Kronforst Marcus R, Gilbert Lawrence E
FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA.
Proc Biol Sci. 2008 Mar 7;275(1634):493-500. doi: 10.1098/rspb.2007.1378.
Theory predicts strong stabilizing selection on warning patterns within species and convergent evolution among species in Müllerian mimicry systems yet Heliconius butterflies exhibit extreme wing pattern diversity. One potential explanation for the evolution of this diversity is that genetic drift occasionally allows novel warning patterns to reach the frequency threshold at which they gain protection. This idea is controversial, however, because Heliconius butterflies are unlikely to experience pronounced population subdivision and local genetic drift. To examine the fine-scale population genetic structure of Heliconius butterflies we genotyped 316 individuals from eight Costa Rican Heliconius species with 1428 AFLP markers. Six species exhibited evidence of population subdivision and/or isolation by distance indicating genetic differentiation among populations. Across species, variation in the extent of local genetic drift correlated with the roles different species have played in generating pattern diversity: species that originally generated the diversity of warning patterns exhibited striking population subdivision while species that later radiated onto these patterns had intermediate levels of genetic diversity and less genetic differentiation among populations. These data reveal that Heliconius butterflies possess the coarse population genetic structure necessary for local populations to experience pronounced genetic drift which, in turn, could explain the origin of mimetic diversity.
理论预测，在缪勒拟态系统中，物种内部的警戒模式会受到强烈的稳定选择，不同物种之间会出现趋同进化，但光明女神闪蝶却展现出了极端的翅型多样性。这种多样性进化的一个潜在解释是，基因漂变偶尔会使新的警戒模式达到获得保护的频率阈值。然而，这一观点存在争议，因为光明女神闪蝶不太可能经历明显的种群细分和局部基因漂变。为了研究光明女神闪蝶的精细种群遗传结构，我们用1428个AFLP标记对来自哥斯达黎加的8种光明女神闪蝶的316个个体进行了基因分型。6个物种表现出种群细分和/或距离隔离的证据，表明种群之间存在遗传分化。在不同物种中，局部基因漂变程度的差异与不同物种在产生模式多样性中所起的作用相关：最初产生警戒模式多样性的物种表现出显著的种群细分，而后来辐射到这些模式上的物种具有中等水平的遗传多样性，种群间的遗传分化较小。这些数据表明，光明女神闪蝶具有局部种群经历显著基因漂变所必需的粗略种群遗传结构，这反过来又可以解释拟态多样性的起源。
