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.

种群中的生态表型变异（ecophenotypic variation）由环境变量的差异所驱动。在海洋环境中，生态表型变异可能由水动力条件、底质类型、水深、温度、盐度、氧浓度以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，但学界目前对时间平均（time-averaging）与空间平均（spatial-averaging）作用于其保存过程的影响仍所知甚少。本研究针对美国华盛顿州圣胡安岛阿尔吉勒溪与阿尔吉勒泻湖这两处研究程度较高的点位，选取了潮间带底内生活（infaunal）、滤食性的双壳类物种Leukoma staminea的两个相邻种群，样本涵盖活体采集个体与死亡组合（death assemblages）。低能环境泻湖中的个体可自由在细粒底质中穴居，而高能环境溪中的蛤类则无法在多岩的水道内穴居。研究结果显示，相邻生境的种群存在体型与形态差异：泻湖种群的个体体型更大、形态更呈盘状，且虹吸管相对更长；溪中种群的个体体型更小、形态更趋近球形，外套窦（pallial sinus）相对更浅。尽管受时间平均与壳体搬运作用的影响，死亡组合中仍保留了该生态表型特征，但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不同的水动力条件与底质类型所诱导，最终引发生理权衡，将资源从摄食与呼吸过程转移至维持躯体稳定性与壳体强度上，而这类特征均有潜力在化石记录中得以保存。