Dynamic Adaptive Evolution and Evolutionary Modularity and Integration in Catfishes of the Superfamily Doradoidea
Adaptation and modularity are two major features of morphological evolution that are increasingly investigated by modern macroevolutionary biologists. However, many such studies assume that adaptive processes or modularity are constant across species. Evolution of morphology and its modularity both relate to the ecological role of morphological traits. Here, we investigate whether morphological adaptation and modularity vary across families of the Neotropical superfamily Doradoidea, comprising the Aspredinidae (banjo catfishes), Auchenipteridae (driftwood catfishes), and Doradidae (thorny catfishes). We quantified morphological diversity using three-dimensional geometric morphometrics and estimated evolutionary rates, shifts between adaptive regimes, and evolutionary modularity and integration differences among families. We found that doradoids diversified into nine adaptive regimes across morphospace. We also found some significant differences in modularity and integration between families. Major morphological shifts have surprising correspondence to previously or currently recognized taxa within the Doradoidea. We found repeated, parallel evolution of body elongation across adaptive regimes, implying a role for selection in driving parallel evolution across a primary axis of shape diversification. However, modularity and integration do not necessarily shift in correspondence with shifts in morphological adaptive peaks.
Landmark scheme shown on the left side of a representative catfish. Paired landmarks (triangles) were digitized as two separate right and left landmarks, while medial landmarks (circles) were digitized once. Colors correspond to body regions analyzed for differential rates and modularity: purple = mouth (mouth anterior, mouth left and right, mouth posterior); red = snout (tip of snout, anterior nares, posterior nares); yellow = cranial region (anterior, medial, posterior, and lateral points of the eyes, dorsal and ventral extent of the opercle opening, posterio-medial supraoccipital); green = abdomen (dorsal-, pectoral-, and pelvic-fin origins, dorsal- and pectoral-fin tips); blue = tail (dorsal-fin insertion, cloaca, anal-fin origin and insertion, dorsal and ventral procurrent caudal-fin rays, end of vertebral column). Black dots indicate adipose-fin landmarks, which are absent in many species and not included in comparative analyses.
Principal component analysis of shape data for all specimens (n = 249) shows different regions of morphospace are occupied by the three families of Doradoidea (indicated by colored convex hulls), clearly showing separation along PC2 and differences in disparity (Table 1). Thin-plate splines of dorsoventral (DV, one side only) and lateral (LAT) views display the mean fish as points (head left). Thin-plate splines are positioned alongside the plot to indicate they display the shape variation explained on the positive and negative extremes of PC1 (below plot) and PC2 (left of plot).
PhylogeneticEM analysis identified multiple shifts toward different optimal shapes in the superfamily Doradoidea. Adaptive regimes are labeled (note that Pseudobunocephalinae and Bunocephalini share an adaptive regime). Eight shift locations are indicated by black circles along edges and colored branches and tips names. Equivalent shift configurations are provided in Supplementary Figure 5 (see Data Accessibility). Species mean values are shown as bars for PC1–5. See Data Accessibility for tree file.
Principal component analysis of species mean shapes (83 spp.). Convex hulls indicate adaptive regimes inferred by PhylogeneticEM (Fig. 3). The adaptive regimes are almost all discretely separated in morphospace of PC1 and PC2. Thin-plate splines of dorsoventral (DV, one side only) and lateral (LAT) views display the mean fish as points (head left). Thin-plate splines are positioned alongside the plot to indicate they display the shape variation explained on the positive and negative extremes of PC1 (below plot) and PC2 (left of plot). As = Aspredinidae, Au = Auchenipteridae, Do = Doradidae.
Contributor Notes
Associate Editor: R. E. Reis.