Ecosystem recovery after climatic extremes enhanced by genotypic diversity

Abstract

Contemporary climate change is characterized both by increasing mean temperature and increasing climate variability such as heat waves, storms, and floods. How populations and communities cope with such climatic extremes is a question central to contemporary ecology and biodiversity conservation. Previous work has shown that species diversity can affect ecosystem functioning and resilience. Here, we show that genotypic diversity can replace the role of species diversity in a species-poor coastal ecosystem, and it may buffer against extreme climatic events. In a manipulative field experiment, increasing the genotypic diversity of the cosmopolitan seagrass Zostera marina enhanced biomass production, plant density, and faunal abundance, despite near-lethal water temperatures due to extreme warming across Europe. Net biodiversity effects were explained by genotypic complementarity rather than by selection of particularly robust genotypes. Positive effects on invertebrate fauna suggest that genetic diversity has second-order effects reaching higher trophic levels. Our results highlight the importance of maintaining genetic as well as species diversity to enhance ecosystem resilience in a world of increasing uncertainty.

Fig. 1.

Water temperature and eelgrass growth. (A) Water temperatures from direct measurements at the experimental site, and predicted vales from a 45 km distant measurement point. The critical temperatures above which Z. marina ceases growing, or starts dying off, are depicted by dashed lines. (B and C) Comparison of mean leaf shoot density (±1 SE) among one-, three-, and six-genotype treatments, and among the six target genotypes, A–F, as monocultures (n = 4) is shown. B also gives natural shoot densities at the experimental site. Data points are set off for clarity. Asterisks indicate results of general linear models including blocking factor, initial density as covariate, and genotypic diversity as continuous predictor at each date. *, P < 0.05; **, P < 0.01.

Fig. 2.

Effects of increasing genotypic diversity on eelgrass (Z. marina) and associated fauna. Shoot number, square-root transformed (A), and dry biomass, log₁₀ transformed (B), in eelgrass (Z. marina) plots as functions of their genotypic diversity. (C–F) Comparisons of the abundance of associated invertebrates (abundance log₁₀ transformed). Regression models take spatial heterogeneity (blocking factor) into account. Shaded circles in A and B indicate treatment means. DW, dry weight.

Fig. 3.

Rate of increase in leaf shoots (final/planted) of eelgrass genotypes A–F in monocultures and in three- and six-genotype treatments.