Megagametophyte development of diploid and polyploid species of Lessingianthus (Vernonieae, Asteraceae)

Abstract

Lessingianthus H.Rob. (Vernonieae, Asteraceae) is a South American genus notable for its remarkably high rate of polyploidy, encompassing multiple ploidy levels based on a consistent base number of x=16. These range from diploids (2n=2x=32) to undecaploids (2n=11x=176). Despite this cytological complexity, the origin of these polyploid taxa and their reproductive biology remain poorly understood, particularly for female gametophyte development that has been scarcely studied and remains fragmented. In this context, we characterize female gametophyte development of 11 Lessingianthus species with different ploidy levels, assess the impact of ploidy on embryo sac formation and female fertility. Finally, we discuss and compare our findings with previous studies on male gametophyte development within the genus. We found that megagametophyte development is conserved across different taxa; the meiotic and gametophytic stages, critical for sexual reproduction, proceed regularly among various cytotypes and suggest a consistent potential for sexual reproduction. These findings increase our understanding of polyploidy and meiotic stability on Lessingianthus and provide a solid source for further investigations into the population dynamics, selective processes, and molecular mechanisms underlying genomic evolution in sympatric polyploid lineages.