Ecotypic divergence in Crepis tectorum (Asteraceae): inferring trait lability and correlational constraints from hormonally manipulated phenotypes

2019 ◽  
Vol 37 (3) ◽  
Author(s):  
Stefan Andersson
Keyword(s):  
Crepis Tectorum

Phenotypic selection in a population of Crepis tectorum ssp. pumila (Asteraceae)

1992 ◽  
Vol 70 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Stefan Andersson
Keyword(s):  
Life History ◽  
Multiple Regression ◽  
Large Scale ◽  
Demographic Data ◽  
Phenotypic Selection ◽  
Direct Selection ◽  
Surprising Result ◽  
Regression Analyses ◽  
Ecotypic Differentiation ◽  
Crepis Tectorum

A 3-year demographic study was conducted to reveal targets of selection on morphology and life history in a population of Crepis tectorum ssp. pumila, a winter annual plant confined to calcareous grasslands (alvars) on the Baltic island of Öland (south Sweden). I calculated the selection differential to describe the change in the mean value of a character due to selection and used multiple regression analyses to partition the direct effect of selection on the trait from indirect responses of selection on other traits. Rosette leaf number, a convenient measure of plant size, was strongly correlated with both viability and fertility (fitness). There was also a strong relationship between fitness and the extent to which the plants expressed traits characterizing this particular taxon. Multiple regression analyses indicated direct selection favouring plants with deeply lobed leaves and a densely branched stem, two distinctive traits of ssp. pumila believed to be adaptive in the alvar habitat. Only stem height was subject to both direct and indirect selection in the wrong direction; taller individuals were more successful than those with a shorter stem, a surprising result considering the inferred advantage of a short stature in the exposed alvar habitat. Selection on other traits assumed to be ecologically important (germination time, flowering time, and seed size) was found to be either absent or variable in direction when other traits were held constant. The failure of plants to survive to the flowering stage in the last two summers indicates strong selection for plants that produce a high percentage of dormant seeds. Overall, the contemporary selection regime as revealed by demographic data was only partly congruent with predictions regarding historical selection pressures based on large-scale patterns of variation (ecotypic differentiation). Key words: Crepis tectorum, ecotypic differentiation, life history, morphology, phenotypic selection.

Seed size as a determinant of germination rate in Crepis tectorum (Asteraceae): evidence from a seed burial experiment

1996 ◽  
Vol 74 (4) ◽  
pp. 568-572 ◽  
Author(s):  
Stefan Andersson
Keyword(s):  
Seed Size ◽  
Germination Rate ◽  
Local Population ◽  
Seed Viability ◽  
Seed Burial ◽  
Small Seed ◽  
Crepis Tectorum ◽  
Winter Annual ◽  
Selection For ◽  
The Relationship

The present study of the winter annual Crepis tectorum examines the relationship between seed (achene) size and the extent to which seeds resist germination during the year of their production. I carried out two seed burial experiments, one at an outcrop site occupied by a small-seeded population, and another in an experimental garden with soil from the same field site, with seeds representing the local population and a segregating generation of a cross between two other populations. Using logistic regression with data corrected for seed viability, I found an association between small seed size and failure to germinate in the first autumn. The small seed size characterizing many outcrop populations may have evolved as a response to selection for delaying germination in a habitat subject to unpredictable droughts during the growth season. Keywords: Crepis tectorum, germination, seed bank, seed size.

Two new naturalized species from Korea, Amaranthus hybridus and Crepis tectorum

2005 ◽  
Vol 35 (3) ◽  
pp. 201-209 ◽  
Author(s):  
You Mi Lee ◽  
Su Hyun Park ◽  
Jae Min Jeong
Keyword(s):  
Amaranthus Hybridus ◽  
Crepis Tectorum

Additions and Range Extensions to the Vascular Plant Flora of the Continental Northwest Territories and Nunavut, Canada, II

2003 ◽  
Vol 117 (3) ◽  
pp. 448 ◽  
Author(s):  
William J. Cody ◽  
Kenneth L. Reading ◽  
Jennifer M. Line
Keyword(s):  
Medicago Sativa ◽  
Northwest Territories ◽  
National Park ◽  
Vascular Plant ◽  
New Taxon ◽  
Field Reconnaissance ◽  
Crepis Tectorum ◽  
Danthonia Spicata

Based on field reconnaissance since the publication of Flora of the Continental Northwest Territories in 1980, particularly in the District of Keewatin and northeastern District of Mackenzie (Nunavut) and Nahanni National Park, information is provided on geographically significant plant occurrences. One new taxon, Polemonium boreale forma albiflorum, is described, fourteen native taxa are reported as new to the region: Carex hoodii, C. microptera, C. petasata, Corispermum hookeri, C. ochotense, Danthonia spicata, Draba stenoloba, Erysisnum coarctatum, Halenia deflexa, Polygonum fowleri, P. ramosissimum, Salix rotundifolia ssp. rotundifolia, Silene uralensis ssp. ogilviensis, and Vaccinium ovalifolium. Five introduced taxa, Crepis tectorum, Corispermum villosum, Deschampsia elongata, D. incisa var. incisa, and Medicago sativa ssp. falcata are new to the flora of the region. Two native taxa, Danthonia intermedia and Potentilla porsildiorum are deleted from the flora and Ranunculus aquatilis var hispidulus is placed in synonymy. Significant range extensions for 125 native and one introduced taxon are included.

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