Emberton Kenneth C
Department of Malacology, Academy of Natural Sciences of Philadelphia, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania, 19103-1195.
Evolution. 1995 Jun;49(3):469-475. doi: 10.1111/j.1558-5646.1995.tb02279.x.
In the southern Appalachian region of North America, the phylogenetically convergent shells of the polygyrid snails Triodopsinae Neohelix major (Binney) and Polygyrinae Mesodon normalis (Pilsbry) are even more convergent in size and shape in sympatry (7 sites) than in allopatry (23 and 10 sites). Environmental correlations account for 34% and 30% of size and shape variations in N. major (larger, taller, and more loosely coiled at northern, high-altitude, sheltered sites), but for only 14% and 9% in M. normalis (larger, flatter, and more loosely coiled at south-facing, exposed sites). The statistical significance of the sympatric convergence dropped out when these correlations were removed. This phenomenon helps account for the many cases in eastern North America of nearly identical land-snail shells in sympatry and questions the importance of competitive character displacement in the evolution of land-snail shell morphology. This apparently nonmimetic case of sympatric convergence provides an unusually precise and well-delimited, naturally replicated experiment in evolutionary morphology, which is analyzed for controlling factors in a follow-up paper.
在北美洲阿巴拉契亚山脉南部地区，多纹螺科蜗牛Triodopsinae Neohelix major（宾尼）和多纹螺亚科Mesodon normalis（皮尔布里）在系统发育上趋同的壳，在同域分布（7个地点）时，其大小和形状比异域分布（分别为23个和10个地点）时更加趋同。环境相关性分别解释了Neohelix major壳大小和形状变异的34%和30%（在北方、高海拔、隐蔽地点的壳更大、更高且螺层更松散），但在Mesodon normalis中仅为14%和9%（在朝南、暴露地点的壳更大、更扁平且螺层更松散）。去除这些相关性后，同域趋同的统计学显著性消失。这种现象有助于解释北美东部许多同域分布的陆地蜗牛壳几乎相同的情况，并对竞争性状替代在陆地蜗牛壳形态进化中的重要性提出质疑。这种明显非拟态的同域趋同案例为进化形态学提供了一个异常精确且界定清晰、自然重复的实验，后续论文将对其控制因素进行分析。
