Re-visioning the evolutionary tree: A map-based visualization for communicating evolution

2012 ◽  
Author(s):  
Sonia Stephens
Keyword(s):  
Evolutionary Tree

Morphological and molecular characterisation of Aporcelaimellus simplex (Thorne & Swanger, 1936) Loof & Coomans, 1970 and a new concept for Aporcella Andrássy, 2002 (Dorylaimida: Aporcelaimidae)

Nematology ◽  
2013 ◽  
Vol 15 (2) ◽  
pp. 165-178 ◽  
Author(s):  
Sergio Álvarez-Ortega ◽  
Sergei A. Subbotin ◽  
Reyes Peña-Santiago
Keyword(s):  
Molecular Data ◽  
Evolutionary Tree ◽  
Valid Species ◽  
Molecular Characterisation ◽  
New Combinations ◽  
Terminal Portion ◽  
Significant Difference ◽  
European Populations ◽  
Emended Diagnosis

This contribution presents a study of Iberian and Californian populations of Aporcelaimellus simplex, including morphological, morphometric and molecular data. The species is characterised and distinguished by its lip region offset by an expansion, pars refringens vaginae absent, and conical tail with a small but distinct hyaline terminal portion. No significant difference exists between American and European populations. Molecular data and the derived evolutionary tree show a topology in which this species forms a well-supported group with members of Discolaiminae, far from other representatives of Aporcelaimellus. Putting special emphasis in the absence of pars refringens vaginae, A. simplex is transferred to the genus Aporcella. The taxonomy of this genus is revised in depth, with the proposal of an emended diagnosis, the provision of a list of 13 valid species (mostly new combinations from Aporcelaimellus) as well as a key to their identification and a compendium of their main morphometrics. Aporcella debruinae sp. n. is proposed for Aporcelaimellus papillatus apud de Bruin & Heyns, 1992.

Three new species of Sectonema Thorne, 1930 (Dorylaimida: Aporcelaimidae) from Vietnam

Nematology ◽  
2016 ◽  
Vol 18 (5) ◽  
pp. 517-536 ◽  
Author(s):  
Sergio Álvarez-Ortega ◽  
Thi Anh Duong Nguyen ◽  
Joaquín Abolafia ◽  
Thi Thanh Tam Vu ◽  
Michael Bonkowski ◽  
...  
Keyword(s):  
New Species ◽  
Phylogenetic Relationship ◽  
Ventral Side ◽  
Molecular Data ◽  
Evolutionary Tree ◽  
Neck Length ◽  
Natural Habitats ◽  
Line Drawings ◽  
Close Phylogenetic Relationship ◽  
Three New Species

Three new species of the genus Sectonema collected from natural habitats in Vietnam are studied, described and illustrated, including line drawings, LM and/or SEM pictures. Sectonema birrucephalum sp. n. is characterised by its 2.73-4.35 mm long body, lip region 18-20 μm broad and offset by deep constriction, odontostyle 10.0-11.5 μm long on its ventral side, 659-989 μm long neck, pharyngeal expansion occupying 63-68% of total neck length, uterus a simple tube, 221-277 μm long, pars refringens vaginae present, V = 54-56, tail short (31-43 μm, c = 85-111, c′ = 0.6-0.8) and rounded, spicules 72-75 μm long, and four or five irregularly spaced ventromedian supplements beyond the range of the spicules. Sectonema buccociliatum sp. n. is distinguished by its 2.00-2.46 mm long body, lip region offset by constriction, 19-20 μm broad and bearing perioral cilia-like structures, odontostyle 13-14 μm long at its ventral side, 530-625 μm long neck, pharyngeal expansion occupying 62-69% of total neck length, uterus a simple tube, 116-152 μm long, pars refringens vaginae present, V = 56-62, tail short (23-31 μm, c = 72-104, c′ = 0.6-0.8) and rounded, spicules 56-68 μm long, and 3-5 spaced and weakly developed ventromedian supplements beyond the range of the spicules. Sectonema ciliatum sp. n. is characterised by its 2.79-3.13 mm long body, lip region offset by constriction, 21-22 μm broad and bearing perioral cilia-like structures, odontostyle 14-15 μm long at its ventral side, 699-722 μm long neck, pharyngeal expansion occupying 60% of total neck length, uterus a simple tube, 201-244 μm long, pars refringens vaginae present, V = 52-53, tail short (33-35 μm, c = 82-92, c′ = 0.6-0.7) and rounded, spicules 70-72 μm long, and three or four spaced and weakly developed ventromedian supplements beyond the range of the spicules. Molecular data obtained for S. ciliatum sp. n. and the derived evolutionary tree show a close phylogenetic relationship with other species of the genus.

Understanding Molecular Clocks and Time Trees

2021 ◽  
pp. 326-337
Author(s):  
Andrew V. Z. Brower ◽  
Randall T. Schuh
Keyword(s):  
Amino Acid ◽  
Molecular Clock ◽  
Significant Error ◽  
Evolutionary Tree ◽  
Molecular Clocks ◽  
Amino Acid Substitutions ◽  
Absolute Minimum ◽  
Short Time ◽  
Over Time ◽  
Age Estimates

This chapter examines molecular clocks and time trees. Although laden with numerous process assumptions that may or may not be true (or knowable), the idea is appealingly straightforward: if amino acid substitutions in proteins occurred at a relatively steady pace that were more or less constant both over time and along each of the branches of a diverging evolutionary tree, then the number of substitutions would be directly related to the time since the taxa in question diverged from one another. However, evidence does not support a universal molecular clock. Evidence might or might not support “local” clocklike evolution among closely related taxa over relatively short time spans. Although absolute minimum ages for clades may be inferred from fossils, from biogeographical patterns, or extrapolated from secondary calibrations, such age estimates are subject to potentially significant error due to vagaries of geological dating as well as ambiguities of fossil identity. The test of a time tree hypothesis is to discover new fossil evidence that corroborates or falsifies it.

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