Our paper examining constraints on the evolution of host use in the Melissa blue butterfly (Lycaeides melissa) was published in today’s issue of Molecular Ecology. We were interested in the potential for limited genetic variation or genetic trade-offs in performance on different host plants to slow or prevent adaptation to a novel host, in this case alfalfa. To address this question we conducted a massive larval rearing experiment (see the image below) and generated and analyzed partial genome sequences (GBS data) from the larvae (we also sequenced and assembled a draft whole genome for L. melissa to provide genomic context for our results). We found that L. melissa harbor genetic variation for performance on alfalfa and that genetic variants that affect performance on alfalfa do not affect performance on a native host plant. In other words, we found no evidence that genetic trade-offs limit diet breadth (cause host plant specialization) in these butterflies. I think this study shows how genomic data can be used to better test a classic hypothesis in evolutionary genetics.