Urquía Diego O, Anslan Sten, Asadobay Pacarina, Moreira-Mendieta Andrés, Vences Miguel, Chaves Jaime A, Páez-Rosas Diego
Maestría en Ecología Tropical y Conservación, Universidad San Francisco de Quito USFQ Quito Ecuador.
Galapagos Science Center, Universidad San Francisco de Quito USFQ Islas Galápagos Ecuador.
Ecol Evol. 2024 Mar 1;14(3):e10921. doi: 10.1002/ece3.10921. eCollection 2024 Mar.
Tropical ecosystems are challenging for pinnipeds due to fluctuating food availability. According to previous research, the Galapagos sea lion (GSL, ) adopts trophic flexibility to face such conditions. However, this hypothesis comes from studies using traditional methods (hard-parts analysis of scat and isotopic analysis from tissue). We studied the diet of five rookeries in the southeastern Galapagos bioregion (which harbors the highest GSL density), via DNA-metabarcoding of scat samples. The DNA-metabarcoding approach may identify consumed prey with a higher taxonomic resolution than isotopic analysis, while not depending on hard-parts remaining through digestion. Our study included five different rookeries to look for evidence of trophic flexibility at the bioregional level. We detected 98 prey OTUs (124 scats), mostly assigned to bony-fish taxa; we identified novel prey items, including a shark, rays, and several deep-sea fish. Our data supported the trophic flexibility of GSL throughout the studied bioregion since different individuals from the same rookery consumed prey coming from different habitats and trophic levels. Significant diet differentiations were found among rookeries, particularly between Punta Pitt and Santa Fe. Punta Pitt rookery, with a more pronounced bathymetry and lower productivity, was distinguished by a high trophic level and consumption of a high proportion of deep-sea prey; meanwhile, Santa Fe, located in more productive, shallow waters over the shelf, consumed a high proportion of epipelagic planktivorous fish. Geographic location and heterogeneous bathymetry of El Malecon, Española, and Floreana rookeries would allow the animals therein to access both, epipelagic prey over the shelf, and deep-sea prey out of the shelf; this would lead to a higher prey richness and diet variability there. These findings provide evidence of GSL adopting a trophic flexibility to tune their diets to different ecological contexts. This strategy would be crucial for this endangered species to overcome the challenges faced in a habitat with fluctuating foraging conditions.
由于食物供应波动，热带生态系统对鳍足类动物来说具有挑战性。根据先前的研究，加拉帕戈斯海狮（GSL）采用营养灵活性来应对这种情况。然而，这一假设来自于使用传统方法（粪便的硬组织分析和组织的同位素分析）的研究。我们通过对粪便样本进行DNA宏条形码分析，研究了加拉帕戈斯生物区域东南部（GSL密度最高）的五个繁殖地的饮食情况。DNA宏条形码方法可能比同位素分析能以更高的分类分辨率识别所消耗的猎物，同时不依赖于消化后残留的硬组织。我们的研究包括五个不同的繁殖地，以寻找生物区域层面营养灵活性的证据。我们检测到98个猎物操作分类单元（124份粪便），大多归为硬骨鱼类分类群；我们识别出了新的猎物种类，包括鲨鱼、鳐鱼和几种深海鱼类。我们的数据支持了GSL在整个研究生物区域内的营养灵活性，因为来自同一繁殖地的不同个体消耗来自不同栖息地和营养级的猎物。在繁殖地之间发现了显著的饮食差异，特别是在蓬塔皮特和圣达菲之间。蓬塔皮特繁殖地，其地形起伏更明显且生产力较低，其特点是营养级较高且消耗高比例的深海猎物；与此同时，位于陆架上生产力更高的浅水区的圣达菲，则消耗高比例的上层浮游食性鱼类。埃尔马勒孔、埃斯帕尼亚拉和弗洛雷阿纳繁殖地的地理位置和地形的异质性，将使其中的动物既能获取陆架上的上层猎物，又能获取陆架外的深海猎物；这将导致那里的猎物丰富度和饮食变异性更高。这些发现提供了GSL采用营养灵活性来根据不同生态环境调整其饮食的证据。这种策略对于这种濒危物种克服在觅食条件波动的栖息地所面临的挑战至关重要。
