Biology subjects

Bastardot, M.

Publications and source records attributed to Bastardot, M..

3 recordsLinked to original sources

bioRxiv2023

Phylogenomics reveals the demography of reverse colonization in a rail species

AimIslands have recently been recognized as potential sources of biodiversity, challenging the traditional view that their small population sizes and low genetic diversity limit such roles. This raises the question of how insular genetic variation becomes incorporated into continental populations, contrary to expectations of unidirectional colonization. Here, we investigate whether and how island-derived genetic variation has influenced a continental population through population establishment and gene flow in a bird species where frequent trans-ocean dispersal is expected. LocationContinental East Asia (Russian Far East), Japanese Archipelago TaxonSwinhoes Rail (Coturnicops exquisitus) Materials and MethodsWe apply integrative phylogenomics to reconstruct the spatiotemporal history of the species. Colonization sequences and gene flow are inferred by comparing four different phylogenetic reconstruction methods, using mitochondrial sequences obtained by Sanger sequencing and genome-wide data obtained by genotyping by sequencing (MIG-seq). We assess a history of colonization and gene flow based on summary statistics, demographic trajectory inference by Stairway Plot2, demographic modeling by fastsimcoal2, and species distribution modeling. ResultsAnalyses collectively supported asymmetric gene flow from the island to the continental population, following divergence around the Middle Pleistocene. Post-divergence, the island maintained a large and stable population, while the continental population underwent a severe bottleneck, suggesting a significant evolutionary role of the island for the continental population. Additionally, evidence of recent re-establishment of the island by continental individuals indicates dynamic exchange and persistence within a continent-island metapopulation. Main conclusionsThe maintenance of insular genetic variation within a dynamic continent-island metapopulation may have enabled the island to act as a genetic and demographic reservoir for the continental population. Thus, continent-island metapopulation dynamics may be a key evolutionary pathway through which island populations contribute to continental genetic diversity.

evolutionary biology↗

bioRxiv2023

Evolution of alternative reproductive systems in Bacillus stick insects

Reproduction is a key feature of all organisms, yet the way in which it is achieved varies greatly across the tree of life. One striking example of this variation is the stick insect genus Bacillus, in which five different reproductive modes have been described: sex, facultative and obligate parthenogenesis, and two highly unusual reproductive modes: hybridogenesis and androgenesis. Under hybridogenesis, the entire genome from the paternal species is eliminated, and replaced each generation by mating with the corresponding species. Under androgenesis, an egg is fertilized but the developing diploid offspring bear two paternal genomes, and no maternal genome, as a consequence of unknown mechanisms. Here, we re-evaluate previous descriptions of Bacillus lineages and the proposed F1 hybrid ancestries of the hybridogenetic and obligately parthenogenetic lineages (based on allozymes and karyotypes) from Sicily, where all these reproductive modes are found. We generate a chromosome-level genome assembly for a facultative parthenogenetic species (B. rossius) and combine extensive field sampling with RADseq and mtDNA data. We identify and genetically corroborate all previously described species and confirm the ancestry of hybrid lineages. All hybrid lineages have fully retained their F1 hybrid constitution throughout the genome, indicating that the elimination of the paternal genome in hybridogens is always complete and that obligate parthenogenesis in Bacillus hybrid species is not associated with an erosion of heterozygosity as known in other hybrid asexuals. Our results provide a stepping stone towards understanding the transitions between reproductive modes and the proximate mechanisms of genome elimination.

evolutionary biology↗

bioRxiv2023

Spring reproductive success influences autumnal malarial load in a passerine bird

Although avian haemosporidian parasites are widely used as model organisms to study fundamental questions in evolutionary and behavorial ecology of host-parasite interactions, some of their basic characteristics, such as seasonal variations in within-host density, are still mostly unknown. In addition, their interplay with host reproductive success in the wild seems to depend on the interaction of many factors, starting with host and parasite species and the temporal scale under study. Here, we monitored the parasitemia of two haemosporidian parasites - Plasmodium relictum (lineage SGS1) and P. homonucleophilum (lineage SW2) - in two wild populations of great tits (Parus major) in Switzerland over three years, to characterize their dynamics. We also collected data on birds reproductive output - laying date, clutch size, fledging success - to determine whether they were associated with parasitemia before (winter), during (spring) and after (autumn) breeding season. Parasitemia of both species dramatically increased in spring, in a way that was correlated to parasitemia in winter. Parasitemia before and during breeding season did not explain reproductive success. However, the birds which fledged the more chicks had higher parasitemia in autumn, which was not associated with their parasitemia in previous spring. Our results tend to indicate that high haemosporidian parasite loads do not impair reproduction in great tits, but high resource allocation into reproduction can leave birds less able to maintain low parasitemia over the following months.

ecology↗