Taxonomic Challenges Research Articles

Integrative taxonomy reveals a new species of pacu (Characiformes: Serrasalmidae: Myloplus) from the Brazilian Amazon

ABSTRACT Pacus of the genus Myloplus represent a formidable taxonomic challenge, and particularly so for the case of M. asterias and M. rubripinnis, two widespread and common species that harbor considerable morphological diversity. Here we apply DNA barcoding and multiple species discovery methods to find candidate species in this complex group. We report on one well-supported lineage that is also morphologically and ecologically distinct. This lineage represents a new species that can be distinguished from congeners by the presence of dark chromatophores on lateral-line scales, which gives the appearance of a black lateral line. It can be further diagnosed by having 25-29 branched dorsal-fin rays (vs. 18-24), 89-114 perforated scales from the supracleithrum to the end of hypural plate (vs. 56-89), and 98-120 total lateral line scales (vs. 59-97). The new species is widely distributed in the Amazon basin, but seems to have a preference for black- and clearwater habitats. This ecological preference and black lateral line color pattern bears a striking similarity to the recently described silver dollar Metynnis melanogrammus.

Application of metagenomic shotgun sequencing to detect vector-borne pathogens in clinical blood samples.

BackgroundVector-borne pathogens are a significant public health concern worldwide. Infections with these pathogens, some of which are emerging, are likely under-recognized due to the lack of widely-available laboratory tests. There is an urgent need for further advancement in diagnostic modalities to detect new and known vector-borne pathogens. We evaluated the utility of metagenomic shotgun sequencing (MGS) as a pathogen agnostic approach for detecting vector-borne pathogens from human blood samples.MethodsResidual whole blood samples from patients with known infection with Babesia microti, Borrelia hermsii, Plasmodium falciparum, Mansonella perstans, Anaplasma phagocytophilum or Ehrlichia chaffeensis were studied. Samples underwent DNA extraction, removal of human DNA, whole genome amplification, and paired-end library preparation, followed by sequencing on Illumina HiSeq 2500. Bioinformatic analysis was performed using the Livermore Metagenomics Analysis Toolkit (LMAT), Metagenomic Phylogenetic Analysis (MetaPhlAn2), Genomic Origin Through Taxonomic CHAllenge (GOTTCHA) and Kraken 2.ResultsEight samples were included in the study (2 samples each for P. falciparum and A. phagocytophilum). An average of 27.5 million read pairs was generated per sample (range, 18.3–38.8 million) prior to removal of human reads. At least one of the analytic tools was able to detect four of six organisms at the genus level, and the organism present in five of eight specimens at the species level. Mansonella and Ehrlichia species were not detected by any of the tools; however, mitochondrial cytochrome c oxidase subunit I amino acid sequence analysis suggested the presence of M. perstans genetic material.ConclusionsMGS is a promising tool with the potential to evolve as a non-hypothesis driven diagnostic test to detect vector-borne pathogens, including protozoa and helminths.

Integrative taxonomy delimits species within the Duranta sprucei complex

Species boundaries in the Duranta sprucei complex have been a taxonomic challenge, displaying complex patterns of variation in vegetative morphology. This complex includes plants distributed in the Neotropical Andes from Bolivia to Colombia and the mountains of Central America. Previous authors delimited taxa morphologically, and different criteria have been reflected in the recognition of a variable number of taxa. Lineage divergence forms a temporal process whence populations may diverge morphologically and/or ecologically, and this contingent property of taxa should provide the criteria necessary for species delimitation. To clarify the taxonomy of the Duranta sprucei complex, an integrative methodology based on a modified Population Aggregation Analysis and a Species Distribution Modelling approach was employed. Morphology was used to discriminate species with different predicted distributions that share environmental parameters. As a result, the complex is here circumscribed to include four previously recognized species, D. benthamii, D. costaricensis, D. penlandii and D. sprucei, one former variety elevated to the rank of species, D. espinosae, and a new species, D. dickinsonii, endemic to the Peruvian Yungas. One new synonym and a new combination are also herein presented.

A New Genome-to-Genome Comparison Approach for Large-Scale Revisiting of Current Microbial Taxonomy

Microbial diversity has always presented taxonomic challenges. With the popularity of next-generation sequencing technology, more unculturable bacteria have been sequenced, facilitating the discovery of additional new species and complicated current microbial classification. The major challenge is to assign appropriate taxonomic names. Hence, assessing the consistency between taxonomy and genomic relatedness is critical. We proposed and applied a genome comparison approach to a large-scale survey to investigate the distribution of genomic differences among microorganisms. The approach applies a genome-wide criterion, homologous coverage ratio (HCR), for describing the homology between species. The survey included 7861 microbial genomes that excluded plasmids, and 1220 pairs of genera exhibited ambiguous classification. In this study, we also compared the performance of HCR and average nucleotide identity (ANI). The results indicated that HCR and ANI analyses yield comparable results, but a few examples suggested that HCR has a superior clustering effect. In addition, we used the Genome Taxonomy Database (GTDB), the gold standard for taxonomy, to validate our analysis. The GTDB offers 120 ubiquitous single-copy proteins as marker genes for species classification. We determined that the analysis of the GTDB still results in classification boundary blur between some genera and that the marker gene-based approach has limitations. Although the choice of marker genes has been quite rigorous, the bias of marker gene selection remains unavoidable. Therefore, methods based on genomic alignment should be considered for use for species classification in order to avoid the bias of marker gene selection. On the basis of our observations of microbial diversity, microbial classification should be re-examined using genome-wide comparisons.

Testing DNA barcodes against morphology for the ‘tripectinate Abantiades' (Lepidoptera: Hepialidae) reveals a complex relationship between COI sequence data and morphology

AbstractWe analyse COI sequence data from 140 specimens of the Australian ‘tripectinate‐Abantiades' to explore the group's molecular diversity and identify potential taxonomic challenges for future studies. A recent taxonomic revision raised the number of species in the group from three to 10. Our results generally agree with that study, but we identify further potential new species. However, our results also highlight the limitations of single gene taxonomic studies as some otherwise well‐defined species are non‐monophyletic in our analyses – in particular Abantiades argentata Tindale appears paraphyletic with respect to several other lineages, and may comprise more than one species. Overall, the mitochondrial COI diversity of the ‘tripectinate‐Abantiades' can be divided into three major groups, with a majority of the species found in the semi‐arid regions of South Australia and Western Australia.

Wing vein shape signal in Culicoides oxystoma (Schultzei group) in Nigeria – Tool for discrimination (diptera: Ceratopogonidae) using geometric approach

Culicoides oxystoma, C. enderleini, C. schultzei and C. subschultzei belong to the Schultzei group of biting midges in the Order Diptera and are members of the Nematocera sub-order. They are vectors of economically important livestock diseases. Precise morphological identification for discrimination between members of the group has remained ambiguous and incoherent in literature, but necessary in entomologic evaluations of disease transmission and epidemiology in solving taxonomic challenges among groups. Wing phenotypes represent signaling patterns useful for classification of Culicoides in two vegetation zones (Ibadan, rainforest zone and Makurdi, Guinea savannah zone) of Nigeria. This study utilized landmark-based geometric morphometric approach in differentiating wing venation patterns of C. oxystoma, C. enderleini, C. schultzei and C. subschultzei, thus providing baseline data for classification of biting midges in Nigeria. The wing shape of C. oxystoma revealed specific variability with at least two morphologic variants that were hitherto unclassified. Landmarks on the first dorsal and cubital veins contributed 68% and 92% of all variations and distinguished C. oxystoma from others in the group; both shape and size elements were found responsible for species discriminations. Only one morpho-typic variant of C. schultzei was observed with predominance of ecotypes based on geographical location. A consistent morpho-geometry of wing venation found in C. schultzei suggested non-plasticity in morphology while C. enderleini demonstrated the widest variability. Based on landmarks and phylogenetic analyses, it is suggested that the Schultzei group of Culicoides (genus Latreille) in Nigeria be updated with a C. oxystoma subgenus.

DNA Barcoding and Taxonomic Challenges in Describing New Putative Species: Examples from Sootywing and Cloudywing Butterflies (Lepidoptera: Hesperiidae)

DNA barcoding has resulted in the ‘discovery’ of a vast number of new species and subspecies. Assigning formal scientific names to these taxa remains a major challenge. Names sometimes are newly designated. Alternatively, available valid names can be resurrected from synonymy, based on barcode analyses together with classical taxonomic characters. For the most part, however, new putative species revealed by barcoding studies go undescribed. This situation is most often attributed to insufficient taxonomic expertise with the authors conducting the study, together with a critical lack of formally trained taxonomists. However, even with formal training, and additional supportive data from morphological, ecological or life history characters, other factors can arise that impede new species descriptions. In the present paper, several specific taxonomic challenges that have arisen from barcode analyses in two groups of skipper butterflies (Lepidoptera: Hesperiidae), the Sootywings (Pholisora catullus and P. mejicanus) and the Coyote Cloudywing (Achalarus toxeus) are highlighted and discussed. Both P. catullus and A. toxeus show relatively large intraspecific genetic divergences of barcodes (2–3%) which suggests the possibility of previously unrecognized cryptic speciation within each group. Some of the challenges to providing formal names and clarifying taxonomic status of these cryptic taxa could be largely overcome by (1) barcoding type specimens, (2) clarifying imprecise and often vague or suspect type localities, and (3) by conducting in-depth comparative studies on genitalic morphology.

Evolutionary lineages of marine snails identified using molecular phylogenetics and geometric morphometric analysis of shells

The relationship between morphology and inheritance is of perennial interest in evolutionary biology and palaeontology. Using three marine snail genera Penion, Antarctoneptunea and Kelletia, we investigate whether systematics based on shell morphology accurately reflect evolutionary lineages indicated by molecular phylogenetics. Members of these gastropod genera have been a taxonomic challenge due to substantial variation in shell morphology, conservative radular and soft tissue morphology, few known ecological differences, and geographical overlap between numerous species. Sampling all sixteen putative taxa identified across the three genera, we infer mitochondrial and nuclear ribosomal DNA phylogenetic relationships within the group, and compare this to variation in adult shell shape and size. Results of phylogenetic analysis indicate that each genus is monophyletic, although the status of some phylogenetically derived and likely more recently evolved taxa within Penion is uncertain. The recently described species P. lineatus is supported by genetic evidence. Morphology, captured using geometric morphometric analysis, distinguishes the genera and matches the molecular phylogeny, although using the same dataset, species and phylogenetic subclades are not identified with high accuracy. Overall, despite abundant variation, we find that shell morphology accurately reflects genus-level classification and the corresponding deep phylogenetic splits identified in this group of marine snails.

The Taxonomy and Population Structure of the Buckeye Butterflies (GenusJunonia, Nymphalidae: Nymphalini) of Florida, USA

The buckeye butterflies (genus Junonia) that occur in Florida, USA have been an ongoing taxonomic challenge for over 100 years. Schwartz (1987. Milwaukee Pub. Mus. Contrib. Biol. Geol. 73: 21) described the situation succinctly: “No other lepidopteran on the Florida Keys nor in south Florida, presents the taxonomic problems as Junonia.” The current consensus recognizes 3 different forms of Junonia in Florida based on morphological characters, but there is a general lack of consensus regarding the appropriate scientific names for each form. Similarities between the species that occur in Florida, intraspecific variation, and possible hybridization between species have often made it challenging to identify specimens, define the population structure of Junonia butterflies, or to understand the relationships of these butterfly populations to those elsewhere in the New World. We use a combination of morphological characters, mitochondrial cytochrome oxidase I barcodes, nuclear wingless DNA sequences, and randomly amplified DNA fingerprints from Junonia from Florida, the Caribbean, and North and South America to resolve issues of taxonomy and population structure in this genus. We conclude that the common buckeye (J. coenia), the mangrove buckeye (J. neildi), and the tropical buckeye (J. zonalis) occur in Florida and that hybridization between these species takes place in this region.

DINA Bits - Small Services Growing in the DINA System

The DINA system (“DIgital information system for NAtural history data”, https://dina-project.net) consists of several web-based services that fulfill specific tasks. Most of the existing services are covering single core features in the collection management system and can be used either as integrated components in the DINA environment, or as stand-alone services. In this presentation single services will be highlighted as they represent technically interesting approaches and practical solutions for daily challenges in collection management, data curation and migration workflows. The focus will be on the following topics: (1) a generic reporting and label printing service, (2) practical decisions on taxonomic references in collection data and (3) the generic management and referencing of related research data and metadata: Reporting as presented in this context is defined as an extraction and subsequent compilation of information from the collection management system rather than just summarizing statistics. With this quite broad understanding of the term the DINA Reports & Labels Service (Museum für Naturkunde Berlin 2018) can assist in several different collection workflows such as generating labels, barcodes, specimen lists, vouchers, paper loan forms etc. As it is based on customizable HTML templates, it can be even used for creating customized web forms for any kind of interaction (e.g. annotations). Many collection management systems try to cope with taxonomic issues, because in practice taxonomy is used not only for determinations, but also for organizing the collections and categorizing storage units (e.g. “Coleoptera hall”). Addressing taxonomic challenges in a collection management system can slow down development and add complexity for the users. The DINA system uncouples these issues in a simple taxonomic service for the sole assignment of names to specimens, for example determinations. This draws a clear line between collection management and taxonomic research, of which the latter can be supported in a separate service. While the digitization of collection data and workflows proceeds, linking related data is essential for data management and enrichment. In many institutions research data is disconnected from the collection specimen data because the type and structure cannot be easily included in the collection management databases. With the DINA Generic Data Module (Museum für Naturkunde Berlin 2017) a service exists that allows for attaching any relational data structures to the DINA system. It can also be used as a standalone service that accommodates structured data within a DINA compliant interface for data management.

Five new species and two new genera of xenophyophores (Foraminifera: Rhizaria) from part of the abyssal equatorial Pacific licensed for polymetallic nodule exploration

Based on a combination of morphological and molecular data, we describe five new species and two new genera of xenophyophores from the Clarion–Clipperton Zone (abyssal eastern Pacific), an area with commercially valuable seafloor deposits of polymetallic nodules. Bizarria bryiformis gen. et sp. nov. displays unusual features, notably an organic-walled test, largely devoid of agglutinated particles, comprising interconnected branches growing upwards from the nodule substrate; the bases of the branches contain dark masses of waste material (stercomare) and pale strands of cytoplasm (granellare), the whitish, tuft-like extremities contain sediment particles. Tendalia reteformis gen. et sp. nov. forms a delicate network of agglutinated tubes. Shinkaiya contorta sp. nov. is characterized by a contorted, partly reticulated plate-like test while the simpler plate-like test of Galatheammina interstincta sp. nov. combines characters typical of Galatheammina and Psammina. In Semipsammina mattaeformis sp. nov., a thin, delicate test with one or more tubular extensions forms a flat canopy over the mat-like stercomare encrusting the nodule substrate. Tendalia reteformis and S. contorta are free-living; the other species are sessile on nodules. Together, they illustrate the considerable morphological diversity of xenophyophores in a region where they dominate the megafauna, and highlight some major taxonomic challenges posed by these giant monothalamous foraminifera.

Phenotypic and mtDNA variation in Philippine Kappaphycus cottonii (Gigartinales, Rhodophyta)

Members of the carrageenan-producing seaweeds of the genus Kappapphycus have a complicated taxonomic history particularly with regard to species identification. Many taxonomic challenges in this group have been currently addressed with the use of mtDNA sequences. The phylogenetic status and genetic diversity of one of the lesser known species, Kappaphycus cottonii, have repeatedly come into question. This study explored the genetic variation in Philippine K. cottonii using the mtDNA COI-5P gene and cox2-3 spacer sequences. The six phenotypic forms in K. cottonii did not correspond to the observed genetic variability; hinting at the greater involvement of environmental factors in determining changes to the morphology of this alga. Our results revealed that the Philippine K. cottonii has the richest number of haplotypes that have been detected, so far, for any Kappaphycus species. Our inferred phylogenetic trees suggested two lineages: a lineage, which exclusively includes K. cottonii and another lineage comprising the four known Kappaphycus species: K. alvarezii, K. inermis, K. malesianus, and K. striatus. The dichotomy supports the apparent synamorphy for each of these lineages (the strictly terete thalli, lack of protuberances, and the presence of a hyphal central core in the latter group, while the opposite of these morphologies in K. cottonii). These findings shed new light on understanding the evolutionary history of the genus. Assessing the breadth of the phenotypic and genetic variation in K. cottonii has implications for the conservation and management of the overall Kappaphycus genetic resources, especially in the Philippines.

Extreme population subdivision or cryptic speciation in the cactus Pilosocereus jauruensis? A taxonomic challenge posed by a naturally fragmented system

In allopatric systems, where gene flow is highly constrained, the distinction between intraspecific differentiation and speciation is a challenging task. Pilosocereus jauruensis is a columnar cactus restricted to patchy dry habitats of Pantanal, Cerrado, and Chaco biomes in south-western Brazil and neighbouring countries. This species was recently reinstated after having been synonymized with P. machriisi, now including P. paraguayensis, P. saudadensis, and P. densivillosus as its synonyms. These taxa have been placed within the informal Aurisetus group. The present study aimed to investigate the genetic structure of P. jauruensis in order to identify possible distinct evolutionary lineages, and to support further refinement of the taxonomy of this species. For this purpose, 10 microsatellite loci were genotyped for 156 individuals of P. jauruensis. To provide a proxy for the expected interspecific differentiation level within this allopatric system, two populations (49 individuals) of P. vilaboensis (a species closely related to P. jauruensis) were also included. Additionally, two cpDNA markers (trnSGCU-trnGUCC and trnT-trnL) for a subsample of 44 individuals of both species were sequenced. The results obtained showed that even though P. jauruensis populations are relatively small and isolated, they still maintain a high level of genetic diversity (e.g., HE = 0.557 to 0.725; HO = 0.253 to 0.409). The study suggests the existence of two distinct taxa/evolutionary lineages through their entire distribution. Two populations found in the same geographic region of the now synonymized P. densivillosus showed significant genetic divergence when compared with other populations of P. jauruensis. In contrast, our results did not support an evolutionary independence hypothesis for populations that occur in the same geographic region of the synonymous P. saudadensis.

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Molecular analyses of Ficus erecta and its allies within the subsection Frutescentiae (Moraceae)

Ficus (Moraceae) is a keystone group in tropical and subtropical forests with remarkable diversity of species and taxonomical challenges as a consequence of fig–pollinator coevolution. Ficus subsect. Frutescentiae includes about 30 species that are predominantly shrubs or small trees with Terminalia branching. Many of these species are difficult to delimit morphologically, and the group includes a tangle of uncertain taxa and incorrectly applied names. We conducted a phylogenetic analysis with internal and external transcribed spacer data (ITS and ETS) and data from 18 polymorphic microsatellite loci to evaluate the species status of the most perplexing members of this subsection. The results confirm the monophyly of subsect. Frutescentiae, with F. pedunculosa as sister to the rest. The F. erecta complex comprises approximately 17 taxa: F. erecta, F. abelii, F. boninsimae, F. nishimurae, F. iidaiana, F. gasparriniana var. laceratifolia, F. gasparriniana var. viridescens, F. pyriformis, F. stenophylla, F. fusuiensis, F. fengkaiensis, F. sinociliata, F. tannoensis, F. vaccinioides, F. formosana, F. pandurata, and F. periptera. The last five of these were supported as good species, while the others were not well supported by the present evidence. Evidence also supported the status of the non-F. erecta complex species including. F. pedunculosa, F. ischnopoda, F. heteromorpha, and F. variolosa. Ficus filicauda and F. neriifolia are possibly conspecific. The species status of F. potingensis should be restored and it should be treated as a member of section Eriosycea. Identification of the remaining taxa (F. gasparriniana var. esquirolii, F. ruyuanensis, F. daimingshanensis, F. chapaensis, F. changii, F. trivia, and F. tuphapensis) and their relationships to the F. erecta complex were not clarified. As a whole, only ten species in this subsection are confirmed, one is excluded, one is synonymous, and the others are either unresolved or short of samples. There appears to be a consistent genetic background among these unresolved groups, which suggests that repeated hybridization (as a result of pollinator host shifts) has filled up the interspecific gaps during the fig–pollinator coevolution process.

Naked hitchhikers: the unknown photography of William A. Rhoads

ABSTRACTWilliam A. Rhoads was an avid photographer of male nudes, mostly sourced from hitchhikers he picked up in California in the 1970s. His efforts were prolific and sustained – and secret – and likely made and retained for private enjoyment. The photographs were never shown in public in Rhoads’ lifetime. I approach his project, firstly, from the perspective of its historical and cultural contexts of emergence and development; and secondly in terms of the taxonomic challenges his photographs pose, in relation to established histories of art and pornography, which were being called strikingly into question in the 1970s. Both approaches allow Rhoads to be understood beyond the traditional aesthetic distinction between art and pornography – or more precisely, between a personal, erotic practice and a formal artistic one.

Feasibility of nuclear ribosomal region ITS1 over ITS2 in barcoding taxonomically challenging genera of subtribe Cassiinae (Fabaceae).

Premise of the StudyThe internal transcribed spacer (ITS) region is situated between 18S and 26S in a polycistronic rRNA precursor transcript. It had been proved to be the most commonly sequenced region across plant species to resolve phylogenetic relationships ranging from shallow to deep taxonomic levels. Despite several taxonomical revisions in Cassiinae, a stable phylogeny remains elusive at the molecular level, particularly concerning the delineation of species in the genera Cassia, Senna and Chamaecrista. This study addresses the comparative potential of ITS datasets (ITS1, ITS2 and concatenated) in resolving the underlying morphological disparity in the highly complex genera, to assess their discriminatory power as potential barcode candidates in Cassiinae.MethodologyA combination of experimental data and an in-silico approach based on threshold genetic distances, sequence similarity based and hierarchical tree-based methods was performed to decipher the discriminating power of ITS datasets on 18 different species of Cassiinae complex. Lab-generated sequences were compared against those available in the GenBank using BLAST and were aligned through MUSCLE 3.8.31 and analysed in PAUP 4.0 and BEAST1.8 using parsimony ratchet, maximum likelihood and Bayesian inference (BI) methods of gene and species tree reconciliation with bootstrapping. DNA barcoding gap was realized based on the Kimura two-parameter distance model (K2P) in TaxonDNA and MEGA.Principal FindingsBased on the K2P distance, significant divergences between the inter- and intra-specific genetic distances were observed, while the presence of a DNA barcoding gap was obvious. The ITS1 region efficiently identified 81.63% and 90% of species using TaxonDNA and BI methods, respectively. The PWG-distance method based on simple pairwise matching indicated the significance of ITS1 whereby highest number of variable (210) and informative sites (206) were obtained. The BI tree-based methods outperformed the similarity-based methods producing well-resolved phylogenetic trees with many nodes well supported by bootstrap analyses.ConclusionThe reticulated phylogenetic hypothesis using the ITS1 region mainly supported the relationship between the species of Cassiinae established by traditional morphological methods. The ITS1 region showed a higher discrimination power and desirable characteristics as compared to ITS2 and ITS1 + 2, thereby concluding to be the locus of choice. Considering the complexity of the group and the underlying biological ambiguities, the results presented here are encouraging for developing DNA barcoding as a useful tool for resolving taxonomical challenges in corroboration with morphological framework.

Reinstatement, Redescription, and Emending of Spiranthes triloba (Orchidaceae): Solving a 118 year old cryptic puzzle

Abstract Spiranthes (Orchidaceae) is a primarily North American genus that has traditionally presented numerous taxonomic challenges. Many species display marked intra-species morphological variation and/or inter-species morphological similarities, such that cryptic speciation may be common. Molecular phylogenetic, morphological, field, and herbarium research concerning the delimitation of Spiranthes odorata necessitates the reinstatement and redescription of Spiranthes triloba, a name alternately synonymized under Spiranthes cernua and Spiranthes odorata for more than a century. While lost under synonymy, plants matching the morphology of Spiranthes triloba were ambiguously described as Spiranthes ×itchetuckneensis and Spiranthes ×folsomii, and these are here synonymized. Although the species has a descriptive specific epithet, the labellum of the holotype is decidedly not tri-lobed; Spiranthes triloba is redescribed and emended here so as to reflect its actual morphology. Spiranthes triloba is restricte...

Tracking the Phylogeny of Seagrasses: Inferred from 18S rRNA Gene and Ancestral State Reconstruction of Morphological Data

Taxonomic challenges of seagrasses were met by using 18S ribosomal subunit of ribosomal deoxyribonucleic acid (18S rDNA) sequence data of 14 seagrass species from India and two temperate species from Germany. The phylogenetic trees presented are based on the 18S rDNA sequence analysis of 41 nucleotide sequences including sequences obtained in the present study as well as previously published sequences of freshwater and saltmarsh plants, and seagrasses for identifying the evolutionary lineage. The 18S rDNA data indicates independent origin of temperate and tropical seagrasses with the genus Halophila as the intermediate group for both the regions. Based on the complex morphological structures the Halophila group represents the basal form among seagrasses whereas Enhalus is considered to be the most recently originated seagrass species. In that context, the marine Hydrocharitaceae group of Enhalus, Thalassia and Halophila has been proposed to be separated into two groups such as Enhalus/Thalassia and Halophila subfamilies. Hence, the present systematic studies warrant a revised taxonomy for seagrasses, which better reflects the phylogenetic results obtained from molecular and conventional data.

Towards a phylogenetic classification of Leptothecata (Cnidaria, Hydrozoa).

Leptothecata are hydrozoans whose hydranths are covered by perisarc and gonophores and whose medusae bear gonads on their radial canals. They develop complex polypoid colonies and exhibit considerable morphological variation among species with respect to growth, defensive structures and mode of development. For instance, several lineages within this order have lost the medusa stage. Depending on the author, traditional taxonomy in hydrozoans may be either polyp- or medusa-oriented. Therefore, the absence of the latter stage in some lineages may lead to very different classification schemes. Molecular data have proved useful in elucidating this taxonomic challenge. We analyzed a super matrix of new and published rRNA gene sequences (16S, 18S and 28S), employing newly proposed methods to measure branch support and improve phylogenetic signal. Our analysis recovered new clades not recognized by traditional taxonomy and corroborated some recently proposed taxa. We offer a thorough taxonomic revision of the Leptothecata, erecting new orders, suborders, infraorders and families. We also discuss the origination and diversification dynamics of the group from a macroevolutionary perspective.