The Amazon basin contains few obvious geographic barriers, yet it is the most biodiverse region on Earth. One hypothesis to explain its diversity is that the very large rivers promote allopatric divergence. Consistent with this, maps of heliconiine butterflies made from museum specimens show high subspecies richness close to the Amazon river, suggesting that it may produce or maintain intra‐specific phenotypic variability. However, museum data are subject to strong spatial biases (the ‘Wallacean shortfall' of distribution data), raising the possibility that this pattern is a sampling artefact. To test this, we systematically collected along a ~900 km north–south transect running through central Amazonia. We found a significant association between phenotypic diversity and major rivers, with distance from the Amazon river explaining 61% of the variance in the mean polymorphism of 25 species. This association is partly because many species exhibit different phenotypes on either side of the river. Nonetheless, we also find sites with high polymorphism close to the river, indicating continual cross‐river dispersal. Our results strongly suggest the presence of a suture zone (a region where multiple species have hybrid zones) near the city of Manaus. However, the effect of the river on spatial patterns of intra‐specific phenotypic diversity depends on a species' mimetic phenotype. Rather than being absolute barriers, our results support the idea that rivers can act as partial barriers that trap moving hybrid zones, resulting in a suture zone. As such, the wide Amazonian rivers help generate and maintain colour pattern diversity, but to date there is no evidence that they lead to speciation in our study group.

中文翻译：

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亚马逊河是多类拟螺旋藻蝴蝶的多系缝合带

亚马逊盆地几乎没有明显的地理障碍，但它是地球上生物多样性最丰富的地区。解释其多样性的一种假设是，非常大的河流促进了异相学分集。与此相一致，由博物馆标本制成的菊苣蝶图显示，亚马孙河附近的亚种丰富度很高，表明它可能产生或维持种内表型变异性。但是，博物馆数据会受到强烈的空间偏差（分布数据的“华莱士短缺”），从而增加了这种模式是抽样人工制品的可能性。为了验证这一点，我们系统地沿着贯穿亚马逊河中部的南北向约900公里的样带进行了收集。我们发现表型多样性与主要河流之间存在显着的关联，与亚马逊河的距离解释了25种物种平均多态性的61％变异。这种关联的部分原因是，许多物种在河的两边表现出不同的表型。尽管如此，我们还在河附近发现了具有高多态性的地点，表明跨河的扩散持续。我们的结果有力地表明，在玛瑙斯市附近存在一个缝合区（多个物种具有杂种区的区域）。但是，河流对种内表型多样性空间格局的影响取决于物种的模拟表型。我们的结果不是绝对的障碍，而是支持河流可以充当部分障碍的想法，这些障碍可以捕获移动的混合区，从而形成缝合区。因此，宽阔的亚马逊河有助于产生和维持颜色图案的多样性，