Do Habitat and Geographic Distribution Influence Decreased Seed Viability in Remnant Populations of a Keystone Bunchgrass?

Abstract

Wiregrass (Aristida stricta) is an important species for restoration of imperiled pine-grassland ecosystems. However, in situ and ex situ seedling establishment is problematic due to highly variable germination. I assessed seed lot quality with respect to the production of viable and non-viable seeds from seven remnant wiregrass populations occurring in xeric or mesic habitats throughout Alabama, Florida, Georgia, and South Carolina. Additionally, I investigated the incidence of contamination and germination following surface sterilization. Approximately 55 to 90% of seeds were non-viable due to lack of seed fill and fungal contamination. The number of empty seeds always outweighed that of infected seeds. Populations were similar for seed lot quality when grouped by habitat. Alternatively, populations were heterogeneous for seed lot quality when grouped by geographic region. Seeds from all populations were infected with Curvularia and most were infected with Sorosporium. Surface sterilization with up to a 10% bleach solution did not eliminate pathogens on otherwise viable, healthy seeds suggesting that internal seed tissues may have harbored infection. The high level of non-viable seeds implies that large quantities of seeds are required in order to meet restoration objectives and that caution should be exercised if inter-population seed movement is needed.