PATERNAL LEAKAGE OF MITOCHONDRIAL DNA IN A FUCUS (PHAEOPHYCEAE) HYBRID ZONE(1)

Area of Science:

• Marine Biology
• Genetics
• Evolutionary Biology

Background:

• Mitochondrial DNA (mtDNA) is typically maternally inherited in eukaryotes.
• mtDNA heteroplasmy, the coexistence of multiple mtDNA types, can arise from various mechanisms, including paternal leakage.
• Paternal leakage of mtDNA has been documented in some eukaryotic lineages but is rare.

Purpose of the Study:

• To investigate the occurrence and persistence of mitochondrial DNA paternal leakage in brown algae.
• To provide the first evidence of paternal mtDNA leakage in the brown algae species *Fucus serratus* and *Fucus evanescens*.

Main Methods:

• Analysis of introgressed individuals resulting from natural hybridization between *Fucus serratus* and *Fucus evanescens*.
• Identification and comparison of distinct mitochondrial haplotypes in hybrid individuals.

Main Results:

• Eight introgressed individuals were identified, each possessing distinct haplotypes from both parental *Fucus* species.
• The presence of heteroplasmy in individuals from multiple generations of backcrosses indicates that paternal leakage occurred in earlier generations.
• The findings suggest that paternal leakage has persisted through several meiotic bottlenecks.

Conclusions:

• This study provides the first evidence of mitochondrial DNA paternal leakage in brown algae.
• Persistent paternal mtDNA transmission can occur in *Fucus* species, contributing to heteroplasmy.
• Paternal leakage and subsequent heteroplasmy can be maintained across multiple generations in hybridizing algae.