Fig. 2
Habitat evolution in apteronotid electric fishes. (a) Time-calibrated phylogeny tracing evolution of adult modal habitat utilization (See SI text). Ecotrait data30; see Table S3. Habitats: DC = Deep Channels, RM = River Margins, FP = Floodplains, RR = Riffles and Rapids, TFS = Terra Firme streams. Purple line = origin modern Amazon c. 10 Ma. Shaded green = Pebas Megawetland c. 22—10 Ma. Star = Adaptive shift to habitat indicated by color. Note 13/163 nodes (8%) with adaptive shifts among these five habitats, indicating 92% functional redundancy. Orange circles (subfamilies): 1 = Sternarchorhamphinae, 2 = Apteronotinae. Yellow circles (tribes): 1 = Adontosternarchini, 2 = Apteronotini, 3 = Platyurosternarchini, 4 = Navajini, 5 = Sternarchorhynchini. (b) Schematic cross section of an Amazonian River floodplain illustrating habitats at high (Hi) and low (Lo) water with characteristic gymnotiform species; Apteronotus albifrons in TF; “Porotergus” bonapartii in FP; Sternarchogiton nattereri in DC. Inset: transect from α a to α’, floodplain margins as dashed lines. Note many apteronotid fishes use floodplain forests and river margins at high water but are constrained to river channels at low water. Created in BioRender. Allen, J. (2025) https://BioRender.com/wwad7x3.
