Research Institute for the Environment and Livelihoods, Charles Darwin University, Ellengowan Dr, Darwin, NT, 0810, Australia.
Australian Rivers Institute, Griffith University, Nathan, QLD, Australia.
Oecologia. 2019 Nov;191(3):579-585. doi: 10.1007/s00442-019-04522-w. Epub 2019 Oct 3.
In gape-limited predators, gape size restricts the maximum prey size a predator is capable to ingest. However, studies investigating the energetic consequences of this relationship remain scarce. In this study, we tested the hypothesis that gape-size variability influences individual body condition (a common proxy for fitness) in one of the largest freshwater teleost predators, the barramundi. We found that individual barramundi with larger gapes relative to body size had higher body condition values compared to conspecifics with smaller gapes. Body condition was highest soon after the wet season, a period of high feeding activity on productive inundated floodplains, and body condition decreased as the dry season progressed when fish were restricted to dry season remnant habitats. The increased condition obtained during the wet season apparently offsets weight loss through the dry season, as individuals with large gapes were still in better condition than fish with small gapes in the late-dry season. Elucidation of the links between intraspecific variability in traits and performance is a critical challenge in functional ecology. This study emphasizes that even small intraspecific variability in morphological trait values can potentially affect individual fitness within a species' distribution.
在口裂受限的捕食者中，口裂大小限制了捕食者能够摄入的最大猎物大小。然而，研究这种关系的能量后果的研究仍然很少。在这项研究中，我们测试了这样一个假设，即口裂大小的变异性会影响最大的淡水硬骨鱼类捕食者之一——巨骨舌鱼的个体身体状况（一种常见的适应度代理）。我们发现，相对于体型而言，口裂较大的个体具有更高的身体状况值，而口裂较小的个体则具有较低的身体状况值。身体状况在湿季过后最高，此时在生产力较高的泛滥洪泛平原上的觅食活动非常活跃，而随着旱季的进行，当鱼类被限制在旱季残留栖息地时，身体状况会下降。在湿季获得的更好的身体状况显然抵消了通过旱季的体重减轻，因为大口裂的个体在旱季末期的身体状况仍然比小口裂的个体好。阐明特征和表现的种内变异性之间的联系是功能生态学的一个关键挑战。这项研究强调，即使在形态特征值方面存在微小的种内变异性，也可能会影响物种分布内的个体适应度。
