Repeated Mitochondrial Capture With Limited Genomic Introgression in a Lizard Group

Area of Science:

• Evolutionary biology
• Genetics
• Zoology

Background:

• Mitochondrial introgression is frequently identified via mitonuclear discordance, where mitochondrial DNA (mtDNA) and nuclear DNA (nuDNA) suggest different evolutionary histories.
• Genomic studies reveal widespread nuclear introgression in animals, impacting genetic and phenotypic diversity, though its correlation with mtDNA introgression varies.
• The Gehyra nana-occidentalis gecko clade exhibits mitonuclear discordance, indicating potential repeated mtDNA introgression.

Purpose of the Study:

• To investigate historical and recent introgression in the Gehyra nana-occidentalis gecko clade.
• To test the hypothesis that mitonuclear discordance in this clade is linked to substantial nuclear introgression.
• To determine the extent of nuclear DNA introgression accompanying mitochondrial DNA introgression.

Main Methods:

• Utilized exon capture and genome-wide single nucleotide polymorphism (SNP) data to assess historical nuclear introgression.
• Analyzed modern contact zones to detect contemporary gene flow.
• Examined morphological phenotypes in relation to introgressed mtDNA.

Main Results:

• Despite evidence of repeated mtDNA introgression, minimal to no historical nuclear DNA introgression was detected.
• No evidence of gene flow was found in modern contact zones, with only one early-generation hybrid identified.
• No transgressive, intermediate, or more variable morphological phenotypes were observed in taxa with introgressed mtDNA.

Conclusions:

• Hybridization in the Gehyra nana-occidentalis system has led to repeated mitochondrial introgression with limited nuclear introgression.
• This pattern suggests that significant nuclear introgression does not always accompany mitochondrial introgression, even with mitonuclear discordance.
• The findings highlight a potentially widespread trend of limited nuclear introgression in animal radiations exhibiting mitonuclear discordance.