Department of Marine Science, University of Texas at Austin, Port Aransas, TX, USA.
Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC, USA.
J Anim Ecol. 2019 Nov;88(11):1743-1754. doi: 10.1111/1365-2656.13067. Epub 2019 Aug 19.
The structure of local ecological communities is thought to be determined by a series of hierarchical abiotic and biotic filters which select for or against species based on their traits. Many human impacts, like fragmentation, serve to alter environmental conditions across a range of spatial scales and may impact trait-environment interactions. We examined the effects of environmental variation associated with habitat fragmentation of seagrass habitat measured from microhabitat to landscape scales in controlling the taxonomic and trait-based community structure of benthic fauna. We measured patterns in species abundance and biomass of seagrass epifauna and infauna sampled using sediment cores from 86 sites (across 21 meadows) in Back Sound, North Carolina, USA. We related local faunal community structure to environmental variation measured at three spatial scales (microhabitat, patch and landscape). Additionally, we tested the value of species traits in predicting species-specific responses to habitat fragmentation across scales. While univariate measures of faunal communities (i.e. total density, biomass and species richness) were positively related to microhabitat-scale seagrass biomass only, overall community structure was predicted by environmental variation at the microhabitat, patch (i.e. patch size) and landscape (i.e. number of patches, landscape seagrass area) scales. Furthermore, fourth-corner analysis revealed that species traits explained as much variation in organismal densities as species identity. For example, species with planktonic-dispersing larvae and deposit-feeding trophic modes were more abundant in contiguous, high seagrass cover landscapes while suspension feeders favoured more fragmented landscapes. We present quantitative evidence supporting hierarchal models of community assembly which predict that interactions between species traits and environmental variation across scales ultimately drive local community composition. Variable responses of individual traits to multiple environmental variables suggest that community assembly processes that act on species via traits related to dispersal, mobility and trophic mode will be altered under habitat fragmentation. Additionally, with increasing global temperatures, the tropical seagrass Halodule wrightii is predicted to replace the temperate Zostera marina as the dominate seagrass in our study region, therefore potentially favouring species with planktonic-dispersing larva and weakening the strength of environmental control on community assembly.
局部生态群落的结构被认为是由一系列分层的非生物和生物过滤器决定的，这些过滤器根据物种的特征选择或反对物种。许多人为影响，如破碎化，改变了一系列空间尺度上的环境条件，并可能影响特征-环境相互作用。我们研究了与海草栖息地破碎化相关的环境变化对底栖动物分类和基于特征的群落结构的影响，这些变化是从小生境到景观尺度测量的。我们测量了美国北卡罗来纳州 Back Sound 的 86 个地点（21 个草甸）的沉积物核心中采集的海草附生动物和底栖动物的物种丰度和生物量模式。我们将当地动物群落结构与在三个空间尺度（小生境、斑块和景观）测量的环境变化联系起来。此外，我们测试了物种特征在预测物种对跨尺度生境破碎化的特定反应方面的价值。虽然动物群落的单变量度量（即总密度、生物量和物种丰富度）仅与小生境尺度的海草生物量呈正相关，但总体群落结构是由小生境、斑块（即斑块大小）和景观（即斑块数量、景观海草面积）尺度的环境变化预测的。此外，第四象限分析表明，物种特征解释了生物密度的变化，与物种身份一样多。例如，具有浮游幼虫和沉积食性营养模式的物种在连续的、高海草覆盖的景观中更为丰富，而悬浮食者则更喜欢更破碎的景观。我们提供了支持群落组装层次模型的定量证据，该模型预测，物种特征与跨尺度环境变化之间的相互作用最终将驱动当地群落组成。个别特征对多个环境变量的可变反应表明，通过与扩散、移动性和营养模式相关的特征作用于物种的群落组装过程将在生境破碎化下发生改变。此外，随着全球温度的升高，热带海草 Halodule wrightii 预计将取代温带 Zostera marina 成为我们研究区域的主要海草，因此可能有利于具有浮游幼虫和弱环境控制对群落组装的物种。
