In both basic and applied studies, quantification of herbivory on foliage is a key metric in characterizing plant–herbivore interactions, which underpin many ecological, evolutionary and agricultural processes. Current methods of quantifying herbivory are slow or inaccurate. We present LeafByte, a free iOS application for measuring leaf area and herbivory. LeafByte can save data automatically, read and record barcodes, handle both light and dark coloured plant tissue, and be used non‐destructively. We evaluate its accuracy and efficiency relative to existing herbivory assessment tools. LeafByte has the same accuracy as ImageJ, the field standard, but is 50% faster. Other tools, such as BioLeaf and grid quantification, are quick and accurate, but limited in the information they can provide. Visual estimation is quickest, but it only provides a coarse measure of leaf damage and tends to overestimate herbivory. LeafByte is a quick and accurate means of measuring leaf area and herbivory, making it a useful tool for research in fields such as ecology, entomology, agronomy and plant science.

In both basic and applied studies, quantification of herbivory on foliage is a key metric in characterizing plant–herbivore interactions, which underpin many ecological, evolutionary and agricultural processes. Current methods of quantifying herbivory are slow or inaccurate. We present LeafByte, a free iOS application for measuring leaf area and herbivory. LeafByte can save data automatically, read and record barcodes, handle both light and dark coloured plant tissue, and be used non‐destructively. We evaluate its accuracy and efficiency relative to existing herbivory assessment tools. LeafByte has the same accuracy as ImageJ, the field standard, but is 50% faster. Other tools, such as BioLeaf and grid quantification, are quick and accurate, but limited in the information they can provide. Visual estimation is quickest, but it only provides a coarse measure of leaf damage and tends to overestimate herbivory. LeafByte is a quick and accurate means of measuring leaf area and herbivory, making it a useful tool for research in fields such as ecology, entomology, agronomy and plant science.

Plants face a constant struggle to acquire nutrients and defend themselves against herbivores. Mycorrhizae are fungal mutualists that provide nutrients that can increase plant growth and alter resistance to herbivores. The beneficial effects of mycorrhizae for nutrient acquisition can depend on the quantity and type of soil nutrients available, with plants usually benefiting more in terms of growth from mycorrhizae when nutrients are limited. However, it is unclear how the addition of different nutrients might shift mycorrhizal‐conferred resistance to herbivores by changing defensive secondary chemistry and nutrient availability. We conducted two concurrent greenhouse experiments to test how three levels of fertilizers (low, medium and high) and three types of fertilizers (organic, organically derived and inorganic) altered mycorrhizae‐conferred resistance to herbivores in tomato plants. In addition, we looked at whether mycorrhizae‐conferred resistance was driven by plant secondary metabolites or the nutrient content of the leaves. Association with mycorrhizae was associated with an increase in biomass at low levels of fertilization and decreased biomass at high levels of fertilization. Interestingly, mycorrhizae increased resistance to herbivores at medium levels of fertilization, but had no effect at low and high levels of fertilization. Mycorrhizae improved resistance most strongly when plants were fertilized with a phosphorus rich, organically derived fertilizer. In both experiments, increased resistance was correlated with changes in the plant's foliar nitrogen content. Synthesis and applications. Our study supports the potential for mycorrhizae to improve either crop growth or pest resistance under lower fertilizer conditions. However, mycorrhizae did not provide both growth and resistance benefits under any treatment. While mycorrhizae have the potential to benefit crops in in lower input systems, it may be challenging to maximize both growth and resistance benefits.

Species invading new habitats experience novel selection pressures that can lead to rapid evolution, which may contribute to invasion success and/or increased impact on native community members. Many studies have hypothesized that plants in the introduced range will be larger than those in the native range, leading to increases in competitive ability. There is mixed support for evolution of larger sizes in the introduced range, but few studies have explicitly tested whether evolutionary changes result in decreased competitive responses or increased competitive effects on other species in the community. Here, we show that introduced Medicago polymorpha genotypes produced 14% more aboveground and 41% more belowground biomass than genotypes from the native range, suggesting that evolutionary changes in size occurred after introduction. However, these size differences were only observed in the absence of competition. The competitive effects of introduced and native range genotypes on three species that commonly co-occur with Medicago in invaded regions were remarkably similar. These results suggest that evolutionary increases in size during biological invasions do not necessarily alter the competitive effects of the invader on other community members, but may increase invasion success in disturbed or low competition environments.

Accumulating evidence supports the importance of belowground interactions for plant performance, ecosystem functioning, and conservation biology. However, studying species interactions belowground has unique challenges relative to the aboveground realm. The structure of the media and spatial scale are among the key aspects that seem to strongly influence belowground interactions. As a consequence, our understanding of species interactions belowground is limited, at least compared to what is known about interactions aboveground. Here we address the general question: Do the ecological concepts that have been developed largely in aboveground systems apply to understanding species interactions in the rhizosphere? We first explore to what extent ecological concepts related to species interactions are considered in rhizosphere studies across various subdisciplines. Next, we explore differences and similarities above-and belowground for fundamental concepts in ecology, choosing topics that are underrepresented in rhizosphere studies but represent a swath of concepts: species diversity, island biogeography, self-organization and ecosystem engineering, trophic cascades, and chemical communication. Finally, we highlight to overcome major challenges of current methodologies to study rhizosphere interactions in order to advance the understanding of belowground interactions in an ecological context. By synthesizing literature related to rhizosphere interactions, we reveal similarities, as well as key differences, in how fundamental ecological concepts are used and tested in above-and belowground studies. Closing the knowledge gaps identified in our synthesis will promote a deeper understanding of the differences above-and belowground and ultimately lead to integration of these concepts.

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