scholarly journals Geographical variation in postzygotic isolation and its genetic basis within and between two Mimulus species

2010 ◽  
Vol 365 (1552) ◽  
pp. 2469-2478 ◽  
Author(s):  
Noland H. Martin ◽  
John H. Willis
Keyword(s):  
Pollen Fertility ◽  
Genetic Basis ◽  
Interspecific Cross ◽  
Local Scale ◽  
Interspecific Crosses ◽  
Postzygotic Isolation ◽  
Hybrid Fitness ◽  
Pure Species ◽  
Geographical Scale ◽  
Germination Success

The aim of this study is to investigate the evolution of intrinsic postzygotic isolation within and between populations of Mimulus guttatus and Mimulus nasutus . We made 17 intraspecific and interspecific crosses, across a wide geographical scale. We examined the seed germination success and pollen fertility of reciprocal F 1 and F 2 hybrids and their pure-species parents, and used biometrical genetic tests to distinguish among alternative models of inheritance. Hybrid seed inviability was sporadic in both interspecific and intraspecific crosses. For several crosses, Dobzhansky–Muller incompatibilities involving nuclear genes were implicated, while two interspecific crosses revealed evidence of cytonuclear interactions. Reduced hybrid pollen fertility was found to be greatly influenced by Dobzhansky–Muller incompatibilities in five out of six intraspecific crosses and nine out of 11 interspecific crosses. Cytonuclear incompatibilities reduced hybrid fitness in only one intraspecific and one interspecific cross. This study suggests that intrinsic postzygotic isolation is common in hybrids between these Mimulus species, yet the particular hybrid incompatibilities responsible for effecting this isolation differ among the populations tested. Hence, we conclude that they evolve and spread only at the local scale.

scholarly journals Laboratory Hybridization Between the Green Lacewings Chrysoperla comanche (Neuroptera: Chrysopidae) and Chrysoperla rufilabris, Predators of the Asian Citrus Psyllid

2019 ◽  
Vol 112 (4) ◽  
pp. 1575-1580
Author(s):  
Marco Gebiola ◽  
Richard Stouthamer
Keyword(s):  
The United States ◽  
Genetic Identity ◽  
Invasive Pest ◽  
Interspecific Crosses ◽  
Asian Citrus Psyllid ◽  
Postzygotic Isolation ◽  
Hybrid Fitness ◽  
Chrysoperla Rufilabris ◽  
Green Lacewings ◽  
Courtship Songs

Abstract Chrysoperla comanche (Banks) and its sibling species Chrysoperla rufilabris (Burmeister) are voracious predators of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), an invasive pest that vectors a bacterium responsible for the lethal and incurable citrus greening disease. The Comanche lacewing naturally occurs in Southern California, whereas C. rufilabris is currently one of only two commercially available green lacewing in the United States. These sister species can be separated by larval morphological traits, by differences in courtship songs, and possibly by three nuclear genes wingless, PepCK, ATPase, yet they are not distinguishable based on the mitochondrial barcode gene (COI). Releasing in a new area a biological control agent capable of hybridizing with a resident species may pose risks that range from local displacement to irreversible loss of genetic identity. Therefore, we performed no-choice laboratory crosses to assess pre- and postzygotic isolation. We show that fertile and viable hybrid progeny could be readily obtained in interspecific crosses and backcrosses and, although there is a trend toward lower hybrid fitness, postzygotic isolation is overall weak and might not prevent loss of genetic identity under natural conditions. It remains to be determined if differences in courtship songs will prevent hybridization in the wild, as shown for other green lacewings. We also report a low prevalence of Rickettsia infection in both species.

scholarly journals Genetic Screens for Factors Involved in the Notum Bristle Loss of Interspecific Hybrids Between Drosophila melanogaster and D. simulans

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 269-282
Author(s):  
Toshiyuki Takano-Shimizu
Keyword(s):  
Drosophila Melanogaster ◽  
Interspecific Cross ◽  
Species Variation ◽  
Genetic Screens ◽  
Pure Species ◽  
Epistatic Interactions ◽  
X Chromosomes ◽  
Powerful Means ◽  
Different Populations ◽  
Deficiency Screening

Abstract Interspecific cross is a powerful means to uncover hidden within- and between-species variation in populations. One example is a bristle loss phenotype of hybrids between Drosophila melanogaster and D. simulans, although both the pure species have exactly the same pattern of bristle formation on the notum. There exists a large amount of genetic variability in the simulans populations with respect to the number of missing bristles in hybrids, and the variation is largely attributable to simulans X chromosomes. Using nine molecular markers, I screened the simulans X chromosome for genetic factors that were responsible for the differences between a pair of simulans lines with high (H) and low (L) missing bristle numbers. Together with duplication-rescue experiments, a single major quantitative locus was mapped to a 13F–14F region. Importantly, this region accounted for most of the differences between H and L lines in three other independent pairs, suggesting segregation of H and L alleles at the single locus in different populations. Moreover, a deficiency screening uncovered several regions with factors that potentially cause the hybrid bristle loss due to epistatic interactions with the other factors.

scholarly journals Epistatic Control of Non-Mendelian Inheritance in Mouse Interspecific Crosses

Genetics ◽  
1996 ◽  
Vol 143 (4) ◽  
pp. 1739-1752 ◽  
Author(s):  
Xavier Montagutelli ◽  
Rowena Turner ◽  
Joseph H Nadeau
Keyword(s):  
X Chromosome ◽  
Genetic Basis ◽  
Mendelian Inheritance ◽  
The Other ◽  
Interspecific Crosses ◽  
Chromosome 2 ◽  
Mus Spretus ◽  
F1 Hybrid ◽  
Strong Deviation ◽  
Marker Loci

Abstract Strong deviation of allele frequencies from Mendelian inheritance favoring Mus spretus-derived alleles has been described previously for X-linked loci in four mouse interspecific crosses. We reanalyzed data for three of these crosses focusing on the location of the gene(s) controlling deviation on the X chromosome and the genetic basis for incomplete deviation. At least two loci control deviation on the X chromosome, one near Xist (the candidate gene controlling X inactivation) and the other more centromerically located. In all three crosses, strong epistasis was found between loci near Xist and marker loci on the central portion of chromosome 2. The mechanism for this deviation from Mendelian expectations is not yet known but it is probably based on lethality of embryos carrying particular combinations of alleles rather than true segregation distortion during oogenesis in F1 hybrid females.

scholarly journals Two Loci Contribute Epistastically to Heterospecific Pollen Rejection, a Postmating Isolating Barrier Between Species

2017 ◽  
Vol 7 (7) ◽  
pp. 2151-2159 ◽  
Author(s):  
Jennafer A P Hamlin ◽  
Natasha A Sherman ◽  
Leonie C Moyle
Keyword(s):  
Female Choice ◽  
Genetic Basis ◽  
Reproductive Tract ◽  
Interspecific Cross ◽  
Solanum Species ◽  
Female Reproductive Tract ◽  
Solanum Pennellii ◽  
Heterospecific Pollen ◽  
Male Gametes ◽  
Pollen Rejection

Abstract Recognition and rejection of heterospecific male gametes occurs in a broad range of taxa, although the complexity of mechanisms underlying these components of postmating cryptic female choice is poorly understood. In plants, the arena for postmating interactions is the female reproductive tract (pistil), within which heterospecific pollen tube growth can be arrested via active molecular recognition and rejection. Unilateral incompatibility (UI) is one such postmating barrier in which pollen arrest occurs in only one direction of an interspecific cross. We investigated the genetic basis of pistil-side UI between Solanum species, with the specific goal of understanding the role and magnitude of epistasis between UI QTL. Using heterospecific introgression lines (ILs) between Solanum pennellii and S. lycopersicum, we assessed the individual and pairwise effects of three chromosomal regions (ui1.1, ui3.1, and ui12.1) previously associated with interspecific UI among Solanum species. Specifically, we generated double introgression (‘pyramided’) genotypes that combined ui12.1 with each of ui1.1 and ui3.1, and assessed the strength of UI pollen rejection in the pyramided lines, compared to single introgression genotypes. We found that none of the three QTL individually showed UI rejection phenotypes, but lines combining ui3.1 and ui12.1 showed significant pistil-side pollen rejection. Furthermore, double ILs (DILs) that combined different chromosomal regions overlapping ui3.1 differed significantly in their rate of UI, consistent with at least two genetic factors on chromosome three contributing quantitatively to interspecific pollen rejection. Together, our data indicate that loci on both chromosomes 3 and 12 are jointly required for the expression of UI between S. pennellii and S. lycopersicum, suggesting that coordinated molecular interactions among a relatively few loci underlie the expression of this postmating prezygotic barrier. In addition, in conjunction with previous data, at least one of these loci appears to also contribute to conspecific self-incompatibility (SI), consistent with a partially shared genetic basis between inter- and intraspecific mechanisms of postmating prezygotic female choice.

Analysis of a Hybrid Swarm Between Eucalyptus risdonii Hook. F. And E. amygdalina Labill

1985 ◽  
Vol 33 (5) ◽  
pp. 543 ◽  
Author(s):  
BM Potts ◽  
JB Reid
Keyword(s):  
Phenotypic Diversity ◽  
Flowering Phenology ◽  
Hybrid Swarm ◽  
Hybrid Fitness ◽  
Seedling Vigour ◽  
Pure Species ◽  
Closely Related Species ◽  
Intermediate Phenotypes ◽  
Disjunct Populations ◽  
Tasmanian Endemic

E. risdonii is a rare Tasmanian endemic which occurs as a series of small disjunct populations within a more-or-less continuous population of a closely related species, E. amygdalina. In localized areas (e.g. Risdon, Tasmania), patches of high phenotypic diversity are encountered, with individuals encompassing the complete phenotypic range between these two species. Progeny trials indicate a large heritable component to this variation. Open-pollinated progenies from intermediate mothers exhibit greater variability than those from either pure species, which strongly suggests that these intermediate phenotypes are a result of hybridization. Progenies from pure species mothers near a hybrid swarm are more variable than those from pure stands. There is a greater proportion of seedlings which match the artificially produced F1 in open-pollinated progenies from E. amygdalina than from E. risdonii mothers. In addition, progenies from intermediate mothers show a bias toward E. risdonii types, which implies that they are predominantly outcrossing to E. risdonii. This evidence suggests an asymmetrical flow of genes by pollen migration from E. risdonii into the hybrid swarm and surrounding E. amygdalina. Little difference in seedling vigour or mortality occurred between seedlings from the various parental phenotypes, although differences in seed output per capsule and germination were apparent. The specific identity of E. risdonii and E. amygdalina is usually maintained in parapatry by a range of mechanisms including their specific ecological preference, reduced hybrid fitness and differences in flowering phenology. The reasons for the major zones of hybridization occurring at boundaries on ridge tops as opposed to those on the dry slopes are discussed.

scholarly journals Assortative mating in hybrid zones is remarkably ineffective in promoting speciation

2019 ◽  
Author(s):  
Darren E. Irwin
Keyword(s):  
Assortative Mating ◽  
F1 Hybrids ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Mating Types ◽  
Postzygotic Isolation ◽  
Small Reduction ◽  
Hybrid Fitness ◽  
Prezygotic Isolation ◽  
Two Populations

AbstractAssortative mating and other forms of partial prezygotic isolation are often viewed as being more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. Here I simulate secondary contact between two populations (‘species’) to examine effects of pre- and postzygotic isolation in preventing blending. A small reduction in hybrid fitness (e.g., 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). This is because, in the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the gradual buildup of a full continuum of intermediates between the two species. The cline is narrower than would result from purely neutral diffusion over the same number of generations, largely due to the frequency-dependent mating disadvantage of individuals of rare mating types. Hybrids tend to pay this cost of rarity more than pure individuals, meaning there is an induced postzygotic isolation effect of assortative mating. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.

scholarly journals FURTHER EVIDENCE FOR A POLYMORPHISM IN GAMETIC SEGREGATION IN THE TETRAPLOID TREEFROG HYLA VERSICOLOR USING A GLUTAMATE OXALOACETIC TRANSAMINASE LOCUS

Genetics ◽  
1983 ◽  
Vol 103 (4) ◽  
pp. 753-769
Author(s):  
Roy G Danzmann ◽  
James P Bogart
Keyword(s):  
Chromosome Segregation ◽  
Null Allele ◽  
Interspecific Cross ◽  
Staining Intensity ◽  
Interspecific Crosses ◽  
Hyla Versicolor ◽  
Hyla Chrysoscelis ◽  
Segregation Ratios ◽  
Aberrant Segregation ◽  
Glutamate Oxaloacetic Transaminase

ABSTRACT Intra- and interspecific cross combinations between the tetraploid treefrog Hyla versicolor, and between H. versicolor and the diploid treefrog Hyla chrysoscelis were performed. Progeny phenotypes resulting from these crosses were examined electrophoretically using a polymorphic glutamate oxaloacetic transminase (GOT-1) locus, to determine the mechanism of chromosome segregation in H. versicolor, and to test theoretical expectations for isozyme expression in interspecific (2n × 4n or 4n × 2n) hybrids. In some intraspecific tetraploid crosses progeny phenotypes fit a disomic mode of segregation, whereas in other crosses a tetrasomic mode of segregation was the most probable. Additional crosses produced phenotypic ratios that conformed to either a disomic or tetrasomic mode of segregation. These results suggest that a polymorphism, with respect to segregation of gametes, exists in H. versicolor, resulting from differences in chromosome pairings during meiosis I. This polymorphism in gametic segregation occurred in both sexes. Certain crosses, however, produced phenotypic ratios that did not conform to any chromosome segregation model. Progeny phenotypes observed from most interspecific crosses conformed to expected interspecific isozyme staining intensity models. Symmetrical heterozygotes, representing either a single dose for both alternate alleles or double doses for both alternate alleles, were also observed. Such phenotypes are unexpected in triploid progeny. A null allele was postulated to account for the aberrant segregation ratios and phenotypes observed in certain intra- and interspecific crosses.

Pollination Sub-Systems Distinguished by Pollen Tube Arrest after Incompatible Interspecific Crosses in Rhododendron (Ericaceae)

1982 ◽  
Vol 53 (1) ◽  
pp. 255-277
Author(s):  
ELIZABETH G. WILLIAMS ◽  
BRUCE R. KNOX ◽  
JOHN L. ROUSE
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Interspecific Cross ◽  
Embryo Sac ◽  
Epifluorescence Microscopy ◽  
Interspecific Crosses ◽  
Abnormal Behaviour ◽  
Callose Deposition ◽  
Variable Diameter ◽  
Stigmatic Exudate

The cytology of compatible and interspecific incompatible pollinations has been followed in selected species of the genus Rhododendron (Ericaceae). Pollinated pistils were fixed, cleared, stained in decolourized aniline blue, and observed by epifluorescence microscopy. Ten different abnormalities of arrested pollen tube tips have been detected, including burst, tapered, swollen, coiled, spiralling, spiky and variable diameter syndromes. A series of five errors of callose deposition in incompatible tubes has also been defined. Six different regions in the pistil for expression of pollen tube arrest have been found, including the stigmatic exudate, the mucilage of the upper and lower style canal, the ovary loculus, the micropyle. There may also be abnormal behaviour after entry into the embryo sac. Both the site of pollen tube arrest within the pistil, and the error syndrome of tip growth and callose deposition anomalies, are characteristic of each interspecific cross. These results are discussed in relation to the genetic control of reproduction.

THE CHROMOSOMAL BASIS OF VIABILITY IN INTERSPECIFIC HYBRIDS BETWEEN DROSOPHILA ARIZONENSIS AND DROSOPHILA MOJAVENSIS

1981 ◽  
Vol 23 (1) ◽  
pp. 65-72 ◽  
Author(s):  
E. Zouros
Keyword(s):  
Hybrid Sterility ◽  
Introgressive Hybridization ◽  
Backcross Progeny ◽  
Interspecific Crosses ◽  
Drosophila Mojavensis ◽  
Pure Species ◽  
Ecological Barriers ◽  
Chromosomal Identification ◽  
Interspecific Crossing

The chromosomal effects on differences in viability among progeny from interspecific crosses was studied in the interfertile pair Drosophila arizonensis and Drosophila mojavensis. Interspecific crossing-over was avoided by crossing hybrid males to pure-species females, and chromosomal identification in backcross progeny was possible by means of electrophoretic markers. The main findings are as follows. One chromosome supresses viability when in the heterospecific state, this being mainly so when the rest of the genotype is predominantly of mojavensis type; the other chromosomes show occasional interspecific heterosis, but are neutral in the majority of cases; interactions are not significant, except in one pair of chromosomes within a mojavensis background; there is no correlation between numbers of heterospecific chromosomes and viability scores. It is concluded that hybrid and backcross progeny inviability is not a very potent mechanism for keeping these species apart. Should etiological and ecological barriers break down, introgressive hybridization is a real possibility. The findings are compared with those from studies concerning hybrid sterility and mating behavior in these two species. It is concluded that there is no common chromosomal basis for these phenomena. In particular, the role of interspecific inversions to speciation remains obscure.

Embryological studies on hybridization between Theobroma cacao and Theobroma grandiflora

1972 ◽  
Vol 50 (11) ◽  
pp. 2117-2124 ◽  
Author(s):  
Veronica A. Martinson
Keyword(s):  
Theobroma Cacao ◽  
Interspecific Cross ◽  
Embryo Sac ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Seed Formation ◽  
Contributory Factors ◽  
Poor Seed ◽  
Endosperm Formation ◽  
Species Hybridization

In a comparative study of embryo development in intraspecific (U6 × K5/353) and interspecific (U6 × T33) crosses of Theobroma, the development of the embryo sac as described by previous authors was confirmed. Disintegration of synergids showed that the growth of the pollen through the style was slightly quicker in intraspecific than in interspecific crosses, but the number of embryo sacs which had received male nuclei 3 days after pollination was about the same. Although gametic fusion and endosperm formation in the intraspecific cross was in advance of those in interspecific cross, the major blockage in species hybridization occurred subsequent to fertilization, and in most instances, well after the proembryo stage. Abnormal cell division and cell differentiation were contributory factors to poor seed formation. Possible causes of the abnormality have been discussed.Autonomous enlargement and the binucleate appearance of the egg cells in the unpollinated flower suggested a tendency to parthenogenesis and diploidization of the egg cell, under special conditions. Although a large proportion of the cacao seeds observed in the species crosses are most probably intraspecific seedlings arising from contamination after controlled pollinations, the occurrence of a small number of true maternal seeds cannot be ruled out altogether.

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