Phylogenetic relationships of the family Carditidae (Bivalvia: Archiheterodonta)

Abstract

Carditidae is a highly speciose group of bivalves but is one of the more neglected and poorly studied families. This work presents the first phylogenetic study of the entire family, using 77 species-level taxa (including fossil and recent terminals) and 144 new morphological characters. Multiple searches were conducted, including comparisons of discrete and continuous characters and equal and implied weighting. Morphological disparity analysis, phylomorphospace construction and phylogenetic signal analysis were performed using the character matrix. A new systematic scheme is suggested on the basis of these results, including the already proposed subfamily Palaeocarditinae, the redefined Carditinae, Thecaliinae (included within Carditinae in some searches), Carditamerinae (with reduced diversity) and Venericardiinae (with extended diversity). The new subfamily Scalaricarditinae and the new clades Eucarditidae (all carditids excluding Palaeocarditinae), Carditida (Carditinae þ Thecaliinae þ Carditamerinae) and Cyclocardida (Cyclocardia þ Pleuromeris þ Scalaricarditinae þ Miodomeridinae) are proposed. The monophyly of the planicostate and alticostate lineages are confirmed within the Venericardiinae (now formally named Venericorini and Venericardiini, respectively). The relationships of Palaeocarditinae with other carditids and the origin of the family are discussed, as well as the phylogenetic placement of other carditid genera not included in the analyses. Homoplasy and the phylogenetic signals of different morphological characters are also explored and discussed.

Is Cyclocardia (Conrad) a wastebasket taxon? Exploring the phylogeny of the most diverse genus of the Carditidae (Archiheterodonta, Bivalvia)

“…According to Adegoke () the use of genera or subgenera without consensus among carditids is confusing and, as it does not imply a priori phylogenetic inferences (Dubois ), here we follow the approach of Pérez (), with all carditid genera or subgenera considered to have generic status. We selected terminals following the systematic scheme of the Carditidae recently proposed by Pérez (). As outgroups, we used Crassatella ponderosa (Gmelin, ; family Crassatellidae) and Astarte sulcata (da Costa, ; family Astartidae).…”

“…Qualitative approaches are included in the works of Harris (), Stewart (), Gardner & Bowles () and Heaslip (), among others. Quantitative approaches were made by McClure & Lockwood (), González & Giribet () and Pérez (). Most of these analyses focused on alticostate and planicostate lineages; only González & Giribet () and Pérez () explored the whole family.…”

“…Quantitative approaches were made by McClure & Lockwood (), González & Giribet () and Pérez (). Most of these analyses focused on alticostate and planicostate lineages; only González & Giribet () and Pérez () explored the whole family. Chavan () placed Cyclocardia in the subfamily Carditamerinae, but Pérez () included this genus in the Cyclocardida Pérez, clade, related to the subfamily Scalaricarditinae Pérez, .…”

“…Most of these analyses focused on alticostate and planicostate lineages; only González & Giribet () and Pérez () explored the whole family. Chavan () placed Cyclocardia in the subfamily Carditamerinae, but Pérez () included this genus in the Cyclocardida Pérez, clade, related to the subfamily Scalaricarditinae Pérez, . Pérez () used eight species of Cyclocardia in his analysis ( C. cannada (Ihering, ), C. dalek Pérez & del Río, , C. mesembria Stilwell & Zinsmeister, , C. ventricosa , C. compressa (Reeve, ), C. borealis , C. awamoensis (Harris, ), C. nortensis del Río, ) and found a mainly monophyletic genus but with low support and occupying a considerably larger range of morphospace than other carditids.…”

“…Here, we first aim to determine whether Cyclocardia is a ‘wastebasket taxon’ as defined by Plotnick & Wagner (). Secondly, we use quantitative phylogenetic tools to assess the phylogenetic relationships within Cyclocardia and between this genus and other members of the family Carditidae, including representatives of all subfamilies recognized by Pérez (), to explore its monophyly. Finally, we explore the morphological disparity in Cyclocardia to examine the features of this genus in comparison with other carditids.…”