Data from: Ecophenotypy, temporal and spatial fidelity, functional morphology, and physiological trade-offs among intertidal bivalves

Ecophenotypic variation in populations is driven by differences in environmental variables. In marine environments, ecophenotypic variation may be caused by differences in hydrodynamic conditions, substrate type, water depth, temperature, salinity, oxygen concentration, and habitat heterogeneity, among others. Instances of ecophenotypic variation in modern and fossil settings are common, but little is known about the influences of time-averaging and spatial-averaging on their preservation. Here we examine the shell morphology of two adjacent populations, both live-collected and death assemblages, of the infaunal, suspension-feeding, intertidal bivalve Leukoma staminea from the well-studied Argyle Creek and Argyle Lagoon locations on San Juan Island, Washington, USA. Individuals in the low energy lagoon are free to burrow in the fine-grained substrate while clams in the high energy creek are precluded from burrowing in the rocky channel. Our results demonstrate variation in size and shape between the adjacent habitats. Lagoon clams are larger, more disc-shaped, and have relatively larger siphons than their creek counterparts, which are smaller, more spherical in shape, and have a relatively shallower pallial sinus. This ecophenotypy is preserved among death assemblages, although with generally greater variation due to time averaging and shell transport. Our interpretation is that ecophenotypic variation, in this case, is induced by differing hydrodynamic regimes and substrate types, cumulatively resulting in physiological tradeoffs diverting resources from feeding and respiration to stability and shell strength, all of which has the potential to be preserved in the fossil record.

种群的生态表型变异（ecophenotypic variation）由环境变量的差异驱动。在海洋环境中，生态表型变异可由水动力条件、底质类型、水深、温度、盐度、氧浓度及生境异质性等因素的差异引发。现代与化石记录中的生态表型变异实例较为常见，但目前学界对时间平均与空间平均作用对其保存过程的影响仍知之甚少。本研究以美国华盛顿州圣胡安岛两处研究充分的点位——阿尔格尔溪与阿尔格尔泻湖为研究区域，针对底栖滤食性潮间带双壳类条纹白樱蛤（Leukoma staminea）的两个相邻种群展开壳体形态分析，两类种群均涵盖现生采集个体与死亡组合（death assemblage）样本。低能环境泻湖中的个体可在细粒底质中自由潜穴，而高能环境溪道中的蛤类则无法在岩质水道中完成潜穴。研究结果显示，相邻生境的种群间存在壳体大小与形态的显著差异。泻湖种群的个体更大、更呈盘状，且虹管相对更长；溪道种群个体更小、形态更趋近球形，外套窦（pallial sinus）相对更浅。该生态表型特征在死亡组合中得以保留，但受时间平均与壳体搬运作用影响，其整体变异程度更高。本研究认为，本案例中的生态表型变异由差异化的水动力环境与底质类型诱导产生，最终引发生理权衡：将资源从摄食与呼吸过程转向维持个体稳定与增强壳体强度，而这类变异均有潜力保存在化石记录中。