Geographic divergence in a species‐rich symbiosis: interactions between Monterey pines and ectomycorrhizal fungi

Hoeksema, Jason D.; Hernández, José Falcón; Rogers, Deborah L.; Mendoza, Luciana Luna; Thompson, John N.

doi:10.1890/11-1715.1

Cited by 35 publications

(34 citation statements)

References 38 publications

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“…The number of different genes involved shows the potential for plants to evolve independently in their interactions with different EM fungal species, as no SNPs were detected associating with more than one trait. These results build on previous phenotypic studies suggesting independent host plant associations with different EM fungi (e.g., Hoeksema et al, ). The percentage of phenotypic variance in mycorrhizal traits attributed to marker effects ( R 2 ) ranged from 0.13 to 0.55 (Table ), which is relatively high, suggesting at least these few genes identified here are responsible for a majority of the variation detected.…”

Section: Discussionsupporting

confidence: 90%

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

et al. 2019

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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.

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Section: Discussionsupporting

confidence: 90%

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

et al. 2019

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“…Single nucleotide polymorphisms (SNPs) were identified using a maximum‐likelihood approach implemented in the RAD Population Genomics Program (Hohenlohe et al. , ).…”

Section: Methodsmentioning

confidence: 99%

Intrapopulation genomics in a model mutualist: Population structure and candidate symbiosis genes under selection in Medicago truncatula

et al. 2016

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Bottom-up evolutionary approaches, including geographically explicit population genomic analyses, have the power to reveal the mechanistic basis of adaptation. Here, we conduct a population genomic analysis in the model legume, Medicago truncatula, to characterize population genetic structure and identify symbiosis-related genes showing evidence of spatially variable selection. Using RAD-seq, we generated over 26,000 SNPs from 191 accessions from within three regions of the native range in Europe. Results from STRUCTURE analysis identify five distinct genetic clusters with divisions that separate east and west regions in the Mediterranean basin. Much of the genetic variation is maintained within sampling sites, and there is evidence for isolation by distance. Extensive linkage disequilibrium was identified, particularly within populations. We conducted genetic outlier analysis with F -based genome scans and a Bayesian modeling approach (PCAdapt). There were 70 core outlier loci shared between these distinct methods with one clear candidate symbiosis related gene, DMI1. This work sets that stage for functional experiments to determine the important phenotypes that selection has acted upon and complementary efforts in rhizobium populations.

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“…When examined as a clinal pattern, pine growth did not vary with distance between host and fungal populations of origin. In another pot experiment, Hoeksema, Hernandez, Rogers, Mendoza, and Thompson () found no evidence for local adaptation of Pinus radiata populations to soils; in fact, plant relative growth rate was lower in sympatric combinations of plants and soils (suggesting possible maladaptation), although the precise characteristics of soils (chemical properties or composition of pathogenic or EM fungi) underlying this pattern could not be ascertained. Across 32 combinations of soil origin and seedling response of Pseudotsuga menziesii , only six showed local adaptation mediated by soil fungi alone (Pickles, Twieg, O'Neill, Mohn, & Simard, ).…”

Section: Discussionmentioning

confidence: 98%

Tree species with limited geographical ranges show extreme responses to ectomycorrhizas

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et al. 2018

Global Ecol Biogeogr

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Aim At continental scales, abiotic factors such as climate are typically used to explain differences in plant ranges. Although biotic interactions also underlie the biogeography of plants, the importance of plant‐associated microbes is often overlooked when predicting ranges. In particular, symbiotic microbes may influence the distribution of plants that engage in strong interactions with them. We tested whether seedling response to inoculation by ectomycorrhizal fungi explains range size of trees. To examine mechanisms underlying the relationship between range size and response to inoculation, we also examined to what extent sympatry between host and fungi influenced this relationship. Location Global. Time period Contemporary. Major taxa studied Trees and fungi forming ectomycorrhizas. Methods Using a dataset of 1,275 observations from 126 papers, we calculated mean biomass response (effect size) of 59 tree species to fungal inoculation. We extracted host range area from digitized maps of native distributions, and determined whether hosts were naturally sympatric with fungal species used as inoculum by searching herbaria databases with geospatially referenced data. Results Tree species with seedling effect sizes falling above or below the average response tended to have small ranges and those with average responses, large ranges. Moreover, hosts inoculated with fungi whose ranges were allopatric to their own had higher biomass compared to those that were inoculated by sympatric fungi, suggesting that the extent of geographical overlap between trees and symbiotic fungi may attenuate the mutualism. Main conclusions We demonstrate that mycorrhizas may underlie host biogeographical patterns at the continental scale. Our study is novel in the scope of species and scale tested, and points to a possible mechanism underlying this pattern related to the process of mutualism breakdown accruing over time at local geographical scales. For ectomycorrhizal tree species, performance may increase when exposed to fungal partners without a recent shared evolutionary history.

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Geographic divergence in a species‐rich symbiosis: interactions between Monterey pines and ectomycorrhizal fungi

Cited by 35 publications

References 38 publications

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

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

Intrapopulation genomics in a model mutualist: Population structure and candidate symbiosis genes under selection in Medicago truncatula

Tree species with limited geographical ranges show extreme responses to ectomycorrhizas

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