Abstract
Barnacles and their allies (Thecostraca) are a biologically diverse, monophyletic crustacean group, which includes both intensely studied taxa, such as the acorn and stalked barnacles, as well as cryptic taxa, for example, Facetotecta. Recent efforts have clarified phylogenetic relationships in many different parts of the barnacle tree, but the outcomes of these phylogenetic studies have not yet been combined into a single hypothesis for all barnacles. In the present study, we applied a new “synthesis” tree approach to estimate the first working Barnacle Tree of Life. Using this approach, we integrated phylogenetic hypotheses from 27 studies, which did not necessarily include the same taxa or used the same characters, with hierarchical taxonomic information for all recognized species. This first synthesis tree contains 2,070 barnacle species and subspecies, including 239 barnacle species with phylogenetic information and 198 undescribed or unidentified species. The tree had 442 bifurcating nodes, indicating that 79.3% of all nodes are still unresolved. We found that the acorn and stalked barnacles, the Thoracica, and the parasitic Rhizocephala have the largest amount of published phylogenetic information. About half of the thecostracan families for which phylogenetic information was available were polyphyletic. We queried publicly available geographic occurrence databases for the group, gaining a sense of geographic gaps and hotspots in our phylogenetic knowledge. Phylogenetic information is especially lacking for deep sea and Arctic taxa, but even coastal species are not fully incorporated into phylogenetic studies.
Highlights
The Thecostraca, which include the barnacles (Cirripedia), and the Facetotecta, Ascothoracida, and possibly the Tantulocarida (Petrunina et al, 2014), is a highly variable crustacean group in terms of both morphology and biology (Ruppert, Fox & Barnes, 2003; Høeg & Møller, 2006) (Fig. 1)
As a consequence of the diverse phylogenetic efforts, few studies have included enough of the same taxa or used the same characters to allow an estimate of the Barnacle Tree of Life up to now
To get as complete a taxonomic representation as possible, the NCBI taxonomy has been supplemented with the Backbone Taxonomy from the Global Biodiversity Information facility, the World Registry of Marine Species (WoRMS) taxonomy, and the Interim Register of Marine and Nonmarine Genera from CSIRO
Summary
The Thecostraca, which include the barnacles (Cirripedia), and the Facetotecta, Ascothoracida, and possibly the Tantulocarida (Petrunina et al, 2014), is a highly variable crustacean group in terms of both morphology and biology (Ruppert, Fox & Barnes, 2003; Høeg & Møller, 2006) (Fig. 1). Recent work has assessed phylogenetic relationships among the barnacles at both the higher (Buckeridge, 1996; Korn, 1995; Harris et al, 2000; Pérez-Losada et al, 2002, 2008; Pérez-Losada, Høeg & Crandall, 2004; Glenner & Hebsgaard, 2006; Mallatt & Giribet, 2006; Høeg et al, 2009) and lower (Mokady et al, 1999; Simon-Blecher, Huchon & Achituv, 2007; Shemesh et al, 2009; Brickner, Simon-Blecher & Achituv, 2010; Pérez-Losada et al, 2014; Lin et al, 2015; Gale, 2018; Lin, Kobasov & Chan, 2016) taxonomic ranks These studies have provided great insight into barnacle evolution, confirming morphological patterns in some cases, and highlighting substantial convergence in others. As a consequence of the diverse phylogenetic efforts, few studies have included enough of the same taxa or used the same characters to allow an estimate of the Barnacle Tree of Life up to now
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