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Hybrid Individuals (hybrid + individual)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Genetic characterization of hybridization and introgression between anadromous rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki)

MOLECULAR ECOLOGY, Issue 4 2001
William P. Young
Abstract Interspecific hybridization represents a dynamic evolutionary phenomenon and major conservation problem in salmonid fishes. In this study we used amplified fragment length polymorphisms (AFLP) and mitochondrial DNA (mtDNA) markers to describe the extent and characterize the pattern of hybridization and introgression between coastal rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki). Hybrid individuals were initially identified using principle coordinate analysis of 133 polymorphic AFLP markers. Subsequent analysis using 23 diagnostic AFLP markers revealed the presence of F1, rainbow trout backcross, cutthroat trout backcross and later-generation hybrids. mtDNA analysis demonstrated equal numbers of F1 hybrids with rainbow and cutthroat trout mtDNA indicating reciprocal mating of the parental types. In contrast, rainbow and cutthroat trout backcross hybrids always exhibited the mtDNA from the recurrent parent, indicating a male hybrid mating with a pure female. This study illustrates the usefulness of the AFLP technique for generating large numbers of species diagnostic markers. The pattern of hybridization raises many questions concerning the existence and action of reproductive isolating mechanisms between these two species. Our findings are consistent with the hypothesis that introgression between anadromous populations of coastal rainbow and coastal cutthroat trout is limited by an environment-dependent reduction in hybrid fitness. [source]

Genetic Evidence for Natural Hybridization between Species of Dioecious Ficus on Island Populations1

BIOTROPICA, Issue 3 2003
Tracey L. Parrish
ABSTRACT Natural hybrids between Ficus septica and two closely related dioecious species, F. fistulosa and F. hispida, were confirmed using amplified fragment length polymorphisms (AFLP) and chloroplast DNA markers. Ficus species have a highly species-specific pollination mutualism with agaonid wasps. Therefore, the identification of cases in which breakdown in this sophisticated system occurs and the circumstances under which it happens is of interest. Various studies have confirmed that Ficus species are able to hybridize and that pollinator-specificity breakdown can occur under certain conditions. This study is the first example in which hybrid identity and the presence of hybrids in the natural distribution of parental species for Ficus have been confirmed with molecular markers. Hybrid individuals were identified on three island locations in the Sunda Strait region of Indonesia. These findings support Janzen's (1979) hypothesis that breakdown in pollinator specificity is more likely to occur on islands. We hypothesized that hybrid events could occur when the population size of pollinator wasps was small or had been small in one of the parental species. Later generation hybrids were identified, indicating that backcrossing and introgression did occur to some extent and that therefore, hybrids could be fertile. The small number of hybrids found indicated that there was little effect of hybridization on parental species integrity over the study area. Although hybrid individuals were not common, their presence at multiple sites indicated that the hybridization events reported here were not isolated incidences. Chloroplast DNA haplotypes of hybrids were not derived solely from one species, suggesting that the seed donor was not of the same parental species in all hybridization events. [source]

Statistical analysis of amplified fragment length polymorphism data: a toolbox for molecular ecologists and evolutionists

MOLECULAR ECOLOGY, Issue 18 2007
A. Bonin
Abstract Recently, the amplified fragment length polymorphism (AFLP) technique has gained a lot of popularity, and is now frequently applied to a wide variety of organisms. Technical specificities of the AFLP procedure have been well documented over the years, but there is on the contrary little or scattered information about the statistical analysis of AFLPs. In this review, we describe the various methods available to handle AFLP data, focusing on four research topics at the population or individual level of analysis: (i) assessment of genetic diversity; (ii) identification of population structure; (iii) identification of hybrid individuals; and (iv) detection of markers associated with phenotypes. Two kinds of analysis methods can be distinguished, depending on whether they are based on the direct study of band presences or absences in AFLP profiles (,band-based' methods), or on allelic frequencies estimated at each locus from these profiles (,allele frequency-based' methods). We investigate the characteristics and limitations of these statistical tools; finally, we appeal for a wider adoption of methodologies borrowed from other research fields, like for example those especially designed to deal with binary data. [source]

Cytonuclear disequilibrium in a hybrid zone involving deep-sea hydrothermal vent mussels of the genus Bathymodiolus

MOLECULAR ECOLOGY, Issue 11 2003
Y. Won
Abstract A hybrid zone involving the deep-sea mussels, Bathymodiolus azoricus and B. puteoserpentis, was recently discovered at Broken Spur hydrothermal vent field (29°10, N, 43°10, W) along an intermediate segment of the Mid-Atlantic Ridge axis. Examination of nuclear (allozymes) and cytoplasmic (mitochondrial DNA) gene markers in a new sample from Broken Spur revealed significant cytonuclear disequilibrium caused by an excess of the parental types (coupling phase) and a deficiency of recombinants (repulsion phase). An assignment test of individual multilocus genotypes also revealed an excess of parental genotypes in the admixed population. These results support the hypothesis that the Broken Spur mussel population comprises a nonequilibrium mixture of parental immigrants and hybrid individuals. [source]

Using faecal DNA sampling and GIS to monitor hybridization between red wolves (Canis rufus) and coyotes (Canis latrans)

MOLECULAR ECOLOGY, Issue 8 2003
J. R. Adams
Abstract The US Fish and Wildlife Service's (USFWS) Red Wolf Recovery Program recognizes hybridization with coyotes as the primary threat to red wolf recovery. Efforts to curb or stop hybridization are hampered in two ways. First, hybrid individuals are difficult to identify based solely on morphology. Second, managers need to effectively search 6000 km2 for the presence of coyotes and hybrids. We develop a noninvasive method to screen large geographical areas for coyotes and hybrids with maternal coyote ancestry by combining mitochondrial DNA sequence analysis of faeces (scat) and geographic information system (GIS) technology. This method was implemented on the Alligator River National Wildlife Refuge (1000 km2) in northeastern North Carolina. A total of 956 scats were collected in the spring of 2000 and 2001 and global positioning system (GPS) coordinates were recorded. Seventy-five percent of the scats were assigned to species and five coyote/hybrid scats were detected. Placement of scat location coordinates on a map of the experimental population area revealed that four of the coyote/hybrid scats were detected within the home ranges of sterilized hybrids. The other coyote/hybrid scat indicated the presence of a previously unknown individual. We suggest this method be expanded to include more of the experimental population area and be optimized for use with nuclear markers to improve detection of hybrid and back-crossed individuals. [source]

Spectrum and inheritance of resistance to the root-knot nematode Meloidogyne hapla in Rosa multiflora and R. indica

PLANT BREEDING, Issue 1 2004
X. Wang
Abstract The spectrum and inheritance of resistance to the root-knot nematode Meloidogyne hapla was studied in the diploid species Rosa multiflora and R. indica. The host suitability of seven rose rootstocks, namely five R. multiflora (K2, K1, Floradale, CE63 and CE65) and two R. indica (CE35 and Maroc) clonal accessions, was evaluated using four geographic isolates of M. hapla. Plants grown under greenhouse conditions were tested at high and durable inoculum pressure of nematodes and rated for nematode infestation five months after inoculation on a 0,5 gall index. Different host suitabilities to M. hapla were demonstrated depending on the nematode isolates: in R. multiflora, the clone K2 had a resistant (R) response to all isolates; the clone K1 ranged from intermediate (I) (isolate ,Canada') to resistant (other isolates), Floradale was shown to be intermediate, whereas CE63 and CE65 were moderate to good hosts (H). In R. indica, both rootstocks were good to excellent hosts for the isolate Canada but resistant to all three other isolates, thus expressing an isolate-specific resistance. A study on the genetics of resistance in R. multiflora to the M. hapla isolate Canada was then conducted using an incomplete diallel cross involving all previous clones except Floradale. A total of 120 hybrid individuals belonging to several progenies representing the cross combinations R × I, R × H, I × H and H × H were evaluated. Individuals of each progeny generally ranged into a monomodal distribution that suggests polygenic inheritance of resistance. In the family Rosaceae, the differences in the resistance genetics to the meiotic species M. hapla and to the mitotic species, M. arenaria, M. incognita and M. javanica are discussed in relation to the reproductive status of the nematodes. [source]

Is the endangered Grevy's zebra threatened by hybridization?

ANIMAL CONSERVATION, Issue 6 2009
J. E. Cordingley
Abstract Hybridization between an abundant species and an endangered species is cause for concern. When such hybridization is observed, it is both urgent and necessary to assess the level of threat posed to the endangered species. We report the first evidence of natural hybridization between two equids: the endangered Grevy's zebra Equus grevyi and the abundant plains zebra Equus burchelli. Grevy's zebra now number <3000 individuals globally, and occur only in northern Kenya and Ethiopia. In recent years, Grevy's zebra have become increasingly concentrated in the south of their range due to habitat loss in the north. Both species are sympatric in the Laikipia ecosystem of northern Kenya, where we have observed purportedly hybrid individuals. Using mitochondrial and Y chromosome DNA, we confirmed the hybrid status of the morphologically identified hybrids and demonstrate conclusively that all first-generation hybrids are the offspring of plains zebra females and Grevy's zebra males. Behaviorally, hybrids integrate themselves into plains zebra society, rather than adopting the social organization of Grevy's zebra. Two hybrids have successfully raised foals to over 3 months in age, including one which has reached adulthood, indicating the fertility of female hybrids and viability of their offspring. We hypothesize that hybridization occurs due to (1) skewed sex ratios, in favor of males, within Grevy's zebra and (2) the numerical dominance of plains zebra in the region where hybridization is occurring. Stakeholders have discussed hybridization as a potential threat to Grevy's zebra survival. We argue, however, based on behavioral observations, that hybridization is unlikely to dilute the Grevy's zebra gene pool in the short term. As a conservation concern, hybridization is secondary to more direct causes of Grevy's zebra declines. [source]