Transgressivity in Key Functional Traits Rather Than Phenotypic Plasticity Promotes Stress Tolerance in A Hybrid Cordgrass.

Blanca Gallego-Tévar,Jesús M Castillo,Brenda J Grewell,Rebecca E Drenovsky

doi:10.3390/plants8120594

Blanca Gallego-Tévar, Jesús M Castillo + Show 2 more

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https://doi.org/10.3390/plants8120594

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Abstract

Hybridization might promote offspring fitness via a greater tolerance to environmental stressors due to heterosis and higher levels of phenotypic plasticity. Thus, analyzing the phenotypic expression of hybrids provides an opportunity to elucidate further plant responses to environmental stress. In the case of coastal salt marshes, sea level rise subjects hybrids, and their parents, to longer tidal submergence and higher salinity. We analyzed the phenotypic expression patterns in the hybrid Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3% showed an additive inheritance, 37% showed mid-parent heterosis, 18% showed best-parent heterosis, and 5% presented worst-parent heterosis. Transgressivity, rather than phenotypic plasticity, in key functional traits of the hybrid, such as tiller height, conveyed greater stress tolerance to the hybrid when compared to the tolerance of its parents. As parental trait variability increased, phenotypic transgressivity of the hybrid increased and it was more important in response to inundation than salinity. Increases in salinity and inundation associated with sea level rise will amplify the superiority of the hybrid over its parental species. These results provide evidence of transgressive traits as an underlying source of adaptive variation that can facilitate plant invasions. The adaptive evolutionary process of hybridization is thought to support an increased invasiveness of plant species and their rapid evolution.

Highlights

Climate change, native biodiversity loss, and their concomitant impacts on ecosystems are global environmental changes of paramount international concern for biological conservation, human health, and quality of life on earth [1]
Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3%
Species with dispersal capacity may migrate to more benign habitats, those with the capacity for phenotypic plasticity may adjust in place, whereas adaptive evolution might support persistence in new environmental conditions [2,3]

Summary

Introduction

Native biodiversity loss, and their concomitant impacts on ecosystems are global environmental changes of paramount international concern for biological conservation, human health, and quality of life on earth [1]. The on-going effects include global warming and sea level rise. In this context, increasing environmental stressors affect plant biodiversity. Hybridization is a powerful evolutionary mechanism that can lead to best-parent heterosis or ‘hybrid vigor’, producing new hybrid phenotypes with higher performance than parental species [4], which can be significant under changing environmental conditions. Hybridization is a mechanism for rapid evolution of invasiveness in exotic plant species [5,6]. Best-parent heterosis may result in hybrids with extreme phenotypes that have higher fitness under stressful conditions than their parental species [5,9,10]

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