Correlation of shell phenotype and local environment suggests a role for natural selection in the evolution of Placostylus snails

The giant edible Placostylus snails of New Caledonia occur across a wide range of environmental conditions, from the dry southwest to the wetter central and northeastern regions. In large, slow-moving animals such as Placostylus, speciation could be assumed to be largely driven by allopatry and genetic drift as opposed to natural selection. We examined variation in shell morphology using geometric morphometrics and genetic structure within two species of Placostylus (P. fibratus, P. porphyrostomus), to determine the drivers of diversity in this group. Despite the current patchy distribution of snails on New Caledonia, both mtDNA and nuclear SNP data sets (>3000 loci) showed weak admixing between populations and species. Shell morphology was concordant with the genetic clusters we identified and had a strong relationship with local environment. The genetic data, in contrast to the morphological data, did not show concordance with climatic conditions, suggesting the snails are not limi...

新喀里多尼亚的可食用巨型扁卷螺属（Placostylus）蜗牛，广泛分布于多样的环境条件中，生境跨度从干燥的西南部，延伸至湿润的中部与东北部区域。对于这类体型庞大、移动缓慢的类群而言，其物种形成过程通常被认为主要由异域分化与遗传漂变驱动，而非自然选择。本研究选取扁卷螺属的两个物种（P. fibratus、P. porphyrostomus），采用几何形态测量学（geometric morphometrics）分析其贝壳形态变异，并探究其遗传结构，以明确该类群多样性的形成驱动机制。尽管目前扁卷螺在新喀里多尼亚的分布呈斑块状，但其线粒体DNA（mtDNA）与核单核苷酸多态性（nuclear SNP）数据集（含超过3000个位点）均显示，种群与物种间的遗传混合程度较弱。贝壳形态与本研究鉴定出的遗传聚类结果一致，且与当地环境条件存在显著关联。与形态学数据不同的是，遗传数据并未与气候条件呈现出一致性关联，这表明该类蜗牛并不受限于……