Genomic architecture of adaptive color pattern divergence and convergence in Heliconius butterflies

Identifying the genetic changes driving adaptive variation in natural populations is key to understanding the origins of biodiversity. The mosaic of mimetic wing patterns in Heliconius butterflies makes an excellent system for exploring adaptive variation using next-generation sequencing. In this study, we use a combination of techniques to annotate the genomic interval modulating red color pattern variation, identify a narrow region responsible for adaptive divergence and convergence in Heliconius wing color patterns, and explore the evolutionary history of these adaptive alleles. We use whole genome resequencing from four hybrid zones between divergent color pattern races of Heliconius erato and two hybrid zones of the co-mimic Heliconius melpomene to examine genetic variation across 2.2 Mb of a partial reference sequence. In the intergenic region near optix, the gene previously shown to be responsible for the complex red pattern variation in Heliconius, population genetic analyses identify a shared 65-kb region of divergence that includes several sites perfectly associated with phenotype within each species. This region likely contains multiple cis-regulatory elements that control discrete expression domains of optix. The parallel signatures of genetic differentiation in H. erato and H. melpomene support a shared genetic architecture between the two distantly related co-mimics; however, phylogenetic analysis suggests mimetic patterns in each species evolved independently. Using a combination of next-generation sequencing analyses, we have refined our understanding of the genetic architecture of wing pattern variation in Heliconius and gained important insights into the evolution of novel adaptive phenotypes in natural populations.

Partial decentralization as a safeguard against favoritism

In this paper I investigate the optimal level of decentralization of tasks for the provision of a local public good. I enrich the well-known trade-off between internalization of spillovers (that favors centralization) and accountability (that favors decentralization) by considering that public goods are produced through multiple tasks. This adds an additional institutional setting, partial decentralization, to the classical choice between full decentralization and full centralization. The main results are that partial decentralization is optimal when both the variance of exogenous shocks to electorate’s utility is large and the electorate expects high performance from politicians. I also show that the optimal institutional setting depends on the degree of substitutability / complementarity between tasks. In particular, I show that a large degree of substitutability between tasks makes favoritism more likely, which increases the desirability of partial decentralization as a safeguard against favoritism.