Phenotypic plasticity of polyploid plant species promotes transgressive behaviour in their hybrids

Hybridization is a common process that leads to relevant evolutionary and ecological consequences. The genotypes resulting from hybridization commonly show phenotypic traits with intermediate values between both parents, however hybrids can also display phenotypic traits outside the ranges of both parents as a result of heterosis or hybrid vigour. This can allow hybrid offspring to tolerate more extreme environments than either parent species. Phenotypic inheritance and phenotypic plasticity are both regulated at genetic and epigenetic levels, but there is a lack of knowledge about the relationship between parental species’ responses to environmental gradients (and variability of these responses) and inheritance in their hybrids.

Parental species and its transgressive hybrid offspring
A comparison of a clear transgressive phenotype (tall tiller height) of an invasive Spartina hybrid (S. maritima x densiflora) and the short tiller height of its native parental species Spartina maritima (small cordgrass) in Guadiana Marshes (Southwest Iberian Peninsula). Image credit: J.M. Castillo.

A recent study by Gallego-Tévar et al. published in AoBP reports the fitness and phenotypic inheritance of two wild invasive Spartina (cordgrass) hybrids in relation to their parental species along a wide estuarine salinity gradient. The main objectives were to compare the performance of the hybrids with that of their parents, to distinguish the phenotypic inheritance operating in the hybrids and to analyse the relationships between the variability in the responses of the parents and the responses of their hybrids to salinity. The hybrids outperformed their parental species showing greater fitness and some transgressive traits. Plant traits displaying greater variability in the polyploid parents led to a higher number of transgressive responses in the hybrids. Both hybrids presented greater salinity tolerance than their parents, showing the highest percentage of transgressive traits at both extremes of the salinity gradient. This work is the continuation of the authors’ research on the tolerance of halophytes to abiotic stresses and their phenotypic plasticity, now adding an evolutionary perspective to the process of hybridization. This finding also supports a new focus to be applied for the artificial development of vigorous hybrid crops.

Researcher highlight

Blanca Gallego-Tévar

Blanca Gallego-Tévar completed a BSc. in Environmental Sciences at the University of Malaga, Spain in 2012. She obtained her Masters degree in Planning and Management of Territorial and Local Development at the University of Seville, Spain in 2014. Currently, Blanca is working on her doctoral thesis in native and invasive plant hybrids of salt marshes in the Department of Plant Biology and Ecology at the University of Seville.

Blanca’s research interests are related to environmental adaptations occurring in the hybridization process in plants. Specifically, the effects that these changes have on the tolerance of plant taxa to climate change, the invasiveness of hybrids and the improvement of crop species through hybridization. Blanca is active on Twitter and her research can be followed here: @BlancaTevar.

Reference List

Gallego-Tévar, B., Rubio-Casal, A. E., de Cires, A., Figueroa, E., Grewell, B. J., & Castillo, J. M. (2018). Phenotypic plasticity of polyploid plant species promotes transgressive behaviour in their hybrids. AoB PLANTS, 10(5). https://doi.org/10.1093/aobpla/ply055