Genomic islands of divergence in the Yellow Tang and the Brushtail Tang Surgeonfishes

Abstract

The current ease of obtaining thousands of molecular markers challenges the notion that full phylogenetic concordance, as proposed by phylogenetic species concepts, is a requirement for defining species delimitations. Indeed, the presence of genomic islands of divergence, which may be the cause, or in some cases the consequence, of speciation, precludes concordance. Here, we explore this issue using thousands of RAD markers on two sister species of surgeonfishes (Teleostei: Acanthuridae), Zebrasoma flavescens and Z. scopas, and several populations within each species. Species are readily distinguished based on their colors (solid yellow and solid brown, respectively), yet populations and species are neither distinguishable using mitochondrial markers (cytochrome c oxidase 1), nor using 5193 SNPs (pairwise Φst = 0.034). In contrast, when using outlier loci, some of them presumably under selection, species delimitations, and strong population structure follow recognized taxonomic positions (pairwise Φst = 0.326). Species and population delimitation differences based on neutral and selected markers are likely due to local adaptation, thus being consistent with the idea that these genomic islands of divergence arose as a consequence of isolation. These findings, which are not unique, raise the question of a potentially important pathway of divergence based on local adaptation that is only evident when looking at thousands of loci.

Genetic Evidence for a Mixed Composition of the Genus Myoxocephalus (Cottoidei: Cottidae) Necessitates Generic Realignment

“…The next-generation sequencing (NGS) provides extensive full nuclear genome data, which is highly efficient for identifying speciation events and taxonomic relationships among non-model fish species. It turned out that a few candidate adaptive genes may demonstrate high divergence and create a barrier for the gene flow leading to reproductive isolation between species, which may be identical for the rest part of the nuclear genome [ 85 , 86 , 87 , 88 ]. A targeted NGS approach makes it possible to identify a suite of loci that can be used in future research to investigate the genomic basis of adaptation, differentiation, speciation, and phylogenetic relationships between sculpins, the most challenging group of fish for genetic and taxonomic studies.…”

Evolutionary Tracks of Chromosomal Diversification in Surgeonfishes (Acanthuridae: Acanthurus) Along the World’s Biogeographic Domains

“…Acanthurus is the most diverse clade with 40 species, of which 90% are endemic to the Indo-Pacific, the origin and dispersion center of the group (Randall, 2001). Despite the growing set of genetic data on Acanthuridae, spanning the nuclear (Bernardi et al, 2018) and the mitochondrial (Ludt et al, 2020) genomes, the cytogenetic features of Acanthuridae are still largely incipient (<10% of species) (Arai and Inoue, 1976;Affonso et al, 2014;Fernandes et al, 2015).…”

Does color matter? Molecular and ecological divergence in four sympatric color morphs of a coral reef fish

“…We identified only those SNPs outside the 99% confidence interval as outliers. Next, we used the F ST values calculated by Genepop v4.7 (Weir & Cockerham, 1984) and considered those loci with F ST values greater than two standard deviations above the mean F ST (2SD) as outliers (modified from Bernardi, Nelson, Paddack, Rulmal, & Crane, 2018).…”