Fig. 3
From: Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments
Evolution of opsins and photic-related characters in mammals. Schematic view of the global nocturnal bottleneck hypothesis, linking both the results from the synteny and the ancestral reconstruction analyses: a nocturnal period (represented in grey) is assumed to affect both the mammalian ancestor and the emerging lineages. Global and lineage-specific losses of opsins are indicated with a red cross; opsin losses that were not supported by a consistent synteny are marked with an asterisk (*). Ancestral reconstructions of the activity pattern are represented in pie charts, each slice representing the probability of each state (nocturnal, diurnal and cathemeral). Ancestral reconstructions of the violet and ultra-violet sensitive (VS and UVS) vision are represented by a violet or a black circle, respectively, near the OPN1sw1 opsin (sw1 was used to perform the inferences). Uncertainties about the opsin presence/absence are marked with a double asterisk (**): UVS vision in the mammalian ancestor node is only hypothetical (it could not be determined because the sw1 is not present in monotremes); the therapsid opsin profile is not known since genetic data is not available for therapsids. The potential vision of ancestral mammals was inferred considering both the conopsin content of each node and their spectral sensitivities [blue for OPN1sw2 (sw2), red for OPN1lw (lw) and saturated pink for UV sw1]. Ancestral inferences of the orbit convergence (OC, degrees) and visual acuity (VA, cycles per degree) are indicated in the corresponding nodes. A reconstruction of a skull with an orbital convergence angle of 46° (which correspond to the inferred angle in the node of mammals) is included. The Shennongjia virgin forest (https://commons.wikimedia.org/wiki/File:Shennongjia_virgin_forest.jpg) and the Pristerognathus (https://commons.wikimedia.org/wiki/File:Pristeroognathus_DB.jpg) are licensed under the Attribution-ShareAlike 3.0 Unported license (the license terms can be found on the following link: https://creativecommons.org/licenses/by-sa/3.0/)
