Trait Response to Nitrogen and Salinity in Rhizophora mangle Propagules and Variation by Maternal Family and Population of Origin

Christina L Richards,David B Lewis,Gordon A Fox,Kristen L Langanke,Jeannie Mounger

doi:10.3389/fmars.2021.756683

Christina L Richards, David B Lewis + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2021.756683

Copy DOI

Abstract

Many coastal foundation plant species thrive across a range of environmental conditions, often displaying dramatic phenotypic variation in response to environmental variation. We characterized the response of propagules from six populations of the foundation species Rhizophora mangle L. to full factorial combinations of two levels of salinity (15 ppt and 45 ppt) reflecting the range of salinity measured in the field populations, and two levels of nitrogen (N; no addition and amended at approximately 3 mg N per pot each week) equivalent to comparing ambient N to a rate of addition of 75 kg per hectare per year. The response to increasing salinity included significant changes, i.e., phenotypic plasticity, in succulence and root to shoot biomass allocation. Propagules also showed plasticity in maximum photosynthetic rate and root to shoot allocation in response to N amendment, but the responses depended on the level of salinity and varied by population of origin. In addition, propagules from different populations and maternal families within populations differed in survival and all traits measured except photosynthesis. Variation in phenotypes, phenotypic plasticity and propagule survival within and among R. mangle populations may contribute to adaptation to a complex mosaic of environmental conditions and response to climate change.

Highlights

Many plant species thrive across an extensive range of environmental conditions, often displaying dramatic phenotypic variation (McKee, 1995; Smith and Snedaker, 1995; Richards et al, 2005; Feller et al, 2010)
We found that some combination of salinity and N treatments were included in the best models for three of the six traits we measured: succulence, root to shoot biomass ratio, and maximum photosynthetic rate (Table 1)
We discovered that seedling survival and the magnitude of almost all responses varied among populations and even maternal families within populations

Summary

Introduction

Many plant species thrive across an extensive range of environmental conditions, often displaying dramatic phenotypic variation (McKee, 1995; Smith and Snedaker, 1995; Richards et al, 2005; Feller et al, 2010). In addition to the naturally dynamic nature of coastal habitats, anthropogenic activities can increase the input of nutrients and alter watersheds, further contributing to environmental variation (Bertness et al, 2002; Barbier et al, 2008; Gedan et al, 2009, 2011; Crotty et al, 2020) Within these dynamic conditions, foundation plant species such as mangroves provide ecosystem services. These species disproportionately contribute to maintaining habitat integrity and ecosystem resilience (Bertness and Callaway, 1994; Keith et al, 2017; Ellison, 2019; Bertness, 2020; Qiao et al, 2021) Understanding how these species cope with challenges from anthropogenic impacts is key to preserving the ecosystems they create and define (Gedan et al, 2009, 2011; Guo et al, 2021)

Methods

Results

Discussion

Conclusion