Broad-scale patterns of genetic diversity and structure in a foundational salt marsh species black needlerush (Juncus roemerianus)

Abstract

Clonal and genetic diversity in foundational plant species are critical for species resiliency and ecosystem processes, both of which contribute to restoration success; however, genetic data is often lacking for common plant species used in many restoration practices. Only a few plant species dominate salt marshes, ecologically and economically valuable ecosystems targeted for restoration due to global decline. Despite being a foundational species in southeastern United States salt marshes black needlerush (Juncus roemerianus Scheele) is understudied, especially in comparison to the co-occurring smooth cordgrass (Spartina alterniflora Loisel). We used a panel of 18 microsatellite markers on 849 samples of J. roemerianus collected at 17 sites across a majority of the species range from Mississippi to South Carolina to measure clonal and genetic diversity and characterize population structure. Results are consistent with previous genetic studies on J. roemerianus and other clonal plant species in that clonal and genetic diversity were higher than expected based on life history literature, with an average genotypic diversity (G D) of 0.67 and average observed heterozygosity (H O) of 0.56. Differences in diversity between the ecologically and environmentally divergent Gulf (G D = 0.64, H O = 0.52) and Atlantic (G D = 0.80, H O = 0.45) coasts suggest that life history strategy may vary by environment. Hierarchical structure was apparent across the study area, with STRU CTU RE analyses identifying three genetic clusters that further subdivided into five clusters and a broad transition zone. The scale of this genetic differentiation should be considered in sourcing plants for salt marsh restoration efforts.

Inheritance of DNA methylation differences in the mangroveRhizophora mangle

“…Studies on native southeastern US S. alterniflora populations have reported diversity levels that are comparable to other outcrossing grasses, despite the fact that this species also spreads prolifically by clonal reproduction (Foust et al, 2016; Richards et al, 2004; Robertson et al, 2017; Zerebecki et al, 2021). Tumas et al (2019) found greater genetic diversity in Gulf of Mexico than Atlantic coast populations of the salt marsh dominant (potential foundation species) plant Juncus roemerianus , but like in R. mangle , measures of genetic diversity varied dramatically across the range. The authors suggest this could be the result of differences in plant community and disturbance regimes or reflect a relationship with population size.…”

Genetic structure in patchy populations of a candidate foundation plant: a case study ofLeymus chinensisusing genetic and clonal diversity

“…Understanding the genetic makeup of foundation plant species in particular, is important for conservation because these species create and define ecological communities and contribute disproportionately to ecosystem function (Ellison et al, 2005; Hughes and Lotterhos, 2014; Lau et al, 2016; Ellison, 2019; Whitham et al, 2020). Foundation grass species often combine clonal and sexual reproduction (Franks et al, 2004; Keeler, 2004; Richards et al, 2004; Tumas et al, 2019). Although our initial analysis found that every ramet of the grass L. chinensis was a unique genotype, further consideration of the reproductive biology of the species and the number and type of markers we used, suggested that we had 13 lineages that were closely associated with patches.…”

“…Studies on another perennial grass Spartina alterniflora reported either that nearly every ramet was unique (Richards et al, 2004; Foust et al, 2016, Robertson et al, 2017) or that the number of ramets per genet varied greatly (Hughes and Lotterhos, 2014). Moreover, Tumas et al (2019) found that measures of genetic and clonal diversity varied dramatically across the range of the salt marsh foundation plant Juncus roemerianus . They found higher genetic diversity and lower clonal diversity in Gulf of Mexico populations than on the Atlantic coast.…”

Genetic structure in patchy populations of a candidate foundation plant: a case study ofLeymus chinensis(Poaceae) using genetic and clonal diversity

“…Foundation grass species often combine clonal and sexual reproduction (Franks et al, 2004;Keeler et al, 2004;Richards et al, 2004;Tumas et al, 2019). Although our initial analysis found that every ramet of the foundation grass L. chinensis was a unique genotype, further consideration of the reproductive biology of the species and the number and type of markers we used, suggest that we have 13 lineages that are closely associated with patches and some small amount of variation that could be due to somatic mutation as well as technical or scoring errors, which requires further study to decipher.…”

“…Studies on another perennial grass Spartina alterniflora reported either that nearly every ramet was unique (Richards et al, 2004;Foust et al, 2016, Robertson et al, 2017 or that the number of ramets per genet varied greatly (Hughes and Lotterhos, 2014). Moreover, Tumas et al (2019) found that measures of genetic and clonal diversity varied dramatically across the range of the salt marsh foundation plant Juncus roemerianus. They found greater genetic diversity and lower clonal diversity in Gulf of Mexico populations than on the Atlantic coast.…”