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GENETIC ORGANIZATION AND EVOLUTIONARY HISTORY IN TWO NORTH AMERICAN SPECIES OF CIRSIUM
1Departments of Systematics and Ecology and Botany, The University of Kansas, Lawrence, KS, 66045.
Summary
Cirsium pitcheri, a Great Lakes thistle, shows significantly lower genetic diversity than its Great Plains relative, Cirsium canescens. This supports a progenitor-derivative species relationship, likely due to population bottlenecks during migration.
Area of Science:
- Evolutionary Biology
- Plant Genetics
- Ecology
Background:
- Progenitor-derivative species relationships are recognized in various plant groups.
- Cirsium pitcheri is a Great Lakes endemic thistle, while Cirsium canescens is found in the central Great Plains.
- Understanding their genetic relationship can shed light on speciation and adaptation.
Purpose of the Study:
- To investigate the probable progenitor-derivative species relationship between Cirsium pitcheri and Cirsium canescens.
- To compare the genetic diversity and variation between these two closely related thistle species.
Main Methods:
- Starch-gel electrophoresis was employed to analyze enzyme loci.
- Genetic diversity metrics, including polymorphic loci and heterozygosity, were quantified.
- Allelic variation was compared between C. pitcheri and C. canescens.
Main Results:
- Both species shared common enzyme loci, indicating close evolutionary ties.
- Cirsium pitcheri exhibited substantially lower genetic diversity compared to Cirsium canescens.
- Fewer polymorphic loci and significantly lower heterozygosity were observed in C. pitcheri.
Conclusions:
- The genetic makeup of C. pitcheri appears to be a reduced subset of C. canescens alleles, supporting the progenitor-derivative hypothesis.
- It is proposed that C. pitcheri colonized Great Lakes dune habitats post-Wisconsin glaciation.
- Low genetic variability in C. pitcheri likely resulted from population bottlenecks during its migration and establishment.
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