TY - THES AB - For self-incompatibility (SI) to be stable in a population, theory predicts that sufficient inbreeding depression (ID) is required: the fitness of offspring from self-mated individuals must be low enough to prevent the spread of self-compatibility (SC). Reviews of natural plant populations have supported this theory, with SI species generally showing high levels of ID. However, there is thought to be an under-sampling of self-incompatible taxa in the current literature. In this thesis, I study inbreeding depression in the SI plant species Antirrhinum majus using both greenhouse crosses and a large collected field dataset. Additionally, the gametophytic S-locus of A. majus is highly heterozygous and polymorphic, thus making assembly and discovery of S-alleles very difficult. Here, 206 new alleles of the male component SLFs are presented, along with a phylogeny showing the high conservation with alleles from another Antirrhinum species. Lastly, selected sites within the protein structure of SLFs are investigated, with one site in particular highlighted as potentially being involved in the SI recognition mechanism. AU - Arathoon, Louise S ID - 14651 SN - 2663 - 337X TI - Investigating inbreeding depression and the self-incompatibility locus of Antirrhinum majus ER - TY - JOUR AB - Chromosomal rearrangements (CRs) have been known since almost the beginning of genetics. While an important role for CRs in speciation has been suggested, evidence primarily stems from theoretical and empirical studies focusing on the microevolutionary level (i.e., on taxon pairs where speciation is often incomplete). Although the role of CRs in eukaryotic speciation at a macroevolutionary level has been supported by associations between species diversity and rates of evolution of CRs across phylogenies, these findings are limited to a restricted range of CRs and taxa. Now that more broadly applicable and precise CR detection approaches have become available, we address the challenges in filling some of the conceptual and empirical gaps between micro- and macroevolutionary studies on the role of CRs in speciation. We synthesize what is known about the macroevolutionary impact of CRs and suggest new research avenues to overcome the pitfalls of previous studies to gain a more comprehensive understanding of the evolutionary significance of CRs in speciation across the tree of life. AU - Lucek, Kay AU - Giménez, Mabel D. AU - Joron, Mathieu AU - Rafajlović, Marina AU - Searle, Jeremy B. AU - Walden, Nora AU - Westram, Anja M AU - Faria, Rui ID - 14742 IS - 11 JF - Cold Spring Harbor Perspectives in Biology KW - General Biochemistry KW - Genetics and Molecular Biology SN - 1943-0264 TI - The impact of chromosomal rearrangements in speciation: From micro- to macroevolution VL - 15 ER - TY - JOUR AB - Understanding the phenotypic and genetic architecture of reproductive isolation is a long‐standing goal of speciation research. In several systems, large‐effect loci contributing to barrier phenotypes have been characterized, but such causal connections are rarely known for more complex genetic architectures. In this study, we combine “top‐down” and “bottom‐up” approaches with demographic modelling toward an integrated understanding of speciation across a monkeyflower hybrid zone. Previous work suggests that pollinator visitation acts as a primary barrier to gene flow between two divergent red‐ and yellow‐flowered ecotypes ofMimulus aurantiacus. Several candidate isolating traits and anonymous single nucleotide polymorphism loci under divergent selection have been identified, but their genomic positions remain unknown. Here, we report findings from demographic analyses that indicate this hybrid zone formed by secondary contact, but that subsequent gene flow was restricted by widespread barrier loci across the genome. Using a novel, geographic cline‐based genome scan, we demonstrate that candidate barrier loci are broadly distributed across the genome, rather than mapping to one or a few “islands of speciation.” Quantitative trait locus (QTL) mapping reveals that most floral traits are highly polygenic, with little evidence that QTL colocalize, indicating that most traits are genetically independent. Finally, we find little evidence that QTL and candidate barrier loci overlap, suggesting that some loci contribute to other forms of reproductive isolation. Our findings highlight the challenges of understanding the genetic architecture of reproductive isolation and reveal that barriers to gene flow other than pollinator isolation may play an important role in this system. AU - Stankowski, Sean AU - Chase, Madeline A. AU - McIntosh, Hanna AU - Streisfeld, Matthew A. ID - 14787 IS - 8 JF - Molecular Ecology KW - Genetics KW - Ecology KW - Evolution KW - Behavior and Systematics SN - 0962-1083 TI - Integrating top‐down and bottom‐up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone VL - 32 ER - TY - JOUR AB - Understanding the factors that have shaped the current distributions and diversity of species is a central and longstanding aim of evolutionary biology. The recent inclusion of genomic data into phylogeographic studies has dramatically improved our understanding in organisms where evolutionary relationships have been challenging to infer. We used whole-genome sequences to study the phylogeography of the intertidal snail Littorina saxatilis, which has successfully colonized and diversified across a broad range of coastal environments in the Northern Hemisphere amid repeated cycles of glaciation. Building on past studies based on short DNA sequences, we used genome-wide data to provide a clearer picture of the relationships among samples spanning most of the species natural range. Our results confirm the trans-Atlantic colonization of North America from Europe, and have allowed us to identify rough locations of glacial refugia and to infer likely routes of colonization within Europe. We also investigated the signals in different datasets to account for the effects of genomic architecture and non-neutral evolution, which provides new insights about diversification of four ecotypes of L. saxatilis (the crab, wave, barnacle, and brackish ecotypes) at different spatial scales. Overall, we provide a much clearer picture of the biogeography of L. saxatilis, providing a foundation for more detailed phylogenomic and demographic studies. AU - Stankowski, Sean AU - Zagrodzka, Zuzanna B AU - Galindo, Juan AU - Montaño-Rendón, Mauricio AU - Faria, Rui AU - Mikhailova, Natalia AU - Blakeslee, April M H AU - Arnason, Einar AU - Broquet, Thomas AU - Morales, Hernán E AU - Grahame, John W AU - Westram, Anja M AU - Johannesson, Kerstin AU - Butlin, Roger K ID - 14833 IS - 1 JF - Evolutionary Journal of the Linnean Society TI - Whole-genome phylogeography of the intertidal snail Littorina saxatilis VL - 2 ER - TY - GEN AB - Fragmented landscapes pose a significant threat to the persistence of species as they are highly susceptible to heightened risk of extinction due to the combined effects of genetic and demographic factors such as genetic drift and demographic stochasticity. This paper explores the intricate interplay between genetic load and extinction risk within metapopulations with a focus on understanding the impact of eco-evolutionary feedback mechanisms. We distinguish between two models of selection: soft selection, characterised by subpopulations maintaining carrying capacity despite load, and hard selection, where load can significantly affect population size. Within the soft selection framework, we investigate the impact of gene flow on genetic load at a single locus, while also considering the effect of selection strength and dominance coefficient. We subsequently build on this to examine how gene flow influences both population size and load under hard selection as well as identify critical thresholds for metapopulation persistence. Our analysis employs the diffusion, semi-deterministic and effective migration approximations. Our findings reveal that under soft selection, even modest levels of migration can significantly alleviate the burden of load. In sharp contrast, with hard selection, a much higher degree of gene flow is required to mitigate load and prevent the collapse of the metapopulation. Overall, this study sheds light into the crucial role migration plays in shaping the dynamics of genetic load and extinction risk in fragmented landscapes, offering valuable insights for conservation strategies and the preservation of diversity in a changing world. AU - Olusanya, Oluwafunmilola O AU - Khudiakova, Kseniia AU - Sachdeva, Himani ID - 14732 T2 - bioRxiv TI - Genetic load, eco-evolutionary feedback and extinction in a metapopulation ER -