19 research outputs found
Macroevolution of protective coloration across caterpillars reflects relationships with host plants
Macroevolution of protective coloration across caterpillars reflects relationships with host plants
data, phylogenetic tree, and other input files used to explore associations between color, pattern, and diet ecology in 1808 species of larval Lepidoptera (caterpillars). Associated scripts are hosted on Github (moria-robinson).</p
Generalists are more specialized in low-resource habitats, increasing stability of ecological network structure
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Generalists are more specialized in low-resource habitats, increasing stability of ecological network structure
Linking mechanistic processes to the stability of ecological networks is a key frontier in ecology. In trophic networks, "modules"-groups of species that interact more with each other than with other members of the community-confer stability, mitigating effects of species loss or perturbation. Modularity, in turn, is shaped by the interplay between species' diet breadth traits and environmental influences, which together dictate interaction structure. Despite the importance of network modularity, variation in this emergent property is poorly understood in complex natural systems. Using two years of field data, we quantified interactions between a rich community of lepidopteran herbivores and their host plants across a mosaic of low-resource serpentine and high-resource nonserpentine soils. We used literature and our own observations to categorize herbivore species as generalists (feeding on more than one plant family) or specialists (feeding on one plant family). In both years, the plant-herbivore network was more modular on serpentine than on nonserpentine soils-despite large differences in herbivore assemblage size across years. This structural outcome was primarily driven by reduction in the breadth of host plant use by generalist species, rather than by changes in the composition of species with different fundamental diet breadths. Greater modularity-and thus greater stability-reflects environmental conditions and plastic responses by generalist herbivores to low host plant quality. By considering the dual roles of species traits and ecological processes, we provide a deeper mechanistic understanding of network modularity, and suggest a role for resource availability in shaping network persistence
Data and code for Ecology MS "When soils cascade: effects of substrate type on assemblage size and structure in a diverse herbivore community"
Please find:<div><br></div><div>1) All datafiles used in this manuscript. </div><div><br></div><div>2) All code, with source files specified. These scripts are *not* 'tidied' to show only the final outputs that I used in the paper. Because choosing the correct analyses was often a lengthy & circuitous process, I include the entire process & annotate the code as best I could.</div><div><br></div><div>Within these long scripts, I tried to specify which analyses were used in the final MS. If I forgot to do so, and you are having trouble identifying the correct analysis, advance apologies & please contact me! </div
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Variability in plant nutrients reduces insect herbivore performance.
The performance and population dynamics of insect herbivores depend on the nutritive and defensive traits of their host plants. The literature on plant-herbivore interactions focuses on plant trait mean values, but recent studies showing the importance of plant genetic diversity for herbivores suggest that plant trait variance may be equally important. The consequences of plant trait variance for herbivore performance, however, have been largely overlooked. Here we report an extensive assessment of the effects of within-population plant trait variance on herbivore performance using 457 performance datasets from 53 species of insect herbivores. We show that variance in plant nutritive traits substantially reduces mean herbivore performance via non-linear averaging of performance relationships that were overwhelmingly concave down. By contrast, relationships between herbivore performance and plant defence levels were typically linear, with variance in plant defence not affecting herbivore performance via non-linear averaging. Our results demonstrate that plants contribute to the suppression of herbivore populations through variable nutrient levels, not just by having low average quality as is typically thought. We propose that this phenomenon could play a key role in the suppression of herbivore populations in natural systems, and that increased nutrient heterogeneity within agricultural crops could contribute to the sustainable control of insect pests in agroecosystems
Variance in plant nutritive traits reduces insect herbivore performance (dataset)
Data and metadata from <div>Wetzel, W. C., H. M. Kharouba, M. Robinson, M. Holyoak, & R. Karban. 2016. Variance in plant nutritive traits reduces insect herbivore performance. Nature. doi: 10.1038/nature20140</div
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Macroevolution of protective coloration across caterpillars reflects relationships with host plants
A critical function of animal coloration is avoiding attack, either by warning predators or reducing detectability. Evolution of these divergent strategies may depend on prey palatability and apparency to predators: conspicuous coloration may be favoured if species are distasteful, or habitats make hiding difficult; by contrast, camouflage may be effective if prey lack defences or environments are visually complex. For insect herbivores, host plants provide both chemical defence and the background against which they are detected or obscured; thus, plant traits may be key to coloration in these foundational terrestrial organisms. We use 1808 species of larval Lepidoptera to explore macroevolution of protective coloration strategy. We find that colour and pattern evolve jointly in caterpillars, similar to an array of species across the animal kingdom, while individual elements of coloration evolve closely with diet ecology. Consistent with key tenets of plant defence and plant-herbivore coevolutionary theory, conspicuous colours are associated with herbaceous host plants-thought to be defended by toxins-while camouflage colours and patterns are associated with woody plants and grasses. Contrary to theory, dietary specialization is not associated with conspicuous coloration. Our results add valuable insights into the evolutionary forces shaping colour and pattern in nature
Novel Insights into Tritrophic Interaction Diversity and Chemical Ecology Using 16 Years of Volunteer-Supported Research
Sixteen years ago, a schoolteacher from New Jersey collected a caterpillar in a Costa Rican rainforest. When a parasitoid emerged several days later, it became the first data point of a long-term volunteer–mediated study on tritrophic interactions across the Americas. The teacher was an Earthwatch Institute scientist and the project an ongoing ecological investigation of caterpillars, host plants, and the wasps and flies (parasitoids) that kill them (Fig. 1). Over the course of 16 years, 1,200 volunteers have contributed to the project, including adult and youth citizen scientists from Earthwatch, teachers, and a number of other volunteers who have offered their time for months or years