A phylogeny reconstruction of the Dendrophylliidae (Cnidaria, Scleractinia) based on molecular and micromorphological criteria, and its ecological implications

The global significance of Scleractinian corals without photoendosymbiosis

Globally tropical Scleractinian corals have been a focal point for discussions on the impact of a changing climate on marine ecosystems and biodiversity. Research into tropical Scleractinian corals, particularly the role and breakdown of photoendosymbiosis in response to warming, has been prolific in recent decades. However, research into their subtropical, temperate, cold- and deep-water counterparts, whose number is dominated by corals without photoendosymbiosis, has not been as prolific. Approximately 50% of Scleractinian corals (> 700 species) do not maintain photoendosymbiosis and as such, do not rely upon the products of photosynthesis for homeostasis. Some species also have variable partnerships with photendosymbionts depending on life history and ecological niche. Here we undertake a systematic map of literature on Scleractinian corals without, or with variable, photoendosymbiosis. In doing so we identify 482 publications spanning 5 decades. In mapping research effort, we find publications have been sporadic over time, predominately focusing on a limited number of species, with greater research effort directed towards deep-water species. We find only 141 species have been studied, with approximately 30% of the total identified research effort directed toward a single species, Desmophyllum pertusum, highlighting significant knowledge gaps into Scleractinian diversity. We find similar limitations to studied locations, with 78 identified from the global data, of which only few represent most research outputs. We also identified inconsistencies with terminology used to describe Scleractinia without photoendosymbiosis, likely contributing to difficulties in accounting for their role and contribution to marine ecosystems. We propose that the terminology requires re-evaluation to allow further systematic assessment of literature, and to ensure it's consistent with changes implemented for photoendosymbiotic corals. Finally, we find that knowledge gaps identified over 20 years ago are still present for most aphotoendosymbiotic Scleractinian species, and we show data deficiencies remain regarding their function, biodiversity and the impacts of anthropogenic stressors.

Cold-water coral diversity along the continental shelf margin of northwestern South China Sea

Scleractinian cold-water corals (CWCs) are one of the most important habitat engineers of the deep sea. Although the South China Sea (SCS) abuts the biodiversity center of scleractinian CWCs in the western Pacific, only a few sporadic records are available. We discovered new CWC sites by means of trawl sampling and video observation along the continental shelf of the northwestern SCS. All trawled scleractinian CWC specimens were identified to species level according to skeleton morphology and structure. The living CWCs and associated fauna recorded in the video were -identified to a higher level of classification. Scleractinian corals were identified to genus level, while non-scleractinian CWCs were identified to family level and given general names such as gorgonian corals, bamboo corals and black corals. Associated benthic dwellers were divided into major categories. A total of 28 scleractinian CWC species were identified to 7 families, 15 genera, and 1 additional subgenus. Among them, 13 species were colonial, including important habitat-forming species in the genera Eguchipsammia, Dendrophyllia and Cladopsammia. Non-scleractinian CWCs were identified to 7 families, including 4 families gorgonian corals, 1 family bamboo corals, and 2 families black corals. Gorgonian corals were the most abundant non-scleractinian CWCs in this region. Meanwhile, starfish, sea anemones, fish, gastropods, echinoderms, and other associated benthic fauna were recorded in the CWC habitats, with starfish belonging to the order Brisingida being most common. New scleractinian CWC assemblages were discovered along the continental seabed mounds in the northwestern SCS. This study highlights the remarkable diversity of cold-water scleractinian corals in the whole SCS, and shows the potential widespread distribution and conservation prospect of CWC habitats in this region.

A hybrid-capture approach to reconstruct the phylogeny of Scleractinia (Cnidaria: Hexacorallia)

A well-supported evolutionary tree representing most major lineages of scleractinian corals is in sight with the development and application of phylogenomic approaches. Specifically, hybrid-capture techniques are shedding light on the evolution and systematics of corals. Here, we reconstructed a broad phylogeny of Scleractinia to test previous phylogenetic hypotheses inferred from a few molecular markers, in particular, the relationships among major scleractinian families and genera, and to identify clades that require further research. We analysed 449 nuclear loci from 422 corals, comprising 266 species spanning 26 families, combining data across whole genomes, transcriptomes, hybrid capture and low-coverage sequencing to reconstruct the largest phylogenomic tree of scleractinians to date. Due to the large number of loci and data completeness (<38% missing data), node supports were high across shallow and deep nodes with incongruences observed in only a few shallow nodes. The "Robust" and "Complex" clades were recovered unequivocally, and our analyses confirmed that Micrabaciidae Vaughan, 1905 is sister to the "Robust" clade, transforming our understanding of the "Basal" clade. Several families remain polyphyletic in our phylogeny, including Deltocyathiidae Kitahara, Cairns, Stolarski & Miller, 2012, Caryophylliidae Dana, 1846, and Coscinaraeidae Benzoni, Arrigoni, Stefani & Stolarski, 2012, and we hereby formally proposed the family name Pachyseridae Benzoni & Hoeksema to accommodate Pachyseris Milne Edwards & Haime, 1849, which is phylogenetically distinct from Agariciidae Gray, 1847. Results also revealed species misidentifications and inconsistencies within morphologically complex clades, such as Acropora Oken, 1815 and Platygyra Ehrenberg, 1834, underscoring the need for reference skeletal material and topotypes, as well as the importance of detailed taxonomic work. The approach and findings here provide much promise for further stabilising the topology of the scleractinian tree of life and advancing our understanding of coral evolution.

Investigating calcification-related candidates in a non-symbiotic scleractinian coral, Tubastraea spp

In hermatypic scleractinian corals, photosynthetic fixation of CO2 and the production of CaCO3 are intimately linked due to their symbiotic relationship with dinoflagellates of the Symbiodiniaceae family. This makes it difficult to study ion transport mechanisms involved in the different pathways. In contrast, most ahermatypic scleractinian corals do not share this symbiotic relationship and thus offer an advantage when studying the ion transport mechanisms involved in the calcification process. Despite this advantage, non-symbiotic scleractinian corals have been systematically neglected in calcification studies, resulting in a lack of data especially at the molecular level. Here, we combined a tissue micro-dissection technique and RNA-sequencing to identify calcification-related ion transporters, and other candidates, in the ahermatypic non-symbiotic scleractinian coral Tubastraea spp. Our results show that Tubastraea spp. possesses several calcification-related candidates previously identified in symbiotic scleractinian corals (such as SLC4-γ, AMT-1like, CARP, etc.). Furthermore, we identify and describe a role in scleractinian calcification for several ion transporter candidates (such as SLC13, -16, -23, etc.) identified for the first time in this study. Taken together, our results provide not only insights about the molecular mechanisms underlying non-symbiotic scleractinian calcification, but also valuable tools for the development of biotechnological solutions to better control the extreme invasiveness of corals belonging to this particular genus.

The complete mitochondrial genome of Dendrophyllia minuscula (Cnidaria: Scleractinia) from the NEOM region of the Northern Red Sea

The scleractinian coral family Dendrophylliidae is a major component of shallow and deep-water coral ecosystems worldwide, but our knowledge on the evolutionary history of the family remains scarce. Here, we used ezRAD coupled with Illumina sequencing technology and reconstructed the complete mitochondrial genome of Dendrophyllia minuscula (GenBank accession number OL634845), from mesophotic depths in the Red Sea NEOM area. The mitochondrial genome of D. minuscula consisted of 19,054 bp, organized in 13 protein-coding genes, 2 rRNA genes, and 2 tRNA genes, in agreement with the Scleractinia typical mitogenome organization. This complete mitochondrial genome contributes toward a better knowledge of mesophotic and deep-water coral diversity and evolutionary history.

High‐resolution imaging sheds new light on a multi‐tier symbiotic partnership between a “walking” solitary coral, a sipunculan, and a bivalve from East Africa

Marine symbioses are integral to the persistence of ecosystem functioning in coral reefs. Solitary corals of the species Heteropsammia cochlea and Heterocyathus aequicostatus have been observed to live in symbiosis with the sipunculan worm Aspidosiphon muelleri muelleri, which inhabits a cavity within the coral, in Zanzibar (Tanzania). The symbiosis of these photosymbiotic corals enables the coral holobiont to move, in fine to coarse unconsolidated substrata, a process termed as “walking.” This allows the coral to escape sediment cover in turbid conditions which is crucial for these light‐dependent species. An additional commensalistic symbiosis of this coral‐worm holobiont is found between the Aspidosiphon worm and the cryptoendolithic bivalve Jousseaumiella sp., which resides within the cavity of the coral skeleton. To understand the morphological alterations caused by these symbioses, interspecific relationships, with respect to the carbonate structures between these three organisms, are documented using high‐resolution imaging techniques (scanning electron microscopy and µCT scanning). Documenting multi‐layered symbioses can shed light on how morphological plasticity interacts with environmental conditions to contribute to species persistence.

Azooxanthellate Scleractinia (Cnidaria, Anthozoa) from South Africa

Globally, South Africa ranks in the top five countries regarding marine species richness per unit area. Given the high diversity, it is not surprising that many invertebrate taxa in the region are poorly characterised. The South African azooxanthellate Scleractinia (Anthozoa) is one such taxonomic group, and was last reviewed by Boshoff in 1980. Although more recent regional publications have reported on some species, there has not been a faunistic review that accounts for the country's species diversity since then. Moreover, numerous unidentified specimens representing more than three decades of sampling effort have accumulated. In this study the authors update the state of knowledge of South African azooxanthellate coral species. Specimens, particularly those within the extensive collections of the Iziko South African and Smithsonian museums, were morphologically examined and identified. Other data considered included historic data represented as imagery data, associated species data from recent research surveys, and the scientific literature. To date, the study has increased the total number of known species from 77 to 108 across eleven families, 28 new South African records, and three are new species with one new genus.

Phylogenomics, Origin, and Diversification of Anthozoans (Phylum Cnidaria)

Anthozoan cnidarians (corals and sea anemones) include some of the world's most important foundation species, capable of building massive reef complexes that support entire ecosystems. Although previous molecular phylogenetic analyses have revealed widespread homoplasy of the morphological characters traditionally used to define orders and families of anthozoans, analyses using mitochondrial genes or rDNA have failed to resolve many key nodes in the phylogeny. With a fully resolved, time-calibrated phylogeny for 234 species constructed from hundreds of ultraconserved elements and exon loci, we explore the evolutionary origins of the major clades of Anthozoa and some of their salient morphological features. The phylogeny supports reciprocally monophyletic Hexacorallia and Octocorallia, with Ceriantharia as the earliest diverging hexacorals; two reciprocally monophyletic clades of Octocorallia; and monophyly of all hexacoral orders with the exception of the enigmatic sea anemone Relicanthus daphneae. Divergence dating analyses place Anthozoa in the Cryogenian to Tonian periods (648-894 Ma), older than has been suggested by previous studies. Ancestral state reconstructions indicate that the ancestral anthozoan was a solitary polyp that had bilateral symmetry and lacked a skeleton. Colonial growth forms and the ability to precipitate calcium carbonate evolved in the Ediacaran (578 Ma) and Cambrian (503 Ma) respectively; these hallmarks of reef-building species have subsequently arisen multiple times independently in different orders. Anthozoans formed associations with photosymbionts by the Devonian (383 Ma), and photosymbioses have been gained and lost repeatedly in all orders. Together, these results have profound implications for the interpretation of the Precambrian environment and the early evolution of metazoans.[Bilateral symmetry; coloniality; coral; early metazoans; exon capture; Hexacorallia; Octocorallia photosymbiosis; sea anemone; ultraconserved elements.].

The earliest diverging extant scleractinian corals recovered by mitochondrial genomes

Evolutionary reconstructions of scleractinian corals have a discrepant proportion of zooxanthellate reef-building species in relation to their azooxanthellate deep-sea counterparts. In particular, the earliest diverging "Basal" lineage remains poorly studied compared to "Robust" and "Complex" corals. The lack of data from corals other than reef-building species impairs a broader understanding of scleractinian evolution. Here, based on complete mitogenomes, the early onset of azooxanthellate corals is explored focusing on one of the most morphologically distinct families, Micrabaciidae. Sequenced on both Illumina and Sanger platforms, mitogenomes of four micrabaciids range from 19,048 to 19,542 bp and have gene content and order similar to the majority of scleractinians. Phylogenies containing all mitochondrial genes confirm the monophyly of Micrabaciidae as a sister group to the rest of Scleractinia. This topology not only corroborates the hypothesis of a solitary and azooxanthellate ancestor for the order, but also agrees with the unique skeletal microstructure previously found in the family. Moreover, the early-diverging position of micrabaciids followed by gardineriids reinforces the previously observed macromorphological similarities between micrabaciids and Corallimorpharia as well as its microstructural differences with Gardineriidae. The fact that both families share features with family Kilbuchophylliidae ultimately points towards a Middle Ordovician origin for Scleractinia.

New approaches to species delimitation and population structure of anthozoans: Two case studies of octocorals using ultraconserved elements and exons

As coral populations decline worldwide in the face of ongoing environmental change, documenting their distribution, diversity and conservation status is now more imperative than ever. Accurate delimitation and identification of species is a critical first step. This task, however, is not trivial as morphological variation and slowly evolving molecular markers confound species identification. New approaches to species delimitation in corals are needed to overcome these challenges. Here, we test whether target enrichment of ultraconserved elements (UCEs) and exons can be used for delimiting species boundaries and population structure within species of corals by focusing on two octocoral genera, Alcyonium and Sinularia, as exemplary case studies. We designed an updated bait set (29,181 baits) to target-capture 3,023 UCE and exon loci, recovering a mean of 1,910 ± 168 SD per sample with a mean length of 1,055 ± 208 bp. Similar numbers of loci were recovered from Sinularia (1,946 ± 227 SD) and Alcyonium (1,863 ± 177 SD). Species-level phylogenies were highly supported for both genera. Clustering methods based on filtered single nucleotide polymorphisms delimited species and populations that are congruent with previous allozyme, DNA barcoding, reproductive and ecological data for Alcyonium, and offered further evidence of hybridization among species. For Sinularia, results were congruent with those obtained from a previous study using restriction site associated DNA sequencing. Both case studies demonstrate the utility of target-enrichment of UCEs and exons to address a wide range of evolutionary and taxonomic questions across deep to shallow timescales in corals.

Discovery of deep-water coral frameworks in the northern Red Sea waters of Saudi Arabia

This paper reports a deep-water coral framework (a single colonial bush or a larger bioconstruction of coral covering the sea bottom), formed entirely by the scleractinian coral Eguchipsammia fistula (Alcock, 1902) (Dendrophylliidae), in the northern Red Sea waters of Saudi Arabia at a depth of about 640 m. The framework consists of mostly live corals with a total area of about 10 m² and the length of the individual coral branches range from 12 to 30 cm. Although E. fistula is ubiquitous, this discovery is the second record of a framework formed by this species and the first discovery of a large living reef in the Red Sea. The results of the genetic study indicate the potential existence of a genetic variation of E. fistula in the Red Sea. This discovery implies that the Red Sea has favorable habitats for framework-forming DWC species and highlights the need for conducting more systematic surveys for understanding their distribution, abundance, and ecology.

Atlantia, a new genus of Dendrophylliidae (Cnidaria, Anthozoa, Scleractinia) from the eastern Atlantic

Atlantia is described as a new genus pertaining to the family Dendrophylliidae (Anthozoa, Scleractinia) based on specimens from Cape Verde, eastern Atlantic. This taxon was first recognized as Enallopsammia micranthus and later described as a new species, Tubastraea caboverdiana, which then changed the status of the genus Tubastraea as native to the Atlantic Ocean. Here, based on morphological and molecular analyses, we compare fresh material of T. caboverdiana to other dendrophylliid genera and describe it as a new genus named Atlantia in order to better accommodate this species. Evolutionary reconstruction based on two mitochondrial and one nuclear marker for 67 dendrophylliids and one poritid species recovered A. caboverdiana as an isolated clade not related to Tubastraea and more closely related to Dendrophyllia cornigera and Leptopsammia pruvoti. Atlantia differs from Tubastraea by having a phaceloid to dendroid growth form with new corallites budding at an acute angle from the theca of a parent corallite. The genus also has normally arranged septa (not Portualès Plan), poorly developed columella, and a shallow-water distribution all supporting the classification as a new genus. Our results corroborate the monophyly of the genus Tubastraea and reiterate the Atlantic non-indigenous status for the genus. In the light of the results presented herein, we recommend an extensive review of shallow-water dendrophylliids from the Eastern Atlantic.

Anthropogenic impact is negatively related to coral health in Sicily (Mediterranean Sea)

Shallow-water marine organisms are among the first to suffer from combined effects of natural and anthropogenic drivers. The orange coral Astroides calycularis is a shallow-water bioconstructor species endemic to the Mediterranean Sea. Although raising conservation interest, also given its special position within the Dendrophylliidae, information about the threats to its health is scant. We investigated the health status of A. calycularis at five locations in northwestern Sicily along a gradient of cumulative human impact and the most probable origin of the threats to this species, including anthropogenic land-based and sea-based threats. Cumulative human impact appeared inversely related to the performance of A. calycularis at population, colony, and polyp levels. Sea-based human impacts appeared among the most likely causes of the variation observed. The reduction in polyp length can limit the reproductive performance of A. calycularis, while the decrease of percent cover and colony area is expected to impair its peculiar feeding behaviour by limiting the exploitable dimensional range of prey and, ultimately, reef functioning. This endangered habitat-forming species appeared susceptible to anthropogenic pressures, suggesting the need to re-assess its vulnerability status. Creating microprotected areas with specific restrictions to sea-based human impacts could be the best practice preserve these bioconstructions.

Rare coral under the genomic microscope: timing and relationships among Hawaiian Montipora

Background

Evolutionary patterns of scleractinian (stony) corals are difficult to infer given the existence of few diagnostic characters and pervasive phenotypic plasticity. A previous study of Hawaiian Montipora (Scleractinia: Acroporidae) based on five partial mitochondrial and two nuclear genes revealed the existence of a species complex, grouping one of the rarest known species (M. dilatata, which is listed as Endangered by the International Union for Conservation of Nature - IUCN) with widespread corals of very different colony growth forms (M. flabellata and M. cf. turgescens). These previous results could result from a lack of resolution due to a limited number of markers, compositional heterogeneity or reflect biological processes such as incomplete lineage sorting (ILS) or introgression.

Results

All 13 mitochondrial protein-coding genes from 55 scleractinians (14 lineages from this study) were used to evaluate if a recent origin of the M. dilatata species complex or rate heterogeneity could be compromising phylogenetic inference. Rate heterogeneity detected in the mitochondrial data set seems to have no significant impacts on the phylogenies but clearly affects age estimates. Dating analyses show different estimations for the speciation of M. dilatata species complex depending on whether taking compositional heterogeneity into account (0.8 [0.05–2.6] Myr) or assuming rate homogeneity (0.4 [0.14–0.75] Myr). Genomic data also provided evidence of introgression among all analysed samples of the complex. RADseq data indicated that M. capitata colour morphs may have a genetic basis.

Conclusions

Despite the volume of data (over 60,000 SNPs), phylogenetic relationships within the M. dilatata species complex remain unresolved most likely due to a recent origin and ongoing introgression. Species delimitation with genomic data is not concordant with the current taxonomy, which does not reflect the true diversity of this group. Nominal species within the complex are either undergoing a speciation process or represent ecomorphs exhibiting phenotypic polymorphisms.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1476-2) contains supplementary material, which is available to authorized users.

Annotated checklist for stony corals of American Sāmoa with reference to mesophotic depth records

An annotated checklist of the stony corals (Scleractinia, Milleporidae, Stylasteridae, and Helioporidae) of American Sāmoa is presented. A total of 377 valid species has been reported from American Sāmoa with 342 species considered either present (251) or possibly present (91). Of these 342 species, 66 have a recorded geographical range extension and 90 have been reported from mesophotic depths (30–150 m). Additionally, four new species records (Acanthastreasubechinata Veron, 2000, Favitesparaflexuosus Veron, 2000, Echinophylliaechinoporoides Veron & Pichon, 1980, Turbinariairregularis Bernard, 1896) are presented. Coral species of concern include species listed under the US Endangered Species Act (ESA) and the International Union for Conservation of Nature’s (IUCN) Red List of threatened species. Approximately 17.5% of the species present or possibly present are categorized as threatened by IUCN compared to 27% of the species globally. American Sāmoa has seven ESA-listed or ESA candidate species, including Acroporaglobiceps (Dana, 1846), Acroporajacquelineae Wallace, 1994, Acroporaretusa (Dana, 1846), Acroporaspeciosa (Quelch, 1886), Fimbriaphylliaparadivisa (Veron, 1990), Isoporacrateriformis (Gardiner, 1898), and Pocilloporameandrina Dana, 1846. There are two additional species possibly present, i.e., Pavonadiffluens (Lamarck, 1816) and Poritesnapopora Veron, 2000.

Complete mitochondrial genome of Echinophylliaaspera (Scleractinia, Lobophylliidae): Mitogenome characterization and phylogenetic positioning

Lack of mitochondrial genome data of Scleractinia is hampering progress across genetic, systematic, phylogenetic, and evolutionary studies concerning this taxon. Therefore, in this study, the complete mitogenome sequence of the stony coral Echinophylliaaspera (Ellis & Solander, 1786), has been decoded for the first time by next generation sequencing and genome assembly. The assembled mitogenome is 17,697 bp in length, containing 13 protein coding genes (PCGs), two transfer RNAs and two ribosomal RNAs. It has the same gene content and gene arrangement as in other Scleractinia. All genes are encoded on the same strand. Most of the PCGs use ATG as the start codon except for ND2, which uses ATT as the start codon. The A+T content of the mitochondrial genome is 65.92% (25.35% A, 40.57% T, 20.65% G, and 13.43% for C). Bayesian and maximum likelihood phylogenetic analysis have been performed using PCGs, and the result shows that E.aspera clustered closely with Sclerophylliamaxima (Sheppard & Salm, 1988), both of which belong to Lobophylliidae, when compared with species belonging to Merulinidae and other scleractinian taxa used as outgroups. The complete mitogenome of E.aspera provides essential and important DNA molecular data for further phylogenetic and evolutionary analyses of corals.

A phylogeny and the evolution of epizoism within the family Hydrozoanthidae with description of a new genus and two new species

The Family Hydrozoanthidae are macrocnemic zoantharians, however their phylogenetic position is closer to brachycnemic zoantharians than to other macrocnemic zoantharians. Previous studies have indicated the presence of undescribed Hydrozoanthidae species from various locations in the Indo-Pacific Ocean. In this study, two new Hydrozoanthidae species, Aenigmanthus segoi gen. n., sp. n. and Hydrozoanthus sils sp. n., are described from Japanese and Palauan waters based on combined morphological and molecular phylogenetic analyses utilizing multiple genetic markers. Additionally, Hydrozoanthidae consists of species with an obligate epizoic relationship with hydroids (Hydrozoanthus) and of species with facultative epizoic relationships (Aenigmanthus gen. n. and Terrazoanthus). Results of ancestral state reconstruction analyses indicate that Hydrozoanthus gained obligate epizoic relationships in their evolutionary history perhaps due to structural differences of host invertebrates.

Resurrecting a subgenus to genus: molecular phylogeny of Euphyllia and Fimbriaphyllia (order Scleractinia; family Euphyllidae; clade V)

BACKGROUND

The corallum is crucial in building coral reefs and in diagnosing systematic relationships in the order Scleractinia. However, molecular phylogenetic analyses revealed a paraphyly in a majority of traditional families and genera among Scleractinia showing that other biological attributes of the coral, such as polyp morphology and reproductive traits, are underutilized. Among scleractinian genera, the Euphyllia, with nine nominal species in the Indo-Pacific region, is one of the groups that await phylogenetic resolution. Multiple genetic markers were used to construct the phylogeny of six Euphyllia species, namely E. ancora, E. divisa, E. glabrescens, E. paraancora, E. paradivisa, and E. yaeyamaensis. The phylogeny guided the inferences on the contributions of the colony structure, polyp morphology, and life history traits to the systematics of the largest genus in Euphyllidae (clade V) and, by extension, to the rest of clade V.

RESULTS

Analyses of cytochrome oxidase 1 (cox1), cytochrome b (cytb), and β-tubulin genes of 36 colonies representing Euphyllia and a confamilial species, Galaxea fascicularis, reveal two distinct groups in the Euphyllia that originated from different ancestors. Euphyllia glabrescens formed a separate group. Euphyllia ancora, E. divisa, E. paraancora, E. paradivisa, and E. yaeyamaensis clustered together and diverged from the same ancestor as G. fascicularis. The 3'-end of the cox1 gene of Euphyllia was able to distinguish morphospecies.

DISCUSSION

Species of Euphyllia were traditionally classified into two subgenera, Euphyllia and Fimbriaphyllia, which represented a dichotomy on colony structure. The paraphyletic groups retained the original members of the subgenera providing a strong basis for recognizing Fimbriaphyllia as a genus. However, colony structure was found to be a convergent trait between Euphyllia and Fimbriaphyllia, while polyp shape and length, sexuality, and reproductive mode defined the dichotomy better. Species in a genus are distinguished by combining polyp morphology and colony form. The cluster of E. glabrescens of the Euphyllia group is a hermaphroditic brooder with long, tubular tentacles with knob-like tips, and a phaceloid colony structure. The Fimbriaphyllia group, with F. paraancora, F. paradivisa, F. ancora, F. divisa, and F. yaeyamaensis, are gonochoric broadcast spawners with short polyps, mixed types of tentacle shapes, and a phaceloid or flabello-meandroid skeleton. Soft-tissue morphology of G. fascicularis and Ctenella chagius were found to be consistent with the dichotomy.

CONCLUSIONS

The paraphyly of the original members of the previous subgenera justify recognizing Fimbriaphyllia as a genus. The integrated approach demonstrates that combining polyp features, reproductive traits, and skeletal morphology is of high systematic value not just to Euphyllia and Fimbriaphyllia but also to clade V; thus, laying the groundwork for resolving the phylogeny of clade V.

Phylogenetic ecology of gall crabs (Cryptochiridae) as associates of mushroom corals (Fungiidae)

Coral‐associated fauna is a relatively understudied topic. Hence, the nature of the relationship between an associated organism and its host is usually unknown. In the present study, the obligate associations between gall crabs (Decapoda: Cryptochiridae) and mushroom corals (Scleractinia: Fungiidae) are reviewed from a phylogenetic perspective. Based on field surveys, examination of museum material and a literature review, a total of 35 fungiid species have been found that act as hosts for four gall crab species. Fungiid‐associated gall crabs appear to be more geographically widespread than previously known, with new records showing their occurrences from the Red Sea and western Indian Ocean all the way to the central Pacific Ocean. The obligate nature of the association between cryptochirids and their hosts makes them an ideal model taxon to test for possible cospeciation events. The congruence between their phylogenies was tested by using the program Jane 4.0, resulting in cospeciation and duplication events between the crabs and their host corals. The sharing of several closely related host coral species by the same gall crab species or genus may provide support to models indicating phylogenetic relationships within the Scleractinia.

Scleractinian corals (Fungiidae, Agariciidae and Euphylliidae) of Pulau Layang-Layang, Spratly Islands, with a note on Pavonamaldivensis (Gardiner, 1905)

Layang-Layang is a small island part of an oceanic atoll in the Spratly Islands off Sabah, Malaysia. As the reef coral fauna in this part of the South China Sea is poorly known, a survey was carried out in 2013 to study the species composition of the scleractinian coral families Fungiidae, Agariciidae and Euphylliidae. A total of 56 species was recorded. The addition of three previously reported coral species brings the total to 59, consisting of 32 Fungiidae, 22 Agariciidae, and five Euphylliidae. Of these, 32 species are new records for Layang-Layang, which include five rarely reported species, i.e., the fungiids Lithophyllonranjithi, Podabaciasinai, Sandalolithaboucheti, and the agariciids Leptoseriskalayaanensis and Leptoseristroglodyta. The coral fauna of Layang-Layang is poor compared to other areas in Sabah, which may be related to its recovery from a crown-of-thorns seastar outbreak in 2010, and its low habitat diversity, which is dominated by reef slopes consisting of steep outer walls. Based on integrative molecular and morphological analyses, a Pavona variety with small and extremely thin coralla was revealed as Pavonamaldivensis. Since specimens from Sabah previously identified as Pavonamaldivensis were found to belong to Pavonaexplanulata, the affinities and distinctions of Pavonamaldivensis and Pavonaexplanulata are discussed.

The Hidden Diversity of Zanclea Associated with Scleractinians Revealed by Molecular Data

Scleractinian reef corals have recently been acknowledged as the most numerous host group found in association with hydroids belonging to the Zanclea genus. However, knowledge of the molecular phylogenetic relationships among Zanclea species associated with scleractinians is just beginning. This study, using the nuclear 28S rDNA region and the fast-evolving mitochondrial 16S rRNA and COI genes, provides the most comprehensive phylogenetic reconstruction of the genus Zanclea with a particular focus on the genetic diversity among Zanclea specimens associated with 13 scleractinian genera. The monophyly of Zanclea associated with scleractinians was strongly supported in all nuclear and mitochondrial phylogenetic reconstructions. Furthermore, a combined mitochondrial 16S and COI phylogenetic tree revealed a multitude of hidden molecular lineages within this group (Clades I, II, III, V, VI, VII, and VIII), suggesting the existence of both host-generalist and genus-specific lineages of Zanclea associated with scleractinians. In addition to Z. gallii living in association with the genus Acropora, we discovered four well-supported lineages (Clades I, II, III, and VII), each one forming a strict association with a single scleractinian genus, including sequences of Zanclea associated with Montipora from two geographically separated areas (Maldives and Taiwan). Two host-generalist Zanclea lineages were also observed, and one of them was formed by Zanclea specimens symbiotic with seven scleractinian genera (Clade VIII). We also found that the COI gene allows the recognition of separated hidden lineages in agreement with the commonly recommended mitochondrial 16S as a DNA barcoding gene for Hydrozoa and shows reasonable potential for phylogenetic and evolutionary analyses in the genus Zanclea. Finally, as no DNA sequences are available for the majority of the nominal Zanclea species known, we note that they will be necessary to elucidate the diversity of the Zanclea-scleractinian association.

Ecological Niche Model used to examine the distribution of an invasive, non-indigenous coral

All organisms have a set of ecological conditions (or niche) which they depend on to survive and establish in a given habitat. The ecological niche of a species limits its geographical distribution. In the particular case of non-indigenous species (NIS), the ecological requirements of the species impose boundaries on the potential distribution of the organism in the new receptor regions. This is a theoretical assumption implicit when Ecological Niche Models (ENMs) are used to assess the potential distribution of NIS. This assumption has been questioned, given that in some cases niche shift may occur during the process of invasion. We used ENMs to investigate whether the model fit with data from the native range of the coral Tubastraea coccinea Lesson, 1829 successfully predicts its invasion in the Atlantic. We also identified which factors best explain the distribution of this NIS. The broad native distributional range of T. coccinea predicted the invaded sites well, especially along the Brazilian coast, the Caribbean Sea and Gulf of Mexico. The occurrence of T. coccinea was positively related to calcite levels and negatively to eutrophy, but was rather unaffected to other variables that often limit other marine organisms, suggesting that this NIS has wide ecological limits, a trait typical of invasive species.

Descriptions of two azooxanthellate Palythoa species (Subclass Hexacorallia, Order Zoantharia) from the Ryukyu Archipelago, southern Japan

Two new species of zoantharians (Hexacorallia, Zoantharia, Sphenopidae), Palythoamizigama sp. n. and Palythoaumbrosa sp. n., are described from the Ryukyu Archipelago, southern Japan. Unlike almost all other known Palythoa spp., both species are azooxanthellate and inhabit low-light environments such as floors or sides of caves, crevasses, or hollows of shallow coral reefs. The two species were initially considered to be the same species from their similar habitat environments and highly similar morphological features. However, phylogenetic analyses of nuclear internal transcribed spacer (ITS) ribosomal DNA, mitochondrial 16S ribosomal DNA, and cytochrome oxidase subunit I (COI) sequences revealed that these two species have a genetically distant relationship within the genus Palythoa. Morphological characteristics, including polyp size, tentacle number, external/internal coloration, and types and sizes of cnidae were examined in this study. As a result, only tentacle coloration was found to be useful for the morphological distinction between the two species. Palythoamizigama possesses white tentacles with black horizontal stripes while Palythoaumbrosa possesses white tentacles without any stripe patterns. Considering their distant phylogenetic relationship, it can be assumed that their unique yet similar morphological and ecological characteristics developed independently in each species as an example of parallel evolution.