Towards a barnacle tree of life: integrating diverse phylogenetic efforts into a comprehensive hypothesis of thecostracan evolution

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.

Testing adaptive hypotheses on the evolution of larval life history in acorn and stalked barnacles

“…All comparative data analyses were carried out in the R environment version 3.3.1 “Bug in Your Hair” (R Development Core Team, ), using the packages “ape” v. 3.5 (Paradis, Claude, & Strimmer, ), “caper” v. 0.5.2 (Orme et al, ), “geiger” v. 2.0.6 (Harmon, Weir, Brock, Glor, & Challenger, ), “nlme” v. 3.1‐128 (Pinheiro, Bates, DebRoy, Sarkar, & R Core Team, ), “phytools” v. 0.5‐38 (Revell, ), “phylolm” v. 2.5 (Ho & Ané, ), and “sensiPhy” v. 0.5‐0 (Paterno, Werner, & Penone, ). Recent efforts have combined all phylogenetic reconstructions available for Thecostraca, which includes the thoracican barnacles, with a taxonomic backbone to generate a complete phylogenetic hypothesis for Thecostraca (Ewers‐Saucedo et al, ). This synthesis tree does not provide meaningful branch lengths.…”

“…We deposited life history and summary environmental data in https://datadryad.org (https://doi.org/10.5061/dryad.s8800t9). We used the synthesis phylogeny for barnacles of Ewers‐Saucedo et al () to account for phylogenetic nonindependence. The editable tree file (Appendix ) is a supplement of their publication in peerJ.…”

“…From publicly available information on species occurrences and environmental remote‐sensing data, we compiled information on depth, ocean temperature and chlorophyll a concentration, the latter being a proxy for food availability of shallow‐water invertebrates (Lorenzen, ; Marshall et al, ). We accounted for phylogenetic nonindependence using the newly synthesized barnacle tree of life (Ewers‐Saucedo et al, ).…”

Anatomy and Ultrastructure of the Cyprid Temporary Adhesive System in Two Species of Acorn Barnacle

“…Cyprids of different ages were not compared here, however, the gland and ducts of the B. amphitrite specimens contained considerably fewer vesicles than the M. coccopoma specimens, implying either a species-specific difference or that unknown factors can influence temporary adhesive production. It is possible that these differences are attributed to the distance in the evolutionary relationships between stalked and acorn barnacles [20,21].…”

<p class="ZootaxaTitle">Hurdles in fungal taxonomy: Effectiveness of recent methods in discriminating taxa

“…Therefore, phylogenomics has the potential to improve resolution by reducing the stochastic error resulting from the finite length of sequences used in the inference (Som 2015;Nafy & Szollosi 2017). Due to the shallow relationships existing among higher ranks, phylogenomic approaches can be used for better resolution in the tree of life (Spatafora et al 2017;Ewers-Saucedo et al 2019). Therefore, if the resources and the time is available, phylogenomics can be used to infer the relationships or the classification of higher ranks.…”