PDF(Pubmed)
Abstract：
Ecological theory predicts niche partitioning between high-level predators living in sympatry as a mechanism to minimise the selective pressure of competition. Accordingly, male Australian fur seals Arctocephalus pusillus doriferus and New Zealand fur seals A. forsteri that live in sympatry should exhibit partitioning in their broad niches (in habitat and trophic dimensions) in order to coexist. However, at the northern end of their distributions in Australia, both are recolonising their historic range after a long absence due to over-exploitation, and their small population sizes suggest competition should be weak and may allow overlap in niche space. We found some niche overlap, yet clear partitioning in diet trophic level (δ15N values from vibrissae), spatial niche space (horizontal and vertical telemetry data) and circadian activity patterns (timing of dives) between males of each species, suggesting competition may remain an active driver of niche partitioning amongst individuals even in small, peripheral populations. Consistent with individual specialisation theory, broad niches of populations were associated with high levels of individual specialisation for both species, despite putative low competition. Specialists in isotopic space were not necessarily specialists in spatial niche space, further emphasising their diverse individual strategies for niche partitioning. Males of each species displayed distinct foraging modes, with Australian fur seals primarily benthic and New Zealand fur seals primarily epipelagic, though unexpectedly high individual specialisation for New Zealand fur seals might suggest marginal populations provide exceptions to the pattern generally observed amongst other fur seals.
摘要：
生态学理论预测，生活在共生中的高级捕食者之间的生态位划分是一种最小化竞争选择性压力的机制。因此，生活在同居中的澳大利亚雄性海狗Arctocaluspusillusdoriferus和新西兰海狗A.forsteri应在其广阔的生态位（在栖息地和营养尺寸上）中表现出分区，以便共存。然而,在澳大利亚分布的北端，由于过度开发而长期缺席，两者都在重新殖民其历史范围，而且他们的人口规模很小，这表明竞争应该很弱，并且可能允许利基空间重叠。我们发现了一些利基重叠，然而，在饮食营养水平上有明确的划分(来自vibrisae的δ15N值)，每个物种雄性之间的空间生态位空间（水平和垂直遥测数据）和昼夜节律活动模式（潜水时间），这表明竞争可能仍然是个体之间利基划分的积极驱动力，即使是在小，外围人群。与个人专业化理论一致，广泛的种群生态位与这两个物种的高水平个体专业化有关，尽管假定的低竞争。同位素空间的专家不一定是空间生态位空间的专家，进一步强调他们不同的个体生态位划分策略。每个物种的雄性表现出不同的觅食模式，澳大利亚海狗主要是底栖的，新西兰海狗主要是上上层的，尽管新西兰海豹的个体专业化程度出乎意料地高，但可能表明边缘种群为其他海豹中普遍观察到的模式提供了例外。
