The interrelationships of the echinoderm classes: morphological and molecular evidence

The relationship between the five echinoderm classes has perplexed phylogeneticists for some time. Although each of the crinoids (C), asteroids (A), ophiuroids (O), echinoids (E) and holothuroids (H) are morphologically distinct, evidence from larval and adult morphology, molecular biology, and stratigraphy have failed to provide a single consensus solution. We have reviewed all available morphological and molecular data, added new data and reanalysed independent data sets individually and in combination, in order to resolve echinoderm class relationships. In total, we present 21 larval and 50 adult morphological characters, partial 28S-like large subunit rRNA gene data for 39 taxa and complete 18S-like small subunit rRNA gene data for 37 taxa. For a 5 taxon problem there are 105 possible rooted tree topologies, and yet we were consistently presented with three competing hypotheses when data sets were analysed both individually and in combination. The total evidence solution favoured (outgroup(C(A(O(E, H))))) although the alternative tree topology, (outgroup(C(O(A(E, H))))) was only one step longer and (outgroup(C((A, O),(E, H)))) was two steps longer. Only these three trees are serious contenders and the distribution of morphological characters suggests we should discount the solution placing ophiuroids as sister group to an asteroid+echinoid + holothurian clade. Thus we are left with (outgroup(C(A(O(E, H))))) and (outgroup(C((A, O),(E, H)))) as the two most plausible phylogenetic hypotheses. Our data showed high levels of phylogenetic signal and these trees best fit the available data.     

The phage-host arms race: shaping the evolution of microbes

Bacteria, the most abundant organisms on the planet, are outnumbered by a factor of 10 to 1 by phages that infect them. Faced with the rapid evolution and turnover of phage particles, bacteria have evolved various mechanisms to evade phage infection and killing, leading to an evolutionary arms race. The extensive co-evolution of both phage and host has resulted in considerable diversity on the part of both bacterial and phage defensive and offensive strategies. Here, we discuss the unique and common features of phage resistance mechanisms and their role in global biodiversity. The commonalities between defense mechanisms suggest avenues for the discovery of novel forms of these mechanisms based on their evolutionary traits.     

Morphological perspective on the classification and evolution of Recent Pterioidea (Mollusca: Bivalvia)

The evolutionary relationships of the Recent Pterioidea are inferred from a phylogenetic analysis of representatives of all pterioidean genera based on original observations of anatomy and shell morphology, and an extensive survey of bivalve literature. The well-resolved cladogram supports monophyly for the superfamily, but renders all but one family (the monotypic Pulvinitidae) polyphyletic. In addition, these results reveal a considerable level of convergence and parallelisms through the Pterioidea. The branching order of pterioid genera in the morphological analysis is largely corroborated by the sequence of their appearance in the fossil record. The palaeontological evidence provides important information on dating lineage splitting events and transitional taxa. The proposed phylogeny integrates the cladistic analysis of the Recent Pterioidea with the fossil record and suggests that the crown-group pterioideans probably originated in the Triassic from the Bakevelliidae, an extinct paraphyletic stem group from which the Ostreoidea are also ultimately derived.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 253–312.     

Early Mesozoic evolution of alivincular bivalve ligaments and its implications for the timing of the ''Mesozoic marine revolution''

The early Mesozoic radiation of the Pteriomorphia was accompanied and furthered by the development of several new types of alivincular ligaments. These new types evolved as modifications of the primitive alivincular-areate (new term) ligament, which is characterized by an ontogenetic shift of both the central resilium and the straight lateral ligament in the direction of main shell growth. Arching of the attachment surface of the ligament led to the alivincular-arcuate (new term) ligament type, which has been realized by the Ostreidae only. By contrast, a replacement of the lateral ligament by hinge teeth, limiting the (primary) ligament to a central groove (alivincular-fossate, new term), has evolved independently in three families (Dimyidae, Plicatulidae and Spondylidae). Functionally, both kinds of modification effectively impede shearing of the valves and are interpreted as an antipredatory adaptation advantageous in the cemented habit of these families. The alivincular-alate (new term) ligament of the Entoliidae and Pectinidae differs from the other types of alivincular ligaments by different growth directions of resilium and lateral ligament, which result in an internal position of the resilium suitable for fast and powerful opening of the valves. This arrangement is an important prerequisite for effective swimming, which, in its turn, is a behaviour chiefly used to escape from predator attacks. The simultaneous early Mesozoic appearance of different antipredatory adaptations within independent clades hints at increased predator pressure as a stimulant and may therefore point to a contemporaneous proliferation of durophagous predators. Hence, an important aspect of the 'Mesozoic marine revolution' might have started earlier than previously thought.     

Phylogeny of the nominotypical subgenus of Culex (Diptera: Culicidae): insights from analyses of anatomical data into interspecific relationships and species groups in an unresolved tree

The aim of this study was to produce the first objective and comprehensive phylogenetic analysis of the speciose subgenus Culex based on morphological data. We used implied and equally weighted parsimony methods to analyse a dataset comprised of 286 characters of the larval, pupal, and adult stages of 150 species of the subgenus and an outgroup of 17 species. We determined the optimal support by summing the GC supports for each MPC, selecting the cladograms with the highest supports to generate a strict consensus tree. We then collapsed the branches with GC support < 1 to obtain the ‘best’ topography of relationships. The analyses largely failed to resolve relationships among the species and the informal groups in which they are currently placed based on morphological similarities and differences. All analyses, however, support the monophyly of genus Culex. With the exception of the Atriceps Group, the analyses failed to find positive support for any of the informal species groups (monophyly of the Duttoni Group could not be established because only one of the two species of the group was included in the analyses). Since the analyses would seem to include sufficient data for phylogenetic reconstruction, lack of resolution appears to be the result of inadequate or conflicting character data, and perhaps incorrect homology assessments. Molecular and other biological data are needed to gain insights into the evolution of subgenus Culex. Nevertheless, we discuss the placement of several taxa in the current morphology-based classification of the subgenus based on insights realized during the study.

     

Phylogeny of the deep‐sea cirripede family Scalpellidae (Crustacea,Thoracica) based on shell capitular plate morphology

A cladistic analysis of 23 extant species of the deep‐sea pedunculate cirripede family Scalpellidae was undertaken, based on 61 shell plate characters, and taking the Jurassic–Cretaceous scalpellomorph genus Cretiscalpellum as an out‐group. The consensus tree shows progressive morphological change from basal to more derived taxa, but a derived group is marked by major morphological innovation, including 27 character state changes that permit subdivision of the family into two sharply demarcated clades – the more basal group is here placed within a redefined Scalpellinae (Arcoscalpellum, A rcuatoscalpellum gen. nov. , D iotascalpellum gen. nov. , Graviscalpellum, R egioscalpellum gen. nov. , and Scalpellum), and a more derived group named A migdoscalpellinae subfam. nov. that shows numerous progressive trends in morphology, permitting the recognition of three genera (Amigdoscalpellum, Catherinum, and Weltnerium). The phylogeny is independently supported by a recently published multiple DNA marker‐based molecular phylogeny. The more basal Scalpellinae appeared in the Aptian (Early Cretaceous, 120 Mya), and derived Amigdoscalpellinae were already present by the Campanian (Late Cretaceous, 78 Mya), represented by C atherinum anglicum sp. nov. and Amigdoscalpellum bellulum from the UK Chalk. Specialized receptacles to accommodate dwarf males in the apical interior of the scutum evolved at least three times during the history of the scalpellids. © 2015 The Linnean Society of London     

Higher-level classification of the Archaea: evolution of methanogenesis and methanogens

We used a phylogenetic approach to analyze the evolution of methanogenesis and methanogens. We show that 23 vertically transmitted ribosomal proteins do not support the monophyly of methanogens, and propose instead that there are two distantly related groups of extant archaea that produce methane, which we have named Class I and Class II. Based on this finding, we subsequently investigated the uniqueness of the origin of methanogenesis by studying both the enzymes of methanogenesis and the proteins that synthesize its specific coenzymes. We conclude that hydrogenotrophic methanogenesis appeared only once during evolution. Genes involved in the seven central steps of the methanogenic reduction of carbon dioxide (CO(2)) are ubiquitous in methanogens and share a common history. This suggests that, although extant methanogens produce methane from various substrates (CO(2), formate, acetate, methylated C-1 compounds), these archaea have a core of conserved enzymes that have undergone little evolutionary change. Furthermore, this core of methanogenesis enzymes seems to originate (as a whole) from the last ancestor of all methanogens and does not appear to have been horizontally transmitted to other organisms or between members of Class I and Class II. The observation of a unique and ancestral form of methanogenesis suggests that it was preserved in two independent lineages, with some instances of specialization or added metabolic flexibility. It was likely lost in the Halobacteriales, Thermoplasmatales and Archaeoglobales. Given that fossil evidence for methanogenesis dates back 2.8 billion years, a unique origin of this process makes the methanogenic archaea a very ancient taxon.     

The limits of adaptation: humans and the predator-prey arms race

In the history of life, species have adapted to their consumers by evolving a wide variety of defenses. By contrast, animal species harvested in the wild by humans have not adapted structurally. Nonhuman predators have high failure rates at one or more stages of an attack, indicating that victim species have spatial refuges or phenotypic defenses that permit further functional improvement. A new compilation confirms that species in the wild cannot achieve immunity from human predation with structural defenses. The only remaining options are to become undesirable or to live in or escape to places where harvesting by people is curtailed. Escalation between prey defenses and predators' weapons may be restricted under human dominance to interactions involving those low-level predators that have benefited from human overexploitation of top consumers.     

Mitochondrial phylogenomics reveals insights into taxonomy and evolution of Penaeoidea (Crustacea: Decapoda)

The taxonomy and phylogeny of Penaeoidea have long been fraught with controversy. Here, we carried out the first mitochondrial phylogenomic analysis on all the penaeoid families and tribes, including nine newly sequenced and 14 published mitogenomes, towards elucidating the phylogeny and evolutionary history of Penaeoidea. All these nine mitogenomes exhibit the pancrustacean ground pattern, except that Benthonectes filipes contains two additional clusters of tRNA^Ala, tRNA^Arg and tRNA^Asn and an uncommon noncoding region. The resulted phylogenetic tree is generally well resolved with Benthesicymidae sister to Aristeidae, forming a clade with Solenoceridae. Contrary to traditional classification, this clade has a sister relationship with the tribe Penaeini of the family Penaeidae. The family Sicyoniidae is deeply nested within the penaeid tribe Trachypenaeini which forms a sister clade with the remaining penaeid tribe, Parapenaeini. As the family Penaeidae is recovered to be polyphyletic, the three tribes in Penaeidae are all elevated to familial status. On the other hand, the family Sicyoniidae is retained to accommodate Trachypenaeini because they are now synonyms and the former name is more senior. This work is the first molecular analysis concurring with the latest findings in fossil assessments showing that Parapeaneini is the most primitive in Penaeoidae. Our results also illustrate a shallow‐water origin and an onshore–offshore evolutionary shift in penaeoid shrimps.     

Oldest cingulate skulls provide congruence between morphological and molecular scenarios of armadillo evolution

The cingulates of the mammalian order Xenarthra present a typical case of disagreement between molecular and morphological phylogenetic studies. We report here the discovery of two new skulls from the Late Oligocene Salla Beds of Bolivia (approx. 26 Ma), which are the oldest known well-preserved cranial remains of the group. A new taxon is described: Kuntinaru boliviensis gen. et sp. nov. A phylogenetic analysis clusters K. boliviensis together with the armadillo subfamily Tolypeutinae. These skulls document an early spotty occurrence for the Tolypeutinae at 26 Ma, in agreement with the temporal predictions of previous molecular studies. The fossil record of tolypeutines is now characterized by a unique occurrence in the Late Oligocene, and a subsequent 12 Myr lack in the fossil record. It is noteworthy that the tolypeutines remain decidedly marginal in the Late Palaeogene and Early Neogene deposits, whereas other cingulate groups diversify. Also, the anatomical phylogenetic analysis herein, which includes K. boliviensis, is congruent with recent molecular phylogenetic analyses. Kuntinaru boliviensis is the oldest confident calibration point available for the whole Cingulata.     

Phylogeny reconstruction in the neogene bryozoan metrarabdotos: A paleontologic evaluation of methodology

An adequate stratigraphic record can not only aid in both cladistic and stratophenetic reconstruction of phytogenies, but can also serve in estimating the temporal consistency of the resulting phylogenetic trees. For hypothetical data sets, cladistically constructed trees can be as consistent with the temporal distribution of sampled populations or species as those constructed stratophenetically. Empirical testing in taxonomic groups with sufficiently dense fossil records is needed to show whether, and under what conditions, this potential can be realized. A stratophenetic tree and cladistic trees based on several approaches to character weighting were constructed for Caribbean Neogene species of the bryozoan Metrarabdotos with multiple‐character data from closely spaced sequential populations. The modular morphology and highly punctuated evolutionary pattern of these species blur the distinction between continuous and discrete characters, so that all available characters are potentially of equal significance in establishing phytogenies, rather than just those with discrete states conventionally used in cladistic analysis. However, only the cladistic trees generated with all characters weighted to emphasize contribution to species discrimination have temporal consistencies that are clearly significant statistically and approach that of the stratophenetic tree in magnitude. These results provide a start toward establishing general guidelines for cladistic analysis of taxa with stratigraphie records too sparse for stratophenetic reconstruction.     

The grand game of metazoan phylogeny: rules and strategies

Many cladistic analyses of animal phylogeny have been published by authors arguing that their results are well supported. Comparison of these analyses indicates that there can be as yet no general consensus about the evolution of the animal phyla. We show that the various cladistic studies published to date differ significantly in methods of character selection, character coding, scoring and weighting, ground-pattern reconstructions, and taxa selection. These methodological differences are seldom made explicit, which hinders comparison of different studies and makes it impossible to assess a particular phylogeny outside its own scope. The effects of these methodological differences must be considered before we can hope to reach a morphological reference framework needed for effective comparison and combination with the evidence obtained from molecular and developmental genetic studies.     

Phylogeny, evolution, and taxonomy of vannellid amoebae

We sequenced 18S rRNA genes from 21 vannellid amoebae (Amoebozoa; Vannellidae), including nearly all available type cultures, and performed a comprehensive phylogenetic analysis for 57 Vannellidae sequences. The results show that species of Vannella and Platyamoeba are completely mixed and do not form distinct clades. Several very closely related species pairs exist, each with a Vannella and a Platyamoeba species differing in only a few nucleotides. Therefore, presence (Vannella) or absence (Platyamoeba) of glycostyles in the cell surface coat is an invalid generic distinction; the genera must be merged. As Vannella has priority, we formally transferred Platyamoeba species into Vannella, except for the non-vannellid P. stenopodia, here renamed Stenamoeba stenopodia gen. n. comb. n. and transferred to the family Thecamoebidae. Our trees show that Vannella glycostyles were probably easily and repeatedly evolutionarily lost. We have established a new genus Ripella, with distinct morphology and sequence signatures for Vannella platypodia and morphologically similar species that form a clearly separate clade, very distant from other Vannellidae. Vannellids form four well-separated single-genus clades: Vannella sensu stricto, Ripella, Clydonella, and Lingulamoeba. Species of the revised genus Vannella comprise four closely related, well-supported subclades: one marine and three freshwater. Here, we provide an illustrated checklist for all 40 known Vannellidae species.     

Phanerozoic marine diversity: rock record modelling provides an independent test of large-scale trends

Sampling bias created by a heterogeneous rock record can seriously distort estimates of marine diversity and makes a direct reading of the fossil record unreliable. Here we compare two independent estimates of Phanerozoic marine diversity that explicitly take account of variation in sampling—a subsampling approach that standardizes for differences in fossil collection intensity, and a rock area modelling approach that takes account of differences in rock availability. Using the fossil records of North America and Western Europe, we demonstrate that a modelling approach applied to the combined data produces results that are significantly correlated with those derived from subsampling. This concordance between independent approaches argues strongly for the reality of the large-scale trends in diversity we identify from both approaches.     

Conodonts Meet Cladistics: Recovering Relationships and Assessing the Completeness of the Conodont Fossil Record

A numerical cladistic analysis of the conodont family Palmatolepidae has been undertaken to determine the applicability of the technique to group-wide systematic revision. Results suggest a new hypothesis of relationships that is considerably more parsimonious than trees compatible with existing hypotheses of relationships, or trees that are even loosely constrained stratigraphically. This may occur either because the fossil record is incomplete, because taxon sampling for the cladistic analysis is low, or because the most parsimonious trees approximate the true tree less well than do stratigraphically-constrained trees (or because of a combination of these factors). Although more taxa and more characters would be preferable in choosing between these possibilities, the tree derived solely from morphological data is adopted. Thus, stratigraphic data can be used to test hypotheses of relationships and construct phylogenies; hypotheses of relationships can be used to test the completeness of the conodont fossil record. Existing schemes of classification within the Palmatolepidae are rejected because most groups within them are either polyphyletic or paraphyletic. A new scheme is presented. Character changes suggest correlated, progressive and mosaic evolution within the Palmatolepidae. Parsimony analysis of partitioned datasets indicates that more phylogenetic information can be recovered from S rather than P or M element positions, although data from all three positional groups are preferable to data from just one. Thus, multielement taxonomy is essential to the resolution of conodont interrelationships.     

Modern hydrophilid clades present and widespread in the Late Jurassic and Early Cretaceous (Coleoptera: Hydrophiloidea: Hydrophilidae)

We present a summary of the fossil evidence documenting the worldwide occurrence of the family Hydrophilidae (Insecta: Coleoptera: Polyphaga: Hydrophiloidea) in the Late Jurassic and Early Cretaceous. We present the first known fossils of the family from the Mesozoic, being c. 100 Myr older than the fossil record available until now. Two Late Jurassic fossils are documented: P rotochares brevipalpis gen. nov., sp. nov. from the Talbragar Fish Bed (New South Wales, Australia) and ‘Mesosperchus’ schultzi Ponomarenko, 1985 from Solnhofen (Bavaria, Germany). The occurrence of the Hydrophilidae in the Early Cretaceous is documented by six species, all of which may be already assigned to modern subfamilies/tribes: B aissalarva hydrobioides gen. nov., sp. nov. from the Baissa outcrops (Buryat Republic, Russia) and C retoxenus australis gen. nov., sp. nov. from Koonwarra outcrops (Victoria, Australia) are both assigned to the tribe Hydrobiusini (Hydrophilinae); A legorius yixianus gen. nov., sp. nov. and Alegorius sp. from the Yixian Formation (Liaoning, China) may represent the Acidocerinae or Enochrinae, H ydroyixia elongata gen. nov., sp. nov. and H . latissima sp. nov. from the same locality are assigned to the Acidocerinae. The phylogenetic position of Baissalarva hydrobioides is also tested by a phylogenetic analysis. The presence of extant clades (Hydrophilinae: Hydrobiusini, Acidocerinae) in the Early Cretaceous and the wide distribution of the Hydrobiusini in both Gondwana and Laurasia at the same time suggests that the principal extant clades of the Hydrophilidae are at least of Early–Middle Jurassic origin. © 2014 The Linnean Society of London