Format: ORAL

Diego Hojsgaard1; Agostina Sassone1; Piyal Karunarathne2

1 Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany 2 Institute of Population Genetic, Heinrich-Heine-Universität, Düsseldorf, Germany

Mapping the geographical distribution of phylogenetic traits helps visualize macroecological patterns (above species regional level) and understand how long standing microevolutionary processes (below species level) shape evolution. These processes are determined by mutation, genetic drift, gene flow, non-random mating, and natural selection, leading to the patterns we see today. We reviewed global occurrences of apomictic species and mapped them according to the Tree_of_Life 3.0. Apomixis (asexual seeds), develops by sporophytic (adventitious embryony) or gametophytic (apospory or diplospory) pathways. Almost 1500 species show evidence of apomixis and c.230 species have anecdotal evidence of apomixis. Most apomicts occur in Asteraceae, Rosaceae and Poaceae, and 6 families have at least 50 apomictic species whose distribution varies significantly among continents. A correlation between developmental phenotypes among apomictic species and families suggests developmental constraints on phenotypic variability, adding to the recognized association between apomixis-derived biodiversity and general biodiversity. To bridge the gap between microevolutionary processes and macroecological patterns and understand the role of apomixis in speciation, we took Paspalum intermedium a grass species with sexual diploids and apomictic tetraploids ecologically differentiated along a latitudinal gradient in South America and use population-level genomics (Genotyping-by-Sequencing), reproductive and environmental/occurrence data (Ecological-Niche-Modelling) to assess microevolutionary processes. Diploids are genetically less variable than tetraploids and shows a narrow diploid gene pool from which tetraploids arise in P.intermedium. STRUCTURE analysis shows three consistent K values that relate to ploidy states, lineage ancestry and ecological attributes. Principal component and minimum spanning network analyses support a narrow cluster of diploids, and more diverse tetraploid lineages differentiated by geographic region (North/Centre/South) and cytotype co-existence (sympatry/parapatry/allopatry). Reproductive mode ratios (sexual/apomictic) associate to environmental variables and within population clonal diversity in marginal areas. Our analyses suggest that differences in gene flow conditions promote intraspecific geographic/genetic differentiation within and between cytotypes, supporting early steps of speciation.