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Proc Biol Sci. 2019 Sep 11;286(1910):20191502. doi: 10.1098/rspb.2019.1502. Epub 2019 Sep 11.

A phylogenomic framework for pelagiarian fishes (Acanthomorpha: Percomorpha) highlights mosaic radiation in the open ocean.

Author information

1
Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA.
2
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA.
3
Department of Earth Sciences, University of Oxford, Oxford, UK.
4
Department of Ecology and Evolutionary Biology, University of California at Los Angeles, Los Angeles, CA, USA.
5
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
6
Museum of Natural Science, Louisiana State University, Baton Rouge, LA, USA.
7
Natural History Museum and Institute, Chiba, Aoba-cho, Chuo-ku, Chiba, Japan.
8
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.
9
Peabody Museum, Yale University, New Haven, CT, USA.

Abstract

The fish clade Pelagiaria, which includes tunas as its most famous members, evolved remarkable morphological and ecological variety in a setting not generally considered conducive to diversification: the open ocean. Relationships within Pelagiaria have proven elusive due to short internodes subtending major lineages suggestive of rapid early divergences. Using a novel sequence dataset of over 1000 ultraconserved DNA elements (UCEs) for 94 of the 286 species of Pelagiaria (more than 70% of genera), we provide a time-calibrated phylogeny for this widely distributed clade. Some inferred relationships have clear precedents (e.g. the monophyly of 'core' Stromateoidei, and a clade comprising 'Gempylidae' and Trichiuridae), but others are unexpected despite strong support (e.g. Chiasmodontidae + Tetragonurus). Relaxed molecular clock analysis using node-based fossil calibrations estimates a latest Cretaceous origin for Pelagiaria, with crown-group families restricted to the Cenozoic. Estimated mean speciation rates decline from the origin of the group in the latest Cretaceous, although credible intervals for root and tip rates are broad and overlap in most cases, and there is higher-than-expected partitioning of body shape diversity (measured as fineness ratio) between clades concentrated during the Palaeocene-Eocene. By contrast, more direct measures of ecology show either no substantial deviation from a null model of diversification (diet) or patterns consistent with evolutionary constraint or high rates of recent change (depth habitat). Collectively, these results indicate a mosaic model of diversification. Pelagiarians show high morphological disparity and modest species richness compared to better-studied fish radiations in contrasting environments. However, this pattern is also apparent in other clades in open-ocean or deep-sea habitats, and suggests that comparative study of such groups might provide a more inclusive model of the evolution of diversity in fishes.

KEYWORDS:

UCE; adaptive radiation; pelagic realm; speciation; ultraconserved elements

PMID:
31506051
PMCID:
PMC6742994
[Available on 2020-09-11]
DOI:
10.1098/rspb.2019.1502

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