Experimental evidence that thermal selection shapes mitochondrial genome evolution.

Area of Science:

• Evolutionary Biology
• Genetics
• Mitochondrial Genomics

Background:

• Mitochondrial DNA (mtDNA) is crucial for cellular energy production and has been a key marker in population genetics.
• Traditionally viewed as maternally inherited and evolutionarily neutral, recent evidence suggests mtDNA polymorphisms are non-neutral and subject to thermal selection.
• The
• mitochondrial climatic adaptation
• hypothesis posits that mtDNA variants are influenced by climate, but prior evidence was correlational.

Purpose of the Study:

• To experimentally test the "mitochondrial climatic adaptation" hypothesis using laboratory evolution.
• To investigate whether thermal selection can alter the frequencies of specific mtDNA haplogroups.
• To determine if mtDNA variants are sensitive to selection pressures related to temperature.

Main Methods:

• Laboratory-based experimental evolution was employed using the fruit fly, *Drosophila melanogaster*.
• Populations were maintained under controlled thermal regimes to observe changes across generations.
• Frequencies of two distinct mtDNA haplogroups, known to show clinal variation with latitude, were monitored.

Main Results:

• Experimental populations exhibited shifts in mtDNA haplogroup frequencies directly correlated with the imposed thermal regimes.
• The results provide direct experimental evidence that temperature influences the frequency dynamics of mtDNA variants.
• Observed changes in haplogroup frequencies occurred across multiple generations under controlled laboratory conditions.

Conclusions:

• Intra-specific mtDNA variants are demonstrably sensitive to selection, challenging the neutral evolution model.
• Spatial distributions of mtDNA variants in natural populations may reflect adaptation to local climatic conditions.
• The findings support the role of climatic adaptation in shaping the geographic patterns of mitochondrial genetic diversity.