Stabilized Morphological Evolution of Spiders Despite Mosaic Changes in Foraging Ecology

Area of Science:

• Evolutionary Biology
• Arachnology
• Macroevolutionary Studies

Background:

• Spiders exhibit diverse foraging strategies, but the link between their morphology and ecology is unclear.
• It's unknown if web use correlates with specific body characteristics in spiders.

Purpose of the Study:

• To investigate the relationship between spider body size, proportions, and foraging ecology.
• To reconstruct the evolution of spider phenotypes and their correlation with behavioral ecology over deep time.

Main Methods:

• Utilized an extensive dataset of morphometric and ecological traits in spiders.
• Applied phylogenetic comparative methods to model trait evolution, including Ornstein-Uhlenbeck and Brownian Motion models.
• Analyzed differences in traits among ecological guilds using multivariate frameworks.

Main Results:

• Most spider traits showed stabilizing selection (Ornstein-Uhlenbeck model), except body length, which followed free trait diffusion (Brownian Motion model).
• The araneoid clade displayed bimodal trends in body length towards miniaturization or gigantism.
• Few morphological traits significantly differed between ecological guilds; leg length and thickness were most prominent, but no clear morphometric set defined ecological modes.

Conclusions:

• Spider body proportions are highly stabilized compared to insects, with ecological adaptations often realized through behavior and extended phenotypes.
• Morphometric traits are unreliable for inferring spider ecology; micro-morphological characters are recommended instead.
• This study highlights the power of integrating phylogenomics with trait-based approaches to understand functional diversity.