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Fig. 5 | BMC Evolutionary Biology

Fig. 5

From: Transcriptomic insights into the genetic basis of mammalian limb diversity

Fig. 5

Evolutionary Age. The evolutionary ages of the genes of each species in this study are shown in (a). Genes were assigned to phylostratums (ps) based on their degree of conservation. At one end of the spectrum, genes that are specific to a single species (i.e., they do not have homologues in other species) were assigned to ps 1, and at the other end genes that are common to all study species were assigned to ps 4. Ps 2 and ps 3 correspond to the branching points of the phylogenetic tree between ps 1 and ps 4. Genes in ps 1, ps 2, ps 3, and ps 4 were assigned evolutionary ages of 1, 2, 3, and 4, respectively. A hierarchical clustering analysis based on the pair-wise number of homologue genes (b) exactly mirrors the phylogeny of the study species. Results shown in (a) were used to calculate the transcriptome age indices (TAIs) of each species across development (c) for the fore- (left) and hind (right) limbs. Smaller TAIs correspond to younger ages, and larger TAIs older ages. Bat is shown in blue, pig in purple, mouse in red, and opossum in green

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