Table 1 Glossary of complexity terms

Alternative Splicing (AS): Molecular mechanism that modifies pre-mRNA constructs prior to translation, which produces a diverse set of mRNA from a single gene.

Transcripts per Gene (TpG): The number of transcripts that can be constructed from a single gene that have been annotated.

Exons per Transcript (EpT): The exons that are annotated within single transcript produced from a single gene.

Exons per Gene (EpG): The union of unique exons annotated within a single gene.

Effective Exon Number (EEN): A distribution of exons across a complexity metric (or gene), given the relative length of the exon to the total length of the region (L_e).

Ortholog: One of a set of homologous genes that have diverged from an ancestor as a consequence of speciation.

Novel Gene: Genes that have emerged inside a defined time frame are novel genes. Novel genes are will be classified by their age. The time frame is not fixed and needs to be defined for each study.

Evolutionary Rate: As defined through Rabosky et al. (2014) interpretation. A macroevolutionary rate dynamic that applies to some part of a phylogenetic tree. All lineages that share a common regime have exactly the same macroevolutionary rate at a given point in time.