The ancestor of A, B and C originally had only one version of gene G, G0. In the example shown in Figure 1, the gene G has two versions (alleles), G0 and G1. When studying a single gene, it can have multiple versions ( alleles) causing different characters to appear (polymorphisms). Suppose two subsequent speciation events occur where an ancestor species gives rise firstly to species A, and secondly to species B and C. The persistence of polymorphisms across different speciation events can cause incomplete lineage sorting. The concept of incomplete lineage sorting has some important implications for phylogenetic techniques. Apparent incomplete lineage sorting: see the text for an explanation. Incomplete lineage sorting: see the text for an explanation. Both are common results in phylogenetic analysis, although it depends on the gene, organism, and sampling technique.Ĭoncept Figure 1. This is in contrast to complete lineage sorting, where the tree produced by the gene is the same as the population or species level tree. Whatever the mechanism, the result is that a generated species level tree may differ depending on the selected genes used for assessment. In other words, the tree produced by a single gene differs from the population or species level tree, producing a discordant tree. It is caused by lineage sorting of genetic polymorphisms that were retained across successive nodes in the species tree. Incomplete lineage sorting, also termed hemiplasy, deep coalescence, retention of ancestral polymorphism, or trans-species polymorphism, describes a phenomenon in population genetics when ancestral gene copies fail to coalesce (looking backwards in time) into a common ancestral copy until deeper than previous speciation events.
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