Fodrie F Joel, Yeager Lauren A, Grabowski Jonathan H, Layman Craig A, Sherwood Graham D, Kenworthy Matthew D
Department of Marine Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, NC, 28557, USA,
Oecologia. 2015 May;178(1):75-87. doi: 10.1007/s00442-014-3212-3. Epub 2015 Feb 12.
Many mobile marine species are presumed to utilize a broad spectrum of habitats, but this seemingly generalist life history may arise from conspecifics specializing on distinct habitat alternatives to exploit foraging, resting/refuge, or reproductive opportunities. We acoustically tagged 34 red drum, and mapped sand, seagrass, marsh, or oyster (across discrete landscape contexts) use by each uniquely coded individual. Using 144,000 acoustic detections, we recorded differences in habitat use among red drum: proportional use of seagrass habitat ranged from 0 to 100%, and use of oyster-bottom types also varied among fish. WIC/TNW and IS metrics (previously applied vis-à-vis diet specialization) consistently indicated that a typical red drum overlapped >70% with population-level niche exploitation. Monte Carlo permutations showed these values were lower than expected had fish drawn from a common habitat-use distribution, but longitudinal comparisons did not provide evidence of temporally consistent individuality, suggesting that differences among individuals were plastic and not reflective of true specialization. Given the range of acoustic detections we captured (from tens to 1,000s per individual), which are substantially larger sample sizes than in many diet studies, we extended our findings by serially reducing or expanding our data in simulations to evaluate sample-size effects. We found that the results of null hypothesis testing for specialization were highly dependent on sample size, with thresholds in the relationship between sample size and associated P-values. These results highlight opportunities and potential caveats in exploring individuality in habitat use. More broadly, exploring individual specialization in fine-scale habitat use suggests that, for mobile marine species, movement behaviors over shorter (≤weeks), but not longer (≥months), timescales may serve as an underlying mechanism for other forms of resource specialization.
许多海洋洄游物种被认为利用广泛的栖息地，但这种看似具有通用性的生活史可能源于同种个体专门利用不同的栖息地选择来获取觅食、休息/避难或繁殖机会。我们对34条红鼓鱼进行了声学标记，并绘制了每条具有独特编码的个体对沙子、海草、沼泽或牡蛎（跨越不同景观环境）的使用情况。利用144000次声学探测，我们记录了红鼓鱼在栖息地利用上的差异：海草栖息地的比例使用范围从0到100%，不同鱼类对牡蛎底类型的使用也有所不同。WIC/TNW和IS指标（以前用于饮食专业化方面）一致表明，典型的红鼓鱼与种群水平的生态位利用重叠率超过70%。蒙特卡洛排列显示，这些值低于从共同栖息地使用分布中抽取鱼类时的预期值，但纵向比较没有提供时间上一致的个体性证据，这表明个体之间的差异是可变的，并非真正专业化的反映。鉴于我们捕获的声学探测范围（每个个体从几十次到数千次），这比许多饮食研究中的样本量要大得多，我们通过在模拟中连续减少或扩大数据来评估样本量效应，从而扩展了我们的研究结果。我们发现，关于专业化的零假设检验结果高度依赖于样本量，样本量与相关P值之间存在阈值关系。这些结果突出了在探索栖息地利用中的个体性方面的机会和潜在注意事项。更广泛地说，探索在精细尺度栖息地利用中的个体专业化表明，对于海洋洄游物种，较短（≤几周）但不是较长（≥几个月）时间尺度上的移动行为可能是其他形式资源专业化的潜在机制。
