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A meta-analysis of local adaptation in plants.

Leimu R, Fischer M - PLoS ONE (2008)

Bottom Line: We show that, overall, local plants performed significantly better than foreign plants at their site of origin: this was found to be the case in 71.0% of the studied sites.Furthermore, we found local adaptation much more common for large plant populations (>1000 flowering individuals) than for small populations (<1000 flowering individuals) for which local adaptation was very rare.Our results suggest that local adaptation is less common in plant populations than generally assumed.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany. roosa.leimu@plants.ox.ac.uk

ABSTRACT
Local adaptation is of fundamental importance in evolutionary, population, conservation, and global-change biology. The generality of local adaptation in plants and whether and how it is influenced by specific species, population and habitat characteristics have, however, not been quantitatively reviewed. Therefore, we examined published data on the outcomes of reciprocal transplant experiments using two approaches. We conducted a meta-analysis to compare the performance of local and foreign plants at all transplant sites. In addition, we analysed frequencies of pairs of plant origin to examine whether local plants perform better than foreign plants at both compared transplant sites. In both approaches, we also examined the effects of population size, and of the habitat and species characteristics that are predicted to affect local adaptation. We show that, overall, local plants performed significantly better than foreign plants at their site of origin: this was found to be the case in 71.0% of the studied sites. However, local plants performed better than foreign plants at both sites of a pair-wise comparison (strict definition of local adaption) only in 45.3% of the 1032 compared population pairs. Furthermore, we found local adaptation much more common for large plant populations (>1000 flowering individuals) than for small populations (<1000 flowering individuals) for which local adaptation was very rare. The degree of local adaptation was independent of plant life history, spatial or temporal habitat heterogeneity, and geographic scale. Our results suggest that local adaptation is less common in plant populations than generally assumed. Moreover, our findings reinforce the fundamental importance of population size for evolutionary theory. The clear role of population size for the ability to evolve local adaptation raises considerable doubt on the ability of small plant populations to cope with changing environments.

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Conceptual graphs of the possible combinations of reaction norms for fitness and corresponding effect sizes (Hedges' d).The effect size measures the difference in fitness of foreign and local plants (“a” or “b”) at one site (“A” or “B”). A positive effect size indicates that local plants perform better than foreign plants at their site of origin. A) The case where local plants perform better than foreign plants at both compared sites, i.e. where the reaction norms for fitness cross and both effect sizes are positive ( = POS-POS). B, C) Plants of one origin (“A”) perform better at both compared sites. In this case of non-crossing reaction norms for fitness one effect size is positive and one is negative ( = POS-NEG). The resulting mean effect size can be positive (B) or negative (C). D) Foreign plants perform better than local plants at both sites indicating maladaptation (effect sizes negative = NEG-NEG).
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pone-0004010-g001: Conceptual graphs of the possible combinations of reaction norms for fitness and corresponding effect sizes (Hedges' d).The effect size measures the difference in fitness of foreign and local plants (“a” or “b”) at one site (“A” or “B”). A positive effect size indicates that local plants perform better than foreign plants at their site of origin. A) The case where local plants perform better than foreign plants at both compared sites, i.e. where the reaction norms for fitness cross and both effect sizes are positive ( = POS-POS). B, C) Plants of one origin (“A”) perform better at both compared sites. In this case of non-crossing reaction norms for fitness one effect size is positive and one is negative ( = POS-NEG). The resulting mean effect size can be positive (B) or negative (C). D) Foreign plants perform better than local plants at both sites indicating maladaptation (effect sizes negative = NEG-NEG).

Mentions: However, in the strict sense (sensu Kawecki and Ebert [12]) examining local adaptation requires comparing the performance of local and foreign plants in a reciprocal manner between two sites or habitat. Therefore, we also took another approach in which we tested whether local plants perform better than foreign plants at both transplanting sites, i.e. pairs of plant origin, which would indicate divergent selection and thus more rigorous evidence for local adaptation [12]. Because the standard meta-analytical techniques do not allow such analysis we analyzed the frequencies of cases where the measures of plant performance were higher for local plants at both sites (“POS-POS”- case of crossing reaction norms, where both effect sizes are positive, Fig. 1a), at only one site (“POS-NEG”-case of non-crossing reaction norms, Fig. 1b, c), or at none of the two sites (“NEG-NEG”- case of crossing reaction norms, Fig. 1d).


A meta-analysis of local adaptation in plants.

Leimu R, Fischer M - PLoS ONE (2008)

Conceptual graphs of the possible combinations of reaction norms for fitness and corresponding effect sizes (Hedges' d).The effect size measures the difference in fitness of foreign and local plants (“a” or “b”) at one site (“A” or “B”). A positive effect size indicates that local plants perform better than foreign plants at their site of origin. A) The case where local plants perform better than foreign plants at both compared sites, i.e. where the reaction norms for fitness cross and both effect sizes are positive ( = POS-POS). B, C) Plants of one origin (“A”) perform better at both compared sites. In this case of non-crossing reaction norms for fitness one effect size is positive and one is negative ( = POS-NEG). The resulting mean effect size can be positive (B) or negative (C). D) Foreign plants perform better than local plants at both sites indicating maladaptation (effect sizes negative = NEG-NEG).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2602971&req=5

pone-0004010-g001: Conceptual graphs of the possible combinations of reaction norms for fitness and corresponding effect sizes (Hedges' d).The effect size measures the difference in fitness of foreign and local plants (“a” or “b”) at one site (“A” or “B”). A positive effect size indicates that local plants perform better than foreign plants at their site of origin. A) The case where local plants perform better than foreign plants at both compared sites, i.e. where the reaction norms for fitness cross and both effect sizes are positive ( = POS-POS). B, C) Plants of one origin (“A”) perform better at both compared sites. In this case of non-crossing reaction norms for fitness one effect size is positive and one is negative ( = POS-NEG). The resulting mean effect size can be positive (B) or negative (C). D) Foreign plants perform better than local plants at both sites indicating maladaptation (effect sizes negative = NEG-NEG).
Mentions: However, in the strict sense (sensu Kawecki and Ebert [12]) examining local adaptation requires comparing the performance of local and foreign plants in a reciprocal manner between two sites or habitat. Therefore, we also took another approach in which we tested whether local plants perform better than foreign plants at both transplanting sites, i.e. pairs of plant origin, which would indicate divergent selection and thus more rigorous evidence for local adaptation [12]. Because the standard meta-analytical techniques do not allow such analysis we analyzed the frequencies of cases where the measures of plant performance were higher for local plants at both sites (“POS-POS”- case of crossing reaction norms, where both effect sizes are positive, Fig. 1a), at only one site (“POS-NEG”-case of non-crossing reaction norms, Fig. 1b, c), or at none of the two sites (“NEG-NEG”- case of crossing reaction norms, Fig. 1d).

Bottom Line: We show that, overall, local plants performed significantly better than foreign plants at their site of origin: this was found to be the case in 71.0% of the studied sites.Furthermore, we found local adaptation much more common for large plant populations (>1000 flowering individuals) than for small populations (<1000 flowering individuals) for which local adaptation was very rare.Our results suggest that local adaptation is less common in plant populations than generally assumed.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany. roosa.leimu@plants.ox.ac.uk

ABSTRACT
Local adaptation is of fundamental importance in evolutionary, population, conservation, and global-change biology. The generality of local adaptation in plants and whether and how it is influenced by specific species, population and habitat characteristics have, however, not been quantitatively reviewed. Therefore, we examined published data on the outcomes of reciprocal transplant experiments using two approaches. We conducted a meta-analysis to compare the performance of local and foreign plants at all transplant sites. In addition, we analysed frequencies of pairs of plant origin to examine whether local plants perform better than foreign plants at both compared transplant sites. In both approaches, we also examined the effects of population size, and of the habitat and species characteristics that are predicted to affect local adaptation. We show that, overall, local plants performed significantly better than foreign plants at their site of origin: this was found to be the case in 71.0% of the studied sites. However, local plants performed better than foreign plants at both sites of a pair-wise comparison (strict definition of local adaption) only in 45.3% of the 1032 compared population pairs. Furthermore, we found local adaptation much more common for large plant populations (>1000 flowering individuals) than for small populations (<1000 flowering individuals) for which local adaptation was very rare. The degree of local adaptation was independent of plant life history, spatial or temporal habitat heterogeneity, and geographic scale. Our results suggest that local adaptation is less common in plant populations than generally assumed. Moreover, our findings reinforce the fundamental importance of population size for evolutionary theory. The clear role of population size for the ability to evolve local adaptation raises considerable doubt on the ability of small plant populations to cope with changing environments.

Show MeSH
Related in: MedlinePlus