Search results for "phylogenetic"
showing 10 items of 1179 documents
Adaptive trends of sequence compositional complexity over pandemic time in the SARS-CoV-2 coronavirus
2021
In the brief time since the outbreak of the COVID 19 pandemic, and despite its proofreading mechanism, the SARS-CoV-2 coronavirus has accumulated a significant amount of genetic variability through recombination and mutation events. To test evolutionary trends that could inform us on the adaptive process of the virus to its human host, we summarize all this variability in the Sequence Compositional Complexity (SCC), a measure of genome heterogeneity that captures the mutational and recombinational changes accumulated by a nucleotide sequence along time. Despite the brief time elapsed, we detected many differences in the number and length of compositional domains, as well as in their nucleot…
Aggressive mimicry coexists with mutualism in an aphid
2015
Understanding the evolutionary transition from interspecific exploitation to cooperation is a major challenge in evolutionary biology. Ant-aphid relationships represent an ideal system to this end because they encompass a coevolutionary continuum of interactions ranging from mutualism to antagonism. In this study, we report an unprecedented interaction along this continuum: aggressive mimicry in aphids. We show that two morphs clonally produced by the aphid Paracletus cimiciformis during its root-dwelling phase establish relationships with ants at opposite sides of the mutualism-antagonism continuum. Although one of these morphs exhibits the conventional trophobiotic (mutualistic) relations…
Phylogeny and inflorescences of Berberidaceae — a morphological survey
1995
The 13 genera of Berberidaceae are investigated morphologically and cladistically in order to examine the phylogenetic relationships among the extant taxa. Cladistic analysis of 59 morphological characters using PAUP resulted in one most parsimonious tree. In the present paper main emphasis is put on inflorescence morphological features, which contributes eight characters to the current data matrix. The analysis resulted in four major clades. Nandina has a basal position, and the next clade includes Berberis and Mahonia. Ranzania is sister genus to Jeffersonia, Diphylleia/Podophyllum and Leontice/Bongardia. These all form the sister group to a clade in which Achlys is sister taxon to Epimed…
Plant Morphology: The Historic Concepts of Wilhelm Troll, Walter Zimmermann and Agnes Arber
2001
Recent molecular systematic and developmental genetic findings have drawn attention to plant morphology as a discipline dealing with the phenotypic appearance of plant forms. However, since different terms and conceptual frameworks have evolved over a period of more than 200 years, it is reasonable to survey the history of plant morphology; this is the first of two papers with this aim. The present paper deals with the historic concepts of Troll, Zimmermann and Arber, which are based on Goethe's morphology. Included are contrasting views of ‘unity and diversity’, ‘position and process’, and ‘morphology and phylogeny’, which, in part, are basic views of current plant morphology, phylogenetic…
The logic of forms in the light of developmental biology and palaeontology.
2010
11 pages; If you ask palaeontologists, and indeed anyone interested in the theory of evolution, for the key words that encapsulate it, you will obtain the following results: adaptation, natural selection, speciation, but also ontogeny and phylogeny. The first three key words apply to the future of the individual and by extension to the future of the species: we are therefore dealing with adults of a reproductive age. The two other key words concern (i) the evolution of the morphology from the egg to the adult (individual ontogeny: short timescale) and especially what goes on in the black box called embryogenesis, and (ii) the modification of ontogenetic sequences over time, resulting in cha…
Selecting networks of nature reserves: methods do affect the long-term outcome
1999
Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodive…
The Centetostoma scabriculum complex—a group of three cryptic species (Arachnida: Opiliones: Nemastomatidae)
2011
Nemastoma scabriculum Simon, 1879 turned out to be a group of three closely related species of the Pyrenees in SW Europe (France and Spain). Though the species are similar in general habit they can easily be recognized by external morphology (structure of the apophysis of male chelicerae) and male genital morphology (penial structure). For Nemastoma scabriculum Simon, 1879 sensu stricto a lectotype is designated. The synonymous Nemastoma ventalloi Mello-Leitao, 1936 is considered to be a distinct species and is re-described. The third species of the group is described as new, Centetostoma juberthiei sp. n. Though partly sympatric in their restricted Pyrenean area, the individual species are…
Hidden Mediterranean diversity: Assessing species taxa by molecular phylogeny within the opilionid family Trogulidae (Arachnida, Opiliones)
2009
This is the first comprehensive study to evaluate the relationships between the western palearctic harvestman families Dicranolasmatidae, Trogulidae and Nemastomatidae with focus on the phylogeny and systematics of Trogulidae, using combined sequence data of the nuclear 28S rRNA and the mitochondrial cytochrome b gene. Bayesian analysis and Maximum parsimony do not reliably resolve Dicranolasma as distinct family but place it on a similar phylogenetic level as several lineages of Trogulidae. Nemastomatidae and Trogulidae turned out to be monophyletic, as did genera Anelasmocephalus and Trogulus within the Trogulidae. The genera Calathocratus, Platybessobius and Trogulocratus each appeared p…
Respiratory proteins in Sipunculus nudus--implications for phylogeny and evolution of the hemerythrin family.
2009
Three major classes of respiratory proteins are known, hemoglobin, molluscan and arthropod hemocyanin, and hemerythrin (Hr). Similar to hemoglobin, respiratory Hr is packed into erythrocytes floating in the coelomic fluid and is only known from sipunculids, brachiopods, and priapulids. Owing to this scattered distribution, the presence of Hr is generally assumed to be the plesiomorphic condition without phylogenetic importance. By sequencing 2000 Expressed Sequence Tags (ESTs) from Sipunculus nudus, we found 75 Hr-coding ESTs assembled to 20 cDNA contigs classified as four distinct Hr isoforms: three polymeric Hrs (subunit A, A', and B) and the monomeric myo-hemerythrin (myoHr). Phylogeneti…
Molecular analysis of the nitrate-reducing community from unplanted and maize-planted soils
2002
ABSTRACT Microorganisms that use nitrate as an alternative terminal electron acceptor play an important role in the global nitrogen cycle. The diversity of the nitrate-reducing community in soil and the influence of the maize roots on the structure of this community were studied. The narG gene encoding the membrane bound nitrate reductase was selected as a functional marker for the nitrate-reducing community. The use of narG is of special interest because the phylogeny of the narG gene closely reflects the 16S ribosomal DNA phylogeny. Therefore, targeting the narG gene provided for the first time a unique insight into the taxonomic composition of the nitrate-reducing community in planted an…