The Role of Reproductive Modes in Shaping Genetic Diversity in Polyploids: A Comparative Study of Selfing, Outcrossing, and Apomictic Paspalum Species

Abstract

Exploring the genetic diversity and reproductive strategies of Paspalum species is essential 20 for advancing forage grass improvement. We compared morpho-phenological, molecular, and gen-21 otypic variation in five tetraploid Paspalum species with contrasting mating systems and reproduc-22 tive modes. Contrary to previous findings, selfing (Paspalum regnellii and P. urvillei) and outcrossing 23 (P. durifolium and P. ionanthum) species exhibited similar phenotypic diversity patterns, with low 24 intrapopulation variability and no morphological differentiation among populations. The apomictic 25 species (P. intermedium) exhibited low intrapopulation phenotypic variation but high population 26 differentiation, indicative of genetic drift and local adaptation. Outcrossing species showed greater 27 intrapopulation genotypic variation than selfing species, which displayed a high population struc-28 ture due to restricted pollen migration. The apomictic species exhibited the lowest intrapopulation 29 molecular diversity, forming uniclonal populations with high interpopulation differentiation, high-30 lighting the fixation of distinct gene pools via apomixis. This is the first report about genetic diver-31 sity in populations of sexual allopolyploid species of Paspalum. Population structure in these allotet-32 raploid Paspalum species is primarily shaped by how reproductive modes, mating systems, and ge-33 ographic distribution influence gene flow via pollen and seeds. Our findings contribute significantly 34 to the conservation and genetic improvement of forage grasses, particularly for developing cultivars 35 with enhanced adaptability and productivity.