Interactive effects of salinity and inundation on native Spartina foliosa, invasive S. densiflora and their hybrid from San Francisco Estuary, California

Abstract

Background and Aims Sea Level Rise (SLR) associated with climate change is intensifying permanent submersion and salinity in salt marshes. In this scenario, hybridization between native and invasive species may result in hybrids having greater tolerance of abiotic stress factors than their parents. Thus, understanding the responses of native and invasive halophytes and their hybrids to interacting physiological stresses imposed by SLR is key to native species conservation. We analyzed how salinity, inundation depth, and their interaction impact the functional traits of native and invasive cordgrass species and their hybrid (Genus Spartina; Poaceae). Methods In a mesocosm experiment, we evaluated interactive stress effects of three inundation depths (4.5, 35.5 and 55 cm) and four aqueous salinities (0.5, 10, 20 and 40 ppt) on 27 functional traits of native Spartina foliosa, invasive S. densiflora and their hybrid S. densiflora x S. foliosa from San Francisco Estuary. Key Results The combined effect of salinity and inundation led to synergetic effects in leaf biochemical stress indicators. S. foliosa behaved as a stress-tolerant species, with high leaf Na exudation rate and glycinebetaine concentrations that also increased with stress. S. foliosa was less sensitive to salinity than S. densiflora and the hybrid but was highly growth-limited in response to increased inundation and salinity. S. densiflora was fast-growing in low stress conditions and tolerated moderate interactive stresses. The hybrid produced more biomass, rhizome reserves, and tillers than its parents, even under the most stressful conditions. Transgressivity improved the hybrid’s capacity to deal with flooding stress more so than its response to increasing salinity. Conclusions Based on our observations, we predict that established populations of both native and invasive cordgrasses will experience reduced vegetative and sexual fitness in response to SLR. In particular, the combined effects of high salinity and deep inundation may decrease floret production in S. densiflora, a key trait for the spread of its invasive populations. In contrast, the hybrid likely will be able to sustain its invasiveness with under SLR based on its ability to maintain growth and biomass production under stressful conditions.

Salinity, not genetic incompatibilities, limits the establishment of the invasive hybrid cattail Typha × glauca in coastal wetlands

“…Other studies have found relatively high levels of salt tolerance in hybrids, for example, the hybrid sunflower Helianthus paradoxus had higher survival and biomass than either parent species under highly saline conditions, and is considered to be transgressive for salt tolerance relative to its progenitors (Welch & Rieseberg, 2002) (Karrenberg et al., 2006). In another example, the hybrid of Spartina densiflora and S. foliosa appears better able than its parent species to deal with the stressors of flooding and salinity associated with sea level rise (Gallego‐Tévar et al., 2020). The relatively high production of ramets by T. × glauca provides an important mechanism for clonal expansion within a coastal site.…”

Estimating the Potential Blue Carbon Gains From Tidal Marsh Rehabilitation: A Case Study From South Eastern Australia

“…It was calculated that a global SLR greater than 26 cm by 2100 would likely be greater than some ecosystems' abilities to accrete sediment and increase elevation over this period of time (Macreadie et al, 2017). In addition, SLR can also have synergic effects with changes in the salinity and inundation conditions which can lead to reduced fitness for some marsh species (Gallego-Tévar et al, 2019).…”

Heat stress effects on sexual reproductive processes of a threatened halophyte

“…Sexual reproduction is a critical life history process that increases the genetic diversity and ability of plants to respond to environmental changes, increases their capacity for long-distance dispersal, and supports long-term persistence and conservation of plant populations (Van Drunen and Dorken, 2012). The capacity to maintain sexual reproduction is especially relevant as plants are exposed to rising levels of synergistic environmental stress factors imposed by global warming (Gallego-T evar et al, 2019a). Climate scientists have documented increasingly warmer conditions at the Earth's surface in each of the last three decades than in any preceding decade since 1850 (IPCC 2013).…”