SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Binomial nomenclature

170

Creation and use of the scientific names of animals are ruled by the International Code of Zoological Nomenclature. Until recently, publication of new names in a work produced with ink on paper was required for their availability. A long awaited amendment to the Code issued in September 2012 by the International Commission on Zoological Nomenclature now allows publication of new names in online-only works, provided that the latter are registered with ZooBank, the Official Register of Animal Names. With this amendment, the rules of zoological nomenclature have been aligned with the opportunities (and needs) of our digital era. However, possible causes for nomenclatural instability remain. These could be completely removed if the Code-compliant publication of new names will be identified with their online registration, under suitable technological and formal (legal) conditions. Future developments of the ZooBank may provide the tool required to make this definitive leap ahead in zoological nomenclature.

Concepts: Animal, Taxonomy, Noun, Binomial nomenclature, Name, International Code of Zoological Nomenclature, Nomenclature, International Code of Botanical Nomenclature

170

Twelve of the 13 bushcricket species of the Saga genus are bisexuals and diploids, except the parthenogenetic and tetraploid bush cricket, Saga pedo. Despite a continuous research effort stretching through the 1900s, the taxonomic relationships of the Saga species are still disputed. In this study, our primary aim was to reveal natural relationships of the European Saga species and three of their Asian relatives, with special attention to the problematic taxonomy of two subspecies: S. campbelli campbelli and S. c. gracilis. Following a phylogenetic analysis of eight species, a comprehensive study was carried out on the above three taxa by using acoustic and morphometric approaches in parallel. Our phylogenetic data showed that European Saga species evolved from a monophyletic lineage. The geographical transitional species S. cappadocica was positioned between European and Asian lineages supporting the idea that the European Saga lineage originated phylogeographically from the Asian clade. The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only. After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies. S. c. gracilis shares the same ITS2 haplotype with S. pedo, indicating that the latter could have evolved from populations of the former, probably through whole genome duplication. Based on acoustic and morphometric differences, we propose to elevate the two subspecies, S. campbelli campbelli and S. c. gracilis, to species level status, as Saga gracilis Kis 1962, and Saga campbelli Uvarov 1921. The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.

Concepts: Evolution, Biology, Species, Gene duplication, Phylogenetics, Polyploidy, Binomial nomenclature, Taxonomic rank

74

Phylosymbiosis was recently proposed to describe the eco-evolutionary pattern, whereby the ecological relatedness of host-associated microbial communities parallels the phylogeny of related host species. Here, we test the prevalence of phylosymbiosis and its functional significance under highly controlled conditions by characterizing the microbiota of 24 animal species from four different groups (Peromyscus deer mice, Drosophila flies, mosquitoes, and Nasonia wasps), and we reevaluate the phylosymbiotic relationships of seven species of wild hominids. We demonstrate three key findings. First, intraspecific microbiota variation is consistently less than interspecific microbiota variation, and microbiota-based models predict host species origin with high accuracy across the dataset. Interestingly, the age of host clade divergence positively associates with the degree of microbial community distinguishability between species within the host clades, spanning recent host speciation events (~1 million y ago) to more distantly related host genera (~108 million y ago). Second, topological congruence analyses of each group’s complete phylogeny and microbiota dendrogram reveal significant degrees of phylosymbiosis, irrespective of host clade age or taxonomy. Third, consistent with selection on host-microbiota interactions driving phylosymbiosis, there are survival and performance reductions when interspecific microbiota transplants are conducted between closely related and divergent host species pairs. Overall, these findings indicate that the composition and functional effects of an animal’s microbial community can be closely allied with host evolution, even across wide-ranging timescales and diverse animal systems reared under controlled conditions.

Concepts: Archaea, Evolution, Biology, Organism, Species, Phylogenetics, Binomial nomenclature, Speciation

35

Morphological data are a conduit for the recognition and description of species, and their acquisition has recently been broadened by geometric morphometric (GM) approaches that co-join the collection of digital data with exploratory ‘big data’ analytics. We employed this approach to dissect the Western Rattlesnake (Crotalus viridis) species-complex in North America, currently partitioned by mitochondrial (mt)DNA analyses into eastern and western lineages (two and seven subspecies, respectively). The GM data (i.e., 33 dorsal and 50 lateral head landmarks) were gleaned from 2,824 individuals located in 10 museum collections. We also downloaded and concatenated sequences for six mtDNA genes from the NCBI GenBank database. GM analyses revealed significant head shape differences attributable to size and subspecies-designation (but not their interactions). Pairwise shape distances among subspecies were significantly greater than those derived from ancestral character states via squared-change parsimony, with the greatest differences separating those most closely related. This, in turn, suggests the potential for historic character displacement as a diversifying force in the complex. All subspecies, save one, were significantly differentiated in a Bayesian discriminant function analysis (DFA), regardless of whether our priors were uniform or informative (i.e., mtDNA data). Finally, shape differences among sister-clades were significantly greater than expected by chance alone under a Brownian model of evolution, promoting the hypothesis that selection rather than drift was the driving force in the evolution of the complex. Lastly, we combine head shape and mtDNA data so as to derived an integrative taxonomy that produced robust boundaries for six OTUs (operational taxonomic units) of the C. viridis complex. We suggest these boundaries are concomitant with species-status and subsequently provide a relevant nomenclature for its recognition and representation.

Concepts: DNA, Scientific method, Evolution, Species, Taxonomy, Binomial nomenclature, Taxonomic rank, Crotalus

29

Biodiversity today is huge, and it has a long history. Identifying rules for the heterogeneity of modern biodiversity-the high to low species richness of different clades-has been hard. There are measurable biodiversity differences between land and sea and between the tropics and temperate-polar regions. Some analyses suggest that the net age of a clade can determine its extinction risk, but this is equivocal. New work shows that, through geological time, clades pass through different diversification regimes, and those regimes constrain the balance of tree size and the nature of branching events.

Concepts: Biodiversity, Conservation biology, Evolution, Tropics, Taxonomy, Binomial nomenclature, Genetic erosion, Biological classification

28

Phylogenetic hypotheses for the large cosmopolitan genus Hypericum (St. John’s wort) have previously been based on morphology, and molecular studies have thus far included only a few species. In this study, we used 360 sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) for 206 species representing Hypericum (incl. Triadenum and Thornea) and three other genera of Hypericaceae to generate an explicit phylogenetic hypothesis for the genus using parsimony and model-based methods. The results indicate that the small genus Triadenum is nested in a clade within Hypericum containing most of the New World species. Sister to Hypericum is Thornea from Central America. Within Hypericum, three large clades and two smaller grades were found; these are based on their general morphology, especially characters used previously in taxonomy of the genus. Relative to the most recent classification, around 60% of the sections of Hypericum were monophyletic. We used a Bayesian approach to reconstruct ancestral states of selected morphological characters, which resulted in recognition of characters that support major clades within the genus and a revised interpretation of morphological evolution in Hypericum. The shrubby habit represents the plesiomorphic state from which herbs evolved several times. Arborescent species have radiated convergently in high-elevation habitats in tropical Africa and South America.

Concepts: DNA, Evolution, Biology, Organism, Species, Phylogenetics, Binomial nomenclature, Biological classification

27

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine and basic research. This phylogenetically-guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for close to a century. Due to recent changes in the International Code of Nomenclature for algae, fungi and plants (16), this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we find unnecessary. Here we argue that our proposal will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice.

Concepts: Biology, Species, Plant, Fungus, Binomial nomenclature, Genus, Kingdom, International Code of Zoological Nomenclature

27

Habenaria is a large genus of terrestrial orchids distributed throughout the tropical and subtropical regions of the world. The integrity and monophyly of this genus have been under discussion for many years, and at one time or another, several genera have been either included in a broadly defined Habenaria or segregated from it. In this study, the phylogenetic relationships of the Neotropical members of the genus and selected groups of African Habenaria were investigated using DNA sequences from the nuclear internal transcribed spacer (ITS) region and the plastid matK gene sampled from 151 taxa of Habenaria from the Neotropics (ca. 51% of the total) as well as 20 species of Habenaria and Bonatea from the Old World. Bayesian and parsimony trees were congruent with each other, and in all analyses, the Neotropical species formed a highly supported group. African species of Habenaria in sections Dolichostachyae, Podandria, Diphyllae, Ceratopetalae and Bilabrellae, and the Neotropical clade formed a highly supported “core Habenaria clade”, which includes the type species of the genus from the New World. The topology of the trees indicates an African origin for the Neotropical clade and the low sequence divergence among the Neotropical species suggests a recent radiation of the genus in the New World. Species of Bonatea and Habenaria sections Chlorinae and Multipartitae formed a well-supported clade that was sister to the “core Habenaria clade”. The Neotropical clade consists of at least 21 well-supported subgroups, but all Neotropical sections of the current sectional classification are paraphyletic or polyphyletic and will need extensive revision and recircumscription. Most of the Neotropical subgroups formed morphologically uniform assemblage of species, but some cases of morphological divergence within subgroups and convergence between subgroups indicated that morphology alone can be misleading for inferring relationships within the genus. The genera Bertauxia, Kusibabella and Habenella, segregated from New World Habenaria, are not monophyletic and a revision of the sectional classification rather than a generic division seems most appropriate. Our results do not support an extensive generic fragmentation of Habenaria as previously suggested and will provide a framework for revising the infrageneric classification and investigating the patterns of morphological evolution and geographical distribution of the genus in the New World.

Concepts: DNA, Organism, Species, Phylogenetics, Polyphyly, Binomial nomenclature, Clade, Biological classification

26

Since the discovery of saponins in sea cucumbers, more than 150 triterpene glycosides have been described for the class Holothuroidea. The family Holothuriidae has been increasingly studied in search for these compounds. With many species awaiting recognition and formal description this family currently consists of five genera and the systematics at the species-level taxonomy is, however, not yet fully understood. We provide a bibliographic review of the triterpene glycosides that has been reported within the Holothuriidae and analyzed the relationship of certain compounds with the presence of Cuvierian tubules. We found 40 species belonging to four genera and 121 compounds. Holothurin A and B are the most common saponins for Actinopyga, Holothuria, and Pearsonothuria. The genus Bohadschia presents mainly bivittoside C and D. Actinopyga has only sulfated saponins mainly oxidized, Bohadschia non-sulfated ones mainly non-oxidized, Holothuria and Pearsonothuria contain both types of compounds, mainly oxidized. Within the genus Holothuria, the subgenus Panningothuria only has non-sulfated saponins. The presence of sulfated and non-sulfated compounds seemingly relates to the expellability or the absence of Cuvierian tubules and the temporal or permanent concealing habits of the species. Our study concludes that better insights into the systematic distribution of saponins in Holothuriidae will only be possible if the identifications of the investigated species are confirmed by a taxonomist, especially in this group wherein cryptic species and variation between life-history stages are common and yet poorly understood. Understanding of saponin distribution within the Holothuriidae would also benefit from a stabilization of triterpene glycoside nomenclature.

Concepts: Species, Taxonomy, Binomial nomenclature, Taxonomic rank, International Code of Zoological Nomenclature, Sea cucumber, Systematics, Holothuroidea

25

Based on a number of isolates of Myceliophthora (Chaetomiaceae, Sordariales, Ascomycota) recently isolated from soil samples collected in USA, the taxonomy of the genus was re-evaluated through phylogenetic analyses of sequences from the nuc rDNA internal transcribed spacer region and genes for the second largest subunit of RNA polymerase II and translation elongation factor 1a. Members of Myceliophthora were split into four monophyletic clades strongly supported by molecular and phenotypic data. Such clades correspond with Myceliophthora, now restricted only to the type species of the genus Corynascus, which is re-established with five species, the new monotypic genus Crassicarpon and also the new genus Thermothelomyces (comprising four species). Myceliophthora lutea is mesophilic and a permanently asexual morph compared to the members of the other three mentioned genera, which also are able to sexually reproduce morphs with experimentally proven links to their asexual morphs. The asexual morph of M. lutea is characterized by broadly ellipsoidal, smooth-walled conidia with a wide, truncate base. Crassicarpon thermophilum is thermophilic and heterothallic and produces spherical to cuneiform, smooth-walled conidia and cleistothecial ascomata of smooth-walled, angular cells and ascospores with a germ pore at each end. Corynascus spp. are homothallic and mesophilic and produce spherical, mostly ornamented conidia and cleistothecial ascomata with textura epidermoidea composed of ornamented wall cells, and ascospores with one germ pore at each end. Thermothelomyces spp. are thermophilic, heterothallic and characterized by similar ascomata and conidia as Corynascus spp., but its ascospores exhibit only a single germ pore. A dichotomous key to distinguish Myceliophthora from the other mentioned genera are provided, as well as dichotomous keys to identify the species of Corynascus and Thermothelomyces. A new species, namely Corynascus fumimontanus, characterized by verrucose ascomatal wall cells and irregularly shaped ascospores, is described and illustrated.

Concepts: DNA, Gene, Biology, Organism, Species, Chromosome, Phylogenetics, Binomial nomenclature