Molecular mechanisms of adaptation and speciation: why do we need an integrative approach?

Understanding divergent adaptation and ecological speciation requires the synthesis of multiple approaches, including phenotypic characterization, genetics and genomics, realistic assessment of fitness and population genetic modelling. Current research in this field often approaches this problem from one of two directions: either a mechanistic approach-seeking to link phenotype, genotype and fitness, or a genomic approach-searching for signatures of divergence or selection across the genome. In most cases, these two approaches are not synthesized, and as a result, our understanding is incomplete. We argue that research in adaptation and evolutionary genetics needs to integrate these approaches for multiple reasons, including progress towards understanding the architecture and evolutionary history of adaptation and speciation loci, the ability to untangle linkage and pleiotropy, increased knowledge of mechanisms of genomic evolution and insights into parallel evolutionary events. Identifying the genetic underpinnings of adaptation and ecological speciation is not necessarily the end goal of research, but it is an integral part of understanding the evolutionary process. As a result, it is critical to utilize both genetic and genomic approaches. Challenges remain, particularly in nonmodel organisms and in our ability to synthesize results from multiple experimental systems. Nonetheless, advances in genetic and genomic techniques are increasingly available in a diverse array of systems, and the time is ripe to exploit the synthesis of these two approaches to increase our understanding of evolution.