Abstract
A third 5-year survey made in 1962 of Carduus acanthoides, C. nutans, and their hybrids in Grey Co., Ontario, revealed that a great decrease in these populations had occurred. C. acanthoides and hybrids similar to this species had survived better than C. nutans but very little spread of either species seemed to have occurred in 1957–1962. In experimental plots the hybrid has been made and backcrossed to the parental species. The species differ in chromosome number (C. acanthoides, 2n = 22; C. nutans, 2n = 16) and hybrids have intermediate numbers. Evidence was found from field and experimental studies that the progeny of the F 1 hybrid included a greater proportion of seedlings with the higher chromosome numbers than with the lower and intermediate numbers. It is suggested that this selection may operate through the rejection of the longer chromosomes received from C. nutans, which, in certain zygotic combinations may constitute an excess of chromatin lethal to the zygote.
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Claims 8
Claim · model-written summary
Carduus populations greatly decreased during the five-year survey.
Verbatim
e0“a great decrease in these populations had occurred”
Claim · model-written summary
C. acanthoides and similar hybrids survived better than C. nutans.
- Taxon
- C. acanthoides
Carduus acanthoidese0 - Material
- hybrids similar to this speciese0
- Outcome
- survivede0
- Direction
- bettere0
- Comparator
- C. nutanse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. acanthoides and hybrids similar to this species had survived better than C. nutans”
Claim · model-written summary
Neither parental Carduus species spread much in 1957–1962.
Verbatim
e0“very little spread of either species seemed to have occurred in 1957–1962”
Claim · model-written summary
C. acanthoides had 2n = 22 chromosomes.
- Taxon
- C. acanthoidesCarduus acanthoidese0
- Outcome
- chromosome numbere0
- Value
- 2n = 22e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The species differ in chromosome number (C. acanthoides, 2n = 22”
Claim · model-written summary
C. nutans had 2n = 16 chromosomes.
- Taxon
- C. nutans
Carduus nutanse0 - Outcome
- chromosome numbere0
- Value
- 2n = 16e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The species differ in chromosome number (C. acanthoides, 2n = 22; C. nutans, 2n = 16”
Claim · model-written summary
Carduus hybrids had intermediate chromosome numbers.
Verbatim
e0“hybrids have intermediate numbers”
Claim · model-written summary
F1 hybrid progeny included more seedlings with higher chromosome numbers than lower or intermediate numbers.
Verbatim
e0“the progeny of the F 1 hybrid included a greater proportion of seedlings with the higher chromosome numbers than with the lower and intermediate numbers”
Claim · model-written summary
The authors suggest that rejection of long C. nutans chromosomes may mediate selection through lethal excess chromatin in some zygotes.
- Taxon
- C. nutansCarduus nutanse0
- Organ / stage
- zygotee0
- Outcome
- selectione0
- Qualifier
- rejection of the longer chromosomese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this selection may operate through the rejection of the longer chromosomes received from C. nutans, which, in certain zygotic combinations may constitute an excess of chromatin lethal to the zygote”