Trait differences in responses to arbuscular mycorrhizal fungi are stronger and more consistent than fixed differences among populations of <i>Asclepias speciosa</i>

Waller, Lauren P.; Hahn, Philip G.; Maron, John L.; Lekberg, Ylva

doi:10.1002/ajb2.1038

Cited by 9 publications

(12 citation statements)

References 60 publications

(85 reference statements)

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“…This is perhaps not surprising since trichomes can increase drought tolerance (Farquhar and Richards, 1984 ; Agrawal et al, 2009 ) in addition to enhancing herbivore defense (Agrawal and Fishbein, 2006 ). We do not know which component of soil biota caused this effect, but inoculations with AMF alone have increased trichome density in a previous study (Waller et al, 2018 ) and all plants were highly colonized by AMF in our study (Figure 4 ). Given this high root colonization, the neutral or even negative plant responses to live soil were surprising, especially because A. speciosa and other Asclepias species generally benefit from AMF inoculations (Wilson and Hartnett, 1998 ; Busby et al, 2011 ; Tao et al, 2016 ; Waller et al, 2018 ).…”

Section: Discussioncontrasting

confidence: 51%

“…The three-way interactions, trait × soil biota × soil inoculum origin or trait × soil biota × watering treatment, would further indicate that the geographic or plastic responses to soil biota differ among plant traits. We do not focus on potential interactions between the experimental treatment and plant populations (i.e., testing whether plant populations respond differently to the treatments), because in a previous study we found no difference in responsiveness to AMF inoculations (Waller et al, 2018 ) and preliminary screening of our data showed no interactions with plant populations. We used post-hoc linear contrasts to evaluate how each trait responded to significant predictor variables and interaction terms.…”

Section: Methodsmentioning

confidence: 99%

“…This plant is highly responsive to AMF (Busby et al, 2011 ); traits related to growth or resource acquisition (biomass, specific leaf area, root:shoot) and defense (latex and trichomes; Agrawal and Fishbein, 2006 ) all respond to AMF (Waller et al, 2018 ). Because A. speciosa traits vary among populations distributed across environments gradients (Waller et al, 2018 ), we collected seeds from five populations spanning the entire resource gradient over which we sampled soils to capture the range of traits values representative of this species (Table S1 ). Within each population, we haphazardly collected one seed pod (i.e., follicle) from 4 to 5 different ramets.…”

Section: Methodsmentioning

confidence: 99%

“…Immediately after individual leaves were harvested from each plant we captured exuded latex from the stem on a pre-weighed 1 cm diameter filter paper, which was then placed into a pre-weighed centrifuge tube. Centrifuge tubes were kept frozen and then weighed to the nearest 0.1 mg. Latex production was quantified as fresh weight (Agrawal and Fishbein, 2006 ; Waller et al, 2018 ). We then measured stem height on each plant from the soil to the apical meristem and harvested all above- and belowground biomass.…”

Section: Methodsmentioning

confidence: 99%

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Effects of Short- and Long-Term Variation in Resource Conditions on Soil Fungal Communities and Plant Responses to Soil Biota

et al. 2018

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Soil biota can strongly influence plant performance with effects ranging from negative to positive. However, shifts in resource availability can influence plant responses, with soil pathogens having stronger negative effects in high-resource environments and soil mutualists, such as arbuscular mycorrhizal fungi (AMF), having stronger positive effects in low-resource environments. Yet the relative importance of long-term vs. short-term variation in resources on soil biota and plant responses is not well-known. To assess this, we grew the perennial herb Asclepias speciosa in a greenhouse experiment that crossed a watering treatment (wet vs. dry treatment) with a manipulation of soil biota (live vs. sterilized soil) collected from two geographic regions (Washington and Minnesota) that vary greatly in annual precipitation. Because soil biota can influence many plant functional traits, we measured biomass as well as resource acquisition (e.g., root:shoot, specific leaf area) and defense (e.g., trichome and latex production) traits. Due to their important role as mutualists and pathogens, we also characterized soil fungal communities in the field and greenhouse and used curated databases to assess fungal composition and potential function. We found that the experimental watering treatment had a greater effect than soil biota origin on plant responses; most plant traits were negatively affected by live soils under wet conditions, whereas responses were neutral or positive in live dry soil. These consistent differences in plant responses occurred despite clear differences in soil fungal community composition between inoculate origin and watering treatments, which indicates high functional redundancy among soil fungi. All plants grown in live soil were highly colonized by AMF and root colonization was higher in wet than dry soil; root colonization by other fungi was low in all treatments. The most parsimonious explanation for negative plant responses in wet soil is that AMF became parasitic under conditions that alleviated resource limitation. Thus, plant responses appeared driven by shifts within rather than between fungal guilds, which highlights the importance of coupling growth responses with characterizations of soil biota to fully understand underlying mechanisms. Collectively these results highlight how short-term changes in environmental conditions can mediate complex interactions between plants and soil biota.

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Section: Discussioncontrasting

confidence: 51%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Effects of Short- and Long-Term Variation in Resource Conditions on Soil Fungal Communities and Plant Responses to Soil Biota

et al. 2018

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“…Despite not finding evidence for clines in growth/physiological traits in the common garden, there was substantial population-level differentiation in most of these traits, consistent with findings from a previous greenhouse experiment using a subset of these populations (Waller et al 2018). Moreover, in a companion study we found very low neutral genetic divergence based on microsatellite markers (K.I.S., unpublished data), suggesting that selection is strong enough to overwhelm genetic drift or gene flow among populations in close proximity.…”

Section: Clines In Growth and Defense Traitssupporting

confidence: 83%

Population Variation, Environmental Gradients, and the Evolutionary Ecology of Plant Defense against Herbivory

Hahn¹,

Agrawal²,

Sussman³

et al. 2019

The American Naturalist

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A central tenet of plant defense theory is that adaptation to the abiotic environment sets the template for defense strategies, imposing a trade-off between plant growth and defense. Yet this tradeoff, commonly found among species occupying divergent resource environments, may not occur across populations of single species. We hypothesized that more favorable climates and higher levels of herbivory would lead to increases in growth and defense across plant populations. We evaluated whether plant growth and defense traits covaried across 18 populations of showy milkweed (Asclepias speciosa) inhabiting an east-west climate gradient spanning 257 of longitude. A suite of traits impacting defense (e.g., latex, cardenolides), growth (e.g., size), or both (e.g., specific leaf area [SLA], trichomes) were measured in natural populations and in a common garden, allowing us to evaluate plastic and genetically based variation in these traits. In natural populations, herbivore pressure increased toward warmer sites with longer growing seasons. Growth and defense traits showed strong clinal patterns and were positively correlated. In a common garden, clines with climatic origin were recapitulated only for defense traits. Correlations between growth and defense traits were also weaker and more negative in the common garden than in the natural populations. Thus, our data suggest that climatically favorable sites likely facilitate the evolution of greater defense at minimal costs to growth, likely because of increased resource acquisition.

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Trait differences in responses to arbuscular mycorrhizal fungi are stronger and more consistent than fixed differences among populations of Asclepias speciosa

Waller

Hahn

Maron

et al. 2018

American J of Botany

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Trait differences in responses to arbuscular mycorrhizal fungi are stronger and more consistent than fixed differences among populations of Asclepias speciosa

Abstract: Our results suggest that while there is substantial population differentiation in many traits of A. speciosa, populations respond similarly to AM fungi, and both positive and negative correlations among trait responses occur.

Cited by 9 publications

References 60 publications

Effects of Short- and Long-Term Variation in Resource Conditions on Soil Fungal Communities and Plant Responses to Soil Biota

Effects of Short- and Long-Term Variation in Resource Conditions on Soil Fungal Communities and Plant Responses to Soil Biota

Population Variation, Environmental Gradients, and the Evolutionary Ecology of Plant Defense against Herbivory

Trait differences in responses to arbuscular mycorrhizal fungi are stronger and more consistent than fixed differences among populations of Asclepias speciosa

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