Responses to salinity of Spartina hybrids formed in San Francisco Bay, California (S. alterniflora × foliosa and S. densiflora × foliosa )

Abstract

San Francisco Bay (SFB), which supports large populations of the California native cordgrass Spartina foliosa, has been the recipient of introductions of S. alterniflora and S. densiflora. Hybrids have arisen between the native and these exotic species. Sterile F1 S. densiflora 9 foliosa hybrids have formed numerous times in a number of marshes, while introgressing S. alterniflora 9 foliosa hybrids are fully fertile and invaded widely in SFB, especially onto naturally-open low tidal flats by inundationtolerant hybrids. Sarcocornia pacifica, pickleweed, dominates the mid-to-upper marsh zones where the hypersaline conditions that occur during the summer drought, characteristic of this climate, exclude S. foliosa. Here we report on two glasshouse experiments investigating the salinity tolerance of hybrid Spartina. Some hybrids of both origins grew well and flowered at high salinity levels while the parental species grew little and did not flower. Our results imply that midzone marshes are also vulnerable to invasion by salinity-tolerant Spartina hybrids. Herbicide control implemented over the last 10 years targeting both the exotic species and their hybrids have reduced their extent. However, efforts in monitoring and management of exotic Spartina and its hybrids must continue as vast areas of tidal marsh restoration are underway and planned in SFB; colonization by Spartina hybrids tolerant to inundation and/or salinity will greatly alter restoration trajectories. These concerns are all the more vital given projections of climate change and its effects on salinity and sea level rise in SFB salt marshes.

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

“…This suggests that relatively few individuals had a high number of unique traits expressing BPH, likely because each hybrid was the product of independent hybridization events. Spartina densiflora x foliosa has been reported as sterile [36,39], which was also observed in our study, given the absence of mature seeds inside florets. Fertility can be developed in sterile F1 hybrids if the process of interspecific hybridization is followed by a chromosomal duplication originating a new allopolyploid species [62,63].…”

“…For example, S. densiflora often has optimal physiological responses under intermediate brackish salinity conditions, rather than at freshwater or hypersalinity [58,59]. In Spartina, different genotypes of S. densiflora x foliosa have previously outperformed both parental taxa by producing taller tillers at high salinities [36]. The same has been observed for the responses of reciprocal hybrids between S. maritima and S. densiflora in response to salinity [25,26].…”

“…Therefore, it is expected that increasing stress levels on halophytes that result from increasing inundation and salinity regimes will lead to decreases in salt marsh productivity [32,33]. Some studies have analyzed the effects of increasing salinity [34][35][36] or waterlogging [37,38] on hybrids. To our knowledge, the combined effect of salinity and inundation on hybrid phenotypes has not been analyzed from the perspective of heterosis and phenotypic plasticity, although enhanced tolerance has been observed to these individual stressors.…”

Changes to the functional traits of phosphoenolpyruvate carboxylase following hybridization in C‐4 halophytes

“…Other studies have described that hybrids between Spartina alterniflora Liosel., Spartina foliosa Trin. and S. densiflora showed higher salinity tolerance than their parental species (Lee et al ), but nothing is known about the PEPC activity of any Spartina hybrid or any other wild hybrid.…”

Genetic structure of Spartina hybrids between native Spartina maritima and invasive Spartina densiflora in Southwest Europe

“…In the genus of polyploid grasses Spartina (syn. Sporobolus following Peterson et al, 2014) (Poaceae), there are several examples of hybrids and allopolyploids between invasive and native species which exhibit transgressive traits that confer hybrid vigor (Ainouche et al, 2009;Ayres et al, 2004;Castillo et al, 2010;Lee et al, 2016;Pakenham-Walsh et al, 2010).…”