The importance of alternative splicing in adaptive evolution

Although alternative splicing is a ubiquitous co-transcriptional gene regulatory mechanism in plants, animals and fungi, its contribution to evolutionary transitions is understudied. Alternative splicing enables different mRNA isoforms to be generated from the same gene, expanding transcriptomic and thus proteomic diversity. While the role of gene expression variation in adaptive evolution is widely accepted, biologists still debate the functional impact of alternative isoforms on phenotype. In light of recent empirical research linking splice variation to ecological adaptations, we propose that alternative splicing is an important substrate for adaptive evolution and speciation, particularly at short timescales. In this article we synthesise what is known about the role of alternative splicing in adaptive evolution. We discuss the contribution of standing splice variation to phenotypic plasticity and how hybridisation can produce novel splice forms. Going forwards, we propose that alternative splicing be included as a standard analysis alongside gene expression analysis so we can better understand of how alternative splicing contributes to adaptive divergence at the micro- and macroevolutionary levels.