Incomplete lineage sorting

Definition

Incomplete lineage sorting is a phenomenon in evolutionary biology where the gene trees of different genes do not perfectly match the species tree due to ancestral polymorphism. This occurs when a population retains genetic variation from its ancestors, leading to situations where the genetic relationships among individuals may not accurately reflect their species relationships. Understanding this concept is crucial for analyzing phylogenetic data and interpreting the evolutionary history of organisms.

5 Must Know Facts For Your Next Test

1. Incomplete lineage sorting is especially common in closely related species where speciation events occur rapidly, making it difficult to resolve true evolutionary relationships.
2. This phenomenon can result in conflicting signals in phylogenetic analysis, where some genes support one tree topology while others support a different one.
3. It can lead to issues in estimating divergence times and inferring the evolutionary history of taxa, especially when relying on single genes or short sequences.
4. To mitigate the effects of incomplete lineage sorting, researchers often use multiple genes or genomic data to reconstruct phylogenetic relationships more accurately.
5. Incomplete lineage sorting highlights the importance of considering both gene trees and species trees when studying evolutionary patterns and processes.

Review Questions

• How does incomplete lineage sorting affect the interpretation of phylogenetic trees?
  • Incomplete lineage sorting can complicate the interpretation of phylogenetic trees because it can result in discrepancies between gene trees and species trees. When genetic variation from ancestral populations persists into descendant lineages, certain genes may indicate different evolutionary relationships than those depicted by the overall species tree. This can lead researchers to erroneous conclusions about how species are related if they rely solely on a limited set of genetic data.
• Discuss the implications of incomplete lineage sorting for estimating divergence times among closely related species.
  • Incomplete lineage sorting poses significant challenges for estimating divergence times among closely related species, as it can create misleading signals regarding when lineages split. If certain genes suggest an earlier divergence due to ancestral variation persisting within populations, it may suggest a timeline that contradicts what is shown by other genes or the overall species tree. Consequently, understanding the extent of incomplete lineage sorting is essential for producing reliable estimates of divergence times and accurately reconstructing evolutionary histories.
• Evaluate how using genomic data instead of single-gene approaches can help address challenges posed by incomplete lineage sorting.
  • Using genomic data rather than single-gene approaches provides a more comprehensive picture of an organism's evolutionary history and helps mitigate the challenges associated with incomplete lineage sorting. Genomic data encompasses a wider array of genetic information, allowing researchers to construct a consensus view that averages out discrepancies caused by individual gene histories. This broader dataset enables more accurate reconstructions of phylogenetic relationships and helps clarify evolutionary patterns, reducing reliance on potentially misleading signals from specific genes affected by incomplete lineage sorting.

Related terms

Phylogenetic tree: A diagram that represents the evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics.

Gene tree: A representation of the evolutionary relationships between different alleles or gene variants, which may differ from the species tree due to incomplete lineage sorting.

Ancestral polymorphism:

The presence of multiple alleles at a locus in a population's ancestor, which can persist over time and lead to genetic variation among descendant species.