Format: ORAL

Mariana Castro1, Maria C. Dias1, Joo Loureiro1, Brian C. Husband2 and Slvia Castro1

1 Centre for Functional Ecology, Associate Laboratory TERRA, Department of Life Sciences, University of Coimbra, Coimbra, Portugal 2 Department of Integrative Biology, University of Guelph, Guelph, Canada

Polyploidization, a common mutation observed throughout the evolutionary history of flowering plants, has played a pivotal role in shaping current plant diversity. While only a small fraction of neopolyploids (newly formed polyploids) successfully establish and spread, several factors contribute to this process. Crucially, neopolyploids must possess certain advantages over their diploid progenitors to gain a foothold, such as enhanced competitive ability. To investigate this competitive advantage, we compared the developmental and physiological responses of natural diploids, tetraploids, and synthetic neotetraploids of Jasione maritima var. maritima to intraspecific competition in controlled conditions. We also examined whether competitive abilities differed among populations within and beyond the contact zone. Diploids grown without competition exhibited superior developmental traits compared to the other cytotypes, such as increased size. Competition differentially impacted cytotypes, with neotetraploids demonstrating the least susceptibility and tetraploids the most significant negative effects. Notably, an asymmetric competitive response emerged across the latitudinal gradient. Populations outside the contact zone were most adversely affected, with tetraploid populations in the south experiencing the strongest negative impact compared to diploid populations in the north. The higher biomass and intermediate competitive capacity of diploids likely contribute to their persistence in northern distribution areas, while the dominance of neotetraploids under intraspecific competition would enable their establishment. Therefore, the asymmetric competitive abilities of cytotypes across their distribution range, potentially linked to environmental gradient adaptations, likely underlie the observed geographical patterns. Conversely, the similar competitive abilities of diploids and tetraploids within the contact zone may contribute to the maintenance of a dynamic and stable contact zone.