Dunn Robert P, Kimball Matthew E, Pfirrmann Bruce W, Bruck Andrew S, Lane Willa M
North Inlet-Winyah Bay National Estuarine Research Reserve, Georgetown, SC, United States of America.
Baruch Marine Field Laboratory, University of South Carolina, Georgetown, SC, United States of America.
PLoS One. 2024 Dec 27;19(12):e0316219. doi: 10.1371/journal.pone.0316219. eCollection 2024.
Habitat partitioning can promote coexistence of closely related competitors. Two congeneric shrimps (brown shrimp, Penaeus aztecus, and white shrimp, Penaeus setiferus) which utilize estuaries in the southeastern U.S. temporally partition much of their nursery habitat occupancy but also experience a period of overlap at the respective tails of their nursery residency. Throughout nursery residency, when conspecific or congeneric abundance can be high, density-dependent (D-D) processes may alter demographic rates, but the relative importance of the potential biotic interactions occurring in these habitats (e.g., intra- and inter-specific competition, cannibalism, among others) remains underexplored. Here, we documented the periods of nursery habitat use for these two penaeid shrimp species within a representative salt marsh estuary. Next, a set of manipulative laboratory experiments was conducted to test if conspecific or congeneric density, as well as the relative proportions of each species, affect growth and mortality. In three experiments designed to simulate each of the phases of penaeid shrimp nursery habitat use (brown only, brown and white overlap, white only), shrimp were maintained at ecologically relevant densities (12.5-37.5 m-2) and tagged to follow growth trajectories. We found varying degrees of density-dependence between species and across response variables (length, mass, mortality), with the effect of additional species identity varying between white and brown shrimp for all three response metrics. Body size was an important predictor of mortality for both brown and white shrimp, with smaller animals exhibiting higher mortality probabilities. These results suggest that changing environmental conditions could lead to D-D impacts on some demographic rates but not others for these ecologically and economically important species during their estuarine residency.
栖息地划分可以促进近缘竞争者的共存。两种同属的虾（棕虾，即褐对虾，和白虾，即脂眼对虾）利用美国东南部的河口，在时间上划分了它们大部分育苗栖息地的占用情况，但在各自育苗期的末尾也有一段重叠期。在整个育苗期，当同种或同属的虾数量可能很多时，密度依赖（D-D）过程可能会改变种群统计学参数，但这些栖息地中潜在生物相互作用（例如种内和种间竞争、同类相食等）的相对重要性仍未得到充分研究。在这里，我们记录了这两种对虾在一个具有代表性的盐沼河口内使用育苗栖息地的时期。接下来，我们进行了一系列实验室操纵实验，以测试同种或同属密度以及每种物种的相对比例是否会影响生长和死亡率。在旨在模拟对虾育苗栖息地使用各阶段（仅棕虾、棕虾和白虾重叠、仅白虾）的三个实验中，将虾维持在生态相关密度（12.5 - 37.5 m-2）并标记以跟踪生长轨迹。我们发现物种之间以及不同响应变量（长度、质量、死亡率）之间存在不同程度的密度依赖性，对于所有三个响应指标，额外物种身份的影响在白虾和棕虾之间有所不同。体型是棕虾和白虾死亡率的一个重要预测指标，较小的个体表现出更高的死亡概率。这些结果表明，不断变化的环境条件可能会导致密度依赖对这些生态和经济上重要的物种在河口栖息期间的某些种群统计学参数产生影响，但对其他参数则不然。
