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Abstract Bumble bees (Bombus) exhibit exceptional diversity in setal body color patterns, largely as a result of convergence onto multiple Mullerian mimicry patterns globally. When multiple species cross the same sets of mimicry complexes, they can acquire the same color polymorphisms, providing replicates of phenotypic evolution. This study examines the genetic basis of parallel color pattern acquisition in three bumble bee taxon pairs in western North America that shift between orange-red and black mid-abdominal segmental coloration in Rocky Mountain and Pacific Coastal mimicry regions: polymorphic Bombus vancouverensis and B. melanopygus, and sister species B. huntii and B. vosnesenskii. Initial gene targets are identified using a genome-wide association study, while cross-developmental transcriptomics reveals genetic pathways leading to final pigmentation genes. The data show all three lineages independently target the regulatory region of a segmental-fate determining Hox gene, Abdominal B (Abd-B), for this color transition. For B. vancouverensis and B. melanopygus, this involves different deletions in the same location, and all mimicry pairs differentially express Abd-B and ncRNAs in this locus. Transcriptomics reveals a shared core gene network across species, where Abd-B interacts with nubbin and pigment enzyme ebony to decrease black melanin production in favor of paler, redder morphs. Expression of multiple genes in the melanin biosynthesis pathway is modified to promote this phenotype, with differing roles by taxon. Replicated morphologies unveil key genes and a Hox gene hotspot, while enabling evolutionary tracking of genetic changes to phenotypic changes and informing how gene regulatory networks evolve. 

Globally, insects have been impacted by climate change, with bumble bees in particular showing range shifts and declining species diversity with global warming. This suggests heat tolerance is a likely factor limiting the distribution and success of these bees. Studies have shown high intraspecific variance in bumble bee thermal tolerance, suggesting biological and environmental factors may be impacting heat resilience. Understanding these factors is important for assessing vulnerability and finding environmental solutions to mitigate effects of climate change. In this study, we assess whether geographic range variation in bumble bees in the eastern United States is associated with heat tolerance and further dissect which other biological and environmental factors explain variation in heat sensitivity in these bees. We examine heat tolerance by caste, sex, and rearing condition (wild/lab) across six eastern US bumble bee species, and assess the role of age, reproductive status, body size, and interactive effects of humidity and temperature on thermal tolerance inBombus impatiens. We found marked differences in heat tolerance by species that correlate with each species' latitudinal range, habitat, and climatic niche, and we found significant variation in thermal sensitivity by caste and sex. Queens had considerably lower heat tolerance than workers and males, with greater tolerance when queens would first be leaving their natal nest, and lower tolerance after ovary activation. Wild bees tended to have higher heat tolerance than lab reared bees, and body size was associated with heat tolerance only in wild‐caught foragers. Humidity showed a strong interaction with heat effects, pointing to the need to regulate relative humidity in thermal assays and consider its role in nature. Altogether, we found most tested biological conditions impact thermal tolerance and highlight the stages of these bees that will be most sensitive to future climate change.