Pancrustacean evolution illuminated by taxon-rich genomic-scale data sets with an expanded remipede sampling

Open Access

Abstract

The relationships of crustaceans and hexapods (Pancrustacea) have been much discussed and partially elucidated following the emergence of phylogenomic data sets. However, major uncertainties still remain regarding the position of iconic taxa such as Branchiopoda, Copepoda, Remipedia, and Cephalocarida, and the sister group relationship of hexapods. We assembled the most taxon-rich phylogenomic pancrustacean data set to date and analyzed it using a variety of methodological approaches. We prioritised low levels of missing data and found that some clades were consistently recovered independently of the analytical approach used. These include, for example, Oligostraca and Altocrustacea. Substantial support was also found for Allotriocarida, with Remipedia as the sister of Hexapoda (i.e., Labiocarida), and Branchiopoda as the sister of Labiocarida, a clade that we name Athalassocarida (="nonmarine shrimps"). Within Allotriocarida, Cephalocarida was found as the sister of Athalassocarida. Finally, moderate support was found for Hexanauplia (Copepoda as sister to Thecostraca) in alliance with Malacostraca. Mapping key crustacean tagmosis patterns and developmental characters across the revised phylogeny suggests that the ancestral pancrustacean was relatively short-bodied, with extreme body elongation and anamorphic development emerging later in pancrustacean evolution. ; J.L.-F. was supported by a Marie Skłodowska-Curie Fellowship (655814) and J.O. was supported by a grant from the Danish Agency for Science, Technology and Innovation (0601-12345B). F.P. was supported by the grant CHALLENGEN (CTM2013-48163) from the Spanish Government and a post-doctoral contract funded by the Beatriu de Pinós Programme of the Generalitat de Catalunya (2014-BPB-00038). J.F.F. was supported by a NERC GW4+ PhD studentship and J.V. and D.P. were supported by a NERC BETR grant (NE/P013678/1). M.G. is supported by a European Marie Curie (ITN – IGNITE) PhD studentship ; Peer reviewed