Phylogeny of Branchiopoda (Crustacea) based on a combined analysis of morphological data and six molecular loci

Abstract

The phylogenetic relationships of branchiopod crustaceans have been in the focus of a number of recent morphological and molecular systematic studies. Although agreeing in some respects, major differences remain. We analyzed molecular sequences and morphological characters for 43 branchiopods and two outgroups. The branchiopod terminals comprise all eight ''orders''. The molecular data include six loci: two nuclear ribosomal genes (18S rRNA, 28S rRNA), two mitochondrial ribosomal genes (12S rRNA, 16S rRNA), one nuclear protein coding gene (elongation factor 1a), and one mitochondrial protein coding gene (cytochrome c oxidase subunit I). A total of 65 morphological characters were analyzed dealing with different aspects of branchiopod morphology, including internal anatomy and larval characters. The morphological analysis resulted in a monophyletic Phyllopoda, with Notostraca as the sister group to the remaining taxa supporting the Diplostraca concept (''Conchostraca'' + Cladocera). ''Conchostraca'' is not supported but Cyclestheria hislopi is the sister group to Cladocera (constituting together Cladoceromorpha) and Spinicaudata is closer to Cladoceromorpha than to Laevicaudata. Cladocera is supported as monophyletic. The combined analysis under equal weighting gave results in some respects similar to the morphological analysis. Within Phyllopoda, Cladocera, Cladoceromorpha and Spinicaudata + Cladoceromorpha are monophyletic. The combined analysis is different from the morphological analysis with respect to the position of Notostraca and Laevicaudata. Here, Laevicaudata is the sister group to the remaining Phyllopoda and Notostraca is sister group to Spinicaudata and Cladoceromorpha. A sensitivity analysis using 20 different parameter sets (different insertion-deletion [indel] ⁄ substitution and transversion ⁄ transition ratios) show the monophyly of Anostraca, Notostraca, Laevicaudata, Spinicaudata, Cladoceromorpha, Cladocera, and within Cladocera, of Onychopoda and Gymnomera under all or almost all (i.e., 19 of 20) parameter sets. Analyses with an indel-to-transversion ratio up to 2 result in monophyletic Phyllopoda, with Laevicaudata as sister group to the remaining Phyllopoda and with Spinicaudata and Cladoceromorpha as sister groups. Almost all analyses (including those with higher indel weights) result in the same topology when only ingroup taxa are considered.Ó The Willi Hennig Society 2007.Branchiopoda comprise approximately 1180 described species of mainly freshwater dwelling crustaceans (Adamowicz and Purvis, 2005). It includes taxa with a general, archaic morphology very similar to that of some Cambrian and Devonian crustacean fossils (Anostraca, Notostraca, Spinicaudata), as well as taxa that are highly specialized for predatory, scraping, parasitism, and advanced filtration such as the water fleas (Scourfield

The Morphological Radiation of Setae in the Cladocera (Crustacea) and Their Potential for Morphogenesis

“…of OLESEN (1999). Developmental data support our version and not the version of RICHTER et al (2007). In contrast, development of the Notostraca and Laevicaudata (MØLLER et al, 2003;OLESEN and GRYGIER, 2003) unambiguously suggests that the paired posterior projections of their bodies are caudal branches.…”

“…In Cyclestheria, the closest relative of the Cladocera, there are other spines on the postabdomen, quite similar to postabdominal claws in morphology and size (see photo by KOTOV, 2006c). mind that the latter animal is a very distant relative of the Cladoceromorpha, and is regarded to be related to Notostraca + Kazacharthra according to RICHTER et al (2007) themselves. So, the appearance of a Castracollis-like caudal portion in this line does not supply us with information on the evolution of the caudal portion in another line, the Phyllopoda.…”

“…17). Paired telsonal setae are present not only in all cladocerans, but also in the cyclestherids, laevicaudatans, spinicaudatans, and notostracans (OLESEN, 1999;OLESEN and GRYGIER, 2003;MØLLER et al, 2003;RICHTER et al, 2007). In cladocerans they are bisegmented (which was checked for other orders) and are called "postabdominal setae" or "setae natatoriae".…”

Molecular phylogeny of the Notostraca

“…This software is among the most accurate programs for multiple sequence alignment of nucleotide data as well as inference of guide trees and it clearly outperforms the traditional programs for gap Table 1 Samples of Notostraca analysed in this study. Voucher numbers refer to tissue vouchers in the 'MTD-TW' tissue collection of the Museum of Zoology, Senckenberg Dresden (Germany), with the exception of the sample of Triops australiensis (from the 'ZMUC CRU' collection of the Zoological Museum, University of Copenhagen, see Richter et al, 2007). Accession numbers in italics refer to sequences previously published in GenBank.…”

The first Cenozoic spinicaudatans from North America

“…Recent phylogenetic analyses (e.g., Richter et al, 2007;Olesen, 2009) have cogently demonstrated that this grouping is paraphyletic. However, the monophyly of the Spinicaudata, which includes the vast majority of "clam shrimp," is firmly established (e.g., Olesen, 2000Olesen, , 2009Stenderup et al, 2006;Richter et al, 2007;Schwentner et al, 2009). A recent review by Astrop and Hegna (2015) examined the relationships among living and fossil spinicaudatans, and their recommendations are followed herein.…”