Bottom‐up control of geographic variation in insect herbivory on wild cotton (Gossypium hirsutum) by plant defenses and climate

Abstract

Premise of study: It has long been recognized that the occurrence and impact of herbivory is shaped by bottom-up forces, primarily plant traits (e.g. defenses) as well as by abiotic factors. Addressing these concurrent effects under a spatial context has been useful in efforts to understand the mechanisms governing variation in plant-herbivore interactions.Still, few studies have evaluated the simultaneous influence of different sources of bottomup variation on spatial variation in herbivory. Methods:We tested to what extent plant chemical (phenolics, gossypol glands) and physical (pubescence) defensive traits and climatic factors are associated with variation in herbivory by leaf-chewing insects among populations of wild cotton (Gossypium hirsutum).Key results: We found substantial variation among cotton populations in leaf defenses and insect leaf herbivory. Leaf pubescence (trichome density), but not gossypol gland density or phenolic content, was significantly negatively associated with herbivory by leaf-chewing insects. In addition, there were direct effects of climate on defenses and herbivory, with leaf pubescence increasing towards drier conditions and leaf damage increasing towards wetter and cooler conditions. There was no evidence, however, of indirect effects (via plant defenses) of climate on herbivory.Conclusions: Spatial variation in insect herbivory on wild G. hirsutum appears to be predominantly driven by concurrent and independent influences of population variation in leaf pubescence and climatic factors.

Effects of soil abiotic factors and plant chemical defences on seed predation on sea fennel (Crithmum maritimum)

“…Recent work of our investigating indirect effects of soil and climatic factors on herbivory via plant defences in other plant taxa has shown mixed evidence. For example, in agreement with present findings, precipitation negatively affected leaf pubescence and positively affected leaf-chewer herbivory in wild cotton, but there was no indirect effect of precipitation on herbivory (Abdala-Roberts et al 2019). However, for English oak (Quercus robur) we found that temperature and precipitation were negatively associated with leaf and seed defences (respectively) and this led to positive indirect effect on seed predation (Moreira et al 2020b); likewise soil physical properties (e.g.…”

Induction by caterpillars of stored and emitted volatiles among populations of wild cotton (Gossypium hirsutum)

“…In contrast, chemotype-specific responses to caterpillar herbivory have been described in another species ( Tanacetum vulgare ) for both leaf-stored and emitted volatiles (Clancy et al, 2020). Despite being confined to coastal habitats, Yucatanese wild cotton is subjected to substantial spatial variability in herbivore pressure and abiotic conditions (Abdala-Roberts et al, 2019; Munguía-Rosas et al, 2019; Quijano-Medina et al, 2019, 2021), which could be associated with the origin of the observed variation in HIPVs. Further work is required to understand the drivers of these differences.…”

“…Interestingly, some plant species specifically increase γ-terpinene concentrations in their tissues under drought conditions (Alavi-Samani et al, 2015;Razavizadeh and Komatsu, 2018), and it has been demonstrated that γ-terpinene has a particularly high antioxidant capacity (Ruberto and Baratta, 2000;De Sousa et al, 2023). Previous work on Yucatanese wild cotton documented that populations in higher-temperature environments tend to exhibit a greater density of glands (albeit non-significantly), while herbivory pressure and gland density are not correlated among populations (Abdala-Roberts et al, 2019). This finding suggests that abiotic conditions could potentially be significant factors driving variation in gland density and their chemical content.…”

Modelagem Espacializada Da Evapotranspiração Real Em Área De Reflorestamento Por Meio Do Pacote Agriwater Em Ambiente R

“…Insect richness results from the balance of several ecological factors (ABDALA-ROBERTS et al, 2019). Insects, which amount to nearly 60% of all animals, are especially useful as bioindicators of environmental changes (ZEQUI et al, 2019).…”