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PubMed1988

Mhc class II DNA polymorphisms within and between chromosomal species of the Spalax ehrenbergi superspecies in Israel.

Restriction fragment length polymorphisms (RFLPs) of two major histocompatibility class II genes (P alpha 1 and Q beta) were studied in 13 populations of four chromosomal species (2n = 52, 54, 58 and 60) of the mole rat, Spalax ehrenbergi superspecies in Israel. A substantial frequency of allelic fragments was found in both genes for all populations, including a desert isolate. In the P alpha 1 gene, one allelic fragment is a result of a deletion mutation which is diagnostic of the 2n = 52 chromosomal species. All other ten allelic variants are the result of point mutations. All mutations are located in a short region flanking the 3' end of the gene. Based on Mhc polymorphisms we confirm earlier evidence that gene flow does not occur between the older chromosomal species (2n = 52, 54, 58), and that reproductive isolation decreases, progressively from the oldest to the youngest species (2n = 60).

Animals↗

PubMed1992

[Descent of ova and embryos in cows superovulated with serum gonadotropin].

The descent and localization of eggs and embryos in individual segments of the reproductive tract of superovulated cows were studied in this work. For the induction of superovulation, serum gonadotropin (PMSG, Ivanovice in Haná) at a dose of 2,500-3,500 I.U. was used, in combination with 0.5 mg of Cloprostenol (Oestrophan, Spofa), administered 48 hours after gonadotropin treatment. The start of superovulation fell on days 9 to 12 of the sexual cycle and was conditioned by the presence of the corpus luteum (CL). After the onset of the heat, 2-3 inseminations were carried out using fresh semen. Donor cows were slaughtered 3, 4, 5, 6, and 7 days after the second insemination and isolated reproductive organs (Fig. 1) were divided into five segments (two on oviducts and three on uterine horns) by the applied ligature. In laboratory conditions superovulation response was determined accurately, the volume of ovaries was assessed according to water displacement and the segments of oviducts and uterus were rinsed with TCM 199 or PBS supplemented with FCS. 3, 4, 5, 6, and 7 days after insemination (Tab. I). 18.1 (+/- 3.55), 12.4 (+/- 0.91), 19.2 (+/- 2.86), 20 and 23 (+/- 2.44) CL on average were recorded, which corresponded to the ovulation of 64, 50, 56, 71 and 72 percent of stimulated follicles (Fig. 2). Within 3 to 7 days after insemination nearly triple enlargement of ovaries was also observed (Tab. I, Fig. 3). During the lavage of individual segments of the tubular reproductive tract, 38 per cent of eggs and embryos were detected in the uterus as early as 3 days after insemination (Tab. II). Unfertilized eggs and degenerated embryos were found in the 2nd and 3rd uterine segment, embryos at the stage of 8-16 blastomeres were localized in the 1st and 2nd segment of the uterus. Four days after insemination (Tab. III), about 64 per cent of eggs and embryos at the stage up to 16 blastomeres were found in the uterus, but embryos up to 32 blastomeres were still flushed out of the oviduct. On day 5 after insemination, 92 per cent of eggs and embryos were released into the uterus, being localized mostly in the cranial and medial part of the uterus (Tab. IV). 7.5 per cent of recovered eggs and embryos at the stage of early or compacted morulae were still detected in the oviducts.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1975

Allozymic and chromosomal similarity in two Drosophila species.

D. setosimentum and ochrobasis are a pair of very close, partly sympatric species endemic to Hawaii island. Males of the two species differ strikingly in wing-pattern and there are altitudinal and breeding-site differences. Similarity indices have been calculated for both chromosomal (C) ald allozymic (A) variants. Within the main populations of each species both kinds of data give coefficients above 0.98. Interspecific comparison of the main populations shows 0.66 (C) and 0.79 (A). An isolated population of ochrobasis from Kohala Volcano (Ohu), when compared with setosimentum, shows 0.68 (C) and 0.98 (A). Chromosomes are thus much more sensitive than allozymes in distinguishing these species; the same is true in the case of D. silvestris and heteroneura from the same forests. These morphologically distinct species, when compared, show 0.96 (A). All four species appear to be very new in the historical sense. In one area, about 2% of wild-caught D. setosimentum/ochrobasis are interspecific hybrids although adequate samples indicate that the separate gene pools have not broken down. The specific names should be retained but the two entities are perhaps best described as quite advanced semispecies in which reproductive isolation in nature is now nearly complete.

Animals↗

PubMed2014

Inter-genomic sexual conflict drives antagonistic coevolution in harvester ants.

The reproductive interests of males and females are not always aligned, leading to sexual conflict over parental investment, rate of reproduction and mate choice. Traits that increase the genetic interests of one sex often occur at the expense of the other, selecting for counter-adaptations leading to antagonistic coevolution. Reproductive conflict is not limited to intraspecific interactions; interspecific hybridization can produce pronounced sexual conflict between males and females of different species, but it is unclear whether such conflict can drive sexually antagonistic coevolution between reproductively isolated genomes. We tested for hybridization-driven sexually antagonistic adaptations in queens and males of the socially hybridogenetic 'J' lineages of Pogonomyrmex harvester ants, whose mating system promotes hybridization in queens but selects against it in males. We conducted no-choice mating assays to compare patterns of mating behaviour and sperm transfer between inter- and intra-lineage pairings. There was no evidence for mate discrimination on the basis of pair type, and the total quantity of sperm transferred did not differ between intra- and inter-lineage pairs; however, further dissection of the sperm transfer process into distinct mechanistic components revealed significant, and opposing, cryptic manipulation of copulatory investment by both sexes. Males of both lineages increased their rate of sperm transfer to high-fitness intra-lineage mates, with a stronger response in the rarer lineage for whom mating mistakes are the most likely. By contrast, the total duration of copulation for intra-lineage mating pairs was significantly shorter than for inter-lineage crosses, suggesting that queens respond to prevent excessive sperm loading by prematurely terminating copulation. These findings demonstrate that sexual conflict can lead to antagonistic coevolution in both intra-genomic and inter-genomic contexts. Indeed, the resolution of sexual conflict may be a key determinant of the long-term evolutionary potential of host-dependent reproductive strategies, counteracting the inherent instabilities arising from such systems.

Animals↗

PubMed1990

The genic nature of gamete eliminator in rice.

The two cultivated rice species, Oryza sativa and Oryza glaberrima, are morphologically alike but are reproductively isolated from each other by hybrid sterility. The hybrid is male sterile but partially female fertile. Backcross experiments were conducted to introduce an alien factor controlling hybrid sterility from O. glaberrima (W025) into O. sativa (T65wx) and examine the genetic basis. An extracted sterility factor, closely linked to the wx locus, induced gametic abortion due to allelic interaction and was tentatively designated as S(t). The segregation patterns for infertility was explained by assuming that W025 and T65wx carried S(t) and S(t)a, respectively, and gametes with S(t)a aborted only in the heterozygote (S(t)/S(t)a) although the elimination of female gametes was incomplete. Thus, S(t) seemed to be intermediate between a gamete eliminator and pollen killer. However, S(t) was proven to be likely the same as S1 which was formerly reported as gamete eliminator in a different genetic background of O. sativa. In addition, a chromosomal segment containing S1 (or S(t] caused a marked suppression of crossing over around it, suggesting the presence of an inversion. Further, female transmission of S1a increased as the segment containing S1 became small by recombination. After S1 was further purified by successive backcrosses up to the BC15 generation, it became pollen killer. The present results give evidence that a profound sterility gene such as gamete eliminator can be made from accumulation of pollen killer and its modifier(s) when pollen killer and modifier(s) are linked, they behave as a gene complex in the hybrid.

Alleles↗

PubMed1985

Mammalian fertilization as seen with the scanning electron microscope.

For several years we have been looking at mammalian gametes and their interactions with the scanning electron microscope (SEM). Examining the images produced by the SEM has given us a three-dimensional view of sperm, eggs, and egg investments. We are particularly impressed with the structural variation among gametes of different mammalian species. In this short report we examine the structure of mammalian spermatozoa, eggs, zonae pellucidae, and cumuli. Our observations and those of others have led us to believe that variation in gamete structure and function may have evolved as a mechanism for reproductive isolation of mammalian species.

Animals↗

PubMed1986

Genetic variation within and among lion tamarins.

The golden lion tamarin Leontopithecus rosalia rosalia, one of the rarest and most endangered of New World primates, has been the focus of an intensive research and conservation effort for two decades. During that period, managed breeding from 44 founders has brought the captive population to over 400 individuals, a number that equals or exceeds the estimated number of free-ranging golden lion tamarins. The extent of genetic variation among golden lion tamarins was estimated with an electrophoretic survey of 47 allozyme loci from 67 captive and 73 free-ranging individuals. The amount of variation was low, compared to 15 other primate species, with 4% of the loci being polymorphic (P), and with an average heterozygosity H estimate of 0.01 in these callitrichids. Electrophoretic analyses of captive and free-ranging animals (N = 31) of two allopatric morphotypes, Leontopithecus rosalia chrysopygus and L. r. chrysomelas, were similar to the L. r. rosalia findings insofar as they also revealed limited genetic polymorphism. Computation of the Nei-genetic distance measurements showed that the three morphotypes were genetically very similar, although discernible differentiation had occurred at two loci. These data are consistent with the occurrence of recent reproductive isolations of these subspecies.

Animals↗

PubMed1991

Characteristics of hamadryas-like male baboons living in anubis baboon troops in the Awash hybrid zone, Ethiopia.

In the twenty-two years since the Awash baboon hybrid zone was first described, about 25-30 hamadryas or hamadryas-like hybrid males have taken up residence in anubis baboon groups. Most enter as mature adults, though some may immigrate as juvenile followers. Long-term tracking of known immigrants indicates that they may reside for four years or more in their adopted troop, during which time they establish a series of comparatively short-term harems, and probably sire hybrid offspring. "Abductions" of anubis females to hamadryas troops, as postulated by early observers, were not seen, though their occurrence cannot be ruled out. Younger, more recent immigrants tend to be "purer" hamadryas in phenotype, perhaps reflecting a more distant origin, or a change in the composition of neighboring hamadryas populations. Coexisting hamadryas and anubis show no signs of reproductive isolation by behavioral barriers, and evidently belong to a single "recognition species."

Age Factors↗

PubMed1989

Cross-fertilization between Syrian and Chinese hamsters.

The role of the zona pellucida in the specificity of fertilization was studied by cross-inseminations between Syrian (Golden) and Chinese hamster gametes. Cumulus-enclosed eggs from both Syrian and Chinese hamsters were placed together in one dish and inseminated with spermatozoa from either one or the other species. Fertilization always took place between gametes of homologous species. Chinese hamster spermatozoa failed to bind to the zona pellucida of Syrian hamster eggs; hence, fertilization was never observed. However, Chinese hamster spermatozoa could fertilize zona-free Syrian hamster eggs. In the reciprocal cross, a large number of Syrian hamster spermatozoa could bind to and penetrate the zonae of Chinese hamster eggs. However, fusion of Syrian hamster spermatozoa with the vitellus of zona-intact Chinese hamster eggs was never observed. After removal of the zona pellucida, only a small percentage (31%) of Syrian hamster spermatozoa could fuse with Chinese hamster vitelli. Thus, in these species, the mechanisms of interspecific gamete recognition and the prevention of interspecies fertilization seem to differ according to the direction of the cross. In Syrian hamster eggs, the block to interspecies fertilization seems to exist at the level of the zona pellucida, while in Chinese hamster eggs the block is at the level of the egg plasma membrane. The implications of these results in analyses of the genetics of spermatozoa, the molecular basis of sperm-egg recognition, and mechanisms of reproductive isolation leading to speciation, are discussed.

Animals↗

PubMed1987

Isozymes as bioprobes for genetic analysis of nonhuman primates.

The identification and the utilization of genetically determined electrophoretic differences of enzymes between the individuals of species as well as between cell lines have played an important role in the advancement of mammalian genetics during the past quarter of a century. In an explicit search we found a number of red cell enzyme polymorphisms in each of the following four species: chimpanzees, orang utans, rhesus monkeys and brown capuchins. Allelic distribution patterns among populations have indicated trends of subspeciation among chimpanzees and orang utans due to geographic barriers leading to reproductive isolation. Investigations of quantitative levels of red cell glucose-6-phosphate dehydrogenase have suggested that relative activity profiles of certain enzymes among species may be helpful in studies of the evolution of physiological traits and their biological significance during speciation. A large number of biochemical genetic markers in primate-rodent (i.e., chimpanzee-, gorilla-, orang utan-, rhesus monkey- and African green monkey-Chinese hamster) somatic cell hybrids have been identified and are useful for primate genetic analysis. Some of the biologically relevant observations on the enzyme markers in the above mentioned primate species are discussed.

Animals↗

PubMed1976

Robertsonian metacentrics in the mouse.

A survey is given on the occurrence, the geographic origin and the arm composition of 27 Robertsonian fusion metacentric chromosomes of wild populations of the mouse. Their study is of twofold interest: a) it is possible to introduce these naturally occuring metacentrics in laboratory strains for experimental use. At present, altogether 34 metacentric chromosomes of different composition are available including 7 cases of metacentrics known form laboratory strains of the mouse. b) With the search for metacentrics in the mouse and with their identification insights are permitted in the role of Robertsonian changes in the course of mammalian evolution--Several separate populations of the mouse with different sets of multiple (up to 9) metacentrics have been found in Switzerland and Italy. Some of the individual metacentrics may occur in different populations. The participation of an acrocentric autosome in the formation of metacentrics seem to be at random, but the sex chromosomes are never included in a metacentric.--Homology of the arms involved in metacentrics is conserved, so that in meiosis of interpopulation hybrids is due to mechanisms of segregational imbalance and subsequent prenatal elimination of fetal offspring, but it follows also the pattern of male limited hybrid sterility.--From an evolutionary view point, karyotype rearrangements of Robertsonian type may initiate reproductive isolation, which prepares the ground for further genetic diversification and, as in the case of the mouse, of incipient speciation.

Animals↗

PubMed1978

Evidence for the presence of two sympatric species of mice (genus Mus L.) in southern France based on biochemical genetics.

Populations of mice established outdoors as well as indoors have been investigated at 24 loci using starch gel electrophoresis. Two reproductively isolated groups are recognized, one of which is referable to a house mouse subspecies, Mus musculus brevirostris, and the other to a different species. Mus spretus, contrary to the view of Schwarz and Schwarz that only one species of Mus is present in the Mediterranean Basin. The genetic distance between these two groups is larger than between any pair of investigated subspecies of M. musculus. M. m. brevirostris is biochemically almost indistinguishable from M. m. domesticus. On the other hand, M. spretus exhibits several allelic variants unknown or at most very infrequent in M. musculus, as for instance at the lactate dehydrogenase B-chain locus.

Animals↗

PubMed1990

Genetic polymorphism of urine deoxyribonuclease I isomerases of subterranean mole rats, Spalax ehrenbergi superspecies, in Israel: ecogeographical patterns and correlates.

Genetic polymorphism of urine deoxyribonuclease I (DNase I) of mole rats was analyzed by isoelectric focusing in a thin-layer polyacrylamide gel (IEF-PAGE). One hundred and three subterranean mole rats, comprising 13 populations belonging to the four chromosomal species (2n = 52, 54, 58, 60) of the actively speciating Spalax ehrenbergi superspecies in Israel, were tested. The following results were indicated. (i) Spalax DNase I consisted of 6-12 major isozymes. (ii) Four phenotypes (numbers in parentheses) were 1 (92), 1-2 (5), 1-3 (4), and 2 (1). The decreasing order of genetic diversity, He, in the four species was 0.37, 0.13, 0.10, and 0.0 for 2n = 58, 52, 54, and 60, respectively. (iii) Spearman rank correlations and multiple regression analyses indicated associations of allele frequencies and genetic diversity with climatic and vegetation factors. We concluded that (a) climatic selection, either directly or indirectly through plant (i.e., food resources) diversity, plays an important role in DNase genetic differentiation and (b) no gene flow and introgression occur between the recent derivative of speciation (2n = 60) and its ancestor (2n = 58), suggesting the operation of reproductive isolation between both species despite natural hybridization.

Animals↗

PubMed1989

Applying the species concept to plant viruses.

Plant virologists who maintain that the concept of species cannot be applied to viruses argue their case in terms of an obsolete concept of biological species defined by gene pools and reproductive isolation and applicable only to sexually reproducing organisms. In fact, various species concepts have been used by biologists and some of them are applicable to asexual organisms. The rationale for applying the species concept in virology is that viruses are biological entities and not chemicals: they possess genes, replicate, specialize, evolve and occupy specific ecological niches. The following definition is proposed: a virus species is a polythetic class of viruses constituting a replicating lineage and occupying a particular ecological niche. Such a definition of the species category does not and cannot provide a list of diagnostic properties for recognizing members of a particular virus species. It should also be stressed that a single property such as an arbitrary level of genome homology or the extent of serological relationship always fails to establish membership in a polythetic class. A binomial system of nomenclature is advocated in which the vernacular English name of the plant virus is adopted as the species name and the group name is assimilated to the level of genus. Adoption of this system would ensure that a universal classification system based on the classical categories of species, genus, and family becomes possible for all viruses.

Phylogeny↗

PubMed1978

[Hybridization between Mus musculus L. and Mus spretus Lataste under laboratory conditions (author's transl)].

2 species of mice Mus musculus brevirostris and Mus spretus are sympatric in Southern France and reproductively isolated. However, under laboratory conditions, they breed and give fully viable F 1 hybrids. This indicates that premating isolating mechanisms probably occur in nature and have yet to be investigated. Moreover, it now enables us to introduce new genetical markers in laboratory strains.

Animals↗

PubMed1976

Assortative mating between chromosome forms of the mole rat, Spalax ehrenbergi.

Females of two parapatric chromosomal forms (2n = 52 and 2n =58) of the fossorial mole rat, Spalax ehrenbergi, in Israel, were tested for mate selection between two alternative, a homo- and a heterochromosomal, males. Estrous females significantly preferred the male of their own chromosomal form, on the basis of several behavioural criteria. The evolutionary significance of the positive assortative mating found, lies presumably in reinforcing reproductive isolation between the chromosome forms, thereby contributing to finalize speciation.

Animals↗

PubMed1991

Sequences homologous to Tc(s) transposable elements of Caenorhabditis elegans are widely distributed in the phylum nematoda.

To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements from Caenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found in Caenorhabditis and in Teratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and in Bursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited to C. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.

Animals↗

PubMed1989

Mitochondrial DNA evolution in the Drosophila nasuta subgroup of species.

The Drosophila nasuta group consists of about 12 closely related species distributed throughout the Indo-Pacific region. They are of great interest because of their evolutionary idiosyncrasies including little morphological differentiation, the ability to intercross in the laboratory often producing fertile offspring, and substantial chromosomal evolution. Studies of metric traits, reproductive isolation, and chromosomal and enzyme polymorphisms have failed to resolve the phylogeny of the species. We report the results of a survey of the mitochondrial DNA (mtDNA) restriction patterns of the species. The phylogeny obtained is consistent with other available information and suggests that D. albomicans may represent the ancestral lineage of the group. The amount of polymorphism in local populations (pi = 1.0% per site) is within the typical range observed in other animals, including Drosophila. The degree of differentiation between species is, however, low: the origin of the group is tentatively dated about 6-8 million years ago. This study confirms the usefulness of mtDNA restriction patterns for ascertaining the phylogeny of closely related species.

Animals↗