Long‐term stasis and short‐term divergence in the phenotypes of microsnails on oceanic islands
Long‐term stasis and short‐term divergence in the phenotypes of microsnails on oceanic islands
复制标题
海岛微型蜗牛表型的长期停滞和短期分化
作者：
Shinichiro Wada;Y. Kameda;S. Chiba
表型分化通常与基因型分化无关。一个极端的例子是尽管遗传相似，但表型分化迅速。另一个极端是形态停滞，尽管有大量的遗传差异。这些相反的模式被认为反映了血统的相反属性。在这项研究中，表型辐射伴随着快速发散和长期保守性记录在小笠原群岛的微型陆生蜗牛Cavernacmella（Asmineidae）的推断分子遗传学中。的人口Cavernacmella的Sekimon石灰岩露头的Hahajima岛壳形态表现出显着的分歧。在这一区域内，一个谱系分化成具有细长炮塔壳、圆锥壳和扁平圆盘状壳的类型，而没有实质性的遗传分化。此外，与这些类型共存的物种发展了更大的壳尺寸。此外，一个血统适应生活在这个地区的洞穴里。与此相反，在其他地区的人口没有表现出形态差异，尽管人口之间的遗传分化。因此，在小笠原的Cavernacmella的表型进化的特点是长期停滞和周期性的变化爆发的模式。这种模式表明，即使是具有表型保守性的谱系也可以转变为允许快速表型分化的另一种状态。
Phenotypic divergence is often unrelated to genotypic divergence. An extreme example is rapid phenotypic differentiation despite genetic similarity. Another extreme is morphological stasis despite substantial genetic divergence. These opposite patterns have been viewed as reflecting opposite properties of the lineages. In this study, phenotypic radiation accompanied by both rapid divergence and long‐term conservatism is documented in the inferred molecular phylogeny of the micro land snails Cavernacmella (Assimineidae) on the Ogasawara Islands. The populations of Cavernacmella on the Sekimon limestone outcrop of Hahajima Island showed marked divergence in shell morphology. Within this area, one lineage diversified into types with elongated turret shells, conical shells and flat disc‐like shells without substantial genetic differentiation. Additionally, a co‐occurring species with these types developed a much larger shell size. Moreover, a lineage adapted to live inside caves in this area. In contrast, populations in the other areas exhibited no morphological differences despite high genetic divergence among populations. Accordingly, the phenotypic evolution of Cavernacmella in Ogasawara is characterized by a pattern of long‐term stasis and periodic bursts of change. This pattern suggests that even lineages with phenotypic conservatism could shift to an alternative state allowing rapid phenotypic divergence.