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1.
Extensive habitat modifications within the Mississippi and Missouri rivers have presumably interfered with the reproductive isolating mechanisms between the endangered pallid sturgeon, Scaphirhynchus albus, and the sympatric shovelnose sturgeon, Scaphirhynchus platorynchus, causing hybridization between these two species. Several character indices were developed to assist fisheries biologists in identifying specimens of S. albus, S. platorynchus, and their putative hybrids. The indices have numerous assumptions, including that pure strains of both parental species are within the sample analyzed and that hybrids are morphologically intermediate relative to their parents. If these indices have produced inaccurate identifications, then previous work on Scaphirhynchus studies in the Mississippi and Missouri rivers are questionable, including status surveys, captive propagation efforts, or the harvesting of tissues for genetic studies. In this study we tested indices by examining progeny of ‘known’ pallid, shovelnose, and hybrid sturgeon propagated, raised, and preserved at hatcheries. These 60 specimens [78–600 mm standard length (SL)] were propagated with breeding stock from the upper Missouri River drainage, where hybridization between these two species presumably does not occur. Existing indices did not correctly identify small (<250 mm SL) or a combination of small and large (>250 mm SL) sizes of S. albus, S. platorynchus, and their hybrids. Indices worked fairly well in identifying large S. platorynchus, but not in differentiating large S. albus from hybrids. We used principal components analysis (PCA) as an alternative approach to character indices. No a priori knowledge of the identity of the specimen is required with this multivariate technique, which avoids potential circular reasoning present in indices. We were able to completely or almost completely separate both sturgeon species and their hybrids by extracting principal components from a correlation matrix of 13 meristic characters in a standard PCA and extracting size‐corrected principal components from a covariance matrix of 51 morphometric variables using a sheared PCA. Additionally, we demonstrated that first generation hybrids were intermediate with respect to their parental species. Multivariate analyses with a reduced character set of six meristic and 12 morphometric variables also led to accurate and reliable specimen identification. Head spines and numerous qualitative characters are also extremely useful in differentiating between Scaphirhynchus species and their hybrids. In addition to all morphometric characters, some meristic characters and the degree of head spine fusion vary significantly with SL of sturgeons. Recording appropriate data from released specimens, including photovouchers, and making this information available is essential for researchers to have any scientific or legal basis for genetic or any other studies involving these sturgeons. 相似文献
2.
Comparative analysis of several morphological characters is conducted in experimentally obtained hybrids between Siberian
sturgeon Acipenser baerii and beluga A. huso, in parental species, and in gynogenetic progeny of Siberian sturgeon. The gynogenetic individuals are similar to Siberian
sturgeon by all characters used for differentiation between Siberian sturgeon and beluga that supports gynogenetic origin
of these individuals. Based on the data obtained on the hybrid specimens, the features of inheritance of the studied characters
in sturgeons and their variation in postlarval ontogeny are discussed. 相似文献
3.
Hybridization and introgression are thought to be important for speciation and adaptation in many plants. However, little is known about the hybridization and introgression among Cypripedium species. To investigate the evidence for hybridization and the pattern of introgression between Cypripedium yunnanense and C. tibeticum in Shangrila County, Yunnan Province, China, morphological characters and amplified fragment length polymorphism (AFLP) data for both the species and their putative hybrids were studied. Hand pollination was also performed to verify the crossability of the putative parents. Principal coordinate analysis based on morphological characters and the AFLP data suggested that the putative hybrids were true hybrids of these two Cypripedium species. Analysis with the NewHybrids software indicated that the putative hybrids were F1 generation individuals and backcrosses to C. yunnanese, but no F2 generation was found. Analysis with the Structure software demonstrated asymmetric introgression from C. tibeticum to C. yunnanense. We conclude that natural hybridization and introgression can occur between these two species and that in situ conservation of the parental species is required before fully assessing the evolutionary potential of hybrids. 相似文献
4.
B. Lennart Johnson 《American journal of botany》1960,47(9):736-742
Johnson , B. Lennart . (U. California, Los Angeles.) Natural hybrids between Oryzopsis and Stipa. I. Oryzopsis hymenoides × S. speciosa. Amer. Jour. Bot. 47(9): 736–742. Illus. 1960.—Spontaneous, sterile hybrids between Oryzopsis hymenoides and Stipa speciosa heretofore have been referred to O. bloomeri, which species in an earlier paper was shown to consist of a series of hybrids between O. hymenoides and various species of Stipa. On many morphological characters (O. hymenoides × speciosa) is intermediate between its parents and similar to the other hybrids formerly classed as O. bloomeri. It is distinct from the other hybrids on characters which reflect S. speciosa, except with respect to indument of the awn which is recessive. Somatic chromosome counts are: O. enoides, 48; S. speciosa, 64; hybrid, 56. Both parents exhibit regular bivalents at meiosis. The hybrid shows only occasional bivalents and mostly asynchronous splitting or random distribution of univalents at metaphase I. Pollen abortion is complete. No evidence of natural amphiploidy or introgression was found. 相似文献
5.
Robb F. Leary Fred W. Allendorf Kathy L. Knudsen 《Evolution; international journal of organic evolution》1985,39(6):1318-1326
Interspecific hybrids have been proposed to have reduced developmental stability in comparison to their parental species because the parental genomes have not undergone selection for the maintenance of developmental stability when they occur together. We present data from four interspecific hybrids of salmonid fishes that support this view. Natural hybrids of bull trout (Salvelinus confluentus) with brook trout (Salvelinus fontinalis) and laboratory hybrids of rainbow trout (Salmo gairdneri) with Yellowstone (Salmo clarki bouvieri), westslope (S. c. lewisi), and coastal (S. c. clarki) cutthroat trout all have higher levels of fluctuating asymmetry than either of their parental species raised in the same environment. Thus, the hybrids have reduced developmental stability. The hybrids do not have meristic counts intermediate to the counts of the parental species. The hybrids usually have counts as high as the species with the higher count for those characters that differ between the parental species and often have higher counts for those characters that do not differ between the parental species. We suggest that the tendency for interspecific hybrids to have high meristic counts may be related to differences between the species in the length and timing of the developmental periods during which the counts of the characters are determined. 相似文献
6.
Previous studies have shown widespread conservation of gene expression levels between species of the Drosophila melanogaster subgroup as well as a positive correlation between coding sequence divergence and expression level divergence between species.
Meanwhile, large-scale misregulation of gene expression level has been described in interspecific sterile hybrids between
D. melanogaster, D. simulans, D. mauritiana, and D. sechellia. Using data from gene expression analysis involving D. simulans, D. melanogaster, and their hybrids, we observed a significant positive correlation between protein sequence divergence and gene expression
differences between hybrids and their parental species. Furthermore, we demonstrate that underexpressed misregulated genes in hybrids are evolving more rapidly at the protein sequence
level than nonmisregulated genes or overexpressed misregulated genes, highlighting the possible effects of sexual and natural
selection as male-biased genes and nonessential genes are the principal gene categories affected by interspecific hybrid misregulation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Carlo G. Artieri and Wilfried Haerty contributed equally to this publication. 相似文献
7.
The intraspecific relationship of selected wood anatomical characters with stem diameter, plant height, and altitude was investigated
in four NepaleseRhododendron species:R. anthopogon, R. lepidotum, R. campanulatum, andR. arboreum, i.e., two shrubs, one subtree, and one tree. We studied 23 to 27 specimens for each species.R. anthopogon grew from 3,380 to 4,950 m,R. lepidotum from 2,060 to 4,720 m,R. campanulatum from 2,790 to 4,140 m, andR. arboreum from 1,430 to 3,460 m. Multiple regression analysis and actual distribution of character values show that the wood anatomical
characters having a significant correlation with non-anatomical factors differ between species. The number of significant
characters are two inR. anthopogon andR. campanulatum, five inR. lepidotum, and nine inR. arboreum and tends to be small in species having smaller altitudinal ranges. Average pore area, most strongly correlated with non-anatomical
factors in interspecific variation, is significantly correlated only inR. lepidotum andR. arboreum. The general trends in intraspecific variation among four NepaleseRhododendron species differ from the trends found in interspecific variation within the genus and are characteristic of each species. 相似文献
8.
Some quantitative characters of three-summer old reciprocal hybrids of beluga Acipenser huso and starred sturgeon A. stellatus,as well as of juveniles of their parental species, are comparatively analyzed. The found maternal and paternal effects in
manifestation of some characteristics in hybrids are considered in connection with elucidation of inheritance type of morphological
characters in acipenserids. The paternal effect observed by some characters in hybrids beluga × starred sturgeon is explained
by prevalence of dominant alleles in the genome of starred sturgeon in comparison with beluga. The maternal effect is elucidated
by a few characteristics related to parameters of the head, first of all to the volume of the brain region of skull. Evidently,
in this case, the matrocliny depends on the fact that information on the number of segments of embryo and their position is
determined by the maternal organism during oogenesis. 相似文献
9.
Joseph S. Nelson 《Journal of morphology》1973,139(2):227-237
Marked external and osteological differences exist between the related cyprinids Couesius plumbeus and Rhinichthys cataractae. C. plumbeus differs from R. cataractae in several external features, such as eye size and mouth shape, any one of which permits identification of individuals. C. plumbeus has postcleithral and nasal bones while R. cataractae does not. Many differences in bone shape also exist. Natural hybrids between the two species from Upper and Lower Kananaskis reservoirs, southwestern Alberta, are intermediate in the average of their external and osteological characters. Some characters in the hybrids, however, are so variable that they fall within the range of both parental species. An individual hybrid may resemble one parental species in one diagnostic character and the other parental species in another. The largest individuals known of the three forms from the Kananaskis system are hybrids. 相似文献
10.
Interspecific somatic hybrids between a dihaploid potato clone H-8105 susceptible to Phytophthora infestans (Mont.) de Bary and a resistant diploid tuberizing species Solanum bulbocastanum were generated and analysed. Only ten regenerants displaying the intermediate morphology with dominating characteristics
of the wild parent (simple leaves, anthocyanin pigmentation) were produced in 15 weeks after a single PEG-mediated fusion
event. The RAPD patterns confirmed the hybridity of all of them. The hybrids rooted poorly and grew slowly in vitro. The cytological analysis revealed a high degree of aneuploidy in the hybrids with morphological and growth anomalies in vitro, while the morphologically normal hybrids were tetraploids. All the S. bulbocastanum (+) H-8105 hybrids were unstable in culture and three of them were consequently lost during three years of propagation in vitro. The possible reasons for instability of somatic hybrids between the distantly related species are discussed. 相似文献
11.
An experimental crossing program was carried out in order to test the hypothesis thatArmeria villosa subsp.carratracensis, a serpentine endemic from Southern Spain, is of hybrid origin. Fruit-set and mainly pollen stainability data in artificial hybrids demonstrate that internal interspecific barriers are weak. Two generations of backcrossing with the two putative parents —A. colorata andA. villosa subsp.longiaristata— can restore pollen stainability to an average of 83.2 and 68.7, respectively. A morphometric analysis of 148 specimens belonging to parental species, different artificial hybrid generations and wild putative hybrid race shows that (1) morphological characters have a strong genetic basis and thus are good markers in identifying hybrids and introgression inArmeria; (2) artificial backcrossing produces in morphometrical characters a variation which conforms in both trend and magnitude to what is commonly attributed in the wild to introgression; (3) the position of the putative hybrid race is intermediate between the two parental species used in the program. These results are in accordance with the hypothesis of hybrid origin ofA. villosa subsp.carratracensis.
Natural and experimental hybridization inArmeria, I 相似文献
12.
Yong-Hong Zhou Chi Yen Jun-Liang Yang You-Liang Zheng 《Plant Systematics and Evolution》1999,217(3-4):215-220
Morphological and cytological studies of three tetraploidRoegneria species,R. tenuispica, R. pendulina andR. ciliaris, and their artificial hybrids were carried out.Roegneria tenuispica was morphologically similar toR. pendulina. The general appearance of the interspecific hybrids was intermediate between the parents. The hybrids showed comparatively high chromosome pairing at meiosis, but were completely or almost completely sterile. The results indicate that the three independent species share two basic genomes (StY) and thatR. tenuispica is more closely related toR. pendulina than toR. ciliaris. The genomes ofR. tenuispica could be designated as S
t
t
Yt. 相似文献
13.
Native Rhododendrons section Brachycaryx in eastern Japan are decreasing in their natural habitats and the need to restore these habitats is increasing. Conservation of genetic diversity in restoring habitat requires clarification of the balance of interspecies genetic exchange which occurs in their natural habitats. In well-preserved natural habitats of Rhododendron dilatatum, R. kiyosumense, and R. wadanum and their natural hybrids R.×kuratanum and R.×hasegawai we investigated their geographical distribution, frequency, and flowering period. DNA analysis of the internal transcribed spacer (ITS) region was also conducted to confirm the species related to hybridization. Our findings in the field survey were: (1) Hybridizations occur in the overlap zones of related species. (2) R.×hasegawai occurs more frequently than R.×kuratanum, probably because the flowering seasons of R. kiyosumense and R. wadanum overlap longer than those of R. dilatatum and R. kiyosumense. (3) Natural hybrid occurrence is, nevertheless, under 9% of all related Rhododendrons section Brachycalyx. Analysis of the ITS region suggested that the two hybrids are generated from interspecific gene exchange, i.e., (4) R. dilatatum and R. kiyosumense relate to the formation of R.×kuratanum. (5) R.×hasegawai is a hybrid of R. wadanum and some species other than R. wadanum. On the basis of these findings we delineated several guidelines for restoring habitats of Rhododendrons of Section Brachycaryx with concerns for genetic diversity: (1) Before use, identify plant materials by morphological traits to determine whether they are original species or hybrids. (2) Investigate the distribution of remnant Rhododendrons section Brachycaryx before restoration. (3) Combine plant materials of original species in the natural distribution. 相似文献
14.
Michael Stech Manuela Sim-Sim M. Glória Esquível Leena luís Susana Fontinha Carlos Lobo 《分类学与生物多样性》2013,11(2):257-268
Relationships of the eight species of the liverwort genus Radula occurring in Portugal (mainland, the Madeira and Azores archipelagos), including the Macaronesian endemics R. jonesii and R. wichurae, were evaluated based on molecular, phytochemical and morphological–anatomical data. Maximum parsimony and Bayesian analyses were performed with sequences from three plastid DNA markers (trnS GGA-rps4 spacer, rps4 gene, trnL UAA intron), volatile oil compounds, as well as qualitative morphological–anatomical characters. In addition, the molecular data were subjected to maximum likelihood analysis. The eight taxa, R. aquilegia, R. carringtonii, R. complanata, R. holtii, R. jonesii, R. lindenbergiana, R. nudicaulis and R. wichurae, can be clearly distinguished from each other, either by molecular data alone or by combination of characters from all three data sets. Radula aquilegia is monophyletic according to the molecular data, but shows considerable, yet undescribed intraspecific morphological and phytochemical variability. Recognition of R. complanata and R. lindenbergiana as separate species, previously based solely on the paroecious vs. dioecious sexual condition, is moderately supported by the molecular phylogenetic analyses and strongly supported by the phytochemical data. The Radula species, narrowly distributed in Macaronesia and Atlantic Europe, probably have two different origins. For Radula holtii and R. nudicaulis, connections with Radula species from the Neotropics are indicated. The other species, among them the two Macaronesian endemics, are closely related with the R. complanata/R. lindenbergiana complex, which is widely distributed in the northern hemisphere. 相似文献
15.
Zhi‐Yuan DU Chun‐Feng YANG Jin‐Ming CHEN You‐Hao GUO Akeem Babalola KADIRI 《植物分类学报:英文版》2010,48(4):265-270
Abstract It is well known that interspecific hybrids occur in the genus Potamogeton. The linear‐leaved Potamogeton species commonly have highly variable morphological characteristics. Their hybrids often show similar vegetative characters to their parental species and their identification based solely on morphology is not always conclusive. In order to clarify whether there are any hybrids from the linear‐leaved Potamogeton plants collected in China, we used internal transcribed spacers (ITS) of nuclear ribosomal DNA and chloroplast rbcL gene sequences to identify the hybrids. Using ITS sequence additivity, we identified four hybrids, namely P. orientalis (P. pusillus×P. oxyphyllus), P. pusillus×P. berchtoldii, P. foliosus×P. octandrus, and P. cristatus×P. octandrus. The latter three hybrids should be considered as new hybrids in Potamogeton. The maternal parents of the four hybrids were confirmed using chloroplast rbcL gene sequences. 相似文献
16.
E. D. Vasil’eva V. P. Vasil’ev E. N. Ponomareva Yu. A. Lapukhin 《Journal of Ichthyology》2010,50(8):605-617
Results are described of experimental crossing for obtaining of triple hybrids of the Russian sturgeon Acipenser gueldenstaedtii, the great sturgeon A. huso, and the starred sturgeon A. stellatus and of comparative analysis of some quantitative morphological characters in these hybrids, in the progeny of parental species
and of reciprocal hybrids of starred sturgeon and great sturgeon. By most investigated characters, in triple hybrids, the
states of the paternal species (Russian sturgeon) are inherited, by some other characters-of great sturgeon-the state of starred
sturgeon is not inherited. Therefore, on the basis of external appearance, they may be identified as the hybrid of Russian
sturgeon with great sturgeon. The observed segregation by the form of gill rakers into paternal, maternal, or intermediate
variants leads to a conclusion of nonmonogenous inheritance of a wide form and a conical form of gill rakers in sturgeons.
On the whole, the obtained results clearly demonstrate how, due to effects of matrocliny and partocliny, and different combination
of dominant and recessive alleles of the genes determining the diagnostic characters, the hybrid individuals may acquire a
different extent of similarity and differences from the parental species. The investigated triple hybrids are an interesting
example of mutual leveling of divergent traits in the course of combination of different genomes within limits of one closely
related Atlantic group of sturgeons. As a result, a certain averaged habitus is formed which might take place also in case
of formation of polyploidy species in the process of evolution. 相似文献
17.
To investigate the potential for natural interspecific hybridization in theRhagoletis pomonella group of sibling fruit fly species, an attempt was made to hybridizeR. pomonella, the apple maggot fly, withR. cornivora, a non-pest feeding on dogwoods. Laboratory hybridization was difficult, with only five F1 hybrids produced. Electrophoretic analysis of the hybrids confirmed their hybrid origin. Allele frequency data for three
diagnostic loci in up to 5,596 individuals of the parental species, gathered from published and unpublished studies, indicate
that the two sibling species hybridize in nature very infrequently, if at all. 相似文献
18.
Štepánka Dlouhá Anne Thielsch Robert H. S. Kraus Jaromír Seda Klaus Schwenk Adam Petrusek 《Hydrobiologia》2010,643(1):107-122
Daphnia galeata Sars, D. longispina O. F. Müller and D. cucullata Sars (Crustacea: Cladocera) are closely related species which often produce interspecific hybrids in natural populations.
Several marker systems are available for taxon determination in this hybridizing complex, but their performance and reliability
has not been systematically assessed. We compared results from identifications by three molecular methods. More than 1,200
individuals from 10 localities in the Czech Republic were identified as parental species or hybrids by allozyme electrophoresis
and the analysis of the restriction fragment length polymorphism of the internal transcribed spacer (ITS-RFLP); over 440 of
them were additionally analyzed and identified by 12 microsatellite loci. Identification by microsatellite markers corresponded
well with allozyme analyses. However, consistent discrepancies between ITS-RFLP and other markers were observed in two out
of 10 studied localities. Although some marker discrepancies may have been caused by occasional recent introgression, consistent
deviations between ITS-RFLP and other markers suggest a long-term maintenance of introgressed alleles. These results warn
against its use as a sole identification method in field studies. Additionally, we quantitatively evaluated the discriminatory
power of geometric morphometric (elliptic Fourier) analysis of body shapes based on photos of over 1,300 individuals pre-classified
by allozyme markers. Furthermore, a randomly selected subset of 240 individuals was independently determined from photos by
several experts. Despite a tendency for morphological divergence among parental Daphnia species, some taxa (especially D. galeata, D. longispina, and their hybrids) substantially overlapped in their body shapes. This was reflected in different determination success
for particular species and hybrids in discriminant analysis based on shape data as well as from photographs. 相似文献
19.
《Plant Ecology & Diversity》2013,6(4):465-474
Background: Hybridisation between locally common and rare plant species is of conservation concern as it may lead to the extinction of the rare taxon. Rumex aquaticus (2n = ca. 200, Polygonaceae) is a widespread Euro-Siberian species but rare in the British Isles. It hybridises freely with the locally abundant congener R. obtusifolius (2n = 40) producing fertile and viable hybrids.Aims: We aimed to establish whether hybridisation poses an extinction threat to R. aquaticus in Britain.Methods: Flow cytometry, AFLPs and morphological characters were used to assess the extent of hybridisation between R. obtusifolius and R. aquaticus.Results: Flow cytometry was the most useful tool to distinguish between hybrids and parental species and indicated that out of 88 samples from two hybrid populations, 85% were likely to be F1s and only 15% were likely to be back-crosses to R. aquaticus. AFLP markers were only able to identify putative F1 hybrids reliably and 11 morphological traits could not distinguish unambiguously between hybrids and pure R. aquaticus.Conclusions: Although our data suggest that genetic assimilation of pure R. aquaticus populations is unlikely to be the case in the future, there is a potential threat from demographic swamping by hybrids and targeted protection of R. aquaticus habitat is proposed as a management strategy. 相似文献
20.
When hybrids are not hybrids: a case study of a putative hybrid zone between Cattleya coccinea and C. brevipedunculata (Orchidaceae)
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Bárbara S. S. Leal Cleber J. N. Chaves Samantha Koehler Eduardo L. Borba 《Botanical journal of the Linnean Society. Linnean Society of London》2016,181(4):621-639
Cattleya coccinea and C. brevipedunculata (Orchidaceae) are closely related species distinguished primarily by geographical distribution, vegetative morphology and flowering period. Both species inhabit high‐elevation regions in south‐eastern Brazil, but are traditionally associated with different habitats, located in cloudy forests and campos rupestres (rocky fields), respectively. We used morphometrics and genetic variation of microsatellite markers to test the occurrence of a hybrid zone between these species located in Parque Estadual do Ibitipoca (PEI), Brazil. Morphological data reveal a continuum of variation between the putative taxa, influenced mainly by characters of leaf, pseudobulb and peduncle. However, genetic data do not support the occurrence of hybridization and introgression in PEI, showing that it is a pure population of C. brevipedunculata. Differences in vegetative characters among individuals from cloudy forests and campos rupestres suggest that morphological variation may be related to phenotypic plasticity in response to environmental light fluctuations, an unknown situation for this species. These results highlight the inconsistency of morphology for the identification of hybrids and the role of vegetative characters as a possible complicating factor for the taxonomy of these species, as they are subject to environmental influence. 相似文献