Sources of controversy surrounding latitudinal patterns in herbivory and defence

This is the accepted manuscript of an article published by Elsevier.Both herbivory and plant defences against herbivores have been predicted to increase toward tropical regions. Early tests of this latitudinal herbivory-defence hypothesis (LHDH) were supportive, but accumulating evidence has been mixed. We argue that the lack of clarity might be due to heterogeneity in methodology and problems with study design and interpretation. Here we suggest possible solutions. Latitudinal studies need to carefully consider spatial and phylogenetic scale, to link plant defence measurements to herbivore performance, and to incorporate additional concepts from plant defence theory such as tolerance and induced defence. Additionally, we call for consistent measures of herbivory to standardize comparisons across biomes. Improving methodology in future studies of LHDH can resolve much of the current controversy.This work was supported by a Natural Sciences and Engineering Research Council (NSERC) Discovery Grant to PMK, an NSERC Vanier grant to DNA, and a Michigan State University Distinguished Fellowship to CAB

Effects of fine-scale population structure on the distribution of heterozygosity in a long-term study of Antirrhinum majus

Here are the research data underlying the publication "Effects of fine-scale population structure on the distribution of heterozygosity in a long-term study of Antirrhinum majus" Further information are summed up in the README document

Effects of fine-scale population structure on the distribution of heterozygosity in a long-term study of Antirrhinum majus

Many studies have quantified the distribution of heterozygosity and relatedness in natural populations, but few have examined the demographic processes driving these patterns. In this study, we take a novel approach by studying how population structure affects both pairwise identity and the distribution of heterozygosity in a natural population of the self-incompatible plant Antirrhinum majus. Excess variance in heterozygosity between individuals is due to identity disequilibrium, which reflects the variance in inbreeding between individuals; it is measured by the statistic g2. We calculated g2 together with FST and pairwise relatedness (Fij) using 91 SNPs in 22,353 individuals collected over 11 years. We find that pairwise Fij declines rapidly over short spatial scales, and the excess variance in heterozygosity between individuals reflects significant variation in inbreeding. Additionally, we detect an excess of individuals with around half the average heterozygosity, indicating either selfing or matings between close relatives. We use 2 types of simulation to ask whether variation in heterozygosity is consistent with fine-scale spatial population structure. First, by simulating offspring using parents drawn from a range of spatial scales, we show that the known pollen dispersal kernel explains g2. Second, we simulate a 1,000-generation pedigree using the known dispersal and spatial distribution and find that the resulting g2 is consistent with that observed from the field data. In contrast, a simulated population with uniform density underestimates g2, indicating that heterogeneous density promotes identity disequilibrium. Our study shows that heterogeneous density and leptokurtic dispersal can together explain the distribution of heterozygosity

Effects of fine-scale population structure on inbreeding in a long-term study of snapdragons (Antirrhinum majus)

Here are the research data underlying the publication " Effects of fine-scale population structure on inbreeding in a long-term study of snapdragons (Antirrhinum majus)" (working title "Estimating inbreeding and its effects in a long-term study of snapdragons (Antirrhinum majus)"). Further information are summed up in the README document

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth