Substrate type induces plastic responses in the craniofacial morphology of a winnowing cichlid

Abstract

Understanding how local populations respond to specific changes in the environment can help us better predict how populations respond to such change. With this topic in mind, we followed up on a previous study by exploring the capabilities of a Geophagini cichlid, known for its unique feeding strategy, to mount a plastic response. We exposed Satanoperca daemon, a winnowing cichlid, to three different substrate types, two of which encouraged winnowing behaviors and a third that prevented winnowing entirely. Using geometric morphometrics, we quantified aspects of craniofacial anatomy to test for morphological differences between the treatments and to test for the integration of different traits across the head. We found significant differences across our experimental populations in both shape and disparity. We report evidence in support of wide-spread integration across craniofacial traits. A notable exception to this pattern was the epibranchial lobe, a structure unique to the Geophagini, which exhibited more modular variation. Since anthropogenic alterations such as the damming of rivers can impact substrate type, these data offer insights into how Geophagini cichlids may respond to environmental change. In addition, this work further illuminates the functional morphology of winnowing foraging behaviors.