Related Experiment Video
Updated: Jun 16, 2026
06:18
Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR
Published on: July 11, 2025
Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids
Meryl C Mims1, C Darrin Hulsey, Benjamin M Fitzpatrick
1School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195, USA.
Molecular Ecology
|February 13, 2010
Summary
Phenotypically distinct Lake Malawi cichlids, Labeotropheus fuelleborni and Metriaclima zebra, show deep nuclear genetic divergence despite shared mitochondrial DNA. Nuclear single nucleotide polymorphism (SNP) data indicate minimal gene flow, suggesting distinct evolutionary trajectories.
Area of Science:
- Evolutionary Biology
- Genomics
- Speciation
Background:
- Lake Malawi cichlids display remarkable phenotypic diversity with similar genomes.
- Shared genetic polymorphism among cichlid forms complicates understanding rapid evolution.
- Potential causes include hybridization or retention of ancestral polymorphism.
Purpose of the Study:
- To investigate the genetic differentiation between phenotypically distinct cichlid species.
- To differentiate between hybridization and ancestral polymorphism as sources of shared genetic variation.
- To assess gene flow in geographically structured populations of Labeotropheus fuelleborni and Metriaclima zebra.
Main Methods:
- Genomic tools were employed to analyze genetic differentiation.
- Mitochondrial DNA (mtDNA) haplotypes and nuclear single nucleotide polymorphism (SNP) data were characterized.
- Bayesian analysis and simulations were used to assess genetic clusters and gene flow.
Main Results:
- Species shared mitochondrial DNA (mtDNA) haplotypes, with greater mtDNA differentiation among localities than between species.
- Nuclear SNP data revealed two distinct genetic clusters corresponding to the species.
- Populations co-occurring at rock reef sites showed slightly greater similarity than expected, suggesting recent gene flow.
Conclusions:
- Nuclear and mitochondrial data provide contrasting views on cichlid species divergence.
- Multi-locus nuclear SNP data offer higher resolution for distinguishing recently diverged species.
- Evidence suggests limited recent gene flow between co-occurring cichlid populations, supporting speciation despite shared ancestral polymorphism.
Related Concept Videos
02:29Hybrid Zones
Hybrid zones are narrow regions where two closely related species interact, mate, and produce hybrids. Relative to either parent species, hybrids may possess distinct phenotypic or genetic differences that impact their survival and reproductive success. The genetic variances introduced by hybridization influence species diversity and speciation processes within the hybrid zone.Gene flow and natural selection are evolutionary mechanisms that shape the outcome of a hybrid zone. Gene flow...
02:39Gene Flow
Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.
01:31Formation of Species
Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the parent species, and barriers to reproduction will typically exist. There are two primary mechanisms, speciation with and without geographic isolation—allopatric and sympatric speciation, respectively.Allopatric SpeciationIn allopatric speciation, gene flow between two populations of the same species is prevented by a geographic barrier, like...
02:16Genetics of Speciation
Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.The genetics of speciation involves the different traits or isolating mechanisms preventing gene exchange, leading to reproductive isolation. Reproductive isolation can be due to reproductive barriers that have effects either before or after the formation of a zygote. Pre-zygotic mechanisms prevent fertilization from occurring, and post-zygotic mechanisms...
02:54Evolutionary Relationships through Genome Comparisons
Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is that if two species share a common feature, it is likely encoded by the DNA sequence conserved between both species. The advent of genome sequencing technologies in the late 20th century enabled scientists to understand the concept of conservation of domains between species and helped them to deduce evolutionary relationships across diverse...
01:07Speciation Rates
Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.