Noss Clay F, Rosenblum Erica Bree
Department of Environmental Science, Policy, and Management, University of California -Berkeley, Berkeley, CA, 94720, USA.
Mojave Desert Land Trust, Joshua Tree, CA, 92252, USA.
Oecologia. 2025 Jan 30;207(1):28. doi: 10.1007/s00442-025-05667-7.
Trophic niche has fundamental ecological importance, but many studies consider few niche metrics and most neglect critical structuring processes. Multiple processes shape trophic niches, including inter and intra-specific competition, predation and resource diversity. These processes interact and effects vary with time and taxa. The White Sands dunefield provides an ecological gradient ideal for understanding variation in niches. We measured population niche width, trophic position and individual specialization in four lizard species across habitats over 2 years. The habitats include White Sands interior, the surrounding desert scrub, and their ecotone. We used arthropod, lizard and plant stable isotopes to quantify niches. We sampled lizard competitors, predators and prey as proxies for ecological processes. We found substantial variation in niches across populations but convergence between species. Individual specialization and population niche width were surprisingly decoupled. Specialization was highest in habitats with low species diversity (White Sands) and population niche width highest at intermediate diversity (ecotone). White Sands lizards may exhibit 'ultra partitioning'; high specialization alongside low individual niche widths. Population niche width is likely constrained within White Sands by low prey diversity. High ecotonal population niche widths may be due to fewer natural enemies than desert scrub but higher resource diversity than White Sands. Trophic position and specialization were positively correlated, suggesting stronger intraspecific competition at higher trophic levels. Prey diversity, inter and intra-specific competition, and predation all interacted to shape niches. Our results highlight the need for measuring multiple components of community structure and niches, as results are likely misleading in isolation.
营养生态位具有重要的基础生态学意义，但许多研究仅考虑了少数生态位指标，且大多忽视了关键的构建过程。多种过程塑造了营养生态位，包括种间和种内竞争、捕食以及资源多样性。这些过程相互作用，其影响会随时间和分类群而变化。白沙沙丘场提供了一个理想的生态梯度，有助于理解生态位的变化。我们在两年时间里，测量了四个蜥蜴物种在不同栖息地的种群生态位宽度、营养级位置和个体专业化程度。这些栖息地包括白沙内部、周边的沙漠灌丛及其交错带。我们使用节肢动物、蜥蜴和植物的稳定同位素来量化生态位。我们对蜥蜴的竞争者、捕食者和猎物进行采样，作为生态过程的代表。我们发现不同种群的生态位存在显著差异，但物种之间存在趋同现象。个体专业化程度和种群生态位宽度出人意料地解耦。在物种多样性较低的栖息地（白沙），专业化程度最高，而在中等多样性的栖息地（交错带），种群生态位宽度最大。白沙蜥蜴可能表现出“超细分”现象；即高度专业化且个体生态位宽度较小。白沙地区的种群生态位宽度可能受到猎物多样性低的限制。交错带较高的种群生态位宽度可能是由于天敌比沙漠灌丛少，但资源多样性比白沙高。营养级位置和专业化程度呈正相关，表明在较高营养级水平上种内竞争更强。猎物多样性、种间和种内竞争以及捕食都相互作用，共同塑造了生态位。我们的研究结果强调了测量群落结构和生态位多个组成部分的必要性，因为孤立的结果可能会产生误导。
