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Entangled effects of allelic and clonal (genotypic) richness in the resistance and resilience of experimental populations of the seagrass Zostera noltii to diatom invasion.

Massa SI, Paulino CM, Serrão EA, Duarte CM, Arnaud-Haond S - BMC Ecol. (2013)

Bottom Line: They also show that at the low genotypic (i.e. clonal) richness levels used in prior experimental approaches, the effects of genotypic and allelic richness could not be disentangled and allelic richness was a likely hidden treatment explaining at least part of the effects hitherto attributed to genotypic richness.Altogether, these results emphasize the need to acknowledge and take into account the interdependency of both genotypic and allelic richness in experimental designs attempting to estimate their importance alone or in combination.These results, on the key species structuring of one of the most threatened coastal ecosystem worldwide, seagrass meadows, support the need to better take into account the distinct compartments of clonal and genetic diversity in management strategies, and in possible restoration plans in the future.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFREMER, Bd Jean Monnet, BP 171, Sète 34203, France. Sophie.Arnaud@ifremer.fr.

ABSTRACT

Background: The relationship between species diversity and components of ecosystem stability has been extensively studied, whilst the influence of the genetic component of biodiversity remains poorly understood. Here we manipulated both genotypic and allelic richness of the seagrass Zostera noltii, in order to explore their respective influences on the resistance of the experimental population to stress. Thus far intra-specific diversity was seldom taken into account in management plans, and restoration actions showed very low success. Information is therefore needed to understand the factors affecting resistance and resilience of populations.

Results: Our results show a positive influence of both allelic and genotypic richness on the resistance of meadows to environmental perturbations. They also show that at the low genotypic (i.e. clonal) richness levels used in prior experimental approaches, the effects of genotypic and allelic richness could not be disentangled and allelic richness was a likely hidden treatment explaining at least part of the effects hitherto attributed to genotypic richness.

Conclusions: Altogether, these results emphasize the need to acknowledge and take into account the interdependency of both genotypic and allelic richness in experimental designs attempting to estimate their importance alone or in combination. A positive influence of allelic richness on resistance to perturbations, and of allelic richness combined with genotypic richness on the recovery (resilience) of the experimental populations is supported by differential mortality. These results, on the key species structuring of one of the most threatened coastal ecosystem worldwide, seagrass meadows, support the need to better take into account the distinct compartments of clonal and genetic diversity in management strategies, and in possible restoration plans in the future.

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Ideal vs. possible experimental designs. 1a) Ideal experimental design for each of the 4 plots containing 9 subplots of 27 shoots, with crossed levels of genotypic and allelic richness designed to disentangle their respective effects. b) Frequency distribution of allelic richness (in total number of alleles) across the three levels of genotypic richness (3 MLGs in light grey, 6 MLGs in medium grey and 9 MLGs in dark grey). c) Evolution of allelic richness for a broader range of levels of genotypic richness. d) Best possible design at the levels of genotypic richness manipulated in the experiments, illustrating the composition of each of the 4 plots made of 9 subplots of 27 shoots each, in terms of allelic richness with increasing levels of genotypic richness. The schemes of plot are designed with nested and increasing orders of richness for illustrative proposes, but the positions of the 36 sub-plots in the aquaculture tank where the experiment took place were randomized.
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Figure 1: Ideal vs. possible experimental designs. 1a) Ideal experimental design for each of the 4 plots containing 9 subplots of 27 shoots, with crossed levels of genotypic and allelic richness designed to disentangle their respective effects. b) Frequency distribution of allelic richness (in total number of alleles) across the three levels of genotypic richness (3 MLGs in light grey, 6 MLGs in medium grey and 9 MLGs in dark grey). c) Evolution of allelic richness for a broader range of levels of genotypic richness. d) Best possible design at the levels of genotypic richness manipulated in the experiments, illustrating the composition of each of the 4 plots made of 9 subplots of 27 shoots each, in terms of allelic richness with increasing levels of genotypic richness. The schemes of plot are designed with nested and increasing orders of richness for illustrative proposes, but the positions of the 36 sub-plots in the aquaculture tank where the experiment took place were randomized.

Mentions: Genotyping of the 376 collected clones returned a total of 343 individuals, fully-genotyped at all loci, of which 164 were distinct MLGs. Allelic richness in one thousand possible combinations of 3, 6 and 9 genotypes ranged from 16 to 31 at G = 3, 24 to 42 at G = 6, and 31 to 48 at G = 9 (Figure 1d), with hardly any overlap between the minimum and the maximum levels (Figure 1b, c). A strong correlation between genotypic and allelic richness was observed at the lower levels of genotypic richness, between 1 and 20 (Figure 1b, c), representative of levels commonly manipulated in experiments (r = 0.904, p < 0.001), although it became marginal at higher levels of genotypic richness more typically observed in natural meadows (G > 20). Across 1000 combinations, Â was 23.93 ± 2.63 for G = 3, 33.44 ± 2.97 for G = 6 and 39.39 ± 2.96 for G = 9, and specific low, medium and high levels of allelic richness had to be defined independently for each MLG level. As a result, identical levels of allelic richness could not be standardized for the three genotypic richness levels, and a fractional factorial design was obtained with five levels corresponding to 16, 25, 31, 41 and 47 alleles to distribute among low, medium and high levels of genotypic richness as detailed in Table 2 (Figure 1d). These levels were therefore not equivalent among genotypic richness plots. As an example, the highest level of allelic richness in plots with three genotypes was the same as the intermediate level for 6 genotypes and the lowest level for 9 genotypes (Figure 1d). There was a clear increase in allelic richness levels parallel to the increase in genotypic richness (Figures 1, 2). As a consequence, combined effects of allelic and genotypic diversities could not be simply disentangled through a two-way ANOVA analysis.


Entangled effects of allelic and clonal (genotypic) richness in the resistance and resilience of experimental populations of the seagrass Zostera noltii to diatom invasion.

Massa SI, Paulino CM, Serrão EA, Duarte CM, Arnaud-Haond S - BMC Ecol. (2013)

Ideal vs. possible experimental designs. 1a) Ideal experimental design for each of the 4 plots containing 9 subplots of 27 shoots, with crossed levels of genotypic and allelic richness designed to disentangle their respective effects. b) Frequency distribution of allelic richness (in total number of alleles) across the three levels of genotypic richness (3 MLGs in light grey, 6 MLGs in medium grey and 9 MLGs in dark grey). c) Evolution of allelic richness for a broader range of levels of genotypic richness. d) Best possible design at the levels of genotypic richness manipulated in the experiments, illustrating the composition of each of the 4 plots made of 9 subplots of 27 shoots each, in terms of allelic richness with increasing levels of genotypic richness. The schemes of plot are designed with nested and increasing orders of richness for illustrative proposes, but the positions of the 36 sub-plots in the aquaculture tank where the experiment took place were randomized.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3818440&req=5

Figure 1: Ideal vs. possible experimental designs. 1a) Ideal experimental design for each of the 4 plots containing 9 subplots of 27 shoots, with crossed levels of genotypic and allelic richness designed to disentangle their respective effects. b) Frequency distribution of allelic richness (in total number of alleles) across the three levels of genotypic richness (3 MLGs in light grey, 6 MLGs in medium grey and 9 MLGs in dark grey). c) Evolution of allelic richness for a broader range of levels of genotypic richness. d) Best possible design at the levels of genotypic richness manipulated in the experiments, illustrating the composition of each of the 4 plots made of 9 subplots of 27 shoots each, in terms of allelic richness with increasing levels of genotypic richness. The schemes of plot are designed with nested and increasing orders of richness for illustrative proposes, but the positions of the 36 sub-plots in the aquaculture tank where the experiment took place were randomized.
Mentions: Genotyping of the 376 collected clones returned a total of 343 individuals, fully-genotyped at all loci, of which 164 were distinct MLGs. Allelic richness in one thousand possible combinations of 3, 6 and 9 genotypes ranged from 16 to 31 at G = 3, 24 to 42 at G = 6, and 31 to 48 at G = 9 (Figure 1d), with hardly any overlap between the minimum and the maximum levels (Figure 1b, c). A strong correlation between genotypic and allelic richness was observed at the lower levels of genotypic richness, between 1 and 20 (Figure 1b, c), representative of levels commonly manipulated in experiments (r = 0.904, p < 0.001), although it became marginal at higher levels of genotypic richness more typically observed in natural meadows (G > 20). Across 1000 combinations, Â was 23.93 ± 2.63 for G = 3, 33.44 ± 2.97 for G = 6 and 39.39 ± 2.96 for G = 9, and specific low, medium and high levels of allelic richness had to be defined independently for each MLG level. As a result, identical levels of allelic richness could not be standardized for the three genotypic richness levels, and a fractional factorial design was obtained with five levels corresponding to 16, 25, 31, 41 and 47 alleles to distribute among low, medium and high levels of genotypic richness as detailed in Table 2 (Figure 1d). These levels were therefore not equivalent among genotypic richness plots. As an example, the highest level of allelic richness in plots with three genotypes was the same as the intermediate level for 6 genotypes and the lowest level for 9 genotypes (Figure 1d). There was a clear increase in allelic richness levels parallel to the increase in genotypic richness (Figures 1, 2). As a consequence, combined effects of allelic and genotypic diversities could not be simply disentangled through a two-way ANOVA analysis.

Bottom Line: They also show that at the low genotypic (i.e. clonal) richness levels used in prior experimental approaches, the effects of genotypic and allelic richness could not be disentangled and allelic richness was a likely hidden treatment explaining at least part of the effects hitherto attributed to genotypic richness.Altogether, these results emphasize the need to acknowledge and take into account the interdependency of both genotypic and allelic richness in experimental designs attempting to estimate their importance alone or in combination.These results, on the key species structuring of one of the most threatened coastal ecosystem worldwide, seagrass meadows, support the need to better take into account the distinct compartments of clonal and genetic diversity in management strategies, and in possible restoration plans in the future.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFREMER, Bd Jean Monnet, BP 171, Sète 34203, France. Sophie.Arnaud@ifremer.fr.

ABSTRACT

Background: The relationship between species diversity and components of ecosystem stability has been extensively studied, whilst the influence of the genetic component of biodiversity remains poorly understood. Here we manipulated both genotypic and allelic richness of the seagrass Zostera noltii, in order to explore their respective influences on the resistance of the experimental population to stress. Thus far intra-specific diversity was seldom taken into account in management plans, and restoration actions showed very low success. Information is therefore needed to understand the factors affecting resistance and resilience of populations.

Results: Our results show a positive influence of both allelic and genotypic richness on the resistance of meadows to environmental perturbations. They also show that at the low genotypic (i.e. clonal) richness levels used in prior experimental approaches, the effects of genotypic and allelic richness could not be disentangled and allelic richness was a likely hidden treatment explaining at least part of the effects hitherto attributed to genotypic richness.

Conclusions: Altogether, these results emphasize the need to acknowledge and take into account the interdependency of both genotypic and allelic richness in experimental designs attempting to estimate their importance alone or in combination. A positive influence of allelic richness on resistance to perturbations, and of allelic richness combined with genotypic richness on the recovery (resilience) of the experimental populations is supported by differential mortality. These results, on the key species structuring of one of the most threatened coastal ecosystem worldwide, seagrass meadows, support the need to better take into account the distinct compartments of clonal and genetic diversity in management strategies, and in possible restoration plans in the future.

Show MeSH