Interspecific variation among metazoans often follows a latitudinal pattern, with species at higher latitudes being larger bodied than related species from lower latitudes (Bergmann's rule). For parasitic species, body sizes within any higher taxon are often correlated with the body sizes of their hosts (Harrison's rule). Whether temperature-driven latitudinal effects or host-driven resource constraints act independently or additively to shape interspecific variation in parasite body sizes remains unknown. We take a comparative approach to test the effects of latitude and host body size on parasite body sizes in two taxa of parasitic worms showing convergent life cycles.

中文翻译：

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具有收敛生命周期的不同寄生虫类群中体型变化的收敛模式

后生动物之间的种间变异通常遵循纬度模式，高纬度的物种比低纬度的相关物种体型更大（伯格曼法则）。对于寄生物种，任何更高分类群中的体型通常与其宿主的体型相关（哈里森法则）。温度驱动的纬度效应或宿主驱动的资源约束是独立起作用还是相加作用来塑造寄生虫体型的种间变化仍然未知。我们采用比较方法来测试纬度和宿主体型对显示趋同生命周期的两种寄生虫类群中寄生虫体型的影响。