We also found that the cline in sexual size dimorphism was partially explainable by a gradient in moisture, though moisture alone was not sufficient to explain the cline. Other ecological or environmental variables must necessarily contribute to differences in selection on male versus female body size. The main implications of our study are that the sexes differ in the magnitude of clinal variation in body size, creating latitudinal variation in sexual size dimorphism, and that clines in body size of seed beetles are likely influenced by variation in host seed size, water availability, and seasonality.