Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis, and the potential for selection mosaics

<p>Abstract</p> <p>Background</p> <p>Geographic selection mosaics, in which species exert different evolutionary impacts on each other in different environments, may drive diversification in coevolving species. We studied the potential for geographic selection mosaics in plant-mycorrhizal interactions by testing whether the interaction between bishop pine (<it>Pinus muricata </it>D. Don) and one of its common ectomycorrhizal fungi (<it>Rhizopogon occidentalis </it>Zeller and Dodge) varies in outcome, when different combinations of plant and fungal genotypes are tested under a range of different abiotic and biotic conditions.</p> <p>Results</p> <p>We used a 2 × 2 × 2 × 2 factorial experiment to test the main and interactive effects of plant lineage (two maternal seed families), fungal lineage (two spore collections), soil type (lab mix or field soil), and non-mycorrhizal microbes (with or without) on the performance of plants and fungi. Ecological outcomes, as assessed by plant and fungal performance, varied widely across experimental environments, including interactions between plant or fungal lineages and soil environmental factors.</p> <p>Conclusion</p> <p>These results show the potential for selection mosaics in plant-mycorrhizal interactions, and indicate that these interactions are likely to coevolve in different ways in different environments, even when initially the genotypes of the interacting species are the same across all environments. Hence, selection mosaics may be equally as effective as genetic differences among populations in driving divergent coevolution among populations of interacting species.</p

The Effect of Local Adaptation on Mycorrhizal Fungi-host Relationships

Background/Question/Methods The successful establishment of a species in a new environment is a result of the complex interaction of genetic, biotic and abiotic factors. Local adaptation, defined as the differential success of genotypes in their native environment relative to a foreign environment, may be one mechanism by which genetic diversity can be maintained within a species; however, it may also lead to divergence of populations and possibly even lead to speciation. Mycorrhizal fungi form symbiotic relationships with 80% of terrestrial plants. These relationships are characterized by the exchange of soil nutrients for carbon from the host. These fungi have been shown to affect essential host traits associated with biotic and to alter competitive interactions within and among plant species. Given the ubiquitous nature of mycorrhizal associations, studies examining plant local adaptation that do not take into account this essential interaction may be missing an important factor in the ability of a plant population to adapt to the environment. Using meta-analysis on a data set comprised of 1591 studies (from 178 papers), we explored the role local adaptation—as determined by relative geographic origin of the plant, fungi, and soil—plays in altering plant response to mycorrhizal fungi. Results/Conclusions Regardless of whether plant, fungus, and/or soil originate in sympatry (same origin) or in allopatry (different origin), the mean effect size of mycorrhizal inoculum on host biomass was positive, emphasizing the mutualistic nature of mycorrhizal fungi relationships. The effect was larger when the plant and fungus originated in sympatry compared to allopatry. Similarly, the effect of mycorrhizal inoculum on host biomass was also larger when the plant and soil originated in sympatry. There was no significant effect of fungal-soil relative origin on effect size. Overall, these results indicate that the effect of mycorrhizal inoculum is positive, but that plant adaptation to local soils and mycorrhizal fungi plays a significant role in altering this effect. While further analyses which account for other sources of variation in experimental outcomes may provide more precise estimates of the importance of local adaptation in mycorrhizal interactions, future experiments considering mycorrhizal fungal relationships should take into account the relative geographic origin of mycorrhiza and the soil used in their experiments

Data from: Genetically determined fungal pathogen tolerance and soil variation influences ectomycorrhizal traits of loblolly pine

1. Selection on genetically correlated traits within species can create indirect effects on one trait by selection on another. The consequences of these trait correlations are of interest because they may influence how suites of traits within species evolve under differing selection pressures, both natural and artificial. 2. By utilizing genetic families of loblolly pine either tolerant (t) or susceptible (s) to two different suites of pathogenic fungi responsible for causing either pine decline (PD) or fusiform rust (FR) disease, we investigated trait variation and trait correlations within loblolly pine (Pinus taeda L.) by determining how ectomycorrhizal (EM) colonization relates to pathogen susceptibility. 3. We detected interactions between susceptibility to pathogenic fungi and soil inoculation source on loblolly pine compatibility with the EM fungi Thelephora, and on relative growth rate of loblolly pine. Additionally, we detected spatial variation in the loblolly pine – EM fungi interaction, and found that variation in colonization rates by some members of the EM community is not dictated by genetic variation in the host plant but rather soil inoculation source alone. 4. The work presented here illustrates the potential for indirect selection on compatibility with symbiotic EM fungi as a result of selection for resistance to fungal pathogens. Additionally, we present evidence that the host plant does not have a single ‘mycorrhizal trait’ governing interactions with all EM fungi, but rather that it can interact with different fungal taxa independently. 5. Synthesis. An understanding of the genetic architecture of essential traits in focal species is crucial if we are to anticipate and manage the results of natural and artificial selection. As demonstrated here, an essential but often overlooked symbiosis (that between plants and mycorrhizal fungi) may be indirectly influenced by directed selection on the host plant

The Effect of Local Adaptation on Mycorrhizal Fungi-host Relationships

Background/Question/Methods The successful establishment of a species in a new environment is a result of the complex interaction of genetic, biotic and abiotic factors. Local adaptation, defined as the differential success of genotypes in their native environment relative to a foreign environment, may be one mechanism by which genetic diversity can be maintained within a species; however, it may also lead to divergence of populations and possibly even lead to speciation. Mycorrhizal fungi form symbiotic relationships with 80% of terrestrial plants. These relationships are characterized by the exchange of soil nutrients for carbon from the host. These fungi have been shown to affect essential host traits associated with biotic and to alter competitive interactions within and among plant species. Given the ubiquitous nature of mycorrhizal associations, studies examining plant local adaptation that do not take into account this essential interaction may be missing an important factor in the ability of a plant population to adapt to the environment. Using meta-analysis on a data set comprised of 1591 studies (from 178 papers), we explored the role local adaptation—as determined by relative geographic origin of the plant, fungi, and soil—plays in altering plant response to mycorrhizal fungi. Results/Conclusions Regardless of whether plant, fungus, and/or soil originate in sympatry (same origin) or in allopatry (different origin), the mean effect size of mycorrhizal inoculum on host biomass was positive, emphasizing the mutualistic nature of mycorrhizal fungi relationships. The effect was larger when the plant and fungus originated in sympatry compared to allopatry. Similarly, the effect of mycorrhizal inoculum on host biomass was also larger when the plant and soil originated in sympatry. There was no significant effect of fungal-soil relative origin on effect size. Overall, these results indicate that the effect of mycorrhizal inoculum is positive, but that plant adaptation to local soils and mycorrhizal fungi plays a significant role in altering this effect. While further analyses which account for other sources of variation in experimental outcomes may provide more precise estimates of the importance of local adaptation in mycorrhizal interactions, future experiments considering mycorrhizal fungal relationships should take into account the relative geographic origin of mycorrhiza and the soil used in their experiments

Association mapping of ectomycorrhizal traits in loblolly pine (Pinus taeda L.)

To understand how diverse mutualisms coevolve and how species adapt to complex environments, a description of the underlying genetic basis of the traits involved must be provided. For example, in diverse coevolving mutualisms, such as the inter‐ action of host plants with a suite of symbiotic mycorrhizal fungi, a key question is whether host plants can coevolve independently with multiple species of symbionts, which depends on whether those interactions are governed independently by sepa‐ rate genes or pleiotropically by shared genes. To provide insight into this question, we employed an association mapping approach in a clonally replicated field experi‐ ment of loblolly pine (Pinus taeda L.) to identify genetic components of host traits governing ectomycorrhizal (EM) symbioses (mycorrhizal traits). The relative abun‐ dances of different EM fungi as well as the total number of root tips per cm root colo‐ nized by EM fungi were analyzed as separate mycorrhizal traits of loblolly pine. Single‐nucleotide polymorphisms (SNPs) within candidate genes of loblolly pine were associated with loblolly pine mycorrhizal traits, mapped to the loblolly pine genome, and their putative protein function obtained when available. The results support the hypothesis that ectomycorrhiza formation is governed by host genes of large effect that apparently have independent influences on host interactions with different sym‐ biont speciesThe authors thank Tom Byram and the Western Gulf Forest Tree Improvement Program, Texas A&M Forest Service for their contribution to this project. This work was financially supported by the National Science Foundation Plant Genome Research Program award #DBI-0501763 and the US Department of Agriculture National Institute of Food and Agriculture AFRI Applied Plant Genomics CAP award #2009-85606-05680. PJMG was supported by USDA NIFA Award #2011-67009-30030 award to Professor David B. Neale at University of California, Davis. USDA/NRI CSREES Plant Genomics Coordinated Agricultural Project (CAP) Award #2007-55300-18603 generated the SNPs. JDH was supported by National Science Foundation award DEB-1119865Peer reviewe

SNP genotypes and mycorrhizal phenotype data for loblolly pine population in Southern Mississippi

This file contains data for 152 loblolly pine genotypes (column 'Tree'). The next 4512 columns contain SNP marker data, followed by 14 columns of ectomycorrhizal colonization data

Data from: Association mapping of ectomycorrhizal traits in loblolly pine (Pinus taeda L.)

To understand how diverse mutualisms coevolve and how species adapt to complex environments, a description of the underlying genetic basis of the traits involved must be provided. For example, in diverse coevolving mutualisms, such as the interaction of host plants with a suite of symbiotic mycorrhizal fungi, a key question is whether host plants can coevolve independently with multiple species of symbionts, which depends on whether those interactions are governed independently by separate genes or pleiotropically by shared genes. To provide insight into this question, we employed an association mapping approach in a clonally replicated field experiment of loblolly pine (Pinus taeda L.) to identify genetic components of host traits governing ectomycorrhizal (EM) symbioses (mycorrhizal traits). The relative abundances of different EM fungi as well as the total number of root tips per cm root colonized by EM fungi were analyzed as separate mycorrhizal traits of loblolly pine. Single-nucleotide polymorphisms (SNPs) within candidate genes of loblolly pine were associated with loblolly pine mycorrhizal traits, mapped to the loblolly pine genome, and their putative protein function obtained when available. The results support the hypothesis that ectomycorrhiza formation is governed by host genes of large effect that apparently have independent influences on host interactions with different symbiont species

Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis, and the potential for selection mosaics-0

Tion. (b) Root tips colonized per unit root length. Means with different letters are significantly different from each other (< 0.05) according to Tukey HSD tests.<p><b>Copyright information:</b></p><p>Taken from "Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis, and the potential for selection mosaics"</p><p>http://www.biomedcentral.com/1741-7007/6/23</p><p>BMC Biology 2008;6():23-23.</p><p>Published online 28 May 2008</p><p>PMCID:PMC2430191.</p><p></p