Hundreds of genetic barcodes of the species-rich hydroid superfamily Plumularioidea (Cnidaria, Medusozoa) provide a guide toward more reliable taxonomy (original) (raw)
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Marine hydroids are important benthic components of shallow and deep waters worldwide, but their taxonomy is controversial because diagnostic morphological characters to categorize taxa are limited. Their genetic relationships are also little investigated. We tested taxonomic hypotheses within the highly speciose superfamily Plumularioidea by integrating a classical morphological approach with DNA barcoding of the 16S and COI mitochondrial markers for 659 and 196 specimens of Plumularioidea, respectively. Adding Genbank sequences, we inferred systematic relationships among 1,114 plumularioids, corresponding to 123 nominal species and 17 novel morphospecies in five families of Plumularioidea. We found considerable inconsistencies in the systematics of nominal families, genera and species. The families Kirchenpaueriidae and Plumulariidae were polyphyletic and the Halopterididae paraphyletic. Most genera of Plumularioidea are not monophyletic. Species diversity is considerably underestimated. Within our study, at least 10% of the morphologically-distinctive morphospecies are undescribed, and about 40% of the overall species richness is represented by cryptic species. Convergent evolution and morphological plasticity therefore blur systematic relationships. Additionally, cryptic taxa occur frequently in sympatry or parapatry, complicating correspondence with type material of described species. Sometimes conspecificity of different morphotypes was found. The taxonomy of hydroids requires continued comprehensive revision.
Molecular systematics and the multidimensional concept of species
Biochemical Systematics and Ecology, 1993
Following a critical review of the species concepts and stressing the need for a single, general classification system to serve both systematists and evolutionary biologists, the author seeks to identify a conceptual framework where matching of taxonomic characters to the biological properties of species is maximized. Sympatric and synchronic populations of amphigonic organisms can almost unequivocally be identified as species when reproductive gaps occur between them. In such situations species are recognized by appropriate descriptors (characters) as genetic units and ecological units. Multivariate statistical methods provide a powerful tool to analyse more complex situations where non-amphigonic organisms and/or allopatric populations are investigated, on condition that appropriate character sets are considered. The increasing availability of molecular data for analysis certainly enhances the recognition of species as genetic unities, whilst much of the ecological role of an organism may be read from a careful choice of morphometric and ethological descriptors. On these premises it is suggested that species can be defined as groups of individuals (populations) which are discretely separated from other such groups in the character space. This definition is phenetical in its form but biological in its meaning since character sifting and weighting are considered essential features at the operational level.
Deviant segments hamper a morphometric approach towards Halimeda taxonomy
2005
Traditional taxonomy of the segmented green algal genus Halimeda is largely based on descriptive expressions of thallus habit, segment shape and anatomical structures. In the course of the last decade, molecular phylogenetic studies have revealed non-monophyly and cryptic diversity in several species. In an attempt to tackle the taxonomic problems that were raised by these molecular studies, a combined molecular and morphometric method was developed. In this study, a morphometric pilot data set is explored. This resulted in the discovery of segments aberrant in morphology and/or anatomy. These are primarily apical and non-calcified segments, and segments from the basal part of the algal body. To answer the question whether incorporation of comparison of discriminant analyses that included and excluded deviant segments demonstrated the negative influence of such segments on the taxonomic power of the data. Omitting non-calcified and apical segments and segments from the basal thallus region yielded the same results as the exclusion of all deviant segments, irrespective of their location in the algal body. This result permits a simple recommendation towards precluding these types of segments from further studies.
An Outline of a Conceptual Framework for Contemporary Biological Systematics
An Outline of a Conceptual Framework for Contemporary Biological Systematics, 2023
Biological systematics, exploring the structure of taxonomic diversity (TD), needs a proper conceptualization that would (a) make it complying with certain universal criteria of scientificity and (b) take into account specificity of its studied object. This article outlines a possible conceptual framework for this natural science discipline based on the ideas of contemporary conceptualism. One of the most fundamental of them includes a concept of cognitive situation shaped by three interrelated basic components-ontic, epistemic, and subjective. Its core position is taken by a taxonomic theory (TT) being a conceptual construct resulted from a "summative" effect of all three components and designed for studying TD. The general TT is shown to be composed by a hierarchically arranged array of partial TTs of various levels of generality, and this construct serves as a conceptual justification of taxonomic pluralism. Several kinds of partial TTs are suggested to recognise, viz., ontology-and epistemology-oriented, aspect-and object-based, etc. The aspect-based TTs are of special importance as the conceptual foundations of particular research programs in systematics. The object-based partial TTs are shown to be implemented by concepts of species and homology. A large-scale relation between taxonomic theory and nomenclature is briefly considered.
Systematics and Diversity This chapter provides a short introduction to systematics: the branch of biological science responsible for recognising, comparing, classifying and naming the millions of different sorts of organisms that exist. As such, systematics provides the basic framework for the whole of biology, and is the fundamental discipline of biodiversity. The work can be divided into a number of activities, including classification, identification and nomenclature. These are often grouped as taxonomy, broadly defined as the classification and naming of organisms. This chapter gives the background for Chapter 3, which discusses some key theoretical and practical problems arising from the concept of the species. BIOLOGICAL CLASSIFICATION The ultimate task of systematics is to document and understand the extent and significance of biological diversity. Within this framework, taxonomy performs four basic functions: differentiation (recognition of taxa), identification (universal diagnosis of taxa), symbolisation (application of universal names), and comparison (relative relationships of taxa). Vernacular or folk taxonomies provide limited local systems for the first three but have little to tell us about the last. Individuals and characters are the most basic units of biological classification. On the basis of features held in common (attributes or characters), individuals can be grouped together into a large number of different classes. These classes are of two kinds (often regarded as sharply distinct, although in reality they form a continuum). On the one hand, individual organisms can be divided into such groups as freshwater, marine, terrestrial, planktonic, nocturnal, pollinators, etc. Alternatively, they can be placed into taxonomic categories of species, genera, families,
The morphological diversity within a species can obscure the correct identification
Zoologischer Anzeiger, 2022
Critical points of various diagnostic characters and a paucity of information relating to the geographical distribution of several marine species can hinder real species delimitation, particularly if they are supposed to be cosmopolitan. Such constraints characterize many amphipod species and are mainly due to the variation in morphological characters during growth. Specifically, the benthic filter-feeding corophiid Cheiriphotis mediterranea Myers, 1983 displays different shapes for the male gnathopod 2 as it grows. This variation has hitherto never been described but an extensive sampling has provided us with the opportunity of studying it in detail. More than six thousand individuals, belonging to C. mediterranea, were collected along the Israeli coast during a five-year soft-bottom monitoring survey, comprising 282 sites at a depth between 4 and 37 m. One of the objectives of this study was to integrate the original description of C. mediterranea with the identification of definite six morphotypes, which alternate during growth. A mtDNA Cytochrome c oxidase subunit I sequence was obtained, representing the first molecular datum for the genus Cheiriphotis. The results offer the possibility of including variable morphological characters and molecular sequences in the identification process. Throughout the survey, C. mediterranea was confirmed to be one of the most abundant five species in the study area, in particular in Haifa Bay, where the environmental conditions are stressful. Barely-known abundance and distribution notes relating to this species are reported in this paper; a putative role of bioindicator is also suggested.
Zoologica Scripta, 2015
Phylogenetic relationships within Aglaopheniidae (Cnidaria, Hydrozoa) reveal unexpected generic diversity.-Zoologica Scripta, 45, 103-114. Morphology can be misleading in the representation of phylogenetic relationships, especially in simple organisms like cnidarians and particularly in hydrozoans. These suspension feeders are widely distributed in many marine ecosystems, and the family Aglaopheniidae Marktanner-Turneretscher, 1890 is among the most diverse and visible, especially on tropical coral reefs. The taxonomy of this family is based on morphological characters with emphasis on reproductive structures for the identification of genera. This study is the most comprehensive molecular phylogeny of the Aglaopheniidae to date, including six genera and 38 species, of which 13 were investigated for the first time and sampled on tropical coral reefs throughout the Indo-Pacific region. For newly sampled individuals, we sequenced the 16S rRNA, the nuclear locus comprising the complete ITS1-5.8S rRNA gene-ITS2 and the first intron of the calmodulin nuclear gene. Phylogenetic analyses of the data revealed and confirmed a general polyphyly, or doubtful monophyly, of all sampled genera in tropical regions based on both the mitochondrial and nuclear markers. Our results revealed that several morphological characters used today are unsuited to resolve phylogenetic relationships between species and genera, as well as the high phyletic diversity within this family. Future revision of the classification of this family will require extensive geographic sampling and the use of an integrative approach.