The arctic-alpine polyploids Cerastium alpinum and C. nigrescens (Caryophyllaceae) in a sympatric situation: breakdown of species integrity?

The high polyploids Cerastium alpinum (8×) and C. nigrescens (12×) were investigated in a mixed population in central Norway to evaluate whether hybridisation has resulted in continuous variation in morphology and genetic markers, a hypothesis previously proposed to account for the extensive taxonom...

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Bibliographic Details
Published in:Plant systematics and evolution 2002-02, Vol.230 (3/4), p.203-219
Main Authors: Hagen, A. R., Sæther, T., Borgen, L., Elven, R., Stabbetorp, O. E., Brochmann, C.
Format: Article
Language:English
Subjects:
Anthers
Bracts
Cerastium alpinum
Cerastium nigrescens
Chromosomes
Fertility
Gene flow
Genetic diversity
Genetic markers
Genetic variation
Hybridity
Hybridization
Hybrids
Integrity
Interspecific
Markers
Morphology
Petals
Phenotypes
Plant morphology
Plants
Pollen
Polyploidy
Seed set
Seeds
Species
Sympatric populations
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Summary:The high polyploids Cerastium alpinum (8×) and C. nigrescens (12×) were investigated in a mixed population in central Norway to evaluate whether hybridisation has resulted in continuous variation in morphology and genetic markers, a hypothesis previously proposed to account for the extensive taxonomic confusion in this species group. Isozyme, fertility, and morphological (37 characters) variation were examined among 347, 265, and 237 plants, respectively. A PCO analysis based on 23 quantitative morphological characters identified two main groups, corresponding to C. alpinum and C. nigrescens. The groups were also clearly separated in isozyme markers, several qualitative morphological characters, and chromosome numbers. Only 20 plants (8.4%) were more or less intermediate in the PCO analysis. These plants had a parental or hybrid isozyme multilocus phenotype and typically few well-developed anthers, low pollen stainability, and no seed set. Several plants within the C. nigrescens group also had reduced pollen stainability. These results indicate that later-generation hybrids and/or backcrosses towards C. nigrescens are formed. Thus, interspecific, interploidal gene flow probably occurs, but at rates that are insufficient to break down species integrity.
ISSN:0378-2697
1615-6110
2199-6881
DOI:10.1007/s006060200005