Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Reproductive Isolation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed2000

Morphological characteristics of the antennal flagellum and its sensilla chaetica with character displacement in the sandfly Phlebotomus argentipes Annandale and Brunetti sensu lato (Diptera: psychodidae).

Using light microscope and scanning electron microscope, the external morphological characteristics of the antennal flagellum and its sensilla are described in the sandfly, Phlebotomus argentipes Annandale and Brunetti sensu lato, a well known vector of visceral leishmaniasis in India. A revised terminology is given for the antennal segments to bring phlebotomine more in line with other subfamilies and families while a description of antennal sensilla is provided for the first time in phlebotomine sandflies. Each flagellum consists of scape, pedicel, flagellomeres I to XIII and apiculus. The antennal segments contain scales and sensilla and the latter consist of sensilla trichodea, s. basiconica, s. auricillica, s. coeloconica and s. chaetica and their putative functions are discussed. The sensilla chaeticum hitherto known as antennal ascoid in the phlebotomine sandflies was used to differentiate within and between species. Differences in its relative size to the flagellomere between the populations of P. argentipes collected from the endemic and non-endemic areas in Tamil Nadu state, southern India were established. These differences are considered to be a character displacement as means of premating reproductive isolating mechanism among the populations/members of species complex.

Animals↗
PubMed2000

Preliminary results on embryo rescue for circumventing hybridization barriers in Asparagus.

Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2001

[Karyological differences of the Northern Dolly Varden Salvelinus malma malma and the white char Salvelinus albus from the Kamchatka River basin].

The karyotypes of northern Dolly Varden and white char, sympathrically inhabiting the Kamchatka River basin, were studied. The karyotype of Dolly Varden was stable: 2n = 78 and NF = 98 + 2, while in white char, polymorphism and mosaicism for the chromosome number were revealed: 2n = 76-79, NF = 98 + 2. Using a routine chromosome staining technique, the karyotype of white char (2n = 78) was shown to be identical to that of Dolly Varden. In both karyotypes, similar sets of marker chromosomes were present: two pairs of submetacentric (SM), one pair of submeta-subtelocentric (SM-ST), one pair of large acrocentric (A), and one pair of large sub-telocentric (ST) chromosomes. However, the karyotypes of Dolly Varden and white char differed in the number and location of nucleolus organizer regions (NORs). In Dolly Varden, single NORs located in the telomeric regions of the marker SM-ST chromosomes were observed. In white char, NORs were multiple and located both in the telomeric regions of the marker SM-ST chromosomes and on the short and long arms of large ST chromosomes. The identical marker chromosomes indicate considerable phylogenetic relatedness between Dolly Varden and white char from the Kamchatka River basin. Variation in NORs provides evidence for the reproductive isolation of these chars and their species status.

Animals↗
PubMed2002

[Phylogenetic relationships among holarctic populations of Chironomus entis and Chironomus plumosus in view of possible horizontal transfer of mitochondrial genes].

In eight Holarctic populations of two typical chironomid sibling species of the plumosus group, Chrionomus entis and Chironomus plumosus, nucleotides sequences of mitochondrial (cytb) and nuclear (gb2b) gene regions were examined. The phylogenetic trees reflecting the evolutionary histories of the nuclear and mitochondrial markers exhibited significant differences. On the tree based on the nuclear gene sequences the populations clustered according to their species affiliation, whereas on the tree based on the mitochondrial gene sequences the populations were grouped according to their geographic position. This discrepancy is probably explained by mitochondrial gene flow between sympatric species with incomplete reproductive isolation (sibling species). Based on our results together with the earlier data on nuclear and mitochondrial gene sequences of some other species from the phylogenetic group plumosus, a scheme of phylogenetic relationships within this group is proposed. This scheme is in many ways different from the traditional view on the evolutionary relationships among species of the plumosus group.

Animals↗
PubMedDate not supplied

[Structure of coadaptive complex of forest entomophylous plants with broad spectrum of pollinators].

Pollinators of common forest entomophylous plants were studied at 1982-1985 near Zvenigorod biological station (Moscow region) and at 1989-1993 near Torma (Jogeva maakond, Estonia). The comparative analysis of spectra of pollinators has allowed to distinguish five groups (subcomplexes) of plants characterized by dominance of different groups of pollinators: myiophylous (flies from superfamily Muscoidea dominate), syrphidophylous (flies from family Syrphidae dominate), nonspecialized melittophylous (Apoidea, mainly bumblebees, dominate), psychophylous (butterflies dominate), and cantharophylous (beetles dominate). The belonging of plants to concrete subcomplex is determined by the morphology of flowers and influorescences, but in some cases habitat and time of blooming are also important. From year to year the composition of pollinators of the same plant species varies because of change in abundance of different groups of pollinators. However for long term these fluctuations are leveled off. External reproductive isolation of plants of myiophylous subcomplex is achieved mainly by spatial (ecological) and time (different time of flowering) isolations. However when two species of the same subcomplex grow together and their flowering time strongly overlap, there are some distinction in their pollinators reducing competition for pollinators.

Animals↗
PubMed2002

The tree Cedrela odorata (Meliaceae): a morphologically subdivided species in Costa Rica.

In Latin America. Cedrela odorata is a wide ranging species that occurs in several environments, where it shows significant morphological variation. A common garden experiment was established with seedlings from 63 families of ten populations from two habitat types (mesic and dry), distributed throughout Costa Rica, to examine the relationships between quantitative variation and site of population origin. Seedlings from dry areas tended to be distinct from those from mesic areas, with climatic grouping of provenance explaining a mean of 52% of the total variance and 80% of the genetic variance. Cluster analysis for seedling traits showed two natural groupings of families, which corresponded for the most part with the regional population groupings into mesic (Atlantic and South Pacific) and dry (North Pacific) groups. Cluster analysis based on seed weight and size also separated populations into mesic and dry climatic groups. Seeds from populations in dry areas were 43% heavier, and seedlings were 61% taller, 117% greater in diameter, and with leaflets 39% longer and 81% wider. These differences may be related to fast growth in the dry zone for taking advantage of early life cycle moisture availability. These findings may indicate incipient speciation in C. odorata in Costa Rica. Evaluation of reproductive isolating mechanisms between populations from the mesic and dry zones, and of clines at potential zones of hybridization would assist in testing a speciation hypothesis.

Analysis of Variance↗
PubMed2002

Estimation of inbreeding, kinship and genetic distances from surnames--coastal population of middle Dalmatia, Croatia.

This work was dedicated to the investigation of the population structure of the middle Dalmatia settlements: Jesenice, Mimice, Zivogosće and Zaostrog by surname distribution study and applying the isonymous method. The surnames of males and females in marital pairs were analyzed as well as of their first and second-generation ancestors on the sample of a total of 3,024 examinees. The analyses of surnames pointed to the rates of inbreeding, kinship and genetic distances of the populations. Although the values of the inbreeding coefficient are high in all the four settlements, the inbreeding coefficient is exceptionally high in Mimice. A total kinship coefficient for the four settlements speaks also in favor of the high rate of kinship in the examined settlements, i.e. of the high rate of the reproductive isolation of the whole region during the analyzed period. The reasons for such high coefficients are natural features of the examined region (the mountains of Mosor, Biokovo and Rilić), poor traffic connection of this region in the past, the patrilineal mode of inheritance and the demographic specifics of the population. The matrix of genetic distances between examined settlement pairs reveals that Mimice, a settlement with the highest share of isonymous marriages, shows the greatest distances in comparison to the other settlements. On the other hand, Jesenice, Zivogosće and Zaostrog are characterized by small genetic distances, which is the fact that speaks in favor of their genetic homogenization and "openness" toward interpopulational migrations, i.e. the gene flow.

Consanguinity↗
PubMed2002

Herbivorous insects: model systems for the comparative study of speciation ecology.

Does ecological divergence drive species-level evolutionary diversification? How so and to what degree? These questions were central to the thinking of the evolutionary synthesis. Only recently, however, has the ecology of speciation become an important focus of empirical study. Here, we argue that ecologically specialized, phylogenetically diverse, and experimentally tractable herbivorous insect taxa offer great opportunities to study the myriad mechanisms by which ecology may cause reproductive isolation and promote speciation. We call for the development and integrated experimental study of a taxonomic diversity of herbivore model systems and discuss the availability and recent evaluation of suitable taxa. Most importantly, we describe a general comparative framework that can be used to rigorously test a variety of hypotheses about the relative contributions and the macroevolutionary generality of particular mechanisms. Finally, we illustrate important issues for the experimental analysis of speciation ecology by demonstrating the consequences of specialized host associations for ecological divergence and premating isolation in Neochlamisus bebbianae leaf beetles.

Animals↗
PubMed2002

The inheritance of mating songs in two cryptic, sibling lacewing species (Neuroptera: Chrysopidae: Chrysoperla).

Speciation often involves incremental responses to natural selection and results in large scale genomic changes, but it may also occur abruptly and with little genetic imprint, as seen in some complexes of cryptic species. Recent attention has focused on sexual selection in rapid speciation, because it can disrupt premating signals that mediate reproductive isolation. Some models require that environmental adaptation assist sexual selection during speciation, while others show that populations can diverge through mate choice alone. We propose that speciation involving environmental adaptation in premating signals is likely to have a polygenic basis, while speciation due to arbitrary changes in premating signals could be accompanied by changes at just a few loci. The sibling species Chrysoperla plorabunda and Chrysoperla johnsoni belong to a large complex of cryptic species of green lacewings, and meet all criteria for speciation via sexual selection. We perform a genetic analysis of line crosses between them, focusing on their substrate-borne premating songs. Measurements of seven song features and their principal components are compared among parentals, F1 and F2 hybrids, and backcrosses. The distributions of phenotypes are consistent with a model of more than one, but not many, genes. Sex linkage and/or maternal effects are negligible. C. plorabunda is dominant for most traits affecting mate choice. Bayesian analyses of segregation variance show significant additive and epistatic effects on line means. A Bayesian Castle-Wright estimate suggests that relatively few effective factors are responsible for variation in volley period (x = two factors), number of volleys per song (x = 1), and PC-1 (x = 4). Our results are consistent with simple genetic architecture of songs, supporting a role for major genes in premating isolation and strengthening the notion that mate choice alone, without significant environmental adaptation, has been responsible for generating new lacewing species.

Acoustic Stimulation↗
PubMed2003

Frequency of multiple inseminations in field-collected Anopheles gambiae females revealed by DNA analysis of transferred sperm.

We investigated the frequencies of single and multiple matings in field-collected female Anopheles gambiae by conducting microsatellite DNA analyses on the sperm contained within their spermatheca. Amplifcation by a polymerase chain reaction (PCR) at four loci allowed the detection of sperm extracts exhibiting more than two alleles per locus, thereby revealing the occurrence of multiple inseminations. Polyandry was found in six of 239 females examined, or 2.5% of the samples. Previous analyses of the molecular form of the sperm and female extracts using a PCR-based diagnostic procedure showed that two of these multiple inseminations involved cross-mating between two chromosomal/molecular forms of An. gambiae s.s. Thus polyandry occurred within-form in 1.7% of examined females while other multiple inseminations may be linked to processes of reproductive isolation between forms of An. gambiae.

Animals↗
PubMed1999

[Hybridization experiments using Anopheles minimus from Hainan and Yunnan].

AIM: To observe whether there were any intra-species differences between Anopheles minimus from Hainan(H) and Yunnan(Y). METHODS: Anopheles minimus were collected from cattle shed on the spot. Each isofemale line was set up in the laboratory. Hybridization experiments were conducted by using forced mating between Anopheles minimus from Hainan and Yunnan, for observing the reproductive ability of F1 hybrids. Ovarian nurse cell polytene chromosomes of F1 hybrid females were examined, to observe any synapsis in different zones of chromosomes. RESULTS: No embryo formation was found within the eggs produced by group Y female x H male, the hatching rate was zero. Low hatching rate was shown in other groups with (H female x Y male) F1, except for groups with (H x Y) F1 x Y. Ovarian nurse cell polytene chromosomes from (H x Y) F1 hybrid females showed constant asynapsis at the 29th, 36th and 37th zones in the chromosome 3R, and at the 4th and 6th zones in the chromosome X. CONCLUSION: Reproductive isolation did appear in An. minimus from Hainan and Yunnan.

Animals↗
PubMed2002

Intraspecific hybridization of Anopheles minimus (Diptera: Culicidae) species A and C in Thailand.

Hybridization tests of laboratory-raised, isolines of Anopheles minimus, species A and C were conducted by induced copulation. The three isolines were established based on three morphological variants of wild-caught, fully engorged females and two distinct types of metaphase chromosomes. They were An. minimus species A: V form (X1,Y1), M form (X2,Y1); species C: P form (X3,Y2). The results of reciprocal and back crosses indicated that the two morphologically variant forms of species A were genetically compatible, providing viable progeny and completely synaptic salivary gland polytene chromosomes, whereas they were genetically incompatible with species C and/or the P form. Hybrid progeny was only obtained from both forms of species A females x species C males, but asynaptic salivary gland polytene chromosomes on 3L and partial development of ovarian follicles in females were seen. Back crosses of F1 hybrid males with parental species A females provided viable progeny, while back crosses of F1 hybrid females with parental species C males provided progeny of low viability and adult males with abnormal spermatozoa, suggesting the partial reproductive isolation of An. minimus species A and C.

Animals↗
PubMedDate not supplied

Glucose-6-phosphate dehydrogenase (G6PD) deficiency in the Albanian ethnic minority of Cosenza province, Italy.

The Albanian ethnic minority of the Cosenza province (Calabria, Southern Italy) is constituted by a population of 42,305 inhabitants living in 19 communes. The first presence of this population, in Southern Italy, dates back to the fifteenth century as a result of different immigrations. We have studied the G6PD in the population of this province by determining both the frequency of the G6PD-deficiency and the type of Gd(-) alleles in samples from 19 communes. The overall frequency estimate turned out to be 0.0294 and those of the 8 highland communes and of the 11 communes located in the valleys were 0.0242 and 0.033 respectively. Both the frequencies and the ratio between the frequencies of the different Gd(-) alleles are significantly different with respect to a previous study carried out on the non-Albanian population of the same areas. The high endogamy rate found among the grandparents' and among the parents of the probands living in the Albanian community, shows that this community is to a large extent reproductively isolated from the neighbouring populations, thus accounting for these differences.

Adolescent↗
PubMed1992

[Hybridization experiments using Anopheles minimus from Guangxi and Yunnan].

Hybridization experiments were conducted by forced mating between Anopheles minimus from Guangxi (G) and Yunnan (Y). F1 hybrid females were all fertile with normally developed ovaries. (Y female x G male) F1 males were all sterile, with abnormally enlarged testes. (G female x Y male) F1 males, though fertile, showed somewhat atrophic testes, and when they were back crossed with parental females, the latter produced eggs with very low hatching rate. Ovarian nurse cell polytene chromosomes from F1 hybrid females showed partial asynapsis in X chromosome as well as in autosonles, asynapsis at 38 zone in 3L being the most constant. It was obvious that there was definite, though partial, reproductive isolation between An minimus from Guangxi and that from Yunnan. Whether they are sibling species remains to be further investigated (Figs. 1-8).

Animals↗
PubMed1992

MtDNA polymorphisms among Tharus of eastern Terai (Nepal).

Tharus--a population of Terai (a region with a severe malarial morbidity in the past)--can be subdivided into three main groups: Western, Central and Southern Tharus. They have usually been considered a Mongoloid population and this has been further substantiated by mtDNA findings on Central Tharus. Studies on the distribution of malaria-related genes have shown an extremely high frequency (0.8) of the alpha-thal gene among Western and Central Tharus. This frequency, however, unexpectedly turned out to be only 0.04 in a sample of Eastern Tharus. This raised doubts on the common notion that Tharus are a single anthropological entity. In the present investigation mtDNA markers were studied in the same sample of Eastern Tharus previously examined for the alpha-thal gene. The findings were: 1. the same three features which confirmed the classification of Central Tharus as Mongoloids (i.e., the common occurrence of HpaI-1/HincII-1 and HaeII-5 morphs, and the lack of BamHI polymorphism) were also present in this sample. Since the only neighbouring population accessible to Tharus, until recently, has been Hindu (Caucasoids), this result strongly supports the notion that Tharus are indeed a single anthropological entity; 2. two statistically significant differences between Eastern and Central Tharus--namely, a much higher HaeII morph 5 frequency among Central Tharus, and the absence in the same group of the mutation at 15.487 bp (very common among Eastern Tharus)--together with the results on alpha-tal gene, suggested that Tharu subgroups underwent an effective reproductive isolation.

Blotting, Southern↗
PubMed2001

[Probable origin of the Robertsonian phenomena in domestic mice in Tunisia].

The Robertsonian phenomenon in house mice (Mus musculus domesticus) from Tunisia consists in the presence of only one 22-chromosome Robertsonian race (22Rb) carrying the maximum number of fusions observed until now. The 22Rb populations exclusively occupy urban centers in the Eastern-Central region of Tunisia where standard population with 40-all acrocentric chromosomes (40Std) occur in surrounding neighborhoods and rural environments. In addition to the habitat partition, allozyme and mitochondrial DNA analyses showed that the 22Rb populations were genetically differentiated from the 40Std ones. This differentiation mostly stemmed from an important decrease in genetic variability in the 22Rb populations from the Sahel towns. The extent of morphological, ecological and genetical divergence observed between these chromosomal races in Tunisia is in agreement with the predictions of the chromosomal speciation model of White which advocates that karyotypic differentiation between taxa can lead to their reproductive isolation and independent evolution. Such a process is verified if the Rb process in Tunisia results from local differentiation which is supported by both the genetic and morphological data. However, the hypothesis of an origin by introduction of these mice from another region of Tunisia or from another country cannot be totally dismissed. In this study, an allozymic analysis of mice (22Rb and 40Std) from the geographically distant city of Kairouan was performed. Results showed that 22Rb and 40Std mice from Kairouan shared the same high degree of variability, and were not genetically differentiated. This contrasts with the results registered in the two chromosomal races in the Sahel towns. Such data argue in favor of a local differentiation of the Robertsonian process in Tunisia and suggest that the decrease in variability of the structural nuclear genes in the Sahel 22Rb populations can be related to an introduction from Kairouan into a Sahel locality resulting in a founder effect or followed by a severe bottleneck prior to its dispersion throughout the Sahel region.

Animals↗
PubMed2005

Countergradient variation in the sexual coloration of guppies (Poecilia reticulata): drosopterin synthesis balances carotenoid availability.

Trinidad guppies (Poecilia reticulata) are distributed along an environmental gradient in carotenoid availability that limits the carotenoid content of the orange spots of males. The amount of synthetic red pteridines (drosopterins) in the orange spots covaries with the carotenoid content, such that the ratio of the two types of pigments is roughly conserved across streams. Carotenoids and drosopterins have different spectral properties and thus the ratio of the two types of pigments affects the shape of the orange spot reflectance spectrum. Geographic conservation of the carotenoid:drosopterin ratio suggests that males may be under selection to maintain a particular hue. We tested this hypothesis by comparing the pigmentation and coloration of guppies from six streams in the field to that of second-generation descendants of the same populations raised on three dietary carotenoid levels in the laboratory. The results show clearly that the geographic variation in drosopterin production is largely genetic and that the hue of the orange spots is conserved among populations in the field, relative to the laboratory diet groups. This is a countergradient pattern because genetic differences between populations in drosopterin production mask the effect of carotenoid availability on the hue of the orange spots. The potential for countergradient sexual selection to contribute to reproductive isolation between populations is discussed.

Animals↗
PubMed2005

Ecological adaptation and species recognition drives vocal evolution in neotropical suboscine birds.

Given that evolutionary divergence in mating signals leads to reproductive isolation in numerous animal taxa, understanding what drives signal divergence is fundamental to our understanding of speciation. Mating signals are thought to diverge via several processes, including (1) as a by-product of morphological adaptation, (2) through direct adaptation to the signaling environment, or (3) to facilitate species recognition. According to the first two hypotheses, birdsongs diversify in different foraging niches and habitats as a product of selection for optimal morphology and efficient sound transmission, respectively. According to the third hypothesis, they diversify as a result of selection against maladaptive hybridization. In this study I test all three hypotheses by examining the influence of morphology, acoustic environment, and the presence of closely related congeners on song structure in 163 species of antbird (Thamnophilidae). Unlike oscine passerines, these Neotropical suboscines make ideal subjects because they develop their songs without learning. In other words, patterns of vocal divergence are not complicated by cultural evolution. In support of the morphological adaptation hypothesis, body mass correlates with the acoustic frequency of songs, and bill size with temporal patterning. These relationships were robust, even when controlling for phylogenetic inertia using independent contrasts, suggesting that there has been correlated evolution between morphological and acoustic traits. The results also support the acoustic adaptation hypothesis: birds which habitually sing in the understory and canopy produce higher-pitched songs than those that sing in the midstory, suggesting that song structure is related to the sound transmission properties of different habitat strata. Finally, the songs of sympatric pairs of closely related species are more divergent than those of allopatric pairs, as predicted by the species recognition hypothesis. To my knowledge, these data provide the first direct evidence that species recognition and ecological adaptation operate in tandem, and that the interplay between these factors drives the evolution of mating signals in suboscine birds.

Acoustics↗