Biology subjects

Gerchen, J. F.

Publications and source records attributed to Gerchen, J. F..

4 recordsLinked to original sources

bioRxiv2026

Centromeric variation is shared across ploidy barriers in Alnus glutinosa agg.

Polyploidy is often thought to cause immediate reproductive isolation due to sterility and inviability of inter-ploidy offspring. However, recent research demonstrated genome-wide introgression in natural populations of diploids and tetraploids. Yet, it still remains unknown whether introgression varies in strength along the genome and what are the forces underlying such variation. Here we analyzed whole-genome resequencing data from natural populations of the Alder tree, Alnus glutinosa agg., which includes a widespread diploid lineage found across large parts of Europe and two autotetraploid lineages with more limited ranges on the Balkan and Iberian Peninsulas. Our sampling involved mixed-ploidy populations, where diploids, triploids and tetraploids co-occur as well as ploidy pure populations. We identified genomic regions of increased admixture, which coincide with putative locations of centromeres. We hypothesize that this pattern of shared variation at pericentromeric regions involves centromere drive, which happens when centromeres increase the likelihood of being included in the oocyte during female meiosis and which has been studied in only a few plant species. While it was previously suggested that centromere drive could cause reproductive isolation and speciation, here we propose that driving centromeres could be able to lift reproductive barriers caused by ploidy differences.

evolutionary biology↗

bioRxiv2026

Evolution of recombination suppression and sex determination on Y chromosomes of the plant genus Mercurialis

Understanding why sex chromosomes repeatedly evolve recombination suppression, gene loss, and repeat accumulation remains a central challenge in evolutionary genomics. Plant sex chromosomes may be particularly informative, because they have often evolved recently from hermaphroditic ancestors. We studied the sex-linked region of the dioecious annual Mercurialis annua using new long-read genome assemblies of an XX female and a YY male, a published female assembly, linkage maps, and population-genomic data from several Mercurialis species. We identify two discrete nested evolutionary strata on the Y chromosome of diploid M. annua. A young stratum was generated by a large inversion and shows little degeneration, whereas an older stratum nested within it exhibits substantial gene loss, transposable-element accumulation, insertion of paralogous gene copies, and elevated X-Y sequence divergence. These findings indicate that recombination suppression evolved in at least two stages, with a recent inversion expanding an older non-recombining region. Comparative analyses among several Mercurialis species further show that the extent of sex-linked differentiation varies markedly among them. We also identify APRR7 as the only gene showing consistent male-specific inheritance across the genus; this gene is a strong candidate master sex-determination gene. Together, our results refine the structure and gene content of the sex-linked region in M. annua and contribute to our understanding of the diversity of sex chromosomes in plants.

evolutionary biology↗

bioRxiv2024

Sex-allocation trade-offs and their genetic architecture revealed by experimental evolution

The theory of sex-allocation is hailed as one of evolutionary biologys great successes. But while it has successfully predicted strategies of resource allocation to sons versus daughters under a wide range of conditions in species with separate sexes, it has been difficult to apply to hermaphroditic species because of the repeated failure to verify the fundamental assumption of a direct genetic trade-off between male and female allocations made by hermaphrodites. This assumption supposes that mutations that increase an individuals male allocation reduce its female allocation in equal measure, yet there is almost no evidence for such trade-off loci in hermaphroditic populations. Here, we use experimental evolution to generate wide variation in hermaphroditic sex allocation in an annual plant and demonstrate a clear trade-off between the two sexual functions within populations as well as over time, with populations evolving both increased male and reduced female allocation. Quantitative trait locus (QTL) analysis performed on multiple crosses further reveals the segregation of allelic variation at trade-off loci. Taken together, our results demonstrate a phenotypic trade-off in sex allocation in hermaphrodites and provide compelling evidence for sex-allocation trade-off loci, verifying the fundamental assumption of sex-allocation theory and securing its general applicability to both dioecious and hermaphroditic species.

evolutionary biology↗

bioRxiv2019

Rapid dissolution of dioecy by experimental evolution

Evolutionary transitions from hermaphroditism to dioecy have been frequent in flowering plants, but recent analysis indicates that reversions from dioecy to hermaphroditism have also been common. Here, we use experimental evolution to expose a mechanism for such reversions. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that varied in their propensity for the occasional production of male flowers; such leaky sex expression is common in both males and females of dioecious plants. Over only four generations, females evolved a 23-fold increase in average male-flower production. The phenotypic masculinization of females was also sufficient to render them effective at siring progeny in the presence of males. Our study illustrates the rapid dissolution of dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion. It thereby experimentally validates a mechanism for a major transition in plant sexual systems..

evolutionary biology↗