Scale-dependent environmental effects on phenotypic distributions in Heliconius butterflies

<p>Examining how environmental factors influence phenotypic distribution might provide valuable information about local adaptation, divergence, and speciation. The red-yellow Müllerian mimicry ring of <em>Heliconius</em> butterflies displays a wide range of color patterns across the Neotropics and is involved in several hybrid zones, making it an excellent system to study color phenotypic distribution. Using a multiscale distribution strategy, we studied whether different phenotypes of the distantly related species <em>H. erato</em> and <em>H. melpomene,</em> belonging to the red-yellow mimetic ring, are associated with different environmental conditions. We show that environmental gradients (particularly heat and precipitation factors) drive <em>Heliconius</em> phenotypic distributions, but that phenotype and environmental correlations vary with spatial scale. While co-mimics are frequently found in similar environments at a broad scale, patterns at the local level are not necessarily consistent (different variables are the best predictors of phenotypic occurrence in different areas) or congruent (co-mimic pairs show distinct associations with the environment). Thus, large-scale analysis may help to identify how environmental heterogeneity influences broad mimic phenotypic distributions, but local studies are needed to understand the context-dependent biotic, abiotic, and historical mechanisms that drive finer-scale phenotypic shifts.</p>