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Friday, August 9, 2013

A new fish family tree

If you had to guess, would you say that tunas are more closely related to swordfish or to seahorses? If you said swordfish, you’d be wrong. So says a new cladogram (family tree) of fish species created by Thomas Near of Yale University and his colleagues. They looked at the phylogeny of acanthomorphs.

Acanthomorphs, aka spiny-rayed or spiny-finned fish, make up a third of all the vertebrate species on Earth. If it’s a non-mammalian vertebrate and it lives in water, there's a good chance it’s an acanthomorph. 

You can see some exceptions below (everything not represented in the top line):
taxon links

Biologists are continually sorting out the evolutionary relationships within that enormous group of other 18,000 species. This time, the researchers compared ten genes sampled from 579 different species, 520 of them acanthomorphs. They came up with the following lovely cladogram.

Time-calibrated phylogenetic tree of Acanthomorpha and results of lineage diversification rate analyses. 
(A) Bayesian inferred maximum clade credibility time tree of 520 acanthomorph species calibrated with 37 fossil-based age constraints. Branch colors and circled numbers identify the nine best-fitting lineage diversification regimes identified using MEDUSA. The dashed gray circle at 66 Ma denotes the K-Pg boundary. The 14 major percomorph clades delimited in this phylogeny are labeled with Roman numerals (I–XIV).  
(B) Time-calibrated phylogeny detailing the earliest divergences within Acanthomorpha. 
(C) Net diversification rate (birth rate minus death rate) estimates. Colors and circled numbers correspond to clades denoted in Fig. 1A
Fish line drawings are by A.D., K. L. Tang, and W.L.S.

Near TJ, Dornburg A, Eytan RI, Keck BP, Smith WL, Kuhn KL, Moore JA, Price SA, Burbrink FT, Friedman M, & Wainwright PC (2013). Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes. Proceedings of the National Academy of Sciences of the United States of America PMID: 23858462.