Speaker
Description
“Lineage-specific” genes appear to have homologs only in a restricted group of related species, strikingly absent from the rest of the tree of life. They are often interpreted as novel genes, receiving much interest related to their apparent potential to underlie evolutionary innovation. An alternative, “null” hypothesis is that these genes are not meaningfully novel: they do have existing homologs that have merely diverged too far to be detected by homology search. Here, we first develop a simple method to test whether a given lineage-specific gene can be explained by this possibility of “divergence beyond detection.” We then apply this tool to all genes that appear to be specific to several ascomycete lineages. We find that divergence beyond detection can explain a majority of fungal lineage-specific genes: no novelty is required. On the flip side, we also find that some fungal lineage-specific genes strongly resist this explanation, flagging them as interesting candidates for true genetic novelty. We discuss the characteristics of these genes and insights they may provide into how, when, and why novel genes may evolve.
