A Framework for Predicting Intraspecific Variation in Plant Defense

Hahn, Philip G.; Maron, John L.

doi:10.1016/j.tree.2016.05.007

Cited by 188 publications

(254 citation statements)

References 92 publications

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“…This supports recent work suggesting that intra-specific trait variation may accord with predictions of resource availability in plant species adapted to low-resource environments (Hahn and Maron 2016). Native generalist Egira perlubens grew more slowly on leaves of serpentine Ceanothus, Quercus, and Adenostoma than non-serpentine congeners or conspecifics.…”

Section: Discussionsupporting

confidence: 88%

“…Focal species in this study were congeners Ceanothus cuneatus (nonserpentine; hereafter, NS) and Ceanothus jepsonii (serpentine; hereafter, S); Arctostaphylos manzanita (NS) and Arctostaphylos viscida (S); Quercus berberidifolia (NS) and Quercus durata (S); and conspecifics of Adenostoma fasciculatum, which grows in both soils (NS, S). Finally, because these species are considered "xerophilous", or broadly adapted to lower-resource conditions, we can predict that intra-specific resource-resistance relationships should be negative, mirroring that expected across species (Hahn and Maron 2016). In addition, these four genera span a diverse phylogenetic range: each belongs to a different family (Ceanothus = Rhamnaceae; Arctostaphylos = Ericaceae; Quercus = Fagaceae; Adenostoma = Rosaceae), allowing us to explore patterns within distinct host-associated herbivore communities.…”

Section: Systemmentioning

confidence: 85%

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Cascading effects of soil type on assemblage size and structure in a diverse herbivore community

Robinson

Strauss

2018

Ecology

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Soil type is understudied as a driver of herbivore community size and structure across host plants. This study extends predictions of resource availability hypotheses to understand how soil types of different resource levels alter plant resistance and structure of herbivore assemblages. In this 2-yr study we use seven dominant chaparral shrub species that grow across a natural mosaic of low and high resource soils to explore effects of soil type on plant resistance, and relate these soil-based differences in resistance to the abundance and diversity of the larval lepidopteran community. We show that growing on low-resource soils increases plant resistance, as measured by herbivore performance, both within and across host plant species, and that resistance may be driven by variation in plant nutritive and defensive traits. We then show that more resistant plants on low-resource soils host less abundant and less diverse herbivore assemblages across a natural soil mosaic in the field.

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Section: Discussionsupporting

confidence: 88%

Section: Systemmentioning

confidence: 85%

Cascading effects of soil type on assemblage size and structure in a diverse herbivore community

Robinson

Strauss

2018

Ecology

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“…Accurately predicting patterns of intraspecific defense variation across biotic and abiotic gradients requires the integration of ecological interactions, physiological mechanisms, and microevolutionary processes into existing theories of plant defense (Hahn and Maron 2016). Here, we show that, by reducing the frequency and intensity of browsing damage, associational refuges cause predictable variation in defense phenotype for species that respond to browsing by inducing defenses.…”

Section: Future Directions and Conclusionmentioning

confidence: 83%

Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants

Coverdale

Goheen²,

Palmer

et al. 2018

Ecology

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Intraspecific variation in plant defense phenotype is common and has wide-ranging ecological consequences. Yet prevailing theories of plant defense allocation, which primarily account for interspecific differences in defense phenotype, often fail to predict intraspecific patterns. Furthermore, although individual variation in defense phenotype is often attributed to ecological interactions, few general mechanisms have been proposed to explain the ubiquity of variable defense phenotype within species. Here, we show experimentally that associational refuges and induced resistance interact to create predictable intraspecific variation in defense phenotype in African savanna plants. Physically defended species from four families (Acanthaceae, Asparagaceae, Cactaceae, and Solanaceae) growing in close association with spinescent Acacia trees had 39-78% fewer spines and thorns than did isolated conspecifics. For a subset of these species, we used a series of manipulative experiments to show that this variability is maintained primarily by a reduction in induced responses among individuals that seldom experience mammalian herbivory, whether due to association with Acacia trees or to experimental herbivore exclusion. Unassociated plants incurred 4- to 16-fold more browsing damage than did associated individuals and increased spine density by 16-38% within one month following simulated browsing. In contrast, experimental clipping induced no net change in spine density among plants growing beneath Acacia canopies or inside long-term herbivore exclosures. Associated and unassociated individuals produced similar numbers of flowers and seeds, but seedling recruitment and survival were vastly greater in refuge habitats, suggesting a net fitness benefit of association. We conclude that plant-plant associations consistently decrease defense investment in this system by reducing both the frequency of herbivory and the intensity of induced responses, and that inducible responses enable plants to capitalize on such associations in heterogeneous environments. Given the prevalence of associational and induced defenses in plant communities worldwide, our results suggest a potentially general mechanism by which biotic interactions might predictably shape intraspecific variation in plant defense phenotype.

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“…For example, the plant defense literature has had some success relating defense to climate by testing the biotic interactions hypothesis, the “resource availability hypothesis,” or both (Pearse and Hipp , Moreira et al. , , Hahn and Maron , Hahn et al. ).…”

Section: Discussionmentioning

confidence: 99%

Multiple metrics of latitudinal patterns in insect pollination and herbivory for a tropical‐temperate congener pair

Baskett

Schroeder

Weber

et al. 2020

Ecological Monographs

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The biotic interactions hypothesis posits that biotic interactions are more important drivers of adaptation closer to the equator, evidenced by "stronger" contemporary interactions (e.g., greater interaction rates) and/or patterns of trait evolution consistent with a history of stronger interactions. Support for the hypothesis is mixed, but few studies span tropical and temperate regions while experimentally controlling for evolutionary history. Here, we integrate field observations and common garden experiments to quantify the relative importance of pollination and herbivory in a pair of tropical-temperate congeneric perennial herbs. Phytolacca rivinoides and P. americana are pioneer species native to the Neotropics and the eastern United States, respectively. We compared plant-pollinator and plant-herbivore interactions between three tropical populations of P. rivinoides from Costa Rica and three temperate populations of P. americana from its northern range edge in Michigan and Ohio. For some metrics of interaction importance, we also included three subtropical populations of P. americana from its southern range edge in Florida. This approach confounds species and region but allows us, uniquely, to measure complementary proxies of interaction importance across a tropicaltemperate range in one system. To test the prediction that lower-latitude plants are more reliant on insect pollinators, we quantified floral display and reward, insect visitation rates, and self-pollination ability (autogamy). To test the prediction that lower-latitude plants experience more herbivore pressure, we quantified herbivory rates, herbivore abundance, and leaf palatability. We found evidence supporting the biotic interactions hypothesis for most comparisons between P. rivinoides and north-temperate P. americana (floral display, insect visitation, autogamy, herbivory, herbivore abundance, and young-leaf palatability). Results for subtropical P. americana populations, however, were typically not intermediate between P. rivinoides and north-temperate P. americana, as would be predicted by a linear latitudinal gradient in interaction importance. Subtropical young-leaf palatability was intermediate, but subtropical mature leaves were the least palatable, and pollination-related traits did not differ between temperate and subtropical regions. These nonlinear patterns of interaction importance suggest future work to link interaction importance to climatic or biotic thresholds. In sum, we found that the biotic interactions hypothesis was more consistently supported at the larger spatial scale of our study.

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A Framework for Predicting Intraspecific Variation in Plant Defense

Cited by 188 publications

References 92 publications

Cascading effects of soil type on assemblage size and structure in a diverse herbivore community

Cascading effects of soil type on assemblage size and structure in a diverse herbivore community

Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants

Multiple metrics of latitudinal patterns in insect pollination and herbivory for a tropical‐temperate congener pair

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