Reconciling innovation and adaptation during recurrent colonization of urban environments: Molecular, genetic, and developmental bases

This chapter explores the developmental and evolutionary origins of beak modifications in the house finch (Carpodacus mexicanus)- modifications that have been linked to the exceptional success of this species in urban environments. First, it describes morphological divergence in and natural selection on beak configurations across urban and natural populations. Second, it examines ways in which innovation and adaptation can be reconciled during adaptive diversifications of beaks. Third, it discusses developmental and genetic basis of such cycles of divergence and convergence to urban adaptations and the ways by which ontogenetic mechanisms can accomplish precise, diverse, and yet reversible adaptations in beak configurations. It suggests that both urban adaptations and population divergence were facilitated by modular organization of beak development, where small regulatory changes in conserved molecular growth factors and significant functional redundancy in resulting configurations produce a wide range of adaptive beak modifications. The chapter concludes with a preliminary analysis of the molecular basis behind such adaptive evolution and directions for future studies.