Diet-Morphology Correlations in the Radiation of South American Geophagine Cichlids (Perciformes: Cichlidae: Cichlinae)

Genera within the South American cichlid tribe Geophagini display specialized feeding and reproductive strategies, with some taxa specialized for both substrate-sifting and mouth brooding. Several lineages within the clade also possess an epibranchial lobe (EBL), a unique pharyngeal structure that has been proposed to have a function in feeding and/or mouth brooding. A recently published genus-level phylogeny of Neotropical cichlids was used as the evolutionary framework for investigating the evolution of morphological features presumably correlated with diet and mouth brooding in the tribe Geophagini. We tested for possible associations between the geophagine epibranchial lobe and benthic feeding and mouth brooding. We also addressed whether the EBL may be associated with unique patterns of diversification in certain geophagine clades. Tests of binary character correlations revealed the EBL was significantly associated with mouth brooding. We also tested for a relationship between diet and morphology. We analyzed stomach contents and morphometric variation among 21 species, with data for two additional species obtained from the literature. Principal Components Analysis revealed axes of morphological variation significantly correlated with piscivory and benthivory, and both morphology and diet were significantly associated with phylogeny. These results suggest that the EBL could be an adaptation for either feeding or mouth brooding. The EBL, however, was not associated with species richness or accelerated rates of phyletic diversification.南美慈鲷族（Geophagini）内的各属类群展现出特化的取食与繁殖策略，其中部分类群同时特化于底质滤食与口育行为。该演化支内的多个类群还拥有上鳃叶（epibranchial lobe, EBL）——一种独特的咽部结构，此前被认为在取食和/或口育过程中发挥功能。本研究以近期发表的新热带区慈鲷属级系统发育树作为演化框架，探究地栖慈鲷族中推测与食性及口育行为相关的形态特征演化。我们检验了地栖慈鲷族的上鳃叶与底栖取食、口育行为之间的潜在关联，同时探讨了EBL是否与特定地栖慈鲷族演化支的独特多样化模式存在关联。二元性状关联检验结果显示，EBL与口育行为存在显著关联。我们还检验了食性与形态之间的关联：分析了21个物种的胃容物与形态计量学变异，并从公开文献中获取了另外2个物种的相关数据。主成分分析（Principal Components Analysis）结果显示，形态变异轴与食鱼性、底栖食性存在显著相关，且形态与食性均与系统发育关系显著关联。上述结果表明，EBL可能是针对取食或口育行为的适应性演化结构。但EBL与物种丰富度或类群演化的加速速率并无关联。