Pyraloid Moth Assemblages Exhibit Complex Morphological Patterns Across an Ecuadorian Mountainous Forest

Abstract

We tested how morphological traits and species diversity of Pyraloidea moth assemblages vary across an Andean rainforest elevational gradient in Ecuador, and how environmental conditions shape these patterns. We analyzed 4161 individuals representing 212 species from a larger dataset of 10,337 individuals and 749 morpho-species, using the latter for cross-validation, and related our findings to ambient temperature and vegetation cover. Our multivariate analysis at 22 sites from 1020 to 2700 m above sea level identified five species assemblage clusters, revealing a near-linear decrease in species diversity with cooler temperatures. Community-weighted means (CWMs) of forewing length, indicating body size, increased nearly linearly with dropping temperatures, contrasting with results found for Geometridae moths at the same sites. Forewing aspect ratio (AR) demonstrated a U-shaped relationship with temperature, while wing loading (WL) followed a hump-shaped trajectory. Around 2000 m, Pyraloidea assemblages exhibited the lowest AR and highest WL, indicating morphological adaptations to dense forests, in contrast to both the more open forests near the treeline and the tall rainforest found at lower elevations. Subfamily-level analyses revealed variable patterns: Acentropinae, with strictly aquatic larvae, showed larger sizes at cooler elevations but less wing shape variation, likely reflecting limited forest dependence on maneuverability. Musotiminae, with a larval diet of diverse ferns, exhibited wing morphologies more related to canopy openness than temperature, indicating adaptations to navigating different fern habitats along the gradient. Our observations reveal complex insect–environment interactions that challenge the applicability of just one common theoretical framework for explaining temperature–size relationships among different moth clades.