A cytogenetic study of five species of Machaeranthera and their Fb1s hybrids
Bibliographic record
Abstract
In the most recent taxonomic treatment by Hartman (1976), Machaeranthera was divided into subgenera and sections.Section Machaeranthera of the subgenus Machaeranthera contains two annual species with chromosome numbers of 2n = 8.M^. tanacetifolia (H.B.K.) Nees and M^.tagetina Greene.In one cross each between one species from Arizona and one from New Mexico, their artificial hybrids were only 3-12 fertile (Stucky, 1978).A similar degree of fertility (6.6%) has been found in hybrids between these two species (Jackson, 1962).In addition, both species have been crossed to M^. arida (2n = 10) of the section Arida, and the pollen fertility of M^. arida X M. tanacetifolia and M. arida X M. tagetina was 5.5 and 0.4%, respectively (Jackson, 1962).Crosses of {1.tanacetifolia to annual and perennial yellow-rayed species of the spinulosus group of Haplopappus gave F^ artificial hybrids with 0.083 to 0.628% pollen fertility (Jackson.pers.comm.).Machaeranthera tanacetifolia is a widely ranging species, occurring in disturbed habitats from Central Mexico to the Canadian border and through the high plains of the United States.M. tagetina, on the other hand, is more restricted and is found only in eastern Arizona, New Mexico, and most likely extends into suitable habitats of bordering northern Mexico.Other species used in this study are M^.parthenium Greene, 2n = 8, M. viscida (Woot.& Standl.)Hartman, 2n = 8, and M. aquifolia Greene, 2n = 8.M^. parthenium, with a restricted distribution in Arizona, was included as a synonym of M^. tanacetifolia (Hartman, 1976).il-viscida was considered to belong to the Haplopappus phyllocephalus complex (Waterfall, 1943), but was placed under H^.spinulosus by Hall (1928).Jackson (1966, 1969) included M. viscida in the section Ha^ vardii.Hartman (1976) using evidence of morphology and karyotype along with chemical data placed M^. viscida in the subgenus Sideranthus of Machaeranthera.M^. aquifolia, a short-lived perennial species, was included in the genus Machaeranthera (Wooton & Standley, 1915).Objectives of this study were to a) determine chromosomal relationships of annuals by examining hybrids between M^. tagetina, M^. tanacetifolia, M^. parthenium, and M^.viscida, b) examine cytogenetic relationships between annual species and a representative perennial species, M^. aguifolia, c) determine if M^. viscida belongs in the genus and if so, identify the appropriate phylogenetic position, d) determine the amount of cytologically visible chromosomal repatterning that may have occurred during the evolution of annual species from perennial species by examining annual X perennial hybrids.Machaeranthera tanacetifolia is a widely ranging species, occurring in disturbed habitats from Central Mexico to the Canadian border and through the high plains of the United States.M. tagetina, on the other hand, is more restricted and is found only in eastern Arizona, New Mexico, and most likely extends into suitable habitats of bordering northern Mexico.Other species used in this study are M.-parthenium Greene, 2n = 8, M. viscida (Woot.& Standl.)Hartman, 2n = 8, and M. aquifolia Greene, 2n = 8.M.. parthenium, with a restricted distribution in Arizona, was included as a synonym of M^. tanacetifolia (Hartman, 1976).M. viscida was considered to belong to the Haplopappus phyllocephalus complex (Waterfall, 1943), but was placed under H_.spinulosus by Hall (1928).Jackson (1966, 1969) included M. viscida in the section Ha^^ vardii.Hartman (1976) using evidence of morphology and karyotype along with chemical data placed M^. viscida in the subgenus Sideranthus of Machaeranthera.M. aquifolia, a short-lived perennial species, was included in the genus Machaeranthera (Wooton & Standley, 1915).Objectives of this study were to a) determine chromosomal relationships of annuals by examining hybrids between Ml. tagetina, M^. tanacetifolia, M^. parthenium, and M^.viscida, b) examine cytogenetic relationships between annual species and a representative perennial species, M^. aquifolia, c) determine if M^. viscida belongs in the genus and if so, identify the appropriate phylogenetic position, d) determine the amount of cytologically visible chromosomal repatterning that may have occurred during the evolution of annual species from perennial species by examining annual X perennial hybrids.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".