Galvez Jacquelyn R, St John Michelle E, McLean Keara, Touokong Cyrille Dening, Gonwouo Legrand Nono, Martin Christopher H
Department of Integrative Biology, University of California, Berkeley, CA, USA.
Museum of Vertebrate Zoology, University of California, Berkeley, CA, USA.
Ecol Freshw Fish. 2022 Oct;31(4):675-692. doi: 10.1111/eff.12661. Epub 2022 Jun 3.
Trophic niche partitioning is observed in many adaptive radiations and is hypothesized to be a central process underlying species divergence. However, patterns of dietary niche partitioning are inconsistent across radiations and there are few studies of niche partitioning in putative examples of sympatric speciation. Here, we conducted the first quantitative study of dietary niche partitioning using stomach contents and stable isotope analyses in one of the most celebrated examples of sympatric speciation: the cichlid radiation from crater lake Barombi Mbo, Cameroon. We found little evidence for trophic niche partitioning among cichlids, including the nine species coexisting in the narrow littoral zone. Stable isotope analyses supported these conclusions of substantial dietary overlap. Our data, however, did reveal that five of eleven species consume rare dietary items, including freshwater sponge, terrestrial ants, and nocturnal foraging on shrimp. Stomach contents of the spongivore () were 20% freshwater sponge, notable considering that only 0.04% of all fishes consume sponges. Overall, we conclude that cichlid species in lake Barombi Mbo overlap considerably in broad dietary niches-in part due to the large proportion of detritus in the stomach contents of all species-but there is evidence for divergence among species in their diet specializations on unique resources. We speculate that these species may utilize these additional specialized resources during periods of low resource abundance in support of Liem's paradox.
在许多适应性辐射中都观察到了营养生态位划分，并且据推测这是物种分化背后的核心过程。然而，不同辐射中的食性生态位划分模式并不一致，而且在同域物种形成的假定例子中，对生态位划分的研究很少。在这里，我们在同域物种形成最著名的例子之一：喀麦隆巴龙比·姆博火山口湖的丽鱼辐射中，利用胃内容物和稳定同位素分析，首次对食性生态位划分进行了定量研究。我们几乎没有发现丽鱼之间存在营养生态位划分的证据，包括在狭窄的沿岸带共存的九个物种。稳定同位素分析支持了这些关于大量食性重叠的结论。然而，我们的数据确实表明，11个物种中有5个食用稀有食物，包括淡水海绵、陆生蚂蚁以及夜间捕食虾类。食海绵动物（）的胃内容物中有20%是淡水海绵，考虑到所有鱼类中只有0.04%食用海绵，这一比例值得注意。总体而言，我们得出结论，巴龙比·姆博湖中的丽鱼物种在广泛的食性生态位上有相当大的重叠——部分原因是所有物种的胃内容物中碎屑占很大比例——但有证据表明物种在对独特资源的食性特化方面存在差异。我们推测，在资源丰度较低的时期，这些物种可能会利用这些额外的特化资源，以支持利姆悖论。
