Effects of latitude and conspecific plant density on insect leaf herbivory in oak saplings and seedlings

Abstract

Abiotic factors and plant species traits have been shown to drive latitudinal gradients in herbivory, and yet, population-level factors have been largely overlooked within this context. One such factor is plant density, which may influence the strength of herbivory and may vary with latitude. METHODS: We measured insect herbivory and conspecific plant density (CPD) of oak (Quercus robur) seedlings and saplings along a 17° latitudinal gradient (2700 km) to test whether herbivory exhibited a latitudinal gradient, whether herbivory was associated with CPD, and whether such an association changed with latitude. RESULTS: We found a positive but saturating association between latitude and leaf herbivory. Furthermore, we found no significant relationship between CPD and herbivory, and such lack of density effects remained consistent throughout the sampled latitudinal gradient. CONCLUSIONS: Despite the apparently negligible influence of plant density on herbivory for Q. robur, further research with other plant taxa and in different types of plant communities are needed to investigate density-dependent processes shaping geographical variation in plant-herbivore interactions.

Initial oak regeneration responses to experimental warming along microclimatic and macroclimatic gradients

“…Survival and performance results of these latter two species could thus be strongly altered if we had studied them during two consecutive growing seasons. Besides frost, latitudinal patterns might also be related to other speciesspecific drivers, such as phenological differences, light quality and quantity, drought or herbivory patterns along the gradients (Ducousso et al 1996;Collet et al 1998;Sevillano et al 2016;Moreira et al 2021).…”

Pierid Butterflies, Legume Hostplants, and Parasitoids in Urban Areas of Southern Florida

“…A plant is more likely to be discovered by its herbivores if it is near other plants of the same type, and herbivore density is correlated with hostplant density and patch size for some species [31] but not others [32], though other factors, such as latitude, may be even more important [33]. The species of plant upon which a caterpillar host feeds influences the extent of parasitoid attack and the diversity of the parasitoids attacking [34].…”