Genetic rescue versus outbreeding depression in Vallisneria americana: Implications for mixing seed sources for restoration

• Published in: Biological conservation 2013-11, Vol.167, p.203-214
• Main Authors: Marsden, Brittany W., Engelhardt, Katharina A.M., Neel, Maile C.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Aquatic plants; Biological and medical sciences; Celery; Chesapeake Bay; Conservation, protection and management of environment and wildlife; crossing; Depression; Differentiation; Environmental degradation: ecosystems survey and restoration; Fundamental and applied biological sciences. Psychology; General aspects; genetic relationships; genetic variation; Genetics; Germination; Inbreeding; inbreeding depression; Local adaptation; mixing; outbreeding; outbreeding depression; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; planning; Plant population restoration; Raw materials; Relatedness; Restoration; risk; Sea water ecosystems; Seeds; Submersed aquatic vegetation; Synecology; Vallisneria americana
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2013.08.012

•Vallisneria americana were crossed within and among populations and regions.•Population differences in seed production and germination suggest local adaptation.•No indication of widespread risks of inbreeding or outbreeding depression.•Reproductive success was not related to genetic relatedness or diversity.•Differentiation among and inbreeding within populations vary independently. The selection of seed stock for restoration remains a complex issue. Using local stock reduces the chances of outbreeding depression or genetic dilution, whereas mixing sources may increase diversity and counteract inbreeding depression. Evaluation of these opposing approaches remains difficult when planning a restoration project but is needed to increase chances of long-term population persistence. We evaluated seed production and germination success of seeds from controlled reproductive crosses of the submersed aquatic plant Vallisneria americana (wild celery) collected from populations throughout the Chesapeake Bay. We assessed differences in seeds, capsules, and germination success in three types of crosses: (1) individuals within-populations, (2) among-populations but within-genetically differentiated regions, and (3) among-regions. We observed population level differences in within-population and among-region crosses. Levels of genetic relatedness among individuals, genetic diversity within populations, or differentiation across populations did not predict reproductive success. Our data show that mixing sources from different populations and regions has both benefits and drawbacks. Thus, minimizing the risks of outbreeding and inbreeding depression, presented as a mostly dichotomous issue in the restoration literature, is not an either-or issue in V. americana.