Abstract
SUMMARY In order to investigate the hypothesis that disruptive selection is acting on Poa annua L. populations within a mosaic environment of bowling greens and flower beds, two experimental approaches were employed. (1) Studies of samples of seedlings, raised from the seed present in soil and surface debris from the two bowling greens and one flower bed, established that in each site the seed population was more variable than the adult. This result is compatible with the notion of disruptive selection. (2) An experiment was set up to examine the response of the two growth forms to clipping and to estimate the effectiveness of clipping as a selective force in the bowling green environment. In the control (unclipped treatment), the erect and prostrate variants differed both in total production and in their relative energy allocation to both vegetative and floral reproduction. These differences have been discussed in relation to r and K selection strategies. Differential response to clipping was observed; the groups in descending order of relative fitness consisted of prostrate individuals from the two bowling green populations > prostrate individuals from the flowerbed populations > erect individuals from flower bed populations. Clipping appears to have two effects on the erect forms resulting in: (1) a greater percentage decrease in total dry matter production in the erect compared with the prostrate forms, and (2) a greater percentage of the dry weight produced being removed by the cut in the erect forms compared with the prostrate forms. Coefficients of selection acting against erect plants under a regime of clipping ranged from 0.53 to 0.68. A selection coefficient of 0.77 was obtained for prostrate plants in the absence of clipping. In the light of the management of the lawns and flower beds, evidence for selection and gene flow is discussed.
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Claims 8
Claim · model-written summary
Seed populations were more variable than adults at each sampled site.
Poa annuaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in each site the seed population was more variable than the adult”
t0“Poa annua L.”
Claim · model-written summary
Unclipped erect and prostrate forms differed in total production.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the erect and prostrate variants differed both in total production and in their relative energy allocation to both vegetative and floral reproduction”
t0“Poa annua L.”
Claim · model-written summary
Unclipped erect and prostrate forms differed in allocation to vegetative and floral reproduction.
- Material
- erect and prostrate variantse0
- Outcome
- relative energy allocation to both vegetative and floral reproductione0
- Direction
- differede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the erect and prostrate variants differed both in total production and in their relative energy allocation to both vegetative and floral reproduction”
t0“Poa annua L.”
Claim · model-written summary
Under clipping, relative fitness ranked bowling-green prostrate above flowerbed prostrate above flowerbed erect forms.
- Material
- prostrate individualse0
- Outcome
- relative fitnesse0
- Direction
- descending ordere0
- Setting
- bowling green populationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“groups in descending order of relative fitness consisted of prostrate individuals from the two bowling green populations > prostrate individuals from the flowerbed populations > erect individuals from flower bed populations”
t0“Poa annua L.”
Claim · model-written summary
Clipping reduced dry matter production more in erect than prostrate forms.
- Material
- erecte0
- Treatment
- Clippinge0
- Outcome
- total dry matter productione0
- Direction
- decreasee0
- Comparator
- prostrate formse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Clipping appears to have two effects on the erect forms resulting in: (1) a greater percentage decrease in total dry matter production in the erect compared with the prostrate forms”
t0“Poa annua L.”
Claim · model-written summary
Clipping removed a greater share of produced dry weight in erect than prostrate forms.
- Material
- erecte0
- Treatment
- clippinge1
- Outcome
- dry weight produced being removed by the cute0
- Direction
- greatere0
- Comparator
- prostrate formse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a greater percentage of the dry weight produced being removed by the cut in the erect forms compared with the prostrate forms”
t0“Poa annua L.”
e1“Clipping appears to have two effects on the erect forms resulting in: (1) a greater percentage decrease in total dry matter production in the erect compared with the prostrate forms”
Claim · model-written summary
Selection coefficients against erect plants under clipping ranged from 0.53 to 0.68.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Coefficients of selection acting against erect plants under a regime of clipping ranged from 0.53 to 0.68”
t0“Poa annua L.”
Claim · model-written summary
The selection coefficient for unclipped prostrate plants was 0.77.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A selection coefficient of 0.77 was obtained for prostrate plants in the absence of clipping”
t0“Poa annua L.”