Macroevolutionary analyses indicate that repeated adaptive shifts towards predatory diets affect functional diversity in Neotropical cichlids

Abstract

During adaptive radiation, diversification within clades is limited by adaptation to the available ecological niches, and this may drive patterns of both trait and species diversity. However, adaptation to disparate niches may result in varied impacts on the timing, pattern and rate of morphological evolution. In this study, we examined the relationship between feeding ecology and functional diversification across a diverse clade of freshwater fishes, the Neotropical cichlids. Species dietary niches were ordinated via multivariate analysis of stomach content data. We investigated changes in the rate and pattern of morphological diversification associated with feeding, including dietary niche and degree of dietary specialization. A major division in dietary niche space was observed between predators that consume fish and macroinvertebrates vs. other groups with diets dominated by small invertebrates, detritus or vegetation. These trophic niches were strongly associated with groupings defined by functional morphospace. Clades within the piscivore/macroinvertivore group rarely transitioned to other dietary niches. Comparatively, high dietary specialization enhanced functional diversification, driving the evolution of more extreme morphologies. Divergent patterns of trophic diversification among Neotropical cichlids appear to derive from different performance demands in regional abiotic and biotic environments associated with biogeographical history.

Functional groups in piscivorous fishes

“…Engulfing via jaw protrusion thus appears to be a relatively recent feeding mode, when compared to grabbing (Figure 6 ). Although the fish investigated herein are coral reef fishes, the functional groups identified in our study are likely to apply to fishes from any aquatic environment (Arbour et al., 2020 ; Camp et al., 2015 ; Keppeler et al., 2020 ; Weller et al., 2020 ).…”

“…This was also found in one of the most extreme cases of jaw elongation and feeding through lateral head movement in sailfish and marlins (Domenici et al., 2014 ; Hansen et al., 2020 ) (Video S1 of their study showing sailfish capturing prey at center of mass). Interestingly, jaw length has been found throughout multiple major taxa to be a primary axis of morphological variation (Arbour et al., 2020 ; Martinez et al., 2018 , 2021 ; Price et al., 2019 ). Such patterns of jaw elongation and dentition have also been found in other vertebrate taxa, such as crocodylomorphs (Stubbs et al., 2013 ).…”

Decoupled jaws promote trophic diversity in cichlid fishes

“…2019; Arbour et al. 2020). Thus, despite the evolutionary independence provided by decoupled prey capture and processing systems in cichlids, many species co‐modify the jaw systems for similar functions (i.e., specialize in mobility or force generation).…”

Insectivory leads to functional convergence in a group of Neotropical rodents

“…Trophic ecology is frequently linked to morphological diversity in vertebrates (Arbour et al., 2020; Dumont et al., 2012; Liem et al., 2001; Martin & Wainwright, 2011). Dietary pressures are often reflected in masticatory muscles, and their sizes and lines of action relate to cranial shape in many groups (Fabre et al., 2018; Herrel et al., 1998; Satoh, 1999).…”