Data from: Morphological integration and pleiotropy in the adaptive body shape of the snail-feeding carabid beetle Damaster blaptoides

The snail-feeding carabid beetle Damaster blaptoides exhibits diverse head and thorax morphologies, and these morphotypes are linked with two alternative feeding behaviors. Stout-shaped beetles feed on snails by crushing the shells, whereas slender-shaped beetles consume snails by inserting their heads into the shells. A trade-off exists between these feeding strategies. Because intermediate-shaped beetles are less proficient in these two behaviors, stout-slender morphological divergence occurs between related species feeding on land snails. To examine the genetic basis of these morphotypes, we conducted morphological analyses and quantitative trait locus (QTL) mapping using backcross offspring between the stout and slender subspecies. The morphological analyses showed that the width and length of the beetle body parts were correlated with each other; in particular, the head width and thorax length were strongly negatively correlated. QTL mapping showed that QTLs for head width and thorax length are located in close proximity to one another on the longest linkage group, and that they have positive and negative additive genetic effects. Our results suggest that the adaptive phenotypic sets of a wide head and short thorax and a narrow head and long thorax are based on the closeness of these QTLs. Morphological integration between the head and thorax may play an important role in the adaptive divergence of these beetles.以蜗牛为食的步甲科甲虫Damaster blaptoides具有丰富多样的头部与胸部形态，这些形态型与两种截然不同的取食行为相关联。体型粗壮的个体通过碾碎螺壳取食蜗牛，而体型纤细的个体则将头部伸入螺壳内取食蜗牛，这两种取食策略之间存在适应性权衡。由于形态介于两者之间的个体在两种取食行为中的表现均欠佳，因此以陆生蜗牛为食的近缘物种间，出现了粗壮-纤细的形态分化。为探究此类形态型的遗传基础，我们针对粗壮亚种与纤细亚种的回交后代开展了形态学分析与数量性状位点（quantitative trait locus, QTL）定位实验。形态学分析结果显示，甲虫身体各部位的宽度与长度彼此相关，其中头部宽度与胸部长度呈现极强的负相关。QTL定位结果表明，控制头部宽度与胸部长度的QTL在最长连锁群上彼此紧密相邻，且二者分别具有正向与负向的加性遗传效应。我们的研究结果提示，宽头短胸与窄头长胸这两类适应性表型组合，正是源于上述QTL的紧密连锁。头部与胸部间的形态整合，可能在这类甲虫的适应性分化中发挥了关键作用。