Contrasting and inconsistent insect trait responses to landscape simplification across latitudinal gradients

Landscape simplification, where landscapes transition from diversified (complex) species-rich systems to simplified species-poor ones, affects the abundance and diversity of insects worldwide. Beyond changes in community composition, land use change also affects insect traits, with intraspecific body size varying across land use gradients due to variation in resources, habitat availability, and many other factors. At the global scale, latitudinal gradients are the most well-documented driver of intraspecific body size variation (ex. Bergmann’s rule), mediated by differences in annual average temperature, seasonality, temporal availability of resources, etc. We hypothesized that latitudinal effects on species traits could interact with land use change to either buffer or exacerbate effects on intraspecific trait distributions, and that species’ functional group or diet specialization could affect these patterns. Our global analysis compiled body size data on 207 arthropod taxa from 14 countries. We found no consistent landscape effect on intraspecific body size, with landscape simplification sometimes associated with body size increases, decreases, and no effect. We also found that as landscapes simplify, body size trends do not differ between low-latitude and high-latitude regions - meaning the variation in body size trends across landscape simplification cannot be explained by the latitudinal gradient, suggesting resilience of body size to land-use change. Further analyses by functional group and diet specialization showed the same resilience of body size to land use gradients. The widely varied response we see from different taxa to land-use change defies generalization, meaning conservation efforts must be targeted to individual taxa in their specific landscape contexts.