Common functional targets of adaptive micro‐ and macro‐evolutionary divergence in killifish. Issue 14 (10th July 2013)

• Record Type: Journal Article
• Authors: Whitehead, Andrew; Zhang, Shujun; Roach, Jennifer L.; Galvez, Fernando
• Is Part Of: Molecular ecology. Volume 22:Issue 14(2013)
• Page Start: 3780
• Page End: 3796
• Publication Date: 2013-07-10
• Subjects: Molecular ecology -- Periodicals; Molecular population biology -- Periodicals; 576
• DOI: 10.1111/mec.12316
• Languages: English
• ISSNs: 0962-1083

Abstract

<abstract abstract-type="main" id="mec12316-abs-0001"> <title>Abstract</title> <p>Environmental salinity presents a key barrier to dispersal for most aquatic organisms, and adaptation to alternate osmotic environments likely enables species diversification. Little is known of the functional basis for derived tolerance to environmental salinity. We integrate comparative physiology and functional genomics to explore the mechanistic underpinnings of evolved variation in osmotic plasticity within and among two species of killifish; <italic>Fundulus majalis</italic> harbours the ancestral mainly salt‐tolerant phenotype, whereas <italic>Fundulus heteroclitus</italic> harbours a derived physiology that retains extreme salt tolerance but with expanded osmotic plasticity towards the freshwater end of the osmotic continuum. Common‐garden comparative hypo‐osmotic challenge experiments show that <italic>F. heteroclitus</italic> is capable of remodelling gill epithelia more quickly and at more extreme osmotic challenge than <italic>F. majalis</italic>. We detect an unusual pattern of baseline transcriptome divergence, where neutral evolutionary processes appear to govern expression divergence within species, but patterns of divergence for these genes between species do not follow neutral expectations. During acclimation, genome expression profiling identifies mechanisms of acclimation‐associated response that are conserved within the genus including regulation of paracellular permeability. In contrast, several responses vary among species including those putatively associated with cell volume regulation, and these same mechanisms are targets for adaptive physiological divergence along osmotic gradients within <italic>F. heteroclitus</italic>. As such, the genomic and physiological mechanisms that are associated with adaptive fine‐tuning within species also contribute to macro‐evolutionary divergence as species diversify across osmotic niches.</p> </abstract>