Detecting Adaptive Evolution in Phylogenetic Comparative Analysis Using the Ornstein–Uhlenbeck Model

ABSTRACTHost interferon-induced transmembrane proteins (IFITMs) are broad-spectrum antiviral restriction factors. Of these, IFITM3 potently inhibits viruses that enter cells through acidic endosomes, many of which are zoonotic and emerging viruses with bats (order Chiroptera) as natural hosts. We previously demonstrated that microbat IFITM3 is antiviral. Here we show that bat IFITMs are characterized by strong adaptive evolution and identify a highly variable and functionally important site - codon 70 - within the conserved CD225 domain of IFITMs. Mutation of this residue in microbat IFITM3 impairs restriction of four different virus families that enter cells via endosomes. This mutant shows altered subcellular localization and reduced S-palmitoylation, a phenotype copied by mutation of conserved cysteine residues in microbat IFITM3. Furthermore, we show that microbat IFITM3 is S-palmitoylated on cysteine residues C71, C72 and C105, mutation of each cysteine residue individually impairs virus restriction, and a triple C71-C72-C105 mutant loses all restriction, concomitant with subcellular re-localization of microbat IFITM3 to Golgi-associated sites. Thus, we propose that S-palmitoylation is critical for Chiropteran IFITM3 function and identify a key molecular determinant of IFITM3 S-palmitoylation.

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Pteridine pigments compensate for environmental availability of carotenoids

10.22541/au.161132817.77514172/v1 ◽

2021 ◽

Author(s):

Devi Stuart-Fox ◽

Katrina Rankin ◽

Adrian Lutz ◽

Adam Elliott ◽

Andrew Hugall ◽

...

Keyword(s):

Sexual Selection ◽

Comparative Analysis ◽

Skin Tissue ◽

Honest Signalling ◽

Colour Variation ◽

Phylogenetic Comparative Analysis ◽

Environmental Availability ◽

Pigment Concentrations ◽

Production Mechanisms

Carotenoid-based colours are a textbook example of honest signalling because carotenoids must be acquired from the environment. However, many species produce similar colours using self-synthesised pteridine pigments. A compelling but untested hypothesis is that pteridines compensate for low environmental availability of carotenoids because it is metabolically cheaper to synthesise pteridines than to acquire and sequester carotenoids. Based on a phylogenetic comparative analysis of 11 pigment concentrations in skin tissue of agamid lizards, we show that pteridine concentrations are higher and carotenoid concentrations lower in less productive environments. Both carotenoid and pteridine pigments were present in all species, but only pteridine concentrations explained colour variation among species. Furthermore, pigment concentrations were uncorrelated with indices of sexual selection. These results suggest that variation among species in pteridine synthesis compensates for environmental availability of carotenoids and challenge the paradigm of honest carotenoid signalling in vertebrates with complex colour production mechanisms.

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Colour dimorphism in labrid fishes as an adaptation to life on coral reefs

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.0167 ◽

2020 ◽

Vol 287 (1923) ◽

pp. 20200167 ◽

Cited By ~ 1

Author(s):

J. R. Hodge ◽

F. Santini ◽

P. C. Wainwright

Keyword(s):

Sexual Selection ◽

Comparative Analysis ◽

Coral Reefs ◽

Environmental Context ◽

Marine Fishes ◽

Clear Water ◽

Phylogenetic Comparative Analysis ◽

Selective Forces ◽

Colour Dimorphism

Conspicuous coloration displayed by animals that express sexual colour dimorphism is generally explained as an adaptation to sexual selection, yet the interactions and relative effects of selective forces influencing colour dimorphism are largely unknown. Qualitatively, colour dimorphism appears more pronounced in marine fishes that live on coral reefs where traits associated with strong sexual selection are purportedly more common. Using phylogenetic comparative analysis, we show that wrasses and parrotfishes exclusive to coral reefs are the most colour dimorphic, but surprisingly, the effect of habitat is not influenced by traits associated with strong sexual selection. Rather, habitat-specific selective forces, including clear water and structural refuge, promote the evolution of pronounced colour dimorphism that manifests colours less likely to be displayed in other habitats. Our results demonstrate that environmental context ultimately determines the evolution of conspicuous coloration in colour-dimorphic labrid fishes, despite other influential selective forces.

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