Abstract The skull often reveals adaptation to ecological and environmental influences. Food availability affects the somatic growth of otariids, and population abundance can influence male intrasexual competition. We hypothesized there would be regional differences between Galapagos sea lion (GSL, Zalophus wollebaeki) rookeries as a result of variance in ecosystem metrics and population abundance. We used skull measures related to individual size and aggressiveness. We analyzed 19 linear measures for size and 15 for aggressiveness taken on 49 adult male skulls of GSL collected in four bioregions of the archipelago. Nine skull measures had a significant effect on individual clustering into bioregions (P < 0.001). The most discriminating measures were snout length, supraorbital process width, nasal length, and canine width. We found a significant relationship between skull grouping patterns and chlorophyll-α levels (proxy marine productivity and body growth) and GSL population abundance (proxy of agonistic behavior) of each bioregion, as well as with the interaction between both variables (P < 0.001). Our results suggest significant regional differences in GSL skull morphometry, which could be associated with resource availability and level of male intrasexual competition in the archipelago. This information is important for understanding the life history of this species.

中文翻译：

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成年雄性加拉帕戈斯海狮头骨形态学的区域差异

摘要 头骨经常显示对生态和环境影响的适应。食物供应会影响 otariids 的体细胞生长，而人口丰富会影响男性的性内竞争。我们假设由于生态系统指标和种群丰度的差异，加拉帕戈斯海狮（GSL，Zalophus wollebaeki）栖息地之间会存在区域差异。我们使用与个体大小和攻击性相关的颅骨测量。我们分析了在群岛的四个生物区域收集的 49 个成年男性 GSL 头骨的 19 个大小线性测量值和 15 个攻击性测量值。九个头骨测量值对个体聚集成生物区域有显着影响（P < 0.001）。最具区别性的测量是吻长、眶上突宽度、鼻长和犬齿宽度。我们发现每个生物区域的头骨分组模式与叶绿素-α水平（代表海洋生产力和身体生长）和 GSL 种群丰度（激动行为的代表）之间以及两个变量之间的相互作用之间存在显着关系（P < 0.001 ）。我们的研究结果表明，GSL 颅骨形态测量存在显着的区域差异，这可能与群岛的资源可用性和男性性内竞争水平有关。这些信息对于了解该物种的生活史很重要。我们的研究结果表明，GSL 颅骨形态测量存在显着的区域差异，这可能与群岛的资源可用性和男性性内竞争水平有关。这些信息对于了解该物种的生活史很重要。我们的研究结果表明 GSL 颅骨形态测量存在显着区域差异，这可能与群岛的资源可用性和男性性内竞争水平有关。这些信息对于了解该物种的生活史很重要。