Leaf Nutritional Content, Tree Richness, and Season Shape the Caterpillar Functional Trait Composition Hosted by Trees

Abstract

Nutritional content of host plants is expected to drive caterpillar species assemblages and their trait composition. These relationships are altered by tree richness-induced neighborhood variation and a seasonal decline in leaf quality. We tested how key functional traits related to the growth and defenses of the average caterpillar hosted by a tree species are shaped by nutritional host quality. We measured morphological traits and estimated plant community-level diet breadth based on occurrences from 1020 caterpillars representing 146 species in a subtropical tree diversity experiment from spring to autumn in one year. We focused on interspecific caterpillar trait variation by analyzing presence-only patterns of caterpillar species for each tree species. Our results show that tree richness positively affected caterpillar species-sharing among tree species, which resulted in lowered trait variation and led to higher caterpillar richness for each tree species. However, community-level diet breadth depended more on the nutritional content of host trees. Higher nutritional quality also supported species-poorer but more abundant communities of smaller and less well-defended caterpillars. This study demonstrates that the leaf nutritional quality of trees shapes caterpillar trait composition across diverse species assemblages at fine spatial scales in a way that can be predicted by ecological theory.

Phylogeny‐based assignment of functional traits to DNA barcodes outperforms distance‐based, in a comparison of approaches

“…There have been reports of using functional diversity indices calculated on specimens that were also barcoded (Anttonen et al, 2022;Baraloto et al, 2012), although methods for sequence-based trait assignment are currently limited to metabolic traits in microbiology (Iwai et al, 2016;Louca et al, 2016;Wemheuer et al, 2020).…”

“…Phylogenetic diversity has sometimes been employed as a proxy for functional diversity (Winter et al, 2013), although more direct inference of functional diversity is curiously lacking in plant and animal studies. There have been reports of using functional diversity indices calculated on specimens that were also barcoded (Anttonen et al, 2022; Baraloto et al, 2012), although methods for sequence‐based trait assignment are currently limited to metabolic traits in microbiology (Iwai et al, 2016; Louca et al, 2016; Wemheuer et al, 2020).…”