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PubMed2025

Extensive Introgression Failed to Erode Species Boundaries Among Multiple Sympatric Closely Related Species of Roscoea.

How species boundaries are maintained among sympatric closely related species experiencing gene flow is a puzzling question in evolutionary biology. Although introgression is commonly documented, the dynamics and gene function of introgression have rarely been explored to probe why frequent introgression does not necessarily destroy species boundaries in sympatry. In this study, we employ whole-genome resequencing data to examine introgression among five closely related species of Roscoea that coexist in a 'sky island' with seventeen distinct morphological traits. Our findings reveal that introgression has led to the phylogenomic discordance between nuclear and chloroplast genomes among these morphologically distinct species. Additionally, introgression is predominantly asymmetrical in both intensity and gene function, particularly concerning recombination. Notably, the majority of gene functions associated with introgressed loci are unrelated to reproductive processes. Our results suggest that closely related species with incomplete allele assortment can coexist despite theoretical predictions, highlighting the semipermeable nature of species boundaries as reproductive isolation develops. This provides a critical conceptual framework for understanding the interplay between introgression and species persistence. Our finding offers insights into how related sympatric species boundaries can be maintained in the face of frequent asymmetrical gene introgression.

Sympatry↗

PubMed1977

Genic similarity of American and European species of the lobster Homarus.

European lobsters (Homarus gammarus) from the Norway coast and from the Irish Sea are examined for electrophoretically detectable genetic variation in seventeen functionally different proteins. Forty-one loci encoding these proteins are homologous with loci studied in a previous survey of eight populations of H. americanus. Progeny hatched from ovigerous Norway females show variation in three enzymes, but Mendelian inheritance is confirmed only for triosephosphate isomerase and for one of the phosphoglucose isomerases. Complex PGI phenotypes are described. The average amounts of genetic variability in European and American lobster populations appear to be equivalent. More than one allele is detected at 20% of the loci, the average number of alleles detected per locus is 1.2 and the average proportion of loci heterozygous per individual is 4.0%. While much less genically variable than other invertebrates, Homarus is not atypical when compared with eleven decapod species that average 5.8% heterozygosity. This is consistent with hypotheses relating genetic variability to adaptive strategy. At thirty loci H. gammarus is monomorphic for the common H. americanus allele. Two acid phosphatase systems are fixed or nearly fixed for alternative alleles in the two species while the remaining polymorphic loci show various degrees of interspecific divergence. Unique H. gammarus alleles are detected at five loci but only contribute significantly to species differences at the Acph-5, Me, and Pgi-4 loci. Acph-1, Est-2, Pgi-3, and Pgm-1 are polymorphic for the same alleles in both species, but again, with various differences in allelic frequencies. In sum, average genetic identity and average genetic distance are: I = 0.896 +/- 0.007 and D = 0.110 +/- 0.007, respectively. Compared to the values for conspecific population comparisons, I = 0.994 +/- 0.001 and D - 0.006 +/- 0.001, it is clear that a small but significant amount of genetic divergence separates the European and American lobster. Based on the premise that protein differences between existing species reflect the amount of time since they shared a common ancestor, it can be speculated that the European and American lobsters were isolated during the Pleistocene. The apparent weakness of reproductive isolating barriers suggests that these populations have evolved allopatrically. Finally, quantification of species' genetic differences, together with recent successes in interspecific laboratory matings, implicates species hybridization as a potentially important breeding practice in lobster aquaculture.

Animals↗

PubMed1990

Correspondence between sexual isolation and allozyme differentiation: a test in the salamander Desmognathus ochrophaeus.

Ethological reproductive isolation and genetic divergence across 26 protein loci were measured among populations of the salamander Desmognathus ochrophaeus in the southern Appalachian Mountains. Levels of ethological isolation varied from none to complete and were statistically significant for all but two pairings between populations inhabiting different mountain ranges. When geographic and genetic distances were treated as independent variables in multiple correlation analyses, they accounted for about half the variance in levels of ethological isolation. When genetic distance is held constant, the remaining relationship between ethological isolation and geographic distance is still statistically significant. When geographic distance is held constant, the remaining relationship between genetic distance and levels of ethological isolation is nonsignificant, as is the relationship between geographic distance and genetic distance when ethological isolation is held constant. Ethological isolation and genetic divergence evidently both reflect the gradual divergence of allopatric populations, but genetic distance is a poor predictor of ethological isolation in these salamanders.

Animals↗

PubMed1992

Genetics of sexual isolation in females of the Drosophila simulans species complex.

Genetic analysis of hybrids between Drosophila simulans and D. sechellia shows that sexual isolation in females is caused by at least two genes, one on each major autosome, while the X chromosome has no effect. These results are similar to those of a previous study of hybrids between D. simulans and another sibling species, D. mauritiana. In this latter hybridization, each arm of the second chromosome carries genes causing sexual isolation in females, implying a total divergence of at least three loci. The genetic similarity between the D. simulans/D. mauritiana and D. simulans/D. sechellia hybridizations probably results from independent evolution and not phylogenetic artifacts, because the dominance relationships and behavioural interactions differ between the two hybridizations. The lack of an X-chromosome effect on sexual isolation contrasts with genetic studies of post-zygotic reproductive isolation, which invariably show strong effects of this chromosome.

Animals↗

PubMed1977

Further studies on gene polymorphism in the mainbody and geographically isolated populations of Drosophila pseudoobscura.

We have examined polymorphism at 22 additional loci in the populations from the mainbody of Drosophila pseudoobscura and an isolated population from Bogotá, Columbia, which also shows partial reproductive isolation from mainbody populations. These studies extend our previous observations of reduced gene polymorphism and apparent lack of unique allele in the Bogotá population.

Alleles↗

PubMed1986

Males, parthenogenesis, and the maintenance of anisogamous sex.

The problem of the maintenance of anisogamous sex is addressed by considering the effect of fertilization on the fitness of parthenogenetic females when such fertilization yields inviable triploid progeny. We consider four types of parthenogenesis: (i) apomixis, (ii) homogametic amphimixis, (iii) heterogametic amphimixis, and (iv) homogametic automixis. Homozygous sexual populations are genetically stable if males or selection eliminate the excess females produced by heterozygous parthenogenetic genotypes. Homozygous parthenogenetic populations are stable if the parthenogenetic output of homozygotes exceeds that of heterozygotes. In turn, sex can only invade heterozygous parthenogenetic populations when sexual output of parthenogens is larger than their parthenogenetic output. The existence of interior stable equilibria generally requires the instability of at least one boundary and some degree of heterosis. In a two-locus model, we study the evolution of mechanisms protecting either sex or parthenogenesis in reproductively polymorphic populations. We find that males do not respond to the presence of parthenogenesis in such a way as to eliminate it, but parthenogenesis is subject to selective pressures increasing reproductive isolation, and thus the success of parthenogenesis. The results suggest that reproductively polymorphic populations are ephemeral.

Animals↗

PubMed1987

[The role of the cholinergic system in the regulation of blood flow through the reproductive organs of swine during the estrous cycle].

The flow in uterine artery (ua) and ovarian artery (oa) of isolated reproductive organs of sows (100-130 kg/head) perfounded with animal own blood and Krebs-Henseleit fluid at the constant pressure of 100 mm Hg was measured. Together with measuring the flow, the tension of the smooth muscle of organ was controlled. Applying acetylocholine (ACh), atropine (A), hexamethonium (H) and phentolamine (F) the analysis of the functions of muscarine (M) and nicotine (N) receptors of the cholinergic system in regulation of blood flow through the reproductive organs during the oestrous cycle was carried out. It was found that application of 0.3 microgram ACh into ua, and 0.5 microgram ACh into oa causes slight increase in the blood flow. Application of ACh in doses of 1 microgram into these vessels causes decrease of the flow and increase in tension and motorics of the organ. A eliminates the influence of ACh upon the tension and motorics of the studied organ and potencializes the decreasing influence of ACh applied in the dose of 1 microgram upon the blood flow. A decreases the flow limiting action of 1 microgram ACh upon the flow, and also eliminates the effect of decrease of flow caused by application of 1 microgram ACh after A. H potencializes the influence of small doses of ACh increasing the flow in ua and oa, but does not influence the flow limiting and tension increasing action of 1 microgram dose of ACh. Both A and H in doses applied cause increase in blood flow in the vessel areas under study. The results of the research indicate that changes in the blood flow through the areas under investigation induced by application of ACh are the resultant of three factors. 1. The vasodilatative effect resulting from the stimulation of the receptor M. 2. Stimulation of the cholinergic receptor N and connected with it freeing catecholamines responsible for the tension of vessels and contraction of smooth muscles of the organ. 3. Pressing influence upon the vessels of contracting smooth muscles connected with stimulation of M and N receptors. The sensitivity of vessels in the oa area to M-cholinergic stimulation is lower than that in the ua artery and it is higher in the luteal phase than in pre- and post-ovulation phases in both vessel areas. The magnitude of nicotine reaction of endogenous catecholamines freeing does not undergo significant changes during the oestrous cycle.

Animals↗

PubMed1991

Nucleotide sequence analysis of Adh genes estimates the time of geographic isolation of the Bogota population of Drosophila pseudoobscura.

The population of Drosophila pseudoobscura at Bogota, Columbia, is geographically and partially reproductively isolated from populations in the main body of the species in North America. The degree of genetic differentiation and time of divergence between populations at Bogota and Apple Hill, CA, were estimated by comparison of 3388 nucleotides in the alcohol dehydrogenase region (Adh and Adh-Dup genes) of 18 strains. Of the 146 polymorphic nucleotide sites detected, 68 and 31 were unique to the Apple Hill and Bogota samples, respectively, and 53 were shared. On the basis of an observed net divergence per nucleotide site of 0.264% between the two samples, the Bogota and North American populations were estimated to have been separated for at least 155,000 years. This divergence time suggests that D. pseudoobscura extended its range from North America to South America in a period of Pleistocene glaciation, when habitat suitable for the species presumably existed in lowland Central America.

Alcohol Dehydrogenase↗

PubMed1992

A dual level model for speciation by multiple pericentric inversions.

A considerable body of evidence suggests that the deleterious meiotic effects of pericentric inversions in F1 hybrids can be overcome by changes in chiasma location and various means of non-homologous pairing. Such overriding mechanisms may render pericentric inversions benign and increase the likelihood of their fixation in population isolates. It has been argued that overriding mechanisms of this type negate the involvement of pericentric inversions as reproductive isolating mechanisms in speciation. It is suggested, however, that the involvement of pericentric inversions in speciation should be considered on two levels. First, that by reducing meiotic effects in F1 hybrids, overriding mechanisms facilitate the fixation of pericentric inversions. Secondly, when contact hybridization occurs between the chromosomally derived and parental populations second-level effects may be encountered. That is, the recombinational effects of pericentric inversion differences on coadapted gene complexes (sensu Brncic, 1954, Shaw & Coates, 1983) enforce profound inviability barriers in F2 and backcross matings. In this way, multiple pericentric inversions may act as significant post-mating isolating mechanisms, whereas individual inversions with less significant second-level effects may not.

Animals↗

PubMed1988

[Analysis of the effects of oxytocin, vasopressin, angiotensin, serotonin and histamine on the blood flow in the reproductive organs of swine the during estrous cycle].

We have measured the magnitude of flow in the uterine artery (ua) and in ovarian artery (oa) in the isolated reproductive organs of pig (100-130 kg/per head) perfused with their own blood or Krebs-Henseleit's solution. The pressure was kept on the constant level 100 mm Hg. Were administered intraarterially Oxytocin (O), vasopressin (W), histamine (H), serotonin (5-HT) and hypertensin (A). Their possible influence on the processes of regulation of blood flow in the porcine reproductive organs during oestrus cycle was analysed. It was stated that O produced a decrease of blood flow (bf) in the periovulatory period (1-2 and 16-18 day of cycle). On the other hand doses many times bigger did not cause significant changes in ua in the luteal phase and in oa in all phases of the cycle. Action of O is connected with its pressing action on the uterine vessels, contracted by the smooth muscular coat of this organ. Limiting bf action of W and A is mainly connected with their direct vasoconstructive effect. Our results indicated that in physiological conditions during oestrous cycle O, W and A did not evoke significant changes in the regulation of blood flow in the porcine reproductive organs. High sensitivity of the investigated vessels on 5-HT in the luteal phase and lower sensitivity in the periovulatory phase could indicate serotonin's influence on the regulating changes of blood flow during oestrous cycle. Vessels of both investigated areas were very sensitive to H. Especially high sensitivity of oa vessels on H is correlated with an increase of sensitivity of the vessels on 5-HT and catecholamines in the luteal phase. It seem that H has significant importance as a factor antagonising influence of 5-HT and catecholamines in the luteal phase of cycle in the pig. Sensitivity of oa vessels on the investigated drugs was lower in all phases of the cycle studied than sensitivity of ua vessels, the only exception was when H was used. We observed similar reaction on used drugs, both in experiments with perfusion with the blood and with the Krebs-Henseleit's solution. It may suggest that vessels reaction depends upon the functional state of the organ and it is not directly connected with the hormones present in the blood.

Angiotensin II↗

PubMed1991

Identification of a serum protein polymorphism via two-dimensional electrophoresis. Family and population studies in two genetically isolated groups: North American Hutterites and Australian aborigines.

We report the identification and initial family and population studies of a previously undescribed serum protein polymorphism with two allelic forms. It was discovered in Hutterites, a reproductively isolated religious sect, and is also present in Australian aborigines and a sample of Chicago residents. A two-allele model is consistent with the segregation pattern observed in five kindreds within our initial study group. This polymorphism, provisionally designated SPPM-158, appears as a horizontal (charge-based) doublet in silver-stained ISO-DALT high-resolution two-dimensional electrophoresis gels. It is a low-concentration polypeptide (approximately 1 mg/dL) that has an apparent MWSDS of 43.6 kD and an isoelectric point of approximately 5.5. We infer that it circulates as a multimer or in a high-molecular-weight (greater than 200 kD) complex with other proteins because it is not observed in normal body fluids derived from physiologically ultrafiltered plasma such as amniotic fluid, urine, or cerebrospinal fluid; however, it is present in urine of patients with glomerular proteinuria. The high heterozygosity rates imply utility of this new serum protein marker for both forensic and population studies.

Australia↗

PubMed1986

Inverted Y chromosome polymorphism in the Gujerati Muslim Indian population of South Africa.

An inverted Y chromosome has been found at a very high frequency in a Muslim Indian community living in the Johannesburg-Witwatersrand area of the Transvaal Province of South Africa: 8 of 141 (5.7%) retrospectively identified Indian males had an inv(Y)(p11.2q11.23) and all were of the Muslim faith. The inversion was found in 22 of 72 (30.5%) prospectively studied normal Muslim Indian males. All the carriers of the inversion were Gujarati-speakers whose families migrated to the Transvaal from the Gujerat Province of India during the first half of this century. The origins of the ancestors of the individuals with inv(Y) were traced to a small village, Kholvad, near the city of Surat, and some neighbouring villages. The polymorphic frequency of the inv(Y) has probably been produced through random genetic drift in a reproductively isolated community, maintained by strict endogamous marriage customs based on religious and linguistic affiliations. There was no indication that the inverted Y was associated with any reproductive disadvantages.

Black People↗

PubMed1977

The Cajuns of Southern Alabama: morphology and serology.

A survey was conducted of 324 members of the Cajun isolate of Southern Alabama. Tradition and appearance suggest that this population of about 3,000 are not entirely White, Black, or Indian but constitute a triracial community somewhat reproductively isolated and inbred. The earliest American settlement in the area, along the banks of the Mobile and Tombigbee Rivers, lay between Spaniards to the South and Indian tribes on the other sides: Creek, Choctaw, and Cherokee. Physical measurements are reported for 71 adults, plus color of skin, eyes, and hair. X-rays were taken of wrist and ankle bones of some 253 children. Red blood samples were typed on adults and children, and haptoglobin, Gm, and Gc types were determined from serum. History and physical examinations were also made. Physical measurements and observations suggest predominantly White ancestry, and D2 analysis confirms this, with least similarity to Indians. Analysis of serological traits implies almost 70% White, almost 30% Black, and very little Indians genes. Few defects of clear genetic etiology were discovered. Growth patterns judged from X-rays appeared normal. All genetic loci testable were in Hardy-Weinberg equilibrium except Gc. While history and some common surnames suggest endogamy in the past, the medical and serological findings, plus some additional surnames, indicate that the isolate has already been largely diluted or dissolved.

Adolescent↗

PubMed1989

Purification and properties of cyclic-3',5'-GMP-dependent protein kinase from the nematode Ascaris suum.

A cyclic-3',5'-GMP-dependent protein kinase was purified 7400-fold from the reproductive tract of female ascarids to a specific activity of 718 nmol min-1 mg-1 (histone as substrate). The yield of the preparation was 25%. The enzyme protein obtained was homogeneous as judged by isoelectrofocusing and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The native enzyme behaved as a dimer of two 82-kDa subunits in gel permeation chromatography on Superose 12. The protein kinase was inactive in the absence of cyclic purine nucleotides. Half-maximum velocity was obtained in the presence of 18 nM cGMP, whereas 400-fold higher concentrations of cAMP were required for the same activity. The enzyme underwent autophosphorylation in first-order kinetics (rate constant 0.054 min-1), leading to maximum incorporation of 0.96 phosphate per subunit. The autophosphorylation led to a 4-fold increase in Vmax, while the Km remained almost unchanged. In an extract from the reproductive tract, cGMP-stimulated phosphorylation was primarily observed in five proteins (molecular masses of 66, 60, 43, 30, and 25 kDa). These proteins also incorporated phosphate when isolated reproductive tracts were incubated in the presence of [32P]phosphate. The phosphate content in cellular proteins was enhanced when the incubation was performed in the presence of 10(-4) M of either octyl-cAMP or octyl-cGMP. In addition to the proteins mentioned above, however, six more electrophoretic bands containing radioactive phosphate were identified after in situ labeling of reproductive tracts with radioactive phosphate.

Animals↗

PubMedDate not supplied

Counter current transfer and back transport of 3H-PGF2 alpha in the cow's broad ligament vasculature ipsilateral and contralateral to the corpus luteum.

Eight cows of similar age (5-7 years) were chosen for the experiment. Isolated reproductive tract was supplied with autologous oxygenated and heated (40 degrees C) blood through the uterine artery and ovarian artery. 3H-PGF2 alpha in total dose of 2 MBq (10(7) cpm) was injected into each of the uterine lumen of isolated organ. Blood samples were collected at 5 min intervals during 120 min of experiment using cannulae inserted into the branches of uterine arteries about 1 cm below the horns and from ovarian arteries inserted 0.5 cm below the ovaries. The concentration of 3H-PGF2 alpha found in blood plasma taken from uterine artery or from ovarian artery on the side with active corpus luteum (CL) was significantly lower (p less than 0.001) compare with contralateral side to active CL. Radioactive PGF2 alpha found in branches of uterine arteries on both ipsilateral and contralateral side to CL was significantly higher (p less than 0.001) compare to ovarian artery of the same side. It is concluded that absorption of 3H-PGF2 alpha from uterine lumen into venous blood as well as its counter current transfer in area of broad ligament vasculature were reduced on the side of uterine horn with active CL probably as an effect of estrogen:progesterone ratio on vascular constriction in area of uterine vasculature.

Adnexa Uteri↗

PubMed1986

The heterochromatin of grasshoppers from the Caledia captiva species complex. I. Sequence evolution and conservation in a highly repeated DNA family.

The restriction enzyme TaqI digests 0.2% of the genomic DNA from the grasshopper Caledia captiva to a family of sequences 168 bp in length (length of consensus sequence). The sequence variation of this "Taq family" of repeat units was examined among four races from C. captiva to assay the pattern of evolution within this highly repeated DNA. The Taq-family repeats are located in C-banded heterochromatin on at least one member of each homologous pair of chromosomes; the locations range from centromeric to telomeric. Thirty-nine cloned repeats isolated from two population 1A individuals along with 11 clones from seven populations taken from three of the races demonstrated sequence variation at 72 positions. Pairwise comparisons of the cloned repeats, both within an individual and between different races, indicate that levels of intraspecific divergence, as measured by reproductive incompatibility, do not correlate with sequence divergence among the 168-bp repeats. A number of subsequences within the repeat remain unchanged among all 50 clones; the longest of these is 18 bp. That the same 18-bp subsequence is present in all clones examined is a finding that departs significantly (P less than 0.01) from what would be expected to occur at random. Two other cloned repeats, from a reproductively isolated race of C. captiva, have sequences that show 56% identity with this 18-bp conserved region. An analysis showed that the frequency of occurrence of an RsaI recognition site within the 168-bp repeat in the entire Taq family agreed with that found in the cloned sequences. These data, along with a partial sequence for the entire Taq family obtained by sequencing uncloned repeats, suggest that the consensus sequence from the cloned copies is representative of this highly repeated family and is not a biased sample resulting from the cloning procedure. The 18-bp conserved sequence is part of a 42-bp sequence that possesses dyad symmetry typical of protein-binding sites. We speculate that this may be significant in the evolution of the Taq family of sequences.

Animals↗

PubMed1976

Olfactory discrimination as an isolating mechanism in speciating mole rats.

Olfactory discrimination was tested in two chromosome forms of the speciating fossorial rodent, Spalax ehrenbergi, in Israel. Females of the chromosome forms 2n = 52 and 2n = 58 were tested for male odour discrimination, the source of odour being either case litter or urine. Estrous females of both forms preferred homochromosomal odurs, whereas diestrous females showed no discrimination. These results suggest that olfactory discrimination may serve as a reproductive isolating mechanism in the speciation of mole rats.

Animals↗

PubMed1992

Genetic distance and species formation in evolving populations.

We compare the behavior of the genetic distance between individuals in evolving populations for three stochastic models. In the first model reproduction is asexual and the distribution of genetic distances reflects the genealogical tree of the population. This distribution fluctuates greatly in time, even for very large populations. In the second model reproduction is sexual with random mating allowed between any pair of individuals. In this case, the population becomes homogeneous and the genetic distance between pairs of individuals has small fluctuations which vanish in the limit of an infinitely large population. In the third model reproduction is still sexual but instead of random mating, mating only occurs between individuals which are genetically similar to each other. In that case, the population splits spontaneously into species which are in reproductive isolation from one another and one observes a steady state with a continual appearance and extinction of species in the population. We discuss this model in relation to the biological theory of speciation and isolating mechanisms. We also point out similarities between these three models of evolving populations and the theory of disordered systems in physics.

Biological Evolution↗