In evolution, a trait shows sporadic distribution if multiple events other than speciation are required to explain its distribution on a phylogenetic tree. Events that create sporadic distributions include lateral gene transfer and gene loss.
Sporadic distribution makes a phylogenetic profile (the listing of strains or species having a particular trait) highly informative. If two different protein families, or a phenotype and a protein family, share the same sporadic distribution, a functional connection between them may be inferred. Any such observation may become the first step in a bioinformatics journey.
Conspicuous examples of Genome Properties and SEED Subsystems that show sporadic distribution in prokaryotic genomes include CRISPR systems, prophage regions, and siderophore biosynthesis systems. In contrast, housekeeping genes tend to show the opposite behavior, and instead are viewed as the most reliable choices of marker for use in computed phylogenetic trees.