Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska

Abstract In root nodule symbioses (RNS) between nitrogen (N)‐fixing bacteria and plants, bacterial symbionts cycle between nodule‐inhabiting and soil‐inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension betwee...

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Main Authors: M. D. Anderson, D. L. Taylor, K. Olson, R. W. Ruess
Format: Article
Language:English
Published: Wiley 2024-07-01
Series:Ecology and Evolution
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Online Access:https://doi.org/10.1002/ece3.11458
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author M. D. Anderson
D. L. Taylor
K. Olson
R. W. Ruess
author_facet M. D. Anderson
D. L. Taylor
K. Olson
R. W. Ruess
author_sort M. D. Anderson
collection DOAJ
description Abstract In root nodule symbioses (RNS) between nitrogen (N)‐fixing bacteria and plants, bacterial symbionts cycle between nodule‐inhabiting and soil‐inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension between host plants and symbiotic bacteria structures naturally occurring bacterial assemblages in soils. We used DNA cloning to examine soil‐dwelling assemblages of the actinorhizal symbiont Frankia in sites with long‐term stable assemblages in Alnus incana ssp. tenuifolia nodules. We compared: (1) phylogenetic diversity of Frankia in soil versus nodules, (2) change in Frankia assemblages in soil versus nodules in response to environmental variation: both across succession, and in response to long‐term fertilization with N and phosphorus, and (3) soil assemblages in the presence and absence of host plants. Phylogenetic diversity was much greater in soil‐dwelling than nodule‐dwelling assemblages and fell into two large clades not previously observed. The presence of host plants was associated with enhanced representation of genotypes specific to A. tenuifolia, and decreased representation of genotypes specific to a second Alnus species. The relative proportion of symbiotic sequence groups across a primary chronosequence was similar in both soil and nodule assemblages. Contrary to expectations, both N and P enhanced symbiotic genotypes relative to non‐symbiotic ones. Our results provide a rare set of field observations against which predictions from theoretical and experimental work in the evolutionary ecology of RNS can be compared.
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spelling doaj-art-19f2ce55f9f048d2bbcbe72346d6eabb2025-08-20T03:31:42ZengWileyEcology and Evolution2045-77582024-07-01147n/an/a10.1002/ece3.11458Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior AlaskaM. D. Anderson0D. L. Taylor1K. Olson2R. W. Ruess3Biology Department Macalester College Saint Paul Minnesota USADepartment of Biology University of New Mexico Albuquerque New Mexico USAInstitute of Arctic Biology University of Alaska Fairbanks Alaska USAInstitute of Arctic Biology University of Alaska Fairbanks Alaska USAAbstract In root nodule symbioses (RNS) between nitrogen (N)‐fixing bacteria and plants, bacterial symbionts cycle between nodule‐inhabiting and soil‐inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension between host plants and symbiotic bacteria structures naturally occurring bacterial assemblages in soils. We used DNA cloning to examine soil‐dwelling assemblages of the actinorhizal symbiont Frankia in sites with long‐term stable assemblages in Alnus incana ssp. tenuifolia nodules. We compared: (1) phylogenetic diversity of Frankia in soil versus nodules, (2) change in Frankia assemblages in soil versus nodules in response to environmental variation: both across succession, and in response to long‐term fertilization with N and phosphorus, and (3) soil assemblages in the presence and absence of host plants. Phylogenetic diversity was much greater in soil‐dwelling than nodule‐dwelling assemblages and fell into two large clades not previously observed. The presence of host plants was associated with enhanced representation of genotypes specific to A. tenuifolia, and decreased representation of genotypes specific to a second Alnus species. The relative proportion of symbiotic sequence groups across a primary chronosequence was similar in both soil and nodule assemblages. Contrary to expectations, both N and P enhanced symbiotic genotypes relative to non‐symbiotic ones. Our results provide a rare set of field observations against which predictions from theoretical and experimental work in the evolutionary ecology of RNS can be compared.https://doi.org/10.1002/ece3.11458AlnusFrankiamutualismnitrogen fixationplant–microbe interactions
spellingShingle M. D. Anderson
D. L. Taylor
K. Olson
R. W. Ruess
Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
Ecology and Evolution
Alnus
Frankia
mutualism
nitrogen fixation
plant–microbe interactions
title Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
title_full Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
title_fullStr Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
title_full_unstemmed Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
title_short Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska
title_sort composition of soil frankia assemblages across ecological drivers parallels that of nodule assemblages in alnus incana ssp tenuifolia in interior alaska
topic Alnus
Frankia
mutualism
nitrogen fixation
plant–microbe interactions
url https://doi.org/10.1002/ece3.11458
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