Genetics and the Human Race: Definition of race on the basis of gene frequencies supplements definition from morphological characters

Science ◽  
1963 ◽  
Vol 140 (3571) ◽  
pp. 1057-1064 ◽  
Author(s):  
W. C. Boyd
2004 ◽  
Vol 35 (3) ◽  
pp. 299-306 ◽  
Author(s):  
◽  
J. M. Tierno de Figueroa ◽  
◽  
◽  

AbstractThe western Mediterranean stonefly genus Tyrrhenoleuctra traditionally includes 3 species: T. minuta (Spain, North Africa, Balearic Islands), T. tangerina (Spain, North Africa), T. zavattarii (Corsica and Sardinia). Since the traditional morphological characters display great and overlapping variation, allozyme electrophoresis was used to clarify taxonomic and phylogenetic relationships within the genus and to discuss biogeographical implications. The results clearly discriminate at least four entities: the Corso-Sardinian unit, for which the name T. zavattarii can be used; the Balearic population, representing an undescribed species; at least two Iberian peninsular species. However, more data on topotypic populations are needed to define the taxonomic status of the Iberian species (including definition of the currently used names T. minuta and T. tangerina). The presence of Tyrrhenoleuctra in Sardinia and Corsica is likely due to an old vicariance event following separation of the Sardinia-Corsica microplate from the Iberian Peninsula. Calibration of the molecular clock (genetic distances vs. Corso-Sardinian plate split from Iberia) resulted in a very low evolutionary rate (0.008 D/my), lower than those found in taxonomically distant groups (including stoneflies) with similar distribution.


2004 ◽  
Vol 175 (5) ◽  
pp. 507-512 ◽  
Author(s):  
Isabelle Rouget ◽  
Pascal Neigeet ◽  
Jean-Louis Dommergues

Abstract Two main types of data are available to resolve phylogenies using fossils data: (1) stratigraphic ordering of taxa, and (2) morphological characters. In most phylogenetic studies dealing with ammonites, authors have given priority to the stratigraphic distribution of taxa. This practice is classically justified by the fact that the ammonite fossil record is frequently outstandingly good. In practice, the level of integration of stratigraphic and morphologic information in a single analysis depends on the confidence that authors have in the quality of data. Besides, many evolutionary concepts, which could differ over time and between authors (e.g. anagenesis, cladogenesis, iterative evolution), are added to these data to help infer phylogenetic relationships. As a result, phylogenetic hypotheses are based on eclectic methods which depend on the relative weight given to stratigraphic and morphologic information as well as on evolutionary concepts used. The validity of relationships proposed by previous authors is not dealt with in this paper. Instead, our goal is to draw attention to problems that these eclectic methods may cause, that is to say: (1) ammonites systematics is poorly formalised and (2) phylogenetic hypotheses as they are classically constructed are not rigorously testable. During the last 10 years, cladistic analysis has been applied to ammonites but is still unpopular among ammonitologists. However, studies have consistently shown that cladistics is not as unsuited a tool for ammonites phylogenetic reconstruction as is widely believed. Moreover, classical works open new questions about ammonite phylogeny and in particular, help to reappraise our view on the definition of morphological characters and their phylogenetic significance.


2016 ◽  
Vol 47 (4) ◽  
pp. 313-346 ◽  
Author(s):  
Luciana Weiler ◽  
Augusto Ferrari ◽  
Jocelia Grazia

Phylogenetic analyses of the 13 species of the subgenusLyciptabased on morphological characters were performed under equal and implied weighting, following the method of Mirande (2009). Species fromDichelops,Ladeaschistus,Proxys,Spinalanx,Euschistus(Euschistus) andEuschistus(Mitripus) were included as outgroups, and the tree rooted onCarpocoris. Sixty-five morphological characters were coded in the data matrix. The cladistic analyses did not recover the monophyly of the subgenusLycipta. A clade was supported based on characters of the pygophore and female ectodermal ducts strengthening a new definition ofEuschistus(Lycipta). One species,Euschistus monrosi, was excluded from the subgenus and transferred to the nominal subgenus.Euschistus(Lycipta) species are distributed in two Neotropical subregions: Brazilian (Pará, Rondônia and Yungas provinces) and Chacoan (Pampean, Atlantic, Parana andAraucariaForests and Puna provinces). Biogeographical analyses of spatial vicariance were performed employing different sets of parameters and allowed to identify five disjunctions nodes.


Nematology ◽  
2009 ◽  
Vol 11 (6) ◽  
pp. 869-881 ◽  
Author(s):  
Natsumi Kanzaki ◽  
Robin M. Giblin-Davis ◽  
Rudolf H. Scheffrahn ◽  
Barbara J. Center ◽  
Kerrie A. Davies

Abstract A species of aphelenchoidid nematode was isolated from a subterranean termite, Cylindrotermes macrognathus, during a survey of termite-associated nematodes in a conserved forest in La Selva, Costa Rica. The nematode was morphologically intermediate between the families Aphelenchidae and Aphelenchoididae, i.e., the nematode had a true bursa supported by bursal limb-like genital papillae but lacked a clear pharyngeal isthmus. The molecular phylogenetic status of the new nematode among tylenchid, cephalobid, panagrolaimid, aphelenchid and aphelenchoidid genera was analysed based on ca 1.2 kb of SSU ribosomal DNA sequence and the inferred position was basal to the family Aphelenchoididae. It was clearly not part of the clade containing the genus Aphelenchus (=Aphelenchidae). This nematode is described herein as Pseudaphelenchus yukiae n. gen., n. sp., and the family definition of Aphelenchoididae is emended to include the unique morphological characters of this new genus. The molecular phylogenetic analysis supported the paraphyly of the three Aphelenchoidinae genera Aphelenchoides, Laimaphelenchus and Schistonchus and the monophyly of Ektaphelenchinae, Seinura (Seinurinae) and Noctuidonema (Acugutturinae). However, many more representatives are needed to resolve the family-genus level phylogeny of Aphelenchoididae.


2017 ◽  
Vol 4 (9) ◽  
pp. 170221 ◽  
Author(s):  
A. L. Vereshchaka

The phylogenetic analysis of Sergestoidea based on 253 morphological characters and encompassing all 99 valid species confirmed all previously recognized genus-level clades. Analysis retrieved five major robust clades that correspond to families Luciferidae, Sergestidae, Acetidae fam.n., Sicyonellidae fam.n. and Petalidiumidae fam.n. Synonymy, emended diagnoses and composition of revealed family-level clades are provided. Three types of morphological characters were important in the phylogeny of the Sergestoidea: general external characters, copulatory organs, and photophores. Novel metrics to quantify the contribution of these character types were tested. General external characters were significant in supporting the major clades (80% of the families and nearly half of the genera). Copulatory organ characters and photophores greatly supported the medium-level clades: Lucifer, Belzebub , Petalidium, Neosergestes, Challengerosergia (copulatory organ characters) and Lucensosergia , Challengerosergia, Gardinerosergia , Phorcosergia (photophores). An evolutionary model of the Sergestoidea showing their pathways into their principal biotopes is proposed: the major clades evolved in a vertical direction (from epi- to bathypelagic); further divergence at the genus level occurred within vertical zones in a horizontal direction, with the invasion of the benthopelagic and neritic (shelf and estuarine) habitats and speciation within these domains.


Plant Disease ◽  
2010 ◽  
Vol 94 (11) ◽  
pp. 1372-1372 ◽  
Author(s):  
M. Lembicz ◽  
K. Górzyńska ◽  
A. Leuchtmann

Agropyron repens (synonym Elymus repens, couch grass) is a species native to Europe and Asia. In Poland, it is a common weed of crop fields. In May 2008, we noticed for the first time symptoms of choke disease (caused by Epichloë spp.) on A. repens at two localities in central Poland. The localities, Pakość (52°47.531′N, 18°06.118′E) and Dulsk (52°45.329′N, 18°20.518′E), are located 16 km apart from each other. The following year, we confirmed the occurrence of choke disease on couch grass at these localities. Stromata were formed on reproductive stems that did not produce inflorescences. They ranged from 16 to 31 mm long and were covered with perithecia 520 to 560 × 160 to 250 μm at a density of 35 to 45 per mm2. Asci measured 270 to 310 × 5.2 to 6.5 μm and ascospores were 225 to 275 × 1.5 to 1.7 μm (specimen deposited in ZT). Morphological characters match with the original description of Epichloë bromicola (4). One strain was isolated from stromatal tissue and the partial DNA sequence of tubB including introns 1 to 3 was obtained as previously described (2). In a phylogenetic analysis, the isolate (GenBank Accession No. GU325782) grouped with Epichloë isolates from other Agropyron spp. from Poland (A. intermedium) and Japan (A. ciliare and A. tsukushiense) and with an isolate from a Roegneria sp. (from China). Experimental mating tests involving isolates from A. intermedium and a Roegneria sp. indicated that these isolates were sexually compatible with Epichloë bromicola from Bromus erectus. Similarly, E. yangsii was compatible with E. bromicola. This suggests that Epichloë isolates from Agropyron, Roegneria, and Bromus hosts form a common mating population, and implies that under a biological species concept the phylogenetic definition of E. bromicola has to be broadened. Epichloë on A. repens has been previously found in Poland (1), Germany (3), Hungary, and Romania (specimen deposited in herbarium of ETH Zurich, ZT) based on incidental records or on herbarium specimens that have been listed under E. typhina. Our study, based on morphology, tubB sequence similarity, and mating compatibility, suggests that the fungus infecting A. repens in Poland is E. bromicola. References: (1) I. Adamska. Acta Mycol. 36:31, 2001. (2) D. Brem and A. Leuchtmann. Evolution 57:37, 2003. (3) J. Kohlmeyer and E. Kohlmeyer. Mycologia 66:77, 1974. (4) A. Leuchtmann and C. L. Schardl. Mycol. Res. 102:1169, 1998.


2009 ◽  
Vol 23 (5) ◽  
pp. 422
Author(s):  
Xiao-Yan Li ◽  
Hong-Zhang Zhou

The paederine genus Paederus s.l. (Coleoptera : Staphylinidae) is a hyperdiverse group of some 500 species worldwide. Although the subtribe Paederina, in which the genus resides, is monophyletic the status of numerous genera and subgenera is questionable and the current classification is likely to be flawed. As part of detailed studies on the paederine fauna of China, we undertook a preliminary morphologically-based phylogenetic analysis to determine the relationships of Paederus (Gnathopaederus) and related subgenera, as a basis for a revision of the subgenus, and as an attempt to provide a better framework for future taxonomic studies on the group as a whole. The analysis was based on 66 adult morphological characters for 30 ingroup taxa, including all six species of P. (Gnathopaederus). The results show that P. (Gnathopaederus) and P. (Paederus), and the genera Megalopaederus, Pachypaederus and Paederidus are monophyletic, and that P. (Eopaederus) and P. (Harpopaederus) are paraphylyetic. However, our analysis did not offer a robust solution to relationships among other clades within Paederus s.l. although it seems clear that Paederus s.l. is not monophyletic with respect to the above genera. The monophyly of P. (Gnathopaederus) is supported by the mandibular basal medial tooth having two cuspids separated dorsoventrally. Based largely on this character state, the definition of the subgenus is refined; six species are recognized, including two new species described from China as follows: P. (G.) daozhenensis, sp. nov. from Guizhou, and P. (G.) jilongensis, sp. nov. from Xizang; three species, P. bursavacua Willers, P. yunnanensis Willers and P. solodovnikovi Willers, are newly assigned to the subgenus according to a revised subgeneric definition. New morphological characters including important secondary sexual characters and sexual dimorphism are described and male genitalia are illustrated for the first time for the type species of the subgenus, P. (G.) szechuanus (Chapin). A key to the six species is presented and the distribution of each species is documented and discussed.


1962 ◽  
Vol 11 (3) ◽  
pp. 269-283
Author(s):  
William C. Boyd

The intimate connection between natural selection and heredity is indicated by Prof. Dobshansky's definition of evolution as essentially just a change in gene frequencies, for natural selection is the agency that causes gene frequencies to change. Just as mutations are the raw material of evolution, selection is the force that preserves good genes, eliminates bad genes, and produces the changes that lead to the formation of races, and eventually species.The problem of the action of selection on gene frequencies can be treated, with suitable simplifying assumptions, mathematically, and many years ago Prof. J. B. S. Haldane published a series of papers on this subject (tab. I). The rate at which gene frequencies would change under the action of slow selection is shown in fig. 1. It will be seen that selection acts more slowly, at first, on recessive genes than on dominants, but in the long run the frequencies change from nearly zero to nearly one, or vice versa. Deleterious genes are often never completely eliminated, because they are continually recruited by recurring mutations.That selection is effective in bringing about considerable changes in organisms is shown by the achievements of domestic plant and animal breeders. The results of selecting for long shanks in chickens are shown in fig. 2, and for a larger number of abdominal chaetae in fruit flies in fig. 3. Though it is not shown here, selection for a lower number of chaetae is also effective.


Nematology ◽  
2011 ◽  
Vol 13 (7) ◽  
pp. 787-804 ◽  
Author(s):  
Natsumi Kanzaki ◽  
Noritoshi Maehara ◽  
Takuya Aikawa ◽  
Hayato Masuya ◽  
Robin M. Giblin-Davis

Abstract A Bursaphelenchus species was isolated from an ambrosia beetle, Xyleborus seriatus, during a biodiversity survey of entomophilic nematodes in a conserved forest in the Shirakami mountain range, Aomori, Japan. The nematode has several interesting morphological characters that do not fit the morphological definition of Bursaphelenchus, e.g., males have a tail spike instead of a bursal flap and lack the P1 ventral single papilla, and females have a very long and tapering tail (filiform). The molecular phylogenetic status of the new species inferred by the near-full-length small subunit (SSU: 18S) and the D2/D3 expansion segments of the large subunit (LSU: 28S) suggests, however, that the nematode is included in the B. fungivorus group, and is most closely related to B. thailandae and B. willibaldi. Despite these unique morphological characters, its spicule morphology, which is almost identical to that of B. gonzalezi, B. thailandae and B. willibaldi, and vulval structure, i.e., lacking a vulval flap, are in accordance with the molecular phylogenetic status of the nematode. The new species, which shows evidence of secondary loss of the bursal flap and P1 papilla, is described herein as B. kiyoharai n. sp. The typological descriptions of the genus and Parasitaphelenchinae were reconsidered and the taxonomic framework of the Aphelenchoidinae and Parasitaphelenchinae revised. Bursaphelenchus asiaticus n. comb. is proposed for Ruehmaphelenchus asiaticus.


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