Ecological variation in South American geophagine cichlids arose during an early burst of adaptive morphological and functional evolution

Abstract

Diversity and disparity are unequally distributed both phylogenetically and geographically. This uneven distribution may be owing to differences in diversification rates between clades resulting from processes such as adaptive radiation. We examined the rate and distribution of evolution in feeding biomechanics in the extremely diverse and continentally distributed South American geophagine cichlids. Evolutionary patterns in multivariate functional morphospace were examined using a phylomorphospace approach, disparity-through-time analyses and by comparing Brownian motion (BM) and adaptive peak evolutionary models using maximum likelihood. The most species-rich and functionally disparate clade (CAS) expanded more efficiently in morphospace and evolved more rapidly compared with both BM expectations and its sister clade (GGD). Members of the CAS clade also exhibited an early burst in functional evolution that corresponds to the development of modern ecological roles and may have been related to the colonization of a novel adaptive peak characterized by fast oral jaw mechanics. Furthermore, reduced ecological opportunity following this early burst may have restricted functional evolution in the GGD clade, which is less species-rich and more ecologically specialized. Patterns of evolution in ecologically important functional traits are consistent with a pattern of adaptive radiation within the most diverse clade of Geophagini.

Continental cichlid radiations: functional diversity reveals the role of changing ecological opportunity in the Neotropics

“…Contrastingly, analysis of functionally explicit traits indicated that all South American lineages (i.e. additionally tribes Cichlini, Astronotini, Retroculini, Chaetobranchini, Cichlasomatini and some Heroini) contributed to a pattern of decreasing rates of functional evolution and finer partitioning of morphospace through time in the major clades of South American cichlids, alongside Geophagini [38]. Altogether, current evidence supports an early adaptive radiation of cichlids in South America, but support for an equivalent radiation in Central America remains ambiguous.…”

“…This morphospace was derived from phylogenetic principal components analysis ( pPCA) of 10 morphological and biomechanical variables from 75 species representing all major lineages of Cichlinae [29], which were selected to represent as many tribes, genera and ecological variation as possible given specimen availability. These variables included two oral jaw muscle masses (1, adductor mandibulae and 2, sternohyoideus mass); 3, the mass of the lower pharyngeal jaw (fifth ceratobranchial); 4, maximum jaw protrusion distance; 5 -6, lower and upper jaw opening and closing mechanical advantages; 7, bite occlusion patterns (quadrate offset); 8-9 oral jaw and hyoid four bar lever transmission coefficients and 10, an index of suction feeding capability [29,38], and see the electronic supplementary material, table S1 for additional details. Data were collected from one to six specimens (housed at or on loan to the Royal Ontario Museum) per species (median ¼ 3; electronic supplementary material, table S6).…”

Body Size Diversity and Frequency Distributions of Neotropical Cichlid Fishes (Cichliformes: Cichlidae: Cichlinae)

“…Recently, strong partitioning of ecologically meaningful body shape attributes [43] and trophic functional morphospace [46] was found in Cichlinae and it is likely that this ecological differentiation is correlated with patterns in BSFDs across the group. The distribution of body size in the GGD clade of Geophagini was found to be located between the two modes of the CAS clade, producing a third mode of body size that suggests partitioning of total body size morphospace.…”

Teleocichla preta, a new species of cichlid from the Rio Xingu Basin in Brazil (Teleostei: Cichlidae)

“…More generally, recent studies including T . preta have related the macroevolutionary diversification of the Crenicichla–Teleocichla clade to the emergence of adaptive peaks driven by innovative adaptive changes in swimming and feeding functional morphology (Arbour & López‐Fernández, , ; Astudillo‐Clavijo et al , ). The body and caudal peduncle of other species of Teleocichla from Rio Xingu tend to be more elongated, suggesting that there may be further variation in attributes of swimming performance within the genus.…”

“…preta is similar to that of many species in the clade, a common divergence of dentition and functional decoupling of the oral and pharyngeal sets of jaws widespread in cichlids (Hulsey et al , ). Arbour & López‐Fernández (, ) included T . preta in biomechanical analyses performed in the context of the Crenicichla–Teleocichla clade and of other Neotropical lineages of Cichlidae, respectively.…”