scholarly journals Analysis of suspected hybrid swarms in the genus Eucalyptus

Heredity ◽  
1954 ◽  
Vol 8 (2) ◽  
pp. 259-269 ◽  
Author(s):  
H T Clifford
Keyword(s):  
Hybrid Swarms ◽  
Genus Eucalyptus

Higher-level relationships among the eucalypts are resolved by ITS-sequence data

2002 ◽  
Vol 15 (1) ◽  
pp. 49 ◽  
Author(s):  
Dorothy A. Steane ◽  
Dean Nicolle ◽  
Gay E. McKinnon ◽  
René E. Vaillancourt ◽  
Brad M. Potts
Keyword(s):  
Internal Transcribed Spacer ◽  
Sequence Data ◽  
Its Region ◽  
Molecular Data ◽  
Nuclear Ribosomal Dna ◽  
Its Sequence ◽  
Phylogenetic Groups ◽  
Single Section ◽  
Western Australian ◽  
Genus Eucalyptus

This expanded survey of ITS sequences represents the largest analysis of molecular data ever attempted on Eucalyptus. Sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA were included in an analysis of 90 species of Eucalyptus s.s. and 28 species representing eight other genera (Allosyncarpia, Angophora, Arillastrum, Corymbia, Eucalyptopsis, Stockwellia, Lophostemon and Metrosideros). The results of the study indicate that Angophora and Corymbia form a well-supported clade that is highly differentiated from Eucalyptus s.s. Corymbia species are divided between two clades, one of which may be the sister to Angophora. Allosyncarpia, Arillastrum, Eucalyptopsis and ‘Stockwellia’ are also highly differentiated from Eucalyptus s.s. If the genus Eucalyptus is to be expanded to include Angophora and Corymbia(sensu Brooker 2000), ITS data suggest that Allosyncarpia, Eucalyptopsis, ‘Stockwellia’ and potentially Arillastrum should also be included in Eucalyptus s.l. The ITS data suggest that subg. Symphyomyrtus is paraphyletic and that subg. Minutifructus should be included within it. Within subg.Symphyomyrtus, only sect. Maidenaria appears to be monophyletic. Sections Adnataria and Dumaria are probably monophyletic; sections Exsertaria and Latoangulatae are very close and probably should be combined in a single section. Section Bisectae is polyphyletic and is divided into two distinct lineages. The phylogenetic groups depicted by ITS data are consistent with the frequency of natural inter-specific hybridisations as well as data from controlled crosses within subgenus Symphyomyrtus. The ITS data illustrate that subg. Idiogenes and western Australian monocalypts are early evolutionary lines relative to E. diversifolia, E. rubiginosa (monotypic subg. Primitiva) and the eastern monocalypts and that subg. Primitiva should be sunk into subg. Eucalyptus. Subgenus Eudesmia may be monophyletic, grouping with subgenera Idiogenes and Eucalyptus. Further work is required to confirm the phylogenetic positions of the monotypic subgenera Alveolata, Cruciformes, Acerosae and Cuboidea.

Population Dynamics and Regeneration of a Hybrid Zone Between Eucalyptus risdonii Hook-F and E amygdalina Labill

1986 ◽  
Vol 34 (3) ◽  
pp. 305 ◽  
Author(s):  
BM Potts
Keyword(s):  
Hybrid Zone ◽  
Null Point ◽  
Asymmetric Distribution ◽  
Hybrid Swarm ◽  
Population Response ◽  
Pure Species ◽  
Seed Migration ◽  
Hybrid Swarms ◽  
Population Turnover ◽  
Phenotypic Fitness

Regeneration of a hybrid zone between E. amygdalina and E. risdonii and pure species stands following wildfire is reported, as well as the reproductive and vegetative fitness of parental and hybrid phenotypes. E. risdonii phenotypes dominated the seed rain and seedling cohort and there was clearly a marked fitness differential between E. amygdalina and E. risdonii at their boundary. When the F1 type hybrid is in competition with both parental types it is generally reproductively the least fit, although frequently vegetatively vigorous. Reduced fitness appears to extend to advanced generations as hybrid phenotypes tending.toward either species are, on average, less fit than the corresponding parental type. The pattern of phenotypic fitness suggests that the species' boundary is in disequilibrium and it is argued that E. risdonii is invading the range of E. amygdalina by both pollen and seed migration. There is an asymmetric distribution of F1 type hybrids across the boundary and the hybrid swarm examined is being invaded by E. risdonii genes. It is suggested that hybridization may be associated with natural disequilibrium and, where seed migration is limited, boundary movements may be preceded by a wave of hybridization due partly to pollen swamping of the least fit species. Hybrid swarms may develop but, at the boundary of large stands, are probably transitory. There is a marked inertia in the population response to the prevailing selective regime due to the extremely slow population turnover and limited dispersal potential. This is discussed in the broader context of non-equilibrium models where it is argued that dispersal may be the factor limiting population response to perturbation of a shallow environmental gradient. This is due to large geographical shifts in the position of the null point and would be accentuated in a patchy environment where migration as a front is prevented.

scholarly journals From Hybrid Swarms to Swarms of Hybrids

2014 ◽  
Vol 2 (8) ◽  
pp. 311-318 ◽  
Author(s):  
Thomas J. Stohlgren ◽  
Allen L. Szalanski ◽  
John Gaskin ◽  
Nicholas Young ◽  
Amanda West ◽  
...  
Keyword(s):  
Hybrid Swarms

Geographic Patterns of Interspecific Hybridization between Spotted Knapweed (Centaurea stoebe) and Diffuse Knapweed (C. diffusa)

2009 ◽  
Vol 2 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Amy C. Blair ◽  
Ruth A. Hufbauer
Keyword(s):  
North America ◽  
North American ◽  
Management Strategies ◽  
Spotted Knapweed ◽  
The North ◽  
Hybrid Swarms ◽  
Hybrid Plants ◽  
Introduced Range ◽  
Diffuse Knapweed ◽  
A Site

AbstractHybridization between species has the potential to change invasion dynamics. Field observations suggest that spotted knapweed and diffuse knapweed, two ecologically and economically destructive invasive plants, hybridize in their introduced range. As a first step towards understanding whether hybridization has affected the dynamics of the invasion of these species, we conducted field surveys in the introduced (North American) and native (European) ranges to discern patterns of hybridization and measured fitness-related traits among field hybrids and parental species. In North America we detected plants with hybrid morphology in 97% of the diffuse knapweed sites (n= 40); such hybrid plants were taller and more often exhibited polycarpy than plants with typical diffuse knapweed morphology. Hybrids were not detected in North American spotted knapweed sites (n= 22). In most regions surveyed in Europe, diffuse knapweed and spotted knapweed were isolated from each other and existed as distinct, nonhybridizing species. However, in Ukraine, the two species frequently coexisted within a site, resulting in hybrid swarms. On average, the plants from the North American diffuse knapweed sites (including plants with both diffuse and hybrid morphology), were larger than the apparently pure diffuse knapweed in the native range. The cross-continental patterns of hybridization likely are explained by differences in cytology. It recently has been confirmed that the spotted knapweed in North America is tetraploid whereas the diffuse knapweed is diploid. Genetic incompatibilities associated with these two cytotypes likely prevent ongoing hybridization. We hypothesize that hybrid individuals were introduced to North America along with diffuse knapweed. Because plants with hybrid morphology are found in nearly all North American diffuse knapweed sites, the introduction of hybrids likely occurred early in the invasion of diffuse knapweed. Thus, although the presence of hybrids might facilitate the ongoing invasion of diffuse knapweed into North America, elevated concern regarding their presence might not be warranted. Because such individuals are not likely to represent a new hybridization event, currently effective management strategies used in diffuse knapweed sites should not need alteration.

Host Range of Some Eucalypt Mycorrhizal Fungi

1973 ◽  
Vol 21 (1) ◽  
pp. 103 ◽  
Author(s):  
GA Chilvers
Keyword(s):  
Host Range ◽  
Host Species ◽  
Mycorrhizal Fungi ◽  
Wide Range ◽  
Genus Eucalyptus

Various fungi are shown to form mycorrhizas with a wide range of host species within the genus Eucalyptus. In general, the same fungi do not appear to be capable of forming mycorrhizas with Pinus.

The anatomy of bark. I. The genus Eucalyptus

1953 ◽  
Vol 1 (3) ◽  
pp. 402 ◽  
Author(s):  
MM Chattaway
Keyword(s):  
Detailed Structure ◽  
Microscopic Features ◽  
Genus Eucalyptus

The most characteristic microscopic features of the bark of over 150 species of Eucalyptus are described.The structure of the phloem and cortex of the eucalypt twig, the changes that occur with increasing diameter, and the differences between the deciduous and persistent barks are described and illustrated.The detailed structure of the fully developed bark and the development of features characteristic of some of the most distinctive bark types have been studied, especially in the following groups: Corymbosae and Corymbosaepeltatae, Trarwersae, Exsertae and Sub-exsertae, Globuhes, Viminules, Pachyphloiae, Frasinales, Longitudinales, Piperitales, Psathyroxyla, Buxeales, Siderophtoiae.

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