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PubMed2000

Behavioural isolation between two closely related Hawaiian Drosophila species: the role of courtship.

Behavioural isolation plays a critical role in several recent models of speciation. A detailed understanding of the process of speciation requires analysis of taxonomic groups that have not completed reproductive isolation. We studied D. silvestris and D. heteroneura because they are still in the process of divergence: behavioural isolation between them is incomplete, and neither postzygotic nor ecological isolation has been detected. Behavioural isolation is due to the failure of courtships between male D. silvestris and female D. heteroneura: there is no postzygotic isolation from either parental species. The F1 hybrids are as successful in courtship with parental individuals as same-species pairs, which suggests that the hybrids resemble male D. heteroneura or female D. silvestris in some behaviour patterns that are crucial to mating success. We searched for this crucial resemblance by examining courtship between F1 hybrids and the parental adults. We found that successful F1 males are somewhat more similar than unsuccessful F1 males to D. heteroneura males, but nevertheless they were intermediate between males of the two species. We also found that in both species the presence of female wings is necessary for courtship to proceed to copulation. These results reinforce an earlier report that behavioural isolation between these species is largely attributable to the decision as to whether to court at all, rather than to the details of courtship. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
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

[A perfusion device for the survival of isolated organs of the reproductive system].

A perfusion device for life supporting in isolated reproductive organs is described. With the device, the following functions are possible: gas exchange in recirculating blood flow, perfusate replacement in the course of perfusion, blood flow generation in a circular circuit with simultaneous provision of hemodynamic parameters closely approximating native ones.

Animals↗
PubMed2000

Evolution of temporal isolation in the wild: genetic divergence in timing of migration and breeding by introduced chinook salmon populations.

The timing of migration and breeding are key life-history traits; they are not only adaptations of populations to their environments, but can serve to increase reproductive isolation, facilitating further divergence among populations. As part of a study of divergence of chinook salmon, Oncorhynchus tshawytscha, populations, established in New Zealand from a common source in the early 1900s, we tested the hypotheses that the timing of migration and breeding are under genetic control and that the populations genetically differ in these traits despite phenotypic overlap in timing in the wild. Representatives of families from two populations were collected within a day or two of each other, reared in a common environment, and then released to sea from each of two different rivers, while other family representatives were retained in fresh water to maturity. The date of maturation of fish held in fresh water and the dates of return from the ocean and maturation of fish released to sea all showed significant differences between the two populations and among families within populations. The very high heritabilities and genetic correlations estimated for migration and maturation date indicated that these traits would respond rapidly to selection. Combined with the results of related studies on these chinook salmon populations, it appears that spawning time may not only evolve during the initial phases of divergence, but it may play an important role in accelerating divergence in other traits.

Animals↗
PubMed2000

Why do females mate multiply? A review of the genetic benefits.

The aim of this review is to consider the potential benefits that females may gain from mating more than once in a single reproductive cycle. The relationship between non-genetic and genetic benefits is briefly explored. We suggest that multiple mating for purely non-genetic benefits is unlikely as it invariably leads to the possibility of genetic benefits as well. We begin by briefly reviewing the main models for genetic benefits to mate choice, and the supporting evidence that choice can increase offspring performance and the sexual attractiveness of sons. We then explain how multiple mating can elevate offspring fitness by increasing the number of potential sires that compete, when this occurs in conjunction with mechanisms of paternity biasing that function in copula or post-copulation. We begin by identifying cases where females use pre-copulatory cues to identify mates prior to remating. In the simplest case, females remate because they identify a superior mate and 'trade up' genetically. The main evidence for this process comes from extra-pair copulation in birds. Second, we note other cases where pre-copulatory cues may be less reliable and females mate with several males to promote post-copulatory mechanisms that bias paternity. Although a distinction is drawn between sperm competition and cryptic female choice, we point out that the genetic benefits to polyandry in terms of producing more viable or sexually attractive offspring do not depend on the exact mechanism that leads to biased paternity. Post-copulatory mechanisms of paternity biasing may: (1) reduce genetic incompatibility between male and female genetic contributions to offspring; (2) increase offspring viability if there is a positive correlation between traits favoured post-copulation and those that improve performance under natural selection; (3) increase the ability of sons to gain paternity when they mate with polyandrous females. A third possibility is that genetic diversity among offspring is directly favoured. This can be due to bet-hedging (due to mate assessment errors or temporal fluctuations in the environment), beneficial interactions between less related siblings or the opportunity to preferentially fertilise eggs with sperm of a specific genotype drawn from a range of stored sperm depending on prevailing environmental conditions. We use case studies from the social insects to provide some concrete examples of the role of genetic diversity among progeny in elevating fitness. We conclude that post-copulatory mechanisms provide a more reliable way of selecting a genetically compatible mate than pre-copulatory mate choice. Some of the best evidence for cryptic female choice by sperm selection is due to selection of more compatible sperm. Two future areas of research seem likely to be profitable. First, more experimental evidence is needed demonstrating that multiple mating increases offspring fitness via genetic gains. Second, the role of multiple mating in promoting assortative fertilization and increasing reproductive isolation between populations may help us to understand sympatric speciation.

Animals↗
PubMed1998

Genetic drift in present human populations: survey of a Mediterranean region (La Alpujarra, South-east Spain).

This paper presents information on the opportunity for genetic drift in La Alpujarra, a rural population of the Spanish Mediterranean. This region is characterized by its historical isolation. The analyses were based on a survey of 45% of the population. The Effective Population Size (NE = 1986), the Effective Migration Rate (M(E) = 12.4) and the Coefficient of Breeding Isolation (CBI = 246.2) of Lasker & Kaplan (1964) were calculated. The value of the latter index indicates that genetic drift in the Alpujarrenian population is negligible at present because of the cessation of reproductive isolation due to the development of communication networks.

Female↗
PubMed1997

Differentiation of European and Far East Asian populations of Saccharomyces paradoxus by allozyme analysis.

Allozyme electrophoresis was used to characterize 39 isolates belonging to the wild yeast species Saccharomyces paradoxus for variation at nine enzyme loci. The data revealed significant genetic differentiation between isolates from two geographically distinct regions, one including continental Europe and the other including the Russian Far East and Japan. The results are consistent with previous observations indicating that there is partial reproductive isolation between isolates collected from these regions, and they suggest the possibility that these two populations represent an early stage in speciation.

Alleles↗
PubMed1996

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. III. Alternative rearing.

We have been utilizing members of the Drosophila paulistorum complex of semispecies to study the development of adult discriminatory behavior. In this study, three rearing methods were used to examine the effects of previous exposure to heterosemispecifics on reproductive isolation among the various semispecies. Experimental flies were exposed to heterosemispecifics by one of three methods: exposure to airborne heterosemispecific stimuli from egg through sexual maturity, physical contact with heterosemispecifics only during the postimaginal period, and mixed culturing (total physical contact with heterosemispecific individuals during each of five preimaginal stages). Effects of the first treatment varied with semispecies. The second treatment had no significant effect on mating behavior. The third treatment of mixed culturing reinforced sexual isolation.

Animals↗
PubMed2000

A biogeographic genetic approach for testing the role of reinforcement: the case of Drosophila pseudoobscura and D. persimilis.

The role of reinforcement in speciation can be explained by two distinct models. In model I, two diverged populations hybridize and produce fertile hybrids that successfully backcross (hybridization with gene flow). In model II, two populations hybridize but succeeding backcrosses are unproductive (hybridization without gene flow). Using Drosophila persimilis and D. pseudoobscura, we have tested model I by comparing the extent of heterospecific introgression in sympatric versus allopatric populations. We show that certain expectations of this particular model of reinforcement, which is based on hybridization and gene flow between divergent populations after secondary contact, are not realized in these two species. The evidence consists of the similarity of genetic distances as well as proportions of unique/rare alleles between sympatric and allopatric heterospecific populations and a negative correlation between genetic distance and geographical distance between heterospecific populations, which suggests ecological differentiation. This approach in quantifying differential gene flow has important consequences to studies that compare sympatric and allopatric isolation using genetic distance. Following model I, one would expect a pattern of higher prezygotic isolation in sympatric species compared to allopatric species of the same genetic distance simply as a result of an underestimation of genetic distance due to introgression between sympatric populations. We suggest more parsimonious explanations such as reinforcement without genetic exchange (model II) and ecological differentiation, which require high levels of preexisting reproductive isolation between populations.

Animals↗
PubMed1993

Differentiation of U.S. and European isolates of porcine reproductive and respiratory syndrome virus by monoclonal antibodies.

Monoclonal antibodies (MAbs) to two U.S. isolates of porcine reproductive and respiratory syndrome (PRRS) virus were prepared. Two MAbs specifically recognized a conserved epitope on the putative 15-kDa nucleocapsid protein of U.S. and European isolates of PRRS virus. Four other MAbs recognized epitopes on the 15-kDa protein of U.S. but not European isolates of PRRS virus. Collectively, this indicates that PRRS viruses contain both conserved and divergent epitopes on the 15-kDa viral protein.

Animals↗
PubMed2000

Trichinella murrelli n. sp: etiological agent of sylvatic trichinellosis in temperate areas of North America.

Trichinella T5, collected from sylvatic carnivores in North America, was identified previously as a different phenotype of Trichinella, with an uncertain taxonomic level due to the availability of only 2 isolates. Cross-breeding experiments carried out with single female and male larvae of 2 strains of Trichinella T5, with single female and male larvae of 2 strains of Trichinella spiralis, Trichinella nativa, Trichinella britovi, Trichinella pseudospiralis, Trichinella nelsoni, and Trichinella T6, showed a reproductive isolation of Trichinella T5. Viable offspring were obtained only when a female of Trichinella T5 was crossed with a male of T. britovi, but not vice versa. Furthermore, the analysis of biological, biochemical, and molecular data of 32 isolates collected from sylvatic animals in the Nearctic region and identified as Trichinella T5 permitted its reassessment at the species level. Trichinella murrelli n. sp. is characterized by the following: distribution in temperate areas of the Nearctic region; newborn larvae production in vitro of 29-36/72 hr; nurse cell development time between 24 and 70 days postinfection; reproductive capacity index in Swiss mice 1.2-9.5, in wild mice 29.5-159.8, in rats 0.7-2.4, and in pigs 0.03-0.0004; no resistance to freezing; ribosomal DNA fragments of 7.2 kb and/or 11.4 kb, plus 2.2 kb and 1.8 kb present after Dra I digested DNA when probed with total T. spiralis RNA; a specific amplicon of 179 bp after polymerase chain reaction (PCR) amplification with the primer set SB147G; a specific fragment of 1,600 bp after PCR amplification with the primer set Ts43CA and Hhb I digestion; long incubation period; and moderate to severe pathogenicity for humans. The new species is most similar to T. britovi, though it differs from T. britovi in the pattern of 2 allozymes, in the patterns of major ribosomal DNA and PCR-restriction fragment length polymorphism fragments, and in geographical distribution.

Animals↗
PubMed1981

Patterns of mortality in the the Old Order Amish. I. Background and major causes of death.

The major causes of death were studied in the Old Order Amish people in three settlements in Indiana, Ohio and Pennsylvania to determine if lifestyle and genetic isolation altered their mortality risk compared to neighboring non-Amish. The Amish are a conservative religious group who live in farm settlements, use horses for work and travel, exercise vigorously, and avoid cigarettes and alcohol. They are reproductively isolated and highly inbred. Death certificates and Amish censuses were used to determine mortality risks, which were summarized using age-adjusted mortality ratio (MRs). Amish mortality patterns were not systematically higher or lower than those of the non-Amish, but differed by age, sex, and cause. Amish males had slightly higher all-cause MRs as children and significantly lower MRs over the age of 40, due primarily to lower rates of cancer (MR = 0.44, age 40-69), and cardiovascular diseases (MR = 0.65, age 40-69). Amish females MRs for all causes of death were lower from age 10-39, not different from 40-69, and higher over age 69. MRs were not significantly different for all cancer sites combined in Amish women and they had higher cardiovascular mortality ratio aged 70 and over (MR =1.34). Other major causes of death were also examined. Because the Amish and other farming groups have similar mortality patterns, it is suggested that lifestyle may be the primary determinant of the overall mortality patterns in the Amish.

Adolescent↗
PubMed1995

Antigenic comparison of Canadian and US isolates of porcine reproductive and respiratory syndrome virus using monoclonal antibodies to the nucleocapsid protein.

Fifteen Canadian field isolates of porcine reproductive and respiratory syndrome (PRRS) virus from Quebec and Ontario were compared with 5 US PRRS virus (PRRSV) isolates and with the European Lelystad isolate using monoclonal antibodies (MAbs) SDOW17, EP147, and VO17 directed to the 15-kDa nucleocapsid protein of PRRSV. All Canadian and US isolates tested by indirect immunofluorescence were recognized by the 3 MAbs, and individual titers of MAbs towards Canadian and US PRRSV isolates were similar as well. In contrast, the Lelystad virus isolate reacted only with the SDOW17 MAb and showed no reactivity with either EP147 or VO17. The reactivity pattern with these MAbs suggests that the Canadian isolates of PRRSV tested are antigenically similar to US isolates of PRRSV, and that these North American isolates share highly conserved epitopes on the 15-kDa nucleocapsid protein that clearly differentiate them from the European Lelystad virus isolate.

Animals↗
PubMed1997

Genetics of a pheromonal difference affecting sexual isolation between Drosophila mauritiana and D. sechellia.

Females of the sibling species Drosophila sechellia and D. mauritiana differ in their cuticular hydrocarbons: the predominant compound in D. sechellia is 7,11-heptacosadiene (7,11-HD), while that in D. mauritiana is 7-tricosene (7-T). We investigate the genetic basis of this difference and its involvement in reproductive isolation between the species. Behavioral studies involving hydrocarbon transfer suggest that these compounds play a large role in the sexual isolation between D. mauritiana males and D. sechellia females, while sexual isolation in the reciprocal hybridization results more from differences in female behavior than hydrocarbons. This interspecific difference in hydrocarbon profile is due to evolutionary change at a minimum of six loci, all on the third chromosome. The localization of evolutionary change to the third chromosome has been seen in very other genetic analysis of female hydrocarbon differences in the D. melanogaster group. We suggest that the high 7,11-HD phenotype seen in two species evolved twice independently from ancestors having the high 7-T phenotype and the recurrent third-chromosome effects are evolutionary convergences that may be due to a concentration of "hydrocarbon genes" on that chromosome.

Alkadienes↗
PubMed2000

Genetic differentiation in Tetranychus urticae (Acari: Tetranychidae): polymorphism, host races or sibling species?

Based on allozyme electrophoresis at the Pgm locus and nuclear ribosomal DNA (ITS2) sequences, we studied the genetic variation of the two-spotted spider mite Tetranychus urticae Koch collected on rose bay, Nerium oleander L. (Apocynaceae), from several localities around the Mediterranean basin. In addition, we compared these results with those of Navajas et al. (1998) and Tsagkarakou (1997) who collected from several other host plants from the Mediterranean. In the western part of this area (Spain, France, Tunisia), we found the individuals collected from rose bay to be clearly genetically differentiated from other samples. No evidence of such host-associated differentiation was detected in the eastern Mediterranean (Italy and Greece). The genetic differentiation of mites collected on rose bay was investigated further by studying the reproductive incompatibilities between populations in Greece and in France and a laboratory strain reared on bean, Phaseolus vulgaris, in France. Reciprocal crosses performed between these strains revealed variable levels of incompatibility, spanning from partial to complete reproductive isolation. In all cases incompatibility was asymmetric. We designed a test based on double-mating to establish the fertilization status of females in fully incompatible crosses. These crosses showed that the females had been inseminated, which suggests that the barrier to reproduction is not of a prezygotic behavioral nature. The data raises the question of the relative role of ecological factors (host plant) and geographical distance, in the ongoing differentiation process potentially leading to speciation.

Alleles↗
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↗
PubMed1994

Cytoplasmic incompatibility. Giant steps sideways.

The horizontal transfer of a bacterial endosymbiont that is intimately associated with reproductive isolation in insects is now feasible and may, in principle, lead to new strategies for biological pest control.

Animals↗
PubMed1996

Natural selection and random genetic drift as causes of evolution on islands.

The evolutionary processes responsible for adaptation and speciation on islands differ in several ways from those on the mainland. Most attention has been given to the random genetic drift that arises when a population is founded from just a few colonizing genomes. Theoretical obstacles to "founder effect speciation' are discussed, together with recent proposals for avoiding them. It is argued that although certain kinds of epistasis can facilitate the evolution of strong reproductive isolation, this favours divergence by selection as much as by random drift.

Alleles↗