A family-level Tree of Life for bivalves based on a Sanger-sequencing approach

Abstract

The systematics of the molluscan class Bivalvia are explored using a 5-gene Sanger-based approach including the largest taxon sampling to date, encompassing 219 ingroup species spanning 93 (or 82%) of the 113 currently accepted bivalve families. This study was designed to populate the bivalve Tree of Life at the family level and to place many genera into a clear phylogenetic context, but also pointing to several major clades where taxonomic work is sorely needed. Despite not recovering monophyly of Bivalvia or Protobranchia-as in most previous Sanger-based approaches to bivalve phylogeny-our study provides increased resolution in many higher-level clades, and supports the monophyly of Autobranchia, Pteriomorphia, Heteroconchia, Palaeoheterodonta, Heterodonta, Archiheterodonta, Euheterodonta, Anomalodesmata, Imparidentia, and Neoheterodontei, in addition to many other lower clades. However, deep nodes within some of these clades, especially Pteriomorphia and Imparidentia, could not be resolved with confidence. In addition, many families are not supported, and several are supported as non-monophyletic, including Malletiidae, Nuculanidae, Yoldiidae, Malleidae, Pteriidae, Arcidae, Propeamussiidae, Iridinidae, Carditidae, Myochamidae, Lyonsiidae, Pandoridae, Montacutidae, Galeommatidae, Tellinidae, Semelidae, Psammobiidae, Donacidae, Mactridae, and Cyrenidae; Veneridae is paraphyletic with respect to Chamidae, although this result appears to be an artifact. The denser sampling however allowed testing specific placement of species, showing, for example, that the unusual Australian Plebidonax deltoides is not a member of Donacidae and instead nests within Psammobiidae, suggesting that major revision of Tellinoidea may be required. We also showed that Cleidothaerus is sister group to the cementing member of Myochamidae, suggesting that Cleidothaeridae may not be a valid family and that cementation in Cleidothaerus and Myochama may have had a single origin. These results highlight the need for an integrative approach including as many genera as possible, and that the monophyly and relationships of many families require detailed reassessment. NGS approaches may be able to resolve the most recalcitrant nodes in the near future.

A Revised List of the Freshwater Mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada

“…Fossil and modern bivalve higher classification has recently been summarized by Carter et al (2011), with standardized endings for higher taxa within Bivalvia. Recent evidence supports the order Unionida as a monophyletic clade (Combosch et al 2017). There have been two recent assessments of the taxonomy for Margaritiferidae (Bolotov et al 2016;Araujo et al 2017).…”

“…Since publication of Turgeon et al (1988Turgeon et al ( , 1998 and Williams et al (1993), many studies have refined our understanding of mussel systematic taxonomy. Several major publications have addressed systematic relationships within the class Bivalvia, including the order Unionida (Bieler et al 2010;Carter et al 2011;Bolotov et al 2016;Araujo et al 2017;Combosch et al 2017). Major studies specific to the Unionida include Graf andÓ Foighil (2000), Hoeh et al (2001Hoeh et al ( , 2002Hoeh et al ( , 2009, Roe and Hoeh (2003), Campbell et al (2005), Walker et al (2006), Graf andCummings (2007, 2017), Cummings and Graf (2010), and Lydeard (2012a, 2012b).…”

The purplish bifurcate mussel Mytilisepta virgata gene expression atlas reveals a remarkable tissue functional specialization

“…To date, only 31 nucleotide and 11 amino acid sequences have been deposited in public repositories for this species (data retrieved from NCBI, June 2017). These include several partial sequences used for phylogenetic analyses [9, 11, 12], microsatellites [13], a complete mitochondrial sequence (KX094521.1) and a few unrelated sequences referring to still unpublished manuscripts, highlighting the still nearly non-existing molecular knowledge of M. virgata , in stark contrast with the extensive investigations carried out in Mytilus spp. since the early 2000’s [14–18].…”

Karyotype differentiation in tellin shells (Bivalvia: Tellinidae)

“…This is further confirmed by the most recent molecular phylogeny of bivalves that, although including scarce tellin shell sampling, displays Tellinidae, and other Tellinoida families, as polyphiletic and highlights the need of denser taxon sampling in clades, such as Tellinoida, with poorly defined families [37]. This denser sampling has to be accompanied by an accurate determination of the specimens using, as proposed by integrative taxonomy [38, 39], a large number of characters to identify them.…”