Data from: Quantitative genetic analysis of subspecific differences in body shape in the snail-feeding carabid beetle Damaster blaptoides

A dimorphic pattern of macrocephalic (wide, short) and stenocephalic (narrow, long) body shapes is observed in snail-feeding carabid beetles globally. The former exhibits high performance in crushing snail shells with powerful jaws, whereas the latter specializes in eating snails' soft body directly by inserting the head into the shell. In the snail-feeding species Damaster blaptoides, the subspecies D. b. capito has a wide short forebody, and D. b. fortunei has a narrow, long forebody. They exhibit distinct morphologies despite their geographic and phylogenetic proximity. To examine the genetic basis of the morphological differences between these two subspecies, we conducted quantitative genetic analyses by crossing these subspecies and producing F_1 and backcross hybrids. The hybrids had body shapes intermediate between the parental subspecies. The variation between wide, short and narrow, long forebodies was based on negative geneti c correlations between width and length of the head and thorax. Between one and eight genetic factors were involved in the morphological differences between subspecies. We suggest that the morphological integration of forebody parts in a small number of loci has facilitated the marked morphological diversification between subspecies of D. blaptoides.

全球范围内的食螺步甲科甲虫均呈现两种形态模式：巨头型（宽短体型）与狭头型（窄长体型）。前者凭借强劲颚部碾碎蜗牛外壳，具备优异的破壳性能；后者则特化出取食策略，通过将头部伸入螺壳内直接取食蜗牛的柔软躯体。在食螺性物种斑大步甲（Damaster blaptoides）中，其亚种D. b. capito拥有宽短的前躯体，而D. b. fortunei的前躯体则窄长。尽管二者地理分布与系统发育关系均较为近缘，但两者的形态特征却差异显著。为探究这两个亚种间形态差异的遗传基础，我们通过杂交这两个亚种并获得F₁代及回交杂种，开展了数量遗传分析。杂交后代的躯体形态介于两个亲本亚种之间。宽短型与窄长型前躯体的形态变异，源于头部与胸部的宽度和长度之间存在负遗传相关。亚种间的形态差异涉及1至8个遗传因子。我们认为，少数位点上的前躯体各部分形态整合，推动了斑大步甲（Damaster blaptoides）亚种间显著的形态分化。