Division of Giardia isolates from humans into two genetically distinct assemblages by electrophoretic analysis of enzymes encoded at 27 loci and comparison with Giardia muris

SUMMARYGiardia that infect humans are known to be heterogeneous but they are assigned currently to a single species, Giardia intestinalis (syn. G. lamblia). The genetic differences that exist within G. intestinalis have not yet been assessed quantitatively and neither have they been compared in magnitude with those that exist between G. intestinalis and species that are morphologically similar (G. duodenalis) or morphologically distinct (e.g. G. muris). In this study, 60 Australian isolates of G. intestinalis were analysed electrophoretically at 27 enzyme loci and compared with G. muris and a feline isolate of G. duodenalis. Isolates of G. intestinalis were distinct genetically from both G. muris (approximately 80% fixed allelic differences) and the feline G. duodenalis isolate (approximately 75% fixed allelic differences). The G. intestinalis isolates were extremely heterogeneous but they fell into 2 major genetic assemblages, separated by fixed allelic differences at approximately 60% of loci examined. The magnitude of the genetic differences between the G. intestinalis assemblages approached the level that distinguished the G. duodenalis isolate from the morphologically distinct G. muris. This raises important questions about the evolutionary relationships of the assemblages with Homo sapiens, the possibility of ancient or contemporary transmission from animal hosts to humans and the biogeographical origins of the two clusters.

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Apparent absence of genetic differences among species of Teladorsagia (Nematoda: Trichostrongylidae)

Journal of Helminthology ◽

10.1017/s0022149x00012311 ◽

1990 ◽

Vol 64 (4) ◽

pp. 290-294 ◽

Cited By ~ 32

Author(s):

R. H. Andrews ◽

I. Beveridge

Keyword(s):

Genetic Variation ◽

Genetic Data ◽

Single Species ◽

Genetic Differences ◽

Morphological Evidence ◽

Allozyme Electrophoresis ◽

Apparent Absence ◽

Enzyme Loci ◽

Data Support ◽

Allelic Differences

ABSTRACTThe technique of allozyme electrophoresis was applied to three species of Teladorsagia present in sheep to determine the extent of genetic variation among species. Thirty-four enzyme loci were established of which 22 were invariant and 12 were shown to be polymorphic. No fixed allelic differences were detected among the species and the level of polymorphism was within the range found commonly between populations of a single species. Therefore, the genetic data support breeding data and existing morphological evidence that T. circumcincta, T. davtiani and T. trifurcata as currently recognized do in fact belong to a single species.

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Arguments that Prehistorical and Modern Humans Belong to the Same Species

10.20944/preprints201905.0038.v1 ◽

2019 ◽

Author(s):

Rainer Kühne

Keyword(s):

Homo Sapiens ◽

Single Species ◽

Homo Erectus ◽

Modern Humans ◽

Homo Neanderthalensis ◽

Out Of Africa

I argue that the evidence of the Out-of-Africa hypothesis and the evidence of multiregional evolution of prehistorical humans can be understood if there has been interbreeding between Homo erectus, Homo neanderthalensis, and Homo sapiens at least during the preceding 700,000 years. These interbreedings require descendants who are capable of reproduction and therefore parents who belong to the same species. I suggest that a number of prehistorical humans who are at present regarded as belonging to different species belong in fact to one single species.  

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Population Control: Natural versus Human

Living within Limits ◽

10.1093/oso/9780195078114.003.0031 ◽

1993 ◽

Author(s):

Garrett Hardin

Keyword(s):

Exponential Growth ◽

Homo Sapiens ◽

Population Control ◽

Single Species ◽

The Self ◽

Human Beings ◽

The Gift ◽

Functional Equivalent ◽

Level Of Living ◽

Over Time

Were we able to talk with other animals, it is extremely unlikely that we should hear them debating the problem of population control. They don't need to debate: nature solves the problem for them. And what is the problem? Simply this: to keep a successful species from being too successful. To keep it from eating itself out of house and home. And the solution? Simply predation and disease, which play the role that human beings might label "providence." As far as the written record reveals, no one recognized the self-elimination of a species as a potential problem for animals until the danger had become suspected among human beings. One of the earliest descriptions of this population problem for other animals was given by the Reverend Joseph Townsend, an English geologist. His key contribution was published in 1786, twelve years before Malthus's celebrated essay (Box 25-1). Townsend was dependent upon others for the outline of his story, and there is some question as to whether the details are historically correct. But the thrust of the story must be true: a single species (goats, in this case) exploiting a resource (plants) cannot, by itself, maintain a stable equilibrium at a comfortable level of living. The animals will either die after eating up all the food, or their numbers will fluctuate painfully. (Details differ, depending on the species and the environment.) Stability and prosperity require that the gift of exponential growth be opposed by some sort of countervailing force (predatory dogs, in Townsend's example). However deplorable predators may be for individuals who happen to be captured and eaten, for the prey population as a whole predators are (over time) a blessing. With millions of different species of animals there are many different particular explanations of how they manage to persist for thousands or millions of years. The species we are most interested in is, of course, Homo sapiens. A meditation on Townsend's account led to a challenging set of questions. "If all this great earth be no more than the Island of Juan Fernandes, and if we are the goats, how can we live "the good life" without a functional equivalent of the dogs? Must we create and sustain our own dogs? Can we do so, consciously? And if we can, what manner of beast will they be?"

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Chromosomal Q-Heterochromatin and Atherosclerosis

Journal of Molecular Biology Research ◽

10.5539/jmbr.v7n1p143 ◽

2017 ◽

Vol 7 (1) ◽

pp. 143

Author(s):

A. I. Ibraimov

Keyword(s):

Homo Sapiens ◽

Single Species ◽

Causative Factor ◽

Mean Value ◽

Biological Species ◽

Climatic Conditions ◽

Cold Climate ◽

High Mountain ◽

Mountain Areas ◽

Blood Temperature

We suppose that at study of the pathogenesis of atherosclerosis, it is possible that some evolutionary aspects of the problem are missed. This aspect is related to the peculiarity of human adaptation to climatic geographic conditions of Eurasia, which differ significantly from the climate of East Africa, where Homo sapiens was formed as a tropical biological species and so it has remained to this day. A hypothesis has been put forward that the pathogenesis of atherosclerosis is associated with some previously unknown features of the genome and the physical properties of the human body that arose in the process of its adaptation to a mild and cold climate. These adaptive genetic changes that have contributed to the development (settling) by Homo sapiens of non-tropical, including cold and high mountain areas of the Earth, resulted to the fact that a man became the single species vulnerable (predisposed) to atherosclerosis.Atherosclerosis is apparently a purely human disease that appeared after adaptation of man to climatic conditions of temperate and northern latitudes of the northern hemisphere. The type of vessels (arteries or veins) and the site of their lumen have no role in the development of atherosclerotic changes. The primary and main causative factor in the development of atherosclerosis is blood temperature. The degree of blood cooling in the lungs depends on geographical latitudes and altitude above sea-level of the site of permanent residence of man. The preclinical stage of atherosclerosis may develop into a pathological form predominantly in individuals in the genome of which the amount of chromosomal Q-heterochromatin material is higher than its mean value per individual in the population.

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Consequences of Multispecies Introductions on Island Ecosystems

Annual Review of Ecology Evolution and Systematics ◽

10.1146/annurev-ecolsys-110218-024942 ◽

2019 ◽

Vol 50 (1) ◽

pp. 169-190 ◽

Cited By ~ 4

Author(s):

James C. Russell ◽

Christopher N. Kaiser-Bunbury

Keyword(s):

Introduced Species ◽

Native Species ◽

Single Species ◽

Evolutionary Relationships ◽

Native Range ◽

Top Down ◽

Island Ecosystems ◽

Bottom Up ◽

Species Introductions ◽

Resource Limited

The rate of non-native species introductions continues to increase, with directionality from continents to islands. It is no longer single species but entire networks of coevolved and newly interacting continental species that are establishing on islands. The consequences of multispecies introductions on the population dynamics and interactions of native and introduced species will depend on the form of trophic limitation on island ecosystems. Freed from biotic constraints in their native range, species introduced to islands no longer experience top-down limitation, instead becoming limited by and disrupting bottom-up processes that dominate on resource-limited islands. This framing of the ecological and evolutionary relationships among introduced species with one another and their ecosystem has important consequences for conservation. Whereas on continents the focus of conservation is on restoring native apex species and top-down limitation, on islands the focus must instead be on removing introduced animal and plant species to restore bottom-up limitation.

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An electrophoretic comparison of Schistosoma japonicum (Trematoda) from different provinces in the People's Republic of China suggests the existence of cryptic species

Parasitology ◽

10.1017/s0031182099004837 ◽

1999 ◽

Vol 119 (4) ◽

pp. 375-383 ◽

Cited By ~ 18

Author(s):

N. B. CHILTON ◽

Q. BAO-ZHEN ◽

H. O. BØGH ◽

P. NANSEN

Keyword(s):

Genetic Variation ◽

Schistosoma Japonicum ◽

Species Complex ◽

Mainland China ◽

Single Species ◽

People’S Republic Of China ◽

People's Republic Of China ◽

Electrophoretic Study ◽

Republic Of China ◽

Animal Hosts

Schistosoma japonicum from the People's Republic of China is considered to represent a single species comprising either 1 or 4 ‘strains’. We conducted an allozyme electrophoretic study to examine the extent of genetic variation in S. japonicum from mainland China. The allelic profiles of S. japonicum from 7 provinces were established at 16 enzyme loci. S. japonicum from Sichuan had 3–5 (19–31%) fixed differences compared with those from Zhejiang, Anhui, Jiangxi, Hunan, Hubei and Yunnan, suggesting that S. japonicum in mainland China represents a species complex. In addition, genetic markers were also established for different laboratory-maintained populations of S. japonicum which has significant implications for studying the biology of these organisms in human and animal hosts, and for the control and surveillance of human schistosomiasis in China.

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Electrophoretic contributions to the systematics of the freshwater crayfish genus Engaeus Erichson (Decapoda : Parastacidae)

Invertebrate Systematics ◽

10.1071/it9900615 ◽

1990 ◽

Vol 4 (3) ◽

pp. 615 ◽

Cited By ~ 7

Author(s):

P Horwitz ◽

M Adams ◽

P Baverstock

Keyword(s):

Allelic Variation ◽

Threshold Level ◽

Sympatric Species ◽

Biological Species ◽

Genetic Differences ◽

Freshwater Crayfish ◽

Electrophoretic Data ◽

Allelic Differences ◽

Low Levels ◽

Group Relationships

As part of an examination into the systematics of the freshwater crayfish genus Engaeus, an electrophoretic evaluation of specimens from a large number of collecting sites has been undertaken. From a total of 76 sample sets, a minimum of 30 distinct biological species have been delineated. Strong evidence from sites of both sympatry and allopatry suggests some further delineations of species but these must await additional discriminatory information. Sympatric species were detected on 11 separate occasions. In each case, fixed allelic differences were found, indicating an absence of interbreeding between each sympatric pair. Allopatric species were delineated where genetic differences between populations exceeded a threshold level determined from observed genetic differences between sympatric Engaeus species and between other (mainly decapod) species in the literature. The results of this analysis have confirmed low levels of heterozygosity in Engaeus species. Frequent isoIation of small populations of Engaeus species, and consequent loss of allelic variation, is suggested as a possible cause of these low levels. Some species have shown variation of allelic frequencies over their geographical range and, in some cases, this variation could be interpreted as showing clinal properties. Finally, the electrophoretic data have been interpreted to produce some information regarding the phylogenetic affinities of delineated species. Several groups of species were found which shared closer intra-group relationships than they did to the other species of Engaeus.

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Fossil Hominids - an Empirical Premise of the Descriptive Definition of homo sapiens

Forum Philosophicum ◽

10.35765/forphil.2000.0501.7 ◽

1970 ◽

Vol 5 (1) ◽

pp. 141-176

Author(s):

Piotr Lenartowicz ◽

Jolanta Koszteyn

Keyword(s):

Homo Sapiens ◽

Single Species ◽

Stone Tools ◽

Biological Knowledge ◽

Fossil Hominids ◽

Fossil Remains ◽

Definition Of ◽

Modem Human ◽

Descriptive Definition

Since the discovery of the Neandertal bones 1856 (cfr Toussaint, 1996), the extremely old, fragmentary fossil remains of hundreds of man-like bodies have been discovered in Europe, Asia, and Africa (cfr Bonjean, 1996). Even the oldest ones - usually the most incomplete - look man-like and „un-apish", even to a layman, if compared with a modem apish and human correlate. Sometimes, in the vicinity of these remains, primitive stone tools or the evidence of their production have been found. At present, it seems absolutely certain — within the limits of our present physical and biological knowledge - that at least four million years ago, in Africa, some creatures resembling modern man were living, and that at least two and half million years ago, in Africa, stone tools were produced. In contrast with the firm, scientifically-arguable belief that all modem human tribes - however different they are - belong to a single species (cfr Littlefield et al., 1982; Marks, 1995), in paleoanthropology an equally firm scientific belief is maintained that the extinct man-like forms belong to several different, „presapient", „prehuman'', more ape-like species (cfr Wood, 1996).

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Identification of life cycle stages of the nematode Echinocephalus overstreeti by allozyme electrophoresis

Journal of Helminthology ◽

10.1017/s0022149x0001141x ◽

1988 ◽

Vol 62 (2) ◽

pp. 153-157 ◽

Cited By ~ 13

Author(s):

R. H. Andrews ◽

I. Beveridge ◽

M. Adams ◽

P. R. Baverstock

Keyword(s):

Life Cycle ◽

Electrophoretic Analysis ◽

Life Cycles ◽

Allozyme Electrophoresis ◽

Larval Form ◽

Complex Life Cycles ◽

Life Cycle Stages ◽

Allelic Differences ◽

Mollusc Species ◽

Shared Alleles

ABSTRACTData presented in this study highlight the potential of allozyme electrophoresis in providing unequivocal genetic evidence for the identification of life cycle stages, particularly where species have complex life cycles. Adults of the nematode Echinocephalus overstreeti parasitize the elasmobranch Heterodontus portusjacksoni. The putative larval form which is morphologically dissimilar is found in two species of marine molluscs, Chlamys bifrons and Pecten albus. Electrophoretic analysis indicated that the adult and larval forms shared alleles at all of the 34 enzyme loci established. Furthermore, there were no fixed allelic differences between larval forms from different mollusc species.

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