Merwin Andrew C, Hilliard Justin, Larsen Ashley, Lasken Andrew G, Johnson Icesstrená
Department of Biology and Geology Baldwin Wallace University Berea Ohio USA.
Citizens for Los Angeles Wildlife Los Angeles California USA.
Ecol Evol. 2022 May 19;12(5):e8913. doi: 10.1002/ece3.8913. eCollection 2022 May.
Within an animal species, the body sizes of individuals at higher latitudes are often different from individuals at lower latitudes. For homeothermic species that maintain a relatively constant body temperature, such as mammals and birds, individuals at higher latitudes tend to be larger. For ectothermic species, such as insects, that do not retain their own body heat and which often do not maintain a relatively constant body temperature, patterns of body size with latitude are highly variable. This has led some authors to contend that patterns in even closely related species cannot be expected to be similar. Indeed, to our knowledge, no studies of invertebrates have found that more closely related species have more similar relationships between body size and latitude. Further, no studies have investigated the potential influence of diet quality on interspecific differences in these clines. We measured wing lengths of specimens (N = 1753) in eight lycaenid butterfly species and one species of the sister family, Riodinidae to determine if more closely related species have similar latitudinal trends. We also estimated the mean nitrogen content of caterpillars' hosts to investigate whether this often-limiting nutrient influences the strength and direction of latitudinal clines in body size. We found that four species are significantly smaller at higher latitudes, an additional species is marginally smaller at higher latitudes ( < .06), and four species had no significant relationship with latitude. We also found a strong phylogenetic signal for latitudinal clines in body size among our species, which indicates that some closely related species may have similar clines. However, the strength and direction of these clines did not depend on the estimated nitrogen content of caterpillars' hosts. Our results indicate that mean nitrogen content of hosts may not be an important driver in latitudinal clines but that phylogenetic relationships among species should be accounted for when exploring other potential drivers of body-size clines in invertebrate species.
在一个动物物种内，高纬度地区个体的体型往往与低纬度地区的个体不同。对于维持相对恒定体温的恒温物种，如哺乳动物和鸟类，高纬度地区的个体往往体型更大。对于变温物种，如昆虫，它们自身不保留体温且通常不维持相对恒定的体温，体型随纬度的变化模式差异很大。这使得一些作者认为，即使是亲缘关系密切的物种，其模式也不一定相似。事实上，据我们所知，没有关于无脊椎动物的研究发现亲缘关系越近的物种在体型和纬度之间的关系越相似。此外，也没有研究调查过食物质量对这些梯度中种间差异的潜在影响。我们测量了8种灰蝶科蝴蝶物种和一个近缘科——闪蝶科的一个物种的标本（N = 1753）的翅长，以确定亲缘关系越近的物种是否具有相似的纬度趋势。我们还估计了毛虫寄主的平均氮含量，以研究这种通常具有限制作用的营养物质是否会影响体型纬度梯度的强度和方向。我们发现，有4个物种在高纬度地区明显更小，另有1个物种在高纬度地区略小（P < 0.06），还有4个物种与纬度没有显著关系。我们还发现，我们研究的物种在体型的纬度梯度上有很强的系统发育信号，这表明一些亲缘关系密切的物种可能具有相似的梯度。然而，这些梯度的强度和方向并不取决于毛虫寄主的估计氮含量。我们的结果表明，寄主的平均氮含量可能不是纬度梯度的重要驱动因素，但在探索无脊椎动物物种体型梯度的其他潜在驱动因素时，应考虑物种间的系统发育关系。
