Genetic diversity of seagrass seeds influences seedling morphology and biomass

Abstract

Genetic diversity can influence ecological processes throughout ontogeny, yet whether diversity at early life history stages is important in long-lived taxa with overlapping generations is unclear. Seagrass systems provide some of the best evidence for the ecological effects of genetic diversity among adult shoots, but we do not know if the genetic diversity of seeds and seedlings also influences seagrass ecology. We tested the effects of seagrass (Zostera marina) seed diversity and relatedness on germination success, seedling morphology, and seedling production by comparing experimental assemblages of seeds collected from single reproductive shoots ("monocultures") to assemblages of seeds collected from multiple reproductive shoots ("polycultures"). There was no difference in seedling emergence, yet seedlings from polycultures had larger shoots above and below ground than seedlings from monocultures at the end of the 1-yr experiment. Genetic relatedness of the seedlings predicted some aspects of shoot morphology, with more leaves and longer roots and shoots at intermediate levels of relatedness, regardless of seed diversity. Our results suggest that studies of only adult stages may underestimate the importance of genetic diversity if the benefits at early life history stages continue to accrue throughout the life cycle.

Canopy-Mediated Hydrodynamics Contributes to Greater Allelic Richness in Seeds Produced Higher in Meadows of the Coastal Eelgrass Zostera marina

“…Data is available from the authors upon request. sibling seeds in a greenhouse mesocosm experiment (Randall Hughes et al, 2016). Thus, the physical processes that affect pollen delivery in the nearshore environment impact both seed quantity and quality, and this can have important ramifications for population dynamics and genetic structure in eelgrass meadows.…”

Multiple paternity, fertilization success, and male quality: Mating system variation in the eelgrass, Zostera marina

“…Because they rely heavily on sexual reproduction, southern edge‐of‐range meadows may represent valuable genetic diversity hotspots among Z. marina populations (Diekmann & Serrão, 2012 ). Importantly, in Z. marina , genotypic diversity has been associated with resistance and resilience to natural disturbances (Hughes & Stachowicz, 2004 , 2009 , 2011 ; Reusch et al., 2005 ), and allelic richness and relatedness have both been linked to increased biomass and productivity (Hughes et al., 2016 ; Stachowicz et al., 2013 ). Therefore, the mating system can be especially influential in genetic diversity hotspots by impacting standing levels of variation within these populations.…”