Trade-Offs, Spatial Heterogeneity, and the Maintenance of Microbial Diversity

Porter, Stephanie S.; Rice, Kevin J.

doi:10.1111/j.1558-5646.2012.01788.x

Cited by 45 publications

(44 citation statements)

References 100 publications

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“…Together, our results suggest that these interactions influence the competitive hierarchy of rhizobial genotypes, resulting in shifts in rhizobial relative abundance in different ecological contexts. Such variable outcomes could contribute to the maintenance of much of the diversity commonly observed in rhizobial communities (Heath & Tiffin ; Porter & Rice ).…”

Section: Discussionmentioning

confidence: 99%

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Host species and environmental variation can influence rhizobial community composition

2016

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Summary Nitrogen‐fixing rhizobial mutualists display high levels of genetic and phenotypic diversity at multiple spatial scales. Identifying the ecological and environmental drivers of variation in the genetic composition and function of rhizobial communities is critical to understanding rhizobial impacts on community and ecosystem productivity. In this study, we examined how environmental factors and host species jointly affect rhizobial phenotypic diversity and community structure. Individual host plants of two native Australian legumes, Acacia salicina and A. stenophylla, were inoculated with a community of six rhizobial strains (belonging to three genera) previously characterized for symbiotic effectiveness. The plants were grown in a fully factorial experiment under high and low phosphorus and water, and high or no nitrogen. Half the plants were harvested after 19 weeks and the other half after 30 weeks. The relative abundance of the six rhizobial strains was characterized using amplicon sequencing of the rhizobial 16S rRNA gene from DNA extracted from the root nodules of plants after each harvest. Variation in the relative abundance of the six rhizobial strains was best explained by host species, although interactions between environment and host species also emerged as significant predictors of variation in rhizobial community composition. We detected strong host‐specific interactions for two strains, while two other strains were clearly generalists, being relatively abundant in both host species. For both host species, the two generalist strains were as abundant as the best specialist strain within the rhizobial community. Synthesis. Our study show host species identity as the key determinant of rhizobial community structure within the root nodules of Acacia plants. Strains that were efficient at promoting the growth of their host plant had high relative abundance in experimental communities. Furthermore, interaction among host species, rhizobial host‐range, and environmental variation determine the structure of rhizobial communities, although not in clearly predictable ways. Such interactions contributed to the maintenance (albeit at relatively low frequencies) of ineffective strains in nodule communities. These interacting effects could help to explain why rhizobial communities are functionally diverse, such that specialists, generalists and seemingly ineffective rhizobia, can be simultaneously maintained in rhizosphere communities.

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Section: Discussionmentioning

confidence: 99%

“…However, these predictions are clearly at odds with the high genetic and phenotypic diversity frequently observed in rhizobial populations (Thrall et al . ; Porter & Rice ), indicating that host‐rhizobial interactions require further empirical investigation to better understand the processes maintaining diversity.…”

Section: Introductionmentioning

confidence: 99%

Host species and environmental variation can influence rhizobial community composition

2016

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“…Ultramafic substrates are characterised by a high nickel concentration that may impact microbial composition by selecting microorganisms that are tolerant to this metal [99–101]. In New Caledonia, studies have demonstrated that the presence of AMF improves plant tolerance to nickel [102,103] and also the existence of nickel-tolerant ECM fungal Pisolithus albus isolates [36].…”

Section: Discussionmentioning

confidence: 99%

Environmental and Geographical Factors Structure Soil Microbial Diversity in New Caledonian Ultramafic Substrates: A Metagenomic Approach

et al. 2016

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Soil microorganisms play key roles in ecosystem functioning and are known to be influenced by biotic and abiotic factors, such as plant cover or edaphic parameters. New Caledonia, a biodiversity hotspot located in the southwest Pacific, is one-third covered by ultramafic substrates. These types of soils are notably characterised by low nutrient content and high heavy metal concentrations. Ultramafic outcrops harbour diverse vegetation types and remarkable plant diversity. In this study, we aimed to assess soil bacterial and fungal diversity in New Caledonian ultramafic substrates and to determine whether floristic composition, edaphic parameters and geographical factors affect this microbial diversity. Therefore, four plant formation types at two distinct sites were studied. These formations represent different stages in a potential chronosequence. Soil cores, according to a given sampling procedure, were collected to assess microbial diversity using a metagenomic approach, and to characterise the physico-chemical parameters. A botanical inventory was also performed. Our results indicated that microbial richness, composition and abundance were linked to the plant cover type and the dominant plant species. Furthermore, a large proportion of Ascomycota phylum (fungi), mostly in non-rainforest formations, and Planctomycetes phylum (bacteria) in all formations were observed. Interestingly, such patterns could be indicators of past disturbances that occurred on different time scales. Furthermore, the bacteria and fungi were influenced by diverse edaphic parameters as well as by the interplay between these two soil communities. Another striking finding was the existence of a site effect. Differences in microbial communities between geographical locations may be explained by dispersal limitation in the context of the biogeographical island theory. In conclusion, each plant formation at each site possesses is own microbial community resulting from multiple interactions between abiotic and biotic factors.

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“…Although we do not know the exact mechanisms by which these facilitative effects occurred, given that legumes like Acmispon can sometimes facilitate invasions via their effects on soil nitrogen availability (Maron and Connors 1996), Acmispon could facilitate Medicago through nitrogen leakage. Further, these species associate with different species of rhizobia bacteria, and thus are unlikely to compete for mutualists (Porter and Rice 2013). Also surprisingly, insect herbivores did not significantly affect Medicago fitness in the absence of Acmispon.…”

Section: Discussionmentioning

confidence: 99%

Genetic variation in invasive species response to direct and indirect species interactions

terHorst

Lau

2014

Biol Invasions

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Biotic resistance to invasion arises from strong species interactions that decrease the fitness and population growth rates of potential invaders. Strong, direct interactions such as predation and competition are typically thought to drive biotic resistance, but in diverse communities, indirect interactions among species may also affect biotic resistance. Further, genetic variation in traits of the invading species that affect species interactions may allow some genotypes to overcome biotic resistance. We investigated the direct and indirect effects of a native legume (Acmispon wrangelianus) and insect herbivores on the fitness of different genotypes of an invasive legume (Medicago polymorpha) in a California grassland. Insect herbivores decreased Medicago fitness, but only in the presence of Acmispon, suggesting that indirect interactions mediated through insects and Acmispon are important for deterring Medicago invasion. SomeMedicago genotypes were less affected by interactions with other species, however. This genetic variance suggests that while biotic resistance reduced the reproductive success of most genotypes, a few genotypes were able to overcome these complex interactions. However, Medicago invasion was unsuccessful in all treatments at several of our sites, suggesting that factors beyond those manipulated here also play a key role at many sites. At sites where biotic resistance is important, spatial and temporal variation in community composition and the genetic composition of the invasion pool may explain the invasion success of Medicago into this community.

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Trade-Offs, Spatial Heterogeneity, and the Maintenance of Microbial Diversity

Cited by 45 publications

References 100 publications

Host species and environmental variation can influence rhizobial community composition

Host species and environmental variation can influence rhizobial community composition

Environmental and Geographical Factors Structure Soil Microbial Diversity in New Caledonian Ultramafic Substrates: A Metagenomic Approach

Genetic variation in invasive species response to direct and indirect species interactions

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