Ecophysiological and biochemical responses to cold and heat waves of native Spartina maritima, alien S. densiflora and their reciprocal hybrids

Spartina hybrids outperform parental species, showing transgressive acclimation to extreme climates. Native S. maritima demonstrates high seasonal adaptability and invasive S. densiflora low physiological impact, suggesting resilience under climate change. Extreme climatic events, such as cold and heat waves, are becoming more frequent, intense, and prolonged due to climate change. Simultaneously, invasive alien plant species are altering the composition of plant communities. Both climate change and the introduction of alien species pose significant threats to biodiversity. We studied the responses of 25 biochemical and physiological functional traits for native Spartina maritima, alien invasive S. densiflora and their reciprocal hybrids to changing environmental conditions during a cold snap in winter and a heat wave in summer in Guadiana Marshes (Southwest Iberian Peninsula). These four closely related taxa responded differently to seasonal environmental fluctuations. Both hybrid taxa, particularly S. maritima × densiflora, exhibited transgressive responses, allowing them to display a wider range of acclimation responses to air temperature compared to their parental species. Native S. maritima also demonstrated a relatively high acclimation capacity to seasonal meteorological changes. In contrast, alien S. densiflora presented few acclimation responses to seasonal environmental changes, responding primarily to sediment salinity rather than to air temperature. Even so, all four studied Spartina taxa appear to be well-adapted to the occurrence of cold and heat waves in the Gulf of Cadiz. These findings underscore the complexity of plant acclimation strategies in response to extreme climatic events and highlight the potential for hybrid taxa to face the future dynamics of salt marshes under climate change.