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Background and Aims The capacity for dispersal to promote or hinder species’ responses to global change remains a major question in ecology. One ecosystem experiencing rapid change is the tidal marsh, which is migrating inland in response to accelerated sea level rise. Few studies to date have investigated the ecological dynamics that impact this large-scale migration. Seed dispersal and persistence in the soil seed bank is a component that can be strongly indicative of community trajectories. With this in mind, the aim of our study was to characterize the germinable seed bank across a marsh–forest ecotone in the Chesapeake Bay. Methods Soil samples were collected across transects that ran from the high marsh to the coastal loblolly pine forest in a brackish marsh in Blackwater National Wildlife Refuge, MD, USA. Samples were grown in a greenhouse and watered with either freshwater or 3 ppt seawater solution. We compared community composition across transects and between salinity treatments. Additionally, we compared the seed bank with standing vegetation and used seed trait data from the TRY Database to investigate changes in functional traits along this ecotone. Key Results We found halophytic species dispersing up to 15 m into the forest and a general lack of obligate upland species, including near absence of Pinus taeda, the dominant species in the forest canopy. A majority of species detected in the seed bank were wetland species of various types, with species with wide salinity tolerance arising most frequently. Salinity addition had a significant negative influence on seed bank diversity. Conclusion Overall, our seed bank results suggest that dispersal and germination under the conditions of saltwater intrusion will limit forest regeneration and favour marsh plant dispersal. This indicates that the ecological processes that determine the soil seed bank community will support continued migration of marsh species into uplands.

Epigenetic modifications to DNA can be inherited and may play a key role in evolution, with epigenetic influences on life history traits such as the timing of germination and flowering thought to be particularly important in plants. However, few studies have examined the effects of epigenetic modifications through experimental alteration of the methylome under differential growth conditions. In this study, we chemically induced global DNA hypomethylation using 5-azacytidine in three Brassica rapa plant populations differing in life history characteristics and under differing photoperiod treatments. We found that our 5-azacytidine treatment affected the timing of germination and that this effect differed across populations, with the treatment delaying germination in B. rapa Fast Plants, which have been artificially selected for rapid cycling, but accelerating germination in biennials. Rapid cycling B. rapa plants also were smaller and had lower reproductive fitness under the experimental demethylation treatment. There was no main effect of demethylation or photoperiod on flowering time, but the interaction was marginally significant, indicating that demethylation effects on flowering time depend on photoperiod. These results demonstrate that epigenetic modifications can influence phenotypic traits in ways that are dependent on genetic identity, life history, and light availability.

Climate change is driving abiotic shifts that can threaten the conservation of foundation species and the habitats they support. Directional range shifting is one mechanism of escape, but requires the successful colonization of habitats where interspecific interactions may differ from those to which a species has adapted. For plants with multiple reproductive strategies, these range-edge interactions may alter the investment or allocation toward a given reproductive strategy. In this study, we quantified sexual reproduction of the clonal marsh grass Spartina patens across an inland colonization front into maritime forest being driven by sea-level rise. We find that flowering is variable across S. patens meadows, but consistently reduced in low light conditions like those of the forest understory. Observational surveys of S. patens flowering at four sites in the Delmarva Peninsula agreed with the results of two experimental manipulations of light availability (shading experiment in S. patensdominated marsh and a forest dieback manipulation). These three approaches pinpointed light limitation as a principal control on S. patens flowering capacity, suggesting that light competition with taller upland species can suppress S. patens flowering along its upland migration front. Consequently, all propagation in shaded conditions must occur clonally or via seeds from the marsh, a reproductive restriction that could limit the potential for local adaptation and reduce genetic diversity. Future research is needed to determine whether the lack of flowering is the result of a tradeoff between sexual and clonal reproduction or results from insufficient photosynthetic products needed to achieve either reproductive method.