Fig. 4
From: Splendor and misery of adaptation, or the importance of neutral null for understanding evolution
The routes of exaptation. The cartoon schematically shows two types of evolutionary events: exaptation of a function-less transcript that becomes, for example, a lncRNA and exaptation of a MGE that becomes, after transposition, a regulatory region of a pre-existing gene. The thickness of the arrows denotes the increase in expression level that is assumed to occur after exaptation