Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, 35487, USA.
National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20560, USA.
Ecology. 2020 Sep;101(9):e03100. doi: 10.1002/ecy.3100. Epub 2020 Aug 19.
Functional traits are characteristics of an organism that represents how it interacts with its environment and can influence the structure and function of ecosystems. Ecological stoichiometry provides a framework to understand ecosystem structure and function by modeling the coupled flow of elements (e.g. carbon [C], nitrogen [N], phosphorus [P]) between consumers and their environment. Animals tend to be homeostatic in their nutrient requirements and preferentially sequester the element in shortest supply relative to demand, and release relatively more of the element in excess. Tissue stoichiometry is an important functional trait that allows for predictions among the elemental composition of animals, their diet, and their waste products, with important effects on the cycling and availability of nutrients in ecosystems. Here, we examined the tissue stoichiometric niches (C:N:P) and nutrient recycling stoichiometries (N:P) of several filter-feeding freshwater mussels in the subfamily Ambleminae. Despite occupying the same functional-feeding group and being restricted to a single subfamily-level radiation, we found that species occupied distinct stoichiometric niches and that these niches varied, in part, as a function of their evolutionary history. The relationship between phylogenetic divergence and functional divergence suggests that evolutionary processes may be shaping niche complementarity and resource partitioning. Tissue and excretion stoichiometry were negatively correlated as predicted by stoichiometric theory. When scaled to the community, higher species richness and phylogenetic diversity resulted in greater functional evenness and reduced functional dispersion. Filter-feeding bivalves are an ecologically important guild in freshwater ecosystems globally, and our study provides a more nuanced view of the stoichiometric niches and ecological functions performed by this phylogenetically and ecologically diverse assemblage.
功能特征是生物体的一种特征，代表了它与环境的相互作用方式，并能影响生态系统的结构和功能。生态化学计量学通过模拟消费者与其环境之间元素（如碳 [C]、氮 [N]、磷 [P]）的耦合流动，为理解生态系统结构和功能提供了一个框架。动物在营养需求方面往往具有体内平衡的特性，并且优先将相对需求而言最稀缺的元素隔离，并相对释放更多的过剩元素。组织化学计量是一个重要的功能特征，它允许在动物的元素组成、饮食和废物之间进行预测，对营养物质在生态系统中的循环和可用性有重要影响。在这里，我们研究了亚科 Ambleminae 几种滤食性淡水贻贝的组织化学计量生态位（C:N:P）和养分再循环化学计量（N:P）。尽管它们占据相同的功能摄食群，并且仅限于单一的亚科水平辐射，但我们发现，物种占据了独特的化学计量生态位，而这些生态位部分是由于它们的进化历史而变化的。系统发育分歧与功能分歧之间的关系表明，进化过程可能正在塑造生态位互补性和资源分配。组织和排泄化学计量呈负相关，这与化学计量理论的预测相符。当按群落规模进行衡量时，较高的物种丰富度和系统发育多样性导致更高的功能均匀度和降低的功能离散度。滤食性双壳类动物是全球淡水生态系统中具有重要生态意义的类群，我们的研究为这个具有系统发育和生态多样性的组合提供了更细致的化学计量生态位和生态功能观点。
