The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
BMC Evol Biol. 2010 Aug 19;10:252. doi: 10.1186/1471-2148-10-252.
Many butterfly species have been experiencing the northward range expansion and physiological adaptation, probably due to climate warming. Here, we document an extraordinary field case of a species of lycaenid butterfly, Zizeeria maha, for which plastic phenotypes of wing color-patterns were revealed at the population level in the course of range expansion. Furthermore, we examined whether this outbreak of phenotypic changes was able to be reproduced in a laboratory.
In the recently expanded northern range margins of this species, more than 10% of the Z. maha population exhibited characteristic color-pattern modifications on the ventral wings for three years. We physiologically reproduced similar phenotypes by an artificial cold-shock treatment of a normal southern population, and furthermore, we genetically reproduced a similar phenotype after selective breeding of a normal population for ten generations, demonstrating that the cold-shock-induced phenotype was heritable and partially assimilated genetically in the breeding line. Similar genetic process might have occurred in the previous and recent range-margin populations as well. Relatively minor modifications expressed in the tenth generation of the breeding line together with other data suggest a role of founder effect in this field case.
Our results support the notion that the outbreak of the modified phenotypes in the recent range-margin population was primed by the revelation of plastic phenotypes in response to temperature stress and by the subsequent genetic process in the previous range-margin population, followed by migration and temporal establishment of genetically unstable founders in the recent range margins. This case presents not only an evolutionary role of phenotypic plasticity in the field but also a novel evolutionary aspect of range expansion at the species level.
许多蝴蝶物种经历了向北的分布范围扩张和生理适应，这可能是由于气候变暖所致。在这里，我们记录了一个关于斑凤蝶属（Lycaenidae）蝴蝶的非凡案例，在该物种分布范围扩张的过程中，在种群水平上发现了翅膀颜色图案的可塑性表型。此外，我们还研究了这种表型变化的爆发是否可以在实验室中重现。
在该物种最近扩张的北部边缘地区，超过 10%的斑凤蝶种群在三年的时间里表现出了翅膀腹面特征性颜色图案的改变。我们通过对正常南部种群进行人工冷休克处理，在生理上重现了类似的表型，并且通过对正常种群进行十代的选择性繁殖，在遗传上也重现了类似的表型，表明冷休克诱导的表型是可遗传的，并在繁殖系中部分遗传同化。类似的遗传过程可能也发生在之前和最近的分布范围边缘种群中。在繁殖系的第十代中表达的相对较小的修饰以及其他数据表明，在这个野外案例中，奠基者效应起到了一定的作用。
我们的研究结果支持了这样一种观点，即在最近的分布范围边缘种群中出现的改良表型的爆发是由对温度应激的可塑性表型的揭示以及以前分布范围边缘种群中的后续遗传过程引发的，随后是遗传不稳定的奠基者在最近的分布范围边缘的迁移和暂时建立。这种情况不仅展示了表型可塑性在野外的进化作用，也揭示了物种水平上分布范围扩张的一个新的进化方面。
