bims-humivi 2026-07-12 papers

Mol Biol Evol. 2026 Jul 09. pii: msag158. [Epub ahead of print]

Introgression of thermal tolerance alleles drives adaptation despite risk of mitonuclear conflict.

Kamron L Kayhani, Jasmine R Weaver, Molly K Burke, Felipe S Barreto.

Hybridization may offer a form of genetic rescue from warming temperatures through the introgression of heat-adapted alleles from a high-tolerance population into a low-tolerance population. However, the success of adaptive introgression can be impeded by hybrid incompatibility at other loci, especially those that participate in coadapted gene complexes that could lead to unfavorable combinations in hybrids. We tested the success of introgression of heat-adapted alleles in the face of potential fitness tradeoffs associated with hybridized mitonuclear gene complexes in the crustacean Tigriopus californicus. We created reciprocal hybrid crosses of the San Diego (SD) and Strawberry Hill (SH) populations, which show divergence in both thermal tolerance and mitochondrial genomes, then subjected hybrid populations to 10 generations of either selection for thermal tolerance or to control conditions. Lines under selection in both crosses evolved higher thermal tolerance. Moreover, both crosses showed substantial increases in nuclear SD allele frequencies, with the SH♀xSD♂ cross having as much SD introgression as the reciprocal cross despite having higher risk of mitonuclear incompatibilities with its SH mtDNA. This suggests that introgression of warm-adapted alleles was largely successful despite the risk of introducing mitonuclear incompatibilities that could result from genome-wide shifts towards the paternal allele. This outcome was likely made possible by strong Mito nuclear matching being maintained in a few genomic regions on different chromosomes, exclusive of those responding to thermal selection, pointing to components of cytochrome c oxidase, in particular COX6A1, as potentially having a disproportionate impact in mitonuclear coadaptation.

Keywords: Tigriopus ; cytonuclear coadaptation; experimental evolution; hybrids

DOI: https://doi.org/10.1093/molbev/msag158

Proc Natl Acad Sci U S A. 2026 Jul 14. 123(28): e2529208123

Mitonuclear discordance modulates mitochondrial ageing dynamics in natural Drosophila populations.

Stefano Bettinazzi, Avishikta Chakraborty, Finley Grover-Thomas, Damian K Dowling, M Florencia Camus.

Mitochondrial decline is a hallmark of ageing, yet the role of intergenomic compatibility in shaping ageing trajectories remains poorly understood, particularly in an ecologically relevant framework. Hormetic interventions have been proposed as strategies to modulate metabolism and lifespan, but it is unknown how this operates in the context of mitonuclear discordance. Here, we demonstrate that mitonuclear mismatch accelerates age-related mitochondrial decline, elevates reactive oxygen species production, and shortens lifespan. Strikingly, early-life mitochondrial stress induced by dietary modulation counteracts these effects, promoting mitochondrial homeostasis and longevity. Our findings reveal mitonuclear interactions shaping ageing trajectories in natural populations and provide unique evidence that targeted interventions can act as a buffer against the detrimental impact of genetic discordance.

Keywords: Drosophila; ageing; mitochondrial metabolism; mitohormesis; mitonuclear discordance

DOI: https://doi.org/10.1073/pnas.2529208123

Annu Rev Genet. 2026 Jul 09.

Mitochondrial DNA Inheritance and Germline Purifying Selection: Insights From Drosophila.

Zhe Chen, Hong Xu.

The mitochondrial genome resides in a highly mutagenic environment and is typically maternally inherited with little recombination, features that should render mitochondrial DNA (mtDNA) prone to the accumulation of deleterious variants. Contrary to this expectation, mtDNA integrity is remarkably well-preserved over evolution. Purifying selection in the female germline that limits transmission of deleterious mtDNA mutations has been documented in various animal models and in humans. Here, we synthesize the literature, with an emphasis on insights from Drosophila, revealing that replication competition-the preferential propagation of healthy genomes over deleterious ones-is the main mechanism driving mtDNA purifying selection in the germline. We highlight developmentally orchestrated mitochondrial processes that couple genome function to replication, enabling selection based on the bioenergetic performance of individual genomes during oogenesis. Finally, we discuss how replication competition can generate genetic conflicts, particularly through the emergence of selfish mtDNA, and how such conflicts may have shaped mtDNA evolution and features of mitochondrial genetics, including maternal inheritance and the mitochondrial bottleneck.

DOI: https://doi.org/10.1146/annurev-genet-011626-033825

Mol Phylogenet Evol. 2026 Jul 10. pii: S1055-7903(26)00159-4. [Epub ahead of print] 108689

Genome-scale molecular systematics of Madagascar's occipital-lobed chameleons reveals polyphyly and mito-nuclear discordances.

Miguel Vences, Laila-Denise Rothe, Frank Glaw, Mark D Scherz, Philip-Sebastian Gehring, Oliver Hawlitschek, Arianna Kuhn, Malte Multzsch, Alice Petzold, Michaela Preick, Fandresena Rakotoarimalala, Achille P Raselimanana, Fanomezana M Ratsoavina, Sara Ruane, David R Vieites, Michael Hofreiter, Christophe Dufresnes.

Madagascar-endemic chameleons with large, conspicuous occipital lobes currently comprise 12 species that were traditionally classified in the phenetic Calumma cucullatum group. We here use a combination of DNA sequences from Restriction-Associated DNA sequencing (RADseq), museomics shotgun sequencing from historical name-bearing types, and Sanger-sequenced mitochondrial and nuclear gene fragments, to revisit the phylogeny and species delimitation in this group. We find robust phylogenomic evidence for polyphyly of the group, with C. cucullatum sister to the C. furcifer group, and species of the C. nasutum group intercalated between C. malthe and the remainder of ingroup species. Furthermore, according to our mitochondrial tree, C. tsycorne does not belong to the group. Several species such as C. brevicorne and C. malthe are recovered as paraphyletic in the mitochondrial tree while being unambiguously monophyletic in the phylogenomic tree; this mito-nuclear discordance may reflect ancestral introgressive hybridization. In our phylogenomic estimations, most currently recognized species are inferred as deep monophyletic lineages, and the RADseq clustering analysis recovered these as well-defined units. Exceptions were C. jejy, which is placed as sister taxon to the morphologically distinct C. peltierorum with rather shallow sequence divergence, and the C. brevicorne / C. crypticum complex. Combining molecular and morphological data suggests that populations of C. malthe from northern Madagascar represent a distinct species, here described as C. krystalae sp. nov. Our data reveal that chameleons, despite their elaborate phenotypic differences used in intraspecific signalling and their interspecific genital differences, can be characterized by complex evolutionary patterns probably involving hybridization and introgression.

Keywords: Calumma brevicorne; Calumma krystalae sp.nov.; Calumma malthe; Chamaeleonidae; Madagascar; Museomics; RADseq; Species delimitation; Squamata

DOI: https://doi.org/10.1016/j.ympev.2026.108689