Genetic diversity enhances the resistance of a seagrass ecosystem to disturbance

Abstract

Motivated by recent global reductions in biodiversity, empirical and theoretical research suggests that more species-rich systems exhibit enhanced productivity, nutrient cycling, or resistance to disturbance or invasion relative to systems with fewer species. In contrast, few data are available to assess the potential ecosystemlevel importance of genetic diversity within species known to play a major functional role. Using a manipulative field experiment, we show that increasing genotypic diversity in a habitat-forming species (the seagrass Zostera marina) enhances community resistance to disturbance by grazing geese. The time required for recovery to near predisturbance densities also decreases with increasing eelgrass genotypic diversity. However, there is no effect of diversity on resilience, measured as the rate of shoot recovery after the disturbance, suggesting that more rapid recovery in diverse plots is due solely to differences in disturbance resistance. Genotypic diversity did not affect ecosystem processes in the absence of disturbance. Thus, our results suggest that genetic diversity, like species diversity, may be most important for enhancing the consistency and reliability of ecosystems by providing biological insurance against environmental change.

Ecosystem recovery after climatic extremes enhanced by genotypic diversity

“…Other recent work supports a role for genotypic diversity, particularly under disturbance (35). Whereas that study found only transient effects after intense bird grazing, we find strong effects that persist over at least one growth period.…”

“…This result contrasts markedly with several independent experiments that used a similar planting technique during normal climatic conditions; these experiments consistently showed low mortality and a 3-fold increase in shoot density from May through August (30,34), making it unlikely that transplant shock was responsible for this decline (but see ref. 35). During the first major warming event at the beginning of June, unusual signs of heat-stressrelated mortality were already present (discolored meristems, root necrosis, and leaf loss).…”

Community genetics: what have we accomplished and where should we be going?

“…At the patch and population level, increasing genetic diversity (e.g. number of genotypes) increases diversity of associated arthropod communities, confers greater resilience to biotic and abiotic stressors, and affects key aspects of ecosystem function [21,27,28,[31][32][33][34][35]. Recently, studies have begun to extend the scope of community genetics research to examine how genetic variation and population divergence within herbivorous insects, endosymbionts [36][37][38] and predaceous fishes [39][40][41][42] have cascading bottom-up and topdown effects within communities.…”

Complementarity in marine biodiversity manipulations: Reconciling divergent evidence from field and mesocosm experiments

“…Still, even among marine studies, confounded variation in systems and methodologies hampers efforts to explain differences in outcome. Although longer-term studies do tend to find strong effects, these studies are also from colder temperate regions, are conducted intertidally, and are in the field (14)(15)(16). In contrast, studies that find weak or no effects often involve subtidal taxa and are shorter term and/or conducted in mesocosms (7,8,17).…”