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Intrapopulation sex ratio variation in the salt grass Distichlis spicata
S M Eppley1, M L Stanton, R K Grosberg
1Center for Population Biology, University of California, Davis, California 95616, USA.
The American Naturalist
|September 25, 2008
Summary
In the clonal grass Distichlis spicata, true spatial segregation of sexes occurs, not just apparent patterns. Genetic analysis confirmed distinct genotypes and sex-biased patches, regardless of flowering status.
Area of Science:
- Plant reproductive strategies
- Population genetics
- Clonal plant ecology
Background:
- Dioecious plant populations often show spatial sex segregation, posing evolutionary questions.
- Asexual reproduction in clonal plants can create patterns mimicking sex segregation.
- Differential flowering can also lead to apparent sex segregation in populations.
Purpose of the Study:
- To confirm and extend findings on spatial sex segregation in the clonal grass Distichlis spicata.
- To differentiate true sex segregation from patterns arising from clonal growth and differential flowering.
- To investigate the genetic basis of sex determination and its spatial distribution.
Main Methods:
- Random Amplified Polymorphic DNA (RAPD) markers were used to assess genetic diversity.
- RAPD markers were employed to identify genotypes within patches.
- A RAPD marker linked to female phenotype was identified and utilized.
Main Results:
- Flowering ramets of Distichlis spicata are indeed spatially segregated by sex.
- At least 50% of ramets in sex-biased patches were distinct genotypes, indicating true segregation.
- A genetic marker confirmed female phenotype, ruling out environmental determination.
- The majority of patches showed biased sex ratios at both ramet and genet levels.
Conclusions:
- Distichlis spicata exhibits true spatial segregation of sexes, extending beyond apparent patterns.
- Clonal spread and differential flowering do not fully explain the observed sex segregation.
- Genetic factors play a significant role in the spatial distribution of sexes in this species.
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