Phylogeny and evolution of glass sponges (porifera, hexactinellida)

Reconstructing the phylogeny of sponges (Porifera) is one of the remaining challenges to resolve the metazoan Tree of Life and is a prerequisite for understanding early animal evolution. Molecular phylogenetic analyses for two of the three extant classes of the phylum, Demospongiae and Calcarea, are largely incongruent with traditional classifications, most likely because of a paucity of informative morphological characters and high levels of homoplasy. For the third class, Hexactinellida (glass sponges)--predominantly deep-sea inhabitants with unusual morphology and biology--we present the first molecular phylogeny, along with a cladistic analysis of morphological characters. We collected 18S, 28S, and mitochondrial 16S ribosomal DNA sequences of 34 glass sponge species from 27 genera, 9 families, and 3 orders and conducted partitioned Bayesian analyses using RNA secondary structure-specific substitution models (paired-sites models) for stem regions. Bayes factor comparisons of different paired-sites models against each other and conventional (independent-sites) models revealed a significantly better fit of the former but, contrary to previous predictions, the least parameter-rich of the tested paired-sites models provided the best fit to our data. In contrast to Demospongiae and Calcarea, our rDNA phylogeny agrees well with the traditional classification and a previously proposed phylogenetic system, which we ascribe to a more informative morphology in Hexactinellida. We find high support for a close relationship of glass sponges and Demospongiae sensu stricto, though the latter may be paraphyletic with respect to Hexactinellida. Homoscleromorpha appears to be the sister group of Calcarea. Contrary to most previous findings from rDNA, we recover Porifera as monophyletic, although support for this clade is low under paired-sites models.     

Systematics and spicule evolution in dictyonal sponges (Hexactinellida: Sceptrulophora) with description of two new species

In this paper we report on recently collected specimens of glass sponges belonging to Farreidae Gray, 1872, and Tretodictyidae Schulze, 1886 (Porifera: Hexactinellida: Hexactinosida). All specimens represent new geographical records for their genera: Coral Sea for Aspidoscopulia Reiswig, 2002 (Farreidae) and Psilocalyx Ijima, 1927 (Tretodictyidae); north‐west Atlantic for Sarostegia Topsent, 1904 (Farreidae). Two new species, Aspidoscopulia australia Dohrmann, Göcke & Janussen sp. nov. and Aspidoscopulia ospreya Dohrmann, Göcke & Janussen sp. nov. , are described. To investigate further the evolution of hexactinosidan sponges, we sequenced two nuclear (18S and 28S rDNA) and two mitochondrial [16S ribosomal rDNA, cytochrome oxidase subunit I (COI)] genes from these specimens, as well as from a recently described new species of Lonchiphora Ijima, 1927 (Farreidae). Besides corroborating the monophyly of Tretodictyidae, our molecular phylogenetic analyses support a clade of clavule‐bearing sponges with a farreoid dictyonal framework (i.e. Farreidae sensu stricto). In contrast, Sarostegia, which lacks these features, appears unrelated to this clade – instead our data are consistent with an earlier placement of this genus in Euretidae Zittel, 1877. We introduce formally the taxon Sceptrulophora Mehl 1992, and emend the classification of Hexactinosida to reflect this move and our new findings regarding the position of Sarostegia. Finally, we discuss implications of the molecular phylogeny for the evolution of sceptrules, the defining autapomorphy of Sceptrulophora. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1003–1025.     

Phylogenetic inference regarding Parergodrilidae and Hrabeiella periglandulata ('Polychaeta', Annelida) based on 18S rDNA, 28S rDNA and COI sequences

Parergodrilidae and Hrabeiella periglandulata are Annelida showing different combinations of clitellate-like and aclitellate characters. Similarities between both of these taxa and Clitellata have widely been regarded as the result of convergent evolution due to similar selection pressures. The position of the three taxa in the phylogenetic system of Annelida is still in debate. However, in analyses based on 18S rDNA sequences a close relationship of Parergodrilidae with Orbiniidae and Questidae was suggested. To infer their phylogeny the sequences of the 28S rDNA and of the cytochrome oxidase I (COI) gene of Stygocapitella subterranea , Parergodrilus heideri and H. periglandulata were determined. The data were extended by sequences of various species including species from Clitellata and Orbiniidae. Prior to tree reconstruction the dataset was analysed in detail for phylogenetic content by applying a sliding window analysis, a likelihood mapping and Modeltest V.3.04. Subsequently, generalized parsimony and maximum likelihood methods were employed. Clade robustness was estimated by bootstrapping. In addition, combined analyses of the sequences of 18S rDNA and 28S rDNA as well as of 18S rDNA, 28S rDNA and COI were performed. The combination of the data of the two structure genes and a mitochondrial gene improved the resolution obtained with the single datasets slightly. These analyses support a close relationship of Parergodrilidae and Orbiniidae but cannot resolve the position of H. periglandulata . In every analysis Clitellata cluster within 'Polychaeta', confirming previous investigations.     

Molecular phylogenetic evaluation of classification and scenarios of character evolution in calcareous sponges (Porifera, Class Calcarea)

Calcareous sponges (Phylum Porifera, Class Calcarea) are known to be taxonomically difficult. Previous molecular studies have revealed many discrepancies between classically recognized taxa and the observed relationships at the order, family and genus levels; these inconsistencies question underlying hypotheses regarding the evolution of certain morphological characters. Therefore, we extended the available taxa and character set by sequencing the complete small subunit (SSU) rDNA and the almost complete large subunit (LSU) rDNA of additional key species and complemented this dataset by substantially increasing the length of available LSU sequences. Phylogenetic analyses provided new hypotheses about the relationships of Calcarea and about the evolution of certain morphological characters. We tested our phylogeny against competing phylogenetic hypotheses presented by previous classification systems. Our data reject the current order-level classification by again finding non-monophyletic Leucosolenida, Clathrinida and Murrayonida. In the subclass Calcinea, we recovered a clade that includes all species with a cortex, which is largely consistent with the previously proposed order Leucettida. Other orders that had been rejected in the current system were not found, but could not be rejected in our tests either. We found several additional families and genera polyphyletic: the families Leucascidae and Leucaltidae and the genus Leucetta in Calcinea, and in Calcaronea the family Amphoriscidae and the genus Ute. Our phylogeny also provided support for the vaguely suspected close relationship of several members of Grantiidae with giantortical diactines to members of Heteropiidae. Similarly, our analyses revealed several unexpected affinities, such as a sister group relationship between Leucettusa (Leucaltidae) and Leucettidae and between Leucascandra (Jenkinidae) and Sycon carteri (Sycettidae). According to our results, the taxonomy of Calcarea is in desperate need of a thorough revision, which cannot be achieved by considering morphology alone or relying on a taxon sampling based on the current classification below the subclass level.     

ALG11--a new variable DNA marker for sponge phylogeny: comparison of phylogenetic performances with the 18S rDNA and the COI gene

Phylogenetic relationships within sponge classes are highly debated. The low phylogenetic signal observed with some current molecular data can be attributed to the use of few markers, usually slowly-evolving, such as the nuclear rDNA genes and the mitochondrial COI gene. In this study, we conducted a bioinformatics search for a new molecular marker. We sought a marker that (1) is likely to have no paralogs; (2) evolves under a fast evolutionary rate; (3) is part of a continuous exonic region; and (4) is flanked by conserved regions. Our search suggested the nuclear ALG11 as a potential suitable marker. We next demonstrated that this marker can indeed be used for solving phylogenetic relationships within sponges. Specifically, we successfully amplified the ALG11 gene from DNA samples of representatives from all four sponge classes as well as from several cnidarian classes. We also amplified the 18S rDNA and the COI gene for these species. Finally, we analyzed the phylogenetic performance of ALG11 to solve sponge relationships compared to and in combination with the nuclear 18S rDNA and the COI mtDNA genes. Interestingly, the ALG11 marker seems to be superior to the widely-used COI marker. Our work thus indicates that the ALG11 marker is a relevant marker which can complement and corroborate the phylogenetic inferences observed with nuclear ribosomal genes. This marker is also expected to contribute to resolving evolutionary relationships of other apparently slow-evolving animal phyla, such as cnidarians.     

Molecular phylogeny of North American Branchiobdellida (Annelida: Clitellata)

Branchiobdellidans, or crayfish worms, are ectosymbiotic clitellate annelids associated primarily with freshwater crayfishes. The main objectives of our study were to infer a molecular phylogeny for the North American Branchiobdellida, examine its congruence with morphology-based hypotheses of relationships at the subfamily and genus level, and use our dataset to assess consistency of GenBank-archived branchiobdellidan sequences. We used nucleotide sequence data from two mtDNA genes (COI and 16S rDNA) and three nuclear genes (28S rDNA, 18S rDNA, and ITS1) to estimate phylogenetic relationships among 47 described and one undescribed species of Branchiobdellida. We recovered a monophyletic branchiobdellidan clade with generally short branch lengths, suggesting that a large portion of the taxon has likely undergone a recent and rapid radiation in North America. Results from our phylogenetic analyses indicate that current taxonomic groupings are largely unsupported by the molecular data. All four subfamilies are either paraphyletic or polyphyletic, and only three of seven sampled non-monotypic genera were monophyletic. We found a high rate (49%) of inconsistency in GenBank-archived sequences, over 70% of which can be attributed to field- or laboratory-based error.     

Non-monophyly of most supraspecific taxa of calcareous sponges (Porifera, Calcarea) revealed by increased taxon sampling and partitioned Bayesian analysis of ribosomal DNA

Calcareous sponges (Porifera, Calcarea) play an important role for our understanding of early metazoan evolution, since several molecular studies suggested their closer relationship to Eumetazoa than to the other two sponge 'classes,' Demospongiae and Hexactinellida. The division of Calcarea into the subtaxa Calcinea and Calcaronea is well established by now, but their internal relationships remain largely unresolved. Here, we estimate phylogenetic relationships within Calcarea in a Bayesian framework, using full-length 18S and partial 28S ribosomal DNA sequences. Both genes were analyzed separately and in combination and were further partitioned by stem and loop regions, the former being modelled to take non-independence of paired sites into account. By substantially increasing taxon sampling, we show that most of the traditionally recognized supraspecific taxa within Calcinea and Calcaronea are not monophyletic, challenging the existing classification system, while monophyly of Calcinea and Calcaronea is again highly supported.     

New molecular data for tardigrade phylogeny, with the erection of Paramacrobiotus gen. nov.

Up to few years ago, the phylogenies of tardigrade taxa have been investigated using morphological data, but relationships within and between many taxa are still unresolved. Our aim has been to verify those relationships adding molecular analysis to morphological analysis, using nearly complete 18S ribosomal DNA gene sequences (five new) of 19 species, as well as cytochrome oxidase subunit 1 (COI) mitochondrial DNA gene sequences (15 new) from 20 species, from a total of seven families. The 18S rDNA tree was calculated by minimum evolution, maximum parsimony (MP) and maximum likelihood (ML) analyses. DNA sequences coding for COI were translated to amino acid sequences and a tree was also calculated by neighbour-joining, MP and ML analyses. For both trees (18S rDNA and COI) posterior probabilities were calculated by MrBayes. Prominent findings are as follows: the molecular data on Echiniscidae (Heterotardigrada) are in line with the phylogenetic relationships identifiable by morphological analysis. Among Eutardigrada, orders Apochela and Parachela are confirmed as sister groups. Ramazzottius (Hypsibiidae) results more related to Macrobiotidae than to the genera here considered of Hypsibiidae. Macrobiotidae and Macrobiotus result not monophyletic and confirm morphological data on the presence of at least two large groups within Macrobiotus. Using 18S rDNA and COI mtDNA genes, a new phylogenetic line has been identified within Macrobiotus , corresponding to the ' richtersi-areolatus group'. Moreover, cryptic species have been identified within the Macrobiotus ' richtersi group' and within Richtersius . Some evolutionary lines of tardigrades are confirmed, but others suggest taxonomic revision. In particular, the new genus Paramacrobiotus gen. n. has been identified, corresponding to the phylogenetic line represented by the ' richtersi-areolatus group'.     

Eight new mtDNA sequences of glass sponges reveal an extensive usage of + 1 frameshifting in mitochondrial translation

Three previously studied mitochondrial genomes of glass sponges (phylum Porifera, class Hexactinellida) contained single nucleotide insertions in protein coding genes inferred as sites of + 1 translational frameshifting. To investigate the distribution and evolution of these sites and to help elucidate the mechanism of frameshifting, we determined eight new complete or nearly complete mtDNA sequences from glass sponges and examined individual mitochondrial genes from three others. We found nine new instances of single nucleotide insertions in these sequences and analyzed them both comparatively and phylogenetically. The base insertions appear to have been gained and lost repeatedly in hexactinellid mt protein genes, suggesting no functional significance for the frameshifting sites. A high degree of sequence conservation, the presence of unusual tRNAs, and a distinct pattern of codon usage suggest the “out-of-frame pairing” model of translational frameshifting. Additionally, we provide evidence that relaxed selection pressure on glass sponge mtDNA – possibly a result of their low growth rates and deep-water lifestyle – has allowed frameshift insertions to be tolerated for hundreds of millions of years. Our study provides the first example of a phylogenetically diverse and extensive usage of translational frameshifting in animal mitochondrial coding sequences.     

The phylogenetic potential of entire 26S rDNA sequences in plants

18S ribosomal RNA genes are the most widely used nuclear sequences for phylogeny reconstruction at higher taxonomic levels in plants. However, due to a conservative rate of evolution, 18S rDNA alone sometimes provides too few phylogenetically informative characters to resolve relationships adequately. Previous studies using partial sequences have suggested the potential of 26S or large-subunit (LSU) rDNA for phylogeny retrieval at taxonomic levels comparable to those investigated with 18S rDNA. Here we explore the patterns of molecular evolution of entire 26S rDNA sequences and their impact on phylogeny retrieval. We present a protocol for PCR amplification and sequencing of entire (approximately 3.4 kb) 26S rDNA sequences as single amplicons, as well as primers that can be used for amplification and sequencing. These primers proved useful in angiosperms and Gnetales and likely have broader applicability. With these protocols and primers, entire 26S rDNA sequences were generated for a diverse array of 15 seed plants, including basal eudicots, monocots, and higher eudicots, plus two representatives of Gnetales. Comparisons of sequence dissimilarity indicate that expansion segments (or divergence domains) evolve 6.4 to 10.2 times as fast as conserved core regions of 26S rDNA sequences in plants. Additional comparisons indicate that 26S rDNA evolves 1.6 to 2.2 times as fast as and provides 3.3 times as many phylogenetically informative characters as 18S rDNA; compared to the chloroplast gene rbcL, 26S rDNA evolves at 0.44 to 1.0 times its rate and provides 2.0 times as many phylogenetically informative characters. Expansion segment sequences analyzed here evolve 1.2 to 3.0 times faster than rbcL, providing 1.5 times the number of informative characters. Plant expansion segments have a pattern of evolution distinct from that found in animals, exhibiting less cryptic sequence simplicity, a lower frequency of insertion and deletion, and greater phylogenetic potential.      

Molecular systematics of the order anaspidea based on mitochondrial DNA sequence (12S, 16S, and COI)

Fragments from three mitochondrial genes (12S, 16S, and COI) were sequenced to reconstruct a molecular phylogeny of the opisthobranch order Anaspidea. The molecular phylogeny supports the placement of the genus Akera, a taxon previously regarded by some authors as a cephalaspidean, within the Anaspidea. Incongruence between the molecular data and the classifications based on morphology suggests that some of the taxonomic characters (i.e., shell, parapodia fusion) traditionally used for the classification of sea hares must be reevaluated, since they may be homoplastic. The ancestral nature of Notarchus based on the molecular evidence suggests that homoplasy may be an explanation for the morphological resemblance of this species to the more derived sea hares with highly fused parapodia and concentrated nerve ganglia. Finally, examples are given of how comparative studies of the evolution of learning mechanisms in the anaspidean clade will benefit from the phylogenetic hypothesis presented in this paper.     

Glass sponges and bilaterian animals share derived mitochondrial genomic features: a common ancestry or parallel evolution?

Glass sponges (Hexactinellida) are a group of deep-water benthicanimals that have a unique syncytial organization and possessa characteristic siliceous skeleton. Although hexactinellidsare traditionally grouped with calcareous and demosponges inthe phylum Porifera, the monophyly of sponges and the phylogeneticposition of the Hexactinellida remain contentious. We determinedand analyzed the nearly complete mitochondrial genome sequencesof the hexactinellid sponges Iphiteon panicea and Sympagellanux. Unexpectedly, our analysis revealed several mitochondrialgenomic features shared between glass sponges and bilateriananimals, including an Arg Ser change in the genetic code, acharacteristic secondary structure of one of the serine tRNAs,highly derived tRNA and rRNA genes, and the presence of a singlelarge noncoding region. At the same time, glass sponge mtDNAcontains atp9, a gene previously found only in the mtDNA ofdemosponges (among animals), and encodes a with an atypical A11–U24 pair that is alsofound in demosponges and placozoans. Most of our sequence-basedphylogenetic analyses place Hexactinellida as the sister groupto the Bilateria; however, these results are suspect given acceleratedrates of mitochondrial sequence evolution in these groups. Thus,it remains an open question whether shared mitochondrial genomicfeatures in glass sponges and bilaterian animals reflect theirclose phylogenetic affinity or provide a remarkable exampleof parallel evolution.     

Increased taxon sampling provides new insights into the phylogeny and evolution of the subclass Calcaronea (Porifera,Calcarea)

Calcaronean sponges are acknowledged to be taxonomically difficult, and generally, molecular data does not support the current morphology-based classification. In addition, molecular markers that have been successfully employed in other sponge taxa (e.g., COI mtDNA) have proven challenging to amplify due to the characteristics of calcarean mitochondrial genomes. A short fragment of the 28S rRNA gene (C-region) was recently proposed as the most phylogenetically informative marker to be used as a DNA barcode for calcareous sponges. In this study, the C-region and a fragment of the 18S rRNA gene were sequenced for a wide range of calcareous taxa, mainly from the subclass Calcaronea. The resulting dataset includes the most comprehensive taxon sampling of Calcaronea to date, and the inclusion of multiple specimens per species allowed us to evaluate the performance of both markers, as barcoding markers. 18S proved to be highly conserved within Calcaronea and does not have sufficient signal to resolve phylogenetic relationships within the subclass. Although the C-region does not exhibit a “proper” barcoding gap, it provides good phylogenetic resolution for calcaronean sponges. The resulting phylogeny supports previous findings that the current classification of the subclass Calcaronea is highly artificial, and with high levels of homoplasy. Furthermore, the close relationship between the order Baerida and the genus Achramorpha suggest that the order Baerida should be abandoned. Although the C-region currently represents the best available marker for phylogenetic and barcoding studies in Calcaronea, it is necessary to develop additional molecular markers to improve the classification within this subclass.     

Deciphering Metazoan Phylogeny: The Need for Additional Molecular Data

SYNOPSIS. Our interpretation of the evolution of development,morphology, and diversity of multicellular animals hinges ona clear understanding of the phylogenetic relationships of metazoans.Currently, the field of metazoan phylogeny is in a state offlux, with new hypotheses of metazoan relationships emergingfrom analyses of 18S rDNA sequence data. Some of these analyseshave been limited in the numbers of taxa analyzed, others, withnumerous taxa analyzed, have not resolved deep level branchingpatterns, and all are hampered by properties of the 18S geneitself. Corroboration of the results from 18S rDNA analysescan come from additional molecular data sets, such as highlyconserved nuclear coding genes, mitochondria gene order, orgene duplication events. The enormous task of data accumulationfor additional molecular data from many representative taxacan most efficiently be undertaken in a coordinated, collaborativeeffort among different lab groups. Ultimately, a combined analysisof several independent data sets will be possible and may providea more stable, robust phylogeny for the Metazoa.     

基因序列在蚜虫分子系统发育研究中的应用

总结了核基因和线粒体基因在半翅目蚜虫分子系统发育研究中的应用。核基因中EF-1α应用最广泛,适用于探讨属级及属以上的问题; 核rDNA在蚜虫中应用较少,18S rDNA适用于探讨科级以上高级阶元的问题;LWO是新近在蚜虫中开发使用的一个新基因。线粒体基因中,COⅠ/COⅡ使用最多,12S rDNA/16S rDNA、ND1、Cyt b以及F-ATP6均有应用,探讨的问题从属、种级到科级不等。核基因和线粒体基因间以及不同线粒体基因间的联合分析在解决不同层次的问题中均有应用。建议不断尝试新基因以找出适合蚜虫类群的“标准基因”。并对未来蚜虫分子系统发育研究趋势进行了展望。     

Evolution of fossil and living spider flies based on morphological and molecular data (Diptera,Acroceridae)

The phylogeny of spider flies is presented based on an analysis of DNA sequence data combined with morphological characters for both living and fossil species. We sampled 40 extant and extinct genera across all major lineages of Acroceridae, which were compared with outgroup taxa from various lower brachyceran families. In all, 81 morphological characters of 60 extant and 10 extinct ingroup species were combined with 7.1 kb of DNA sequences of two nuclear (CAD and 28S rDNA) and two mitochondrial genes (COI and 16S rDNA). Results strongly support the monophyly of Acroceridae, with major clades contained within classified here in five extant subfamilies (Acrocerinae, Cyrtinae stat. rev. , Ogcodinae stat. rev. , Panopinae and Philopotinae) and one extinct subfamily, Archocyrtinae. The evolution of important spider fly traits is discussed, including genitalia and wing venation. The status of the enigmatic Psilodera Gray and Pterodontia Gray as members of the Panopinae is confirmed based on both molecular and morphological data.     

Integrative taxonomy and molecular phylogeny of genus aplysina (demospongiae: verongida) from mexican pacific

Integrative taxonomy provides a major approximation to species delimitation based on integration of different perspectives (e.g. morphology, biochemistry and DNA sequences). The aim of this study was to assess the relationships and boundaries among Eastern Pacific Aplysina species using morphological, biochemical and molecular data. For this, a collection of sponges of the genus Aplysina from the Mexican Pacific was studied on the basis of their morphological, chemical (chitin composition), and molecular markers (mitochondrial COI and nuclear ribosomal rDNA: ITS1-5.8-ITS2). Three morphological species were identified, two of which are new to science. A. clathrata sp. nov. is a yellow to yellow-reddish or -brownish sponge, characterized by external clathrate-like morphology; A. revillagigedi sp. nov. is a lemon yellow to green, cushion-shaped sometimes lobate sponge, characterized by conspicuous oscules, which are slightly elevated and usually linearly distributed on rims; and A. gerardogreeni a known species distributed along the Mexican Pacific coast. Chitin was identified as the main structural component within skeletons of the three species using FTIR, confirming that it is shared among Verongida sponges. Morphological differences were confirmed by DNA sequences from nuclear ITS1-5.8-ITS2. Mitochondrial COI sequences showed extremely low but diagnostic variability for Aplysina revillagigedi sp. nov., thus our results corroborate that COI has limited power for DNA-barcoding of sponges and should be complemented with other markers (e.g. rDNA). Phylogenetic analyses of Aplysina sequences from the Eastern Pacific and Caribbean, resolved two allopatric and reciprocally monophyletic groups for each region. Eastern Pacific species were grouped in general accordance with the taxonomic hypothesis based on morphological characters. An identification key of Eastern Pacific Aplysina species is presented. Our results constitute one of the first approximations to integrative taxonomy, phylogeny and evolutionary biogeography of Eastern Pacific marine sponges; an approach that will significantly contribute to our better understanding of their diversity and evolutionary history.     

DNA barcoding in autotrophic euglenids: evaluation of COI and 18s rDNA

Autotrophic euglenids (Euglenophyceae) are a common and abundant group of microbial eukaryotes in freshwater habitats. They have a limited number of features, which can be observed using light microscopy, thus species identification is often problematic. Establishing a barcode for this group is therefore an important step toward the molecular identification of autotrophic euglenids. Based on the literature, we selected verified species and used a plethora of available methods to validate two molecular markers: COI and 18S rDNA (the whole sequence and three fragments separately) as potential DNA barcodes. Analyses of the COI gene were performed based on the data set of 43 sequences (42 obtained in this study) representing 24 species and the COI gene was discarded as a DNA barcode mainly due to a lack of universal primer sites. For 18S rDNA analyses we used a data set containing 263 sequences belonging to 86 taxonomically verified species. We demonstrated that the whole 18S rDNA is too long to be a useful marker, but from the three shorter analyzed variable regions we recommend variable regions V2V3 and V4 of 18S rDNA as autotrophic euglenid barcodes due to their high efficiency (above 95% and 90%, respectively).     

Morphological and molecular evolution are not linked in Lamellodiscus (Plathyhelminthes, Monogenea)

Lamellodiscus Johnston & Tiegs 1922 (Monogenea, Diplectanidae) is a genus of common parasites on the gills of sparid fishes. Here we show that this genus is probably undergoing a fast molecular diversification, as reflected by the important genetic variability observed within three molecular markers (partial nuclear 18S rDNA, Internal Transcribed Spacer 1, and mitonchondrial Cytochrome Oxidase I). Using an updated phylogeny of this genus, we show that molecular and morphological evolution are weakly correlated, and that most of the morphologically defined taxonomical units are not consistent with the molecular data. We suggest that Lamellodiscus morphology is probably constrained by strong environmental (host-induced) pressure, and discuss why this result can apply to other taxa. Genetic variability within nuclear 18S and mitochondrial COI genes are compared for several monogenean genera, as this measure may reflect the level of diversification within a genus. Overall our results suggest that cryptic speciation events may occur within Lamellodiscus, and discuss the links between morphological and molecular evolution.     

No speed dating please! Patterns of social preference in male and female house mice

Glass sponges (Class Hexactinellida) are important components of deep-sea ecosystems and are of interest from geological and materials science perspectives. The reconstruction of their phylogeny with molecular data has only recently begun and shows a better agreement with morphology-based systematics than is typical for other sponge groups, likely because of a greater number of informative morphological characters. However, inconsistencies remain that have far-reaching implications for hypotheses about the evolution of their major skeletal construction types (body plans). Furthermore, less than half of all described extant genera have been sampled for molecular systematics, and several taxa important for understanding skeletal evolution are still missing. Increased taxon sampling for molecular phylogenetics of this group is therefore urgently needed. However, due to their remote habitat and often poorly preserved museum material, sequencing all 126 currently recognized extant genera will be difficult to achieve. Utilizing morphological data to incorporate unsequenced taxa into an integrative systematics framework therefore holds great promise, but it is unclear which methodological approach best suits this task. Here, we increase the taxon sampling of four previously established molecular markers (18S, 28S, and 16S ribosomal DNA, as well as cytochrome oxidase subunit I) by 12 genera, for the first time including representatives of the order Aulocalycoida and the type genus of Dactylocalycidae, taxa that are key to understanding hexactinellid body plan evolution. Phylogenetic analyses suggest that Aulocalycoida is diphyletic and provide further support for the paraphyly of order Hexactinosida; hence these orders are abolished from the Linnean classification. We further assembled morphological character matrices to integrate so far unsequenced genera into phylogenetic analyses in maximum parsimony (MP), maximum likelihood (ML), Bayesian, and morphology-based binning frameworks. We find that of these four approaches, total-evidence analysis using MP gave the most plausible results concerning congruence with existing phylogenetic and taxonomic hypotheses, whereas the other methods, especially ML and binning, performed more poorly. We use our total-evidence phylogeny of all extant glass sponge genera for ancestral state reconstruction of morphological characters in MP and ML frameworks, gaining new insights into the evolution of major hexactinellid body plans and other characters such as different spicule types. Our study demonstrates how a comprehensive, albeit in some parts provisional, phylogeny of a larger taxon can be achieved with an integrative approach utilizing molecular and morphological data, and how this can be used as a basis for understanding phenotypic evolution. The datasets and associated trees presented here are intended as a resource and starting point for future work on glass sponge evolution.