300 million years apart: the extreme case of macromorphological skeletal convergence between deltocyathids and a turbinoliid coral (Anthozoa, Scleractinia).

The integration of morphological and molecular lines of evidence has enabled the family Deltocyathidae to be erected to accommodate Deltocyathus species that were previously ascribed to the family Caryophylliidae. However, although displaying the same morphological characteristics as other species of Deltocyathus , molecular data suggested that D. magnificus was phylogenetically distant from Deltocyathidae, falling within the family Turbinoliidae instead. To elucidate the enigmatic evolutionary history of this species and skeletal microstructural features, the phylogenetic relationships of Deltocyathidae and Turbinoliidae were investigated using nuclear ultraconserved and exon loci and complete mitochondrial genomes. Both nuclear and mitochondrial phylogenomic reconstructions confirmed the position of D. magnificus within turbinolids. Furthermore, a novel mitochondrial gene order was uncovered for Deltocyathidae species. This gene order was not present in Turbinoliidae or in D. magnificus that both have the scleractinian canonical gene order, further indicating the taxonomic utility of mitochondrial gene order. D. magnificus is therefore formally moved to the family Turbinoliidae and accommodated in a new genus (Dennantotrochus Kitahara, Vaga & Stolarski, gen. nov.). Surprisingly, turbinolids and deltocyathids do not differ in microstructural organisation of the skeleton that consists of densely packed, individualised rapid accretion deposits and thickening deposits composed of fibres perpendicular to the skeleton surface. Therefore, although both families are clearly evolutionarily divergent, macromorphological features indicate a case of skeletal convergence while these may still share conservative biomineralisation mechanisms. ZooBank: urn:lsid:zoobank.org:pub:5F1C0E25-3CC6-4D1F-B1F0-CD9D0014678E.

The mitochondrial genomes of Crispatotrochus rubescens and Crispatotrochus rugosus (Hexacorallia; Scleractinia): new insights on the phylogeny of the family Caryophylliidae.

BACKGROUND: Caryophylliidae is one of the most diverse scleractinian families, however it was recovered as polyphyletic in multiple molecular studies. Recently, the mitochondrial gene order was proposed as a character for a taxonomic revision of the family. Here we describe the first mitogenome of the caryophylliid genus Crispatotrochus, whose phylogenetic position remains uncertain. METHODS AND RESULTS: The complete mitochondrial genomes of Crispatotrochus rubescens and Crispatotrochus rugosus were sequenced, assembled, and annotated. The two mitogenomes are identical and circular, have a length of 16,536 bp, a GC content of 35.9%, and contain 13 protein-coding genes, 2 ribosomal RNAs and 2 transfer RNAs. Both species have a transposition of a three gene block - cob, nad2, and nad6 - similarly to a group of caryophylliid genera that were recovered as monophyletic, including the type genus (Caryophyllia) of the family. The phylogenetic analyses recovered Crispatotrochus within the clade that presents the gene rearrangement and specifically as sister taxa of the genus Caryophyllia, a result consistent with previous studies and the similar gross morphology of the two genera. CONCLUSIONS: We determined the mitochondrial genomes of the genus Crispatotrochus to investigate their relations within Scleractinia. Results from this study provide insights on the phylogenetic position of the genus and corroborate that the mitochondrial gene order could be used as taxonomic character for the family Caryophylliidae.

Caryophylliids (Anthozoa, Scleractinia) and mitochondrial gene order: Insights from mitochondrial and nuclear phylogenomics.

Molecularly, the family Caryophylliidae is polyphyletic and different sets of genetic data converge towards a consensus that a taxonomic review of this family is necessary. Overall, the order of genes in the mitochondrial genome (mitogenome) together with DNA sequences have been used to successfully untangle evolutionary relationships in several groups of organisms. Published mitogenomes of two caryophylliid genera (Desmophyllum and Solenosmilia) present a transposition of the gene block containing cob, nad2, and nad6, which is located between nad5 5' exon and trnW, while that of Polycyathus chaishanensis presents the same gene order as the majority of scleractinian corals. In molecular-based evolutionary reconstructions, caryophylliids that have the mitochondrial gene rearrangement were recovered as a monophyletic lineage ("true" caryophylliids), while members of the genus Polycyathus were placed in a different position. In this study, additional mitogenomes of this family were assembled and included in evolutionary reconstructions of Scleractinia in order to improve our understanding on whether the mitogenome gene rearrangement is limited to and, therefore, could be a synapomorphy of the actual members of Caryophylliidae. Specimens of Caryophyllia scobinosa, Premocyathus sp., Heterocyathus sulcatus, and Trochocyathus caryophylloides, as well as Desmophyllum pertusum and Solenosmilia variabilis from the Southwest Atlantic were sequenced using Illumina platforms. Then, mitochondrial genomes were assembled and annotated, and nuclear datasets were recovered in-silico from assembled contigs using a previously published set of baits. Evolutionary reconstructions were performed using mitochondrial and nuclear datasets and based on Maximum Likelihood and Bayesian Inference. Obtained mitogenomes are circular and range between 15,816 and 18,225 bp in size and from 30.76% to 36.63% in GC content. The gene rearrangement is only seen in C. scobinosa, D. pertusum, Premocyathus sp., and S. variabilis, which were recovered as a monophyletic clade in both mitochondrial and nuclear phylogenies. On the other hand, the "caryophylliids" with the canonical mitogenome gene order were not recovered within this clade. Differences in features of the skeleton of "true" caryophylliids in comparison to traditional members of the family were observed and offer further support that the gene rearrangement might be seen as a synapomorphy of family Caryophylliidae.

Multiple introductions and secondary dispersion of Tubastraea spp. in the Southwestern Atlantic.

Accidental introduction through ballast water and biofouling are currently the main factors responsible for spreading non-indigenous species in the marine realm. In the Southwestern Atlantic, two scleractinian corals, Tubastraea coccinea and T. tagusensis, have been introduced by opportunistic colonization in 1980 and are now widespread along more than 3,500 km of coastline. To better understand the invasion process and the role of vectors in spreading these species, we sampled 306 and 173 colonies of T. coccinea and T. tagusensis from invaded sites, possible vectors and one native population. Analyses revealed a higher diversity of multi-locus genotypes (MLGs) on vectors, suggesting that they were contaminated prior to their arrival in the Southwestern Atlantic, and a high proportion of clones at invaded sites, with few genotypes spread over ~2,000 km. This broad distribution is most likely a result of secondary introductions through the transport of contaminated vectors. Results also suggest the occurrence of multiple invasions, mainly in the northernmost sites. In summary, clonality, secondary introductions, and multiple invasions are the main reasons for the broad spread and invasive success of Tubastraea spp. in the Southwestern Atlantic. Consequently, the correct control of vectors is the most effective approach for management and prevention of new invasions.

Complete mitochondrial genome sequences of Atlantic representatives of the invasive Pacific coral species Tubastraea coccinea and T. tagusensis (Scleractinia, Dendrophylliidae): Implications for species identification.

Members of the azooxanthellate coral genus Tubastraea are invasive species with particular concern because they have become established and are fierce competitors in the invaded areas in many parts of the world. Pacific Tubastraea species are spreading fast throughout the Atlantic Ocean, occupying over 95% of the available substrate in some areas and out-competing native endemic species. Approximately half of all known coral species are azooxanthellate but these are seriously under-represented compared to zooxanthellate corals in terms of the availability of mitochondrial (mt) genome data. In the present study, the complete mt DNA sequences of Atlantic individuals of the invasive scleractinian species Tubastraea coccinea and Tubastraea tagusensis were determined and compared to the GenBank reference sequence available for a Pacific "T. coccinea" individual. At 19,094bp (compared to 19,070bp for the GenBank specimen), the mt genomes assembled for the Atlantic T. coccinea and T. tagusensis were among the longest sequence determined to date for "Complex" scleractinians. Comparisons of genomes data showed that the "T. coccinea" sequence deposited on GenBank was more closely related to that from Dendrophyllia arbuscula than to the Atlantic Tubastraea spp., in terms of genome length and base pair similarities. This was confirmed by phylogenetic analysis, suggesting that the former was misidentified and might actually be a member from the genus Dendrophyllia. In addition, although in general the COX1 locus has a slow evolutionary rate in Scleractinia, it was the most variable region of the Tubastraea mt genome and can be used as markers for genus or species identification. Given the limited data available for azooxanthellate corals, the results presented here represent an important contribution to our understanding of phylogenetic relationships and the evolutionary history of the Scleractinia.