Lee Won Young, Park Seongseop, Kim Kil Won, Kim Jeong-Hoon, Gal Jong-Ku, Chung Hosung
Division of Polar Life Sciences, Korea Polar Research Institute, Incheon 21990, Korea.
Division of Life Sciences, Incheon National University, Incheon 22012, Korea.
Animals (Basel). 2021 Feb 11;11(2):482. doi: 10.3390/ani11020482.
Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narębski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δC and δN isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δC and δN values than those at NP, and in both locations, Gentoo penguins had higher δC and lower δN values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species.
理论预测，在资源有限的条件下，同域分布的捕食者会争夺食物。由于觅食习性的重叠，即使在同一物种的相邻种群之间也会发生竞争。因此，假设同一物种的相邻种群面临激烈竞争。为了检验由于缺乏生态位划分导致种内竞争比种间竞争更激烈这一假设，我们估计了两个相邻繁殖地的两种群居海鸟的觅食区域和潜水深度。我们使用全球定位系统（GPS）和时间深度记录器，追踪了南极乔治王岛阿德雷岛（AI）和纳伦布斯基角（NP）同域繁殖的南极帽带企鹅和巴布亚企鹅的觅食空间利用情况。GPS追踪显示，两个物种之间的觅食区域重叠比每个物种内部的重叠更大。在潜水参数方面，在同一繁殖地，巴布亚企鹅的潜水深度和时间比南极帽带企鹅更深更长。在繁殖地层面，来自NP的巴布亚企鹅比来自AI的潜水更深更长，而南极帽带企鹅在潜水方面没有表现出这种种内差异。血液中δC和δN同位素的稳定同位素分析显示了种间和种内差异。AI的两种企鹅的δC和δN值均高于NP的，并且在两个地点，巴布亚企鹅的δC值更高，δN值低于南极帽带企鹅。同位素生态位显示种间重叠低于种内重叠。这表明，尽管种内空间重叠较低，但来自不同繁殖地的同种个体的饮食仍然更相似，导致同位素生态位重叠更高。总体而言，我们的结果支持种内竞争高于种间竞争这一假设，导致同一物种的相邻种群出现空间隔离。
