Apomixis frequency in polyploid wild populations of Psidium cattleyanum f. lucidum (Myrteae, Myrtaceae)

Background and Aims Apomictic reproduction and polyploidy are closely related in plants, and their causes and consequences have given rise to numerous hypotheses that continue to evolve as more representative taxa are studied. Psidium cattleyanum is a valuable model for investigating this relationship, as it is a polyploid species with multiple ploidy levels and exhibits pseudogamous gametophytic apomixis. In addition, it is a fruit tree of commercial, agricultural, and medicinal interest in its native range, but it is also an aggressive invasive species in regions where it has been introduced. In this study, we aim to determine the predominant reproductive mode in natural populations of the polyploid Psidium cattleyanum f. lucidum and to investigate whether this mode is associated with specific ploidy levels. Furthermore, we investigate whether these reproductive traits are linked to patterns of genetic diversity and population genetic structure. Methods We assessed the reproductive mode in wild populations representing the four ploidy levels (2C = 5x, 6x, 7x, 8x) present in Uruguay. Reproductive pathways were inferred by combining flow cytometric seed screen (FCSS) analysis with microsatellite (SSR) genotyping of progeny arrays. Population-level differences were evaluated across both data sets. Key Results Pseudogamous apomixis is the predominant reproductive mode in Uruguayan P. cattleyanum f. lucidum populations. The proportions of apomictic versus sexual reproduction, and the types of progenies produced, differed significantly among populations and ploidy levels. Genotyping revealed predominantly clonal progeny, yet with high genetic variability, and populations exhibit strong genetic structure. The ploidy level of the gametes and their combinations were characteristic of each population, leading to different reproductive strategies. Conclusions Facultative pseudogamous apomixis is the primary reproductive mode in natural populations of Psidium cattleyanum f. lucidum . Ploidy level influences reproductive strategy, as reflected in the apomixis/sexuality ratios and the type of progeny produced. Population genetic structure is shaped by the reproductive strategy adopted by each population.