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Genetic variation and evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacán Valley, central
Adriana Otero-Arnaiz1, Alejandro Casas, James L Hamrick
1Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Campus Morelia. Apdo. Postal 27-3 (Xangari) Morelia 58089, Michoacán, México. moteroar@iusb.edu
Molecular Ecology
|April 20, 2005
Summary
Human management of Polaskia chichipe cactus for edible fruits results in minimal genetic variation differences among wild, managed, and cultivated populations. Migration patterns likely homogenize populations, masking effects of artificial selection on genetic diversity.
Area of Science:
- Botany and Plant Genetics
- Conservation Biology
- Agricultural Science
Background:
- Polaskia chichipe, a columnar cactus from central Mexico, is cultivated for its edible fruits.
- Human selection has influenced its traits, but its genetic variation under different management regimes is not fully understood.
Purpose of the Study:
- To investigate the impact of human manipulation on genetic variation in wild, silviculturally managed, and cultivated Polaskia chichipe populations.
- To assess genetic differentiation and distribution across sympatric populations under varying human influence.
Main Methods:
- Analysis of genetic variation using five microsatellite loci across nine populations.
- Estimation of total genetic variation (H(T)), within-population variation (H(S)), and differentiation (F(ST)).
- Calculation of fixation index (F(IS)) and expected heterozygosity (H(E)) for populations grouped by management type.
Main Results:
- Overall genetic variation (H(T) = 0.658) was high and primarily distributed within populations (H(S) = 0.646), with low differentiation among them (F(ST) = 0.015).
- Wild populations exhibited the highest expected heterozygosity (H(E) = 0.631) and lowest F(IS) (0.07), while silviculturally managed populations showed the least variation.
- Low genetic differentiation (F(ST) = 0.005) was observed among populations despite different management types. Migration patterns may contribute to genetic homogenization.
Conclusions:
- Human management practices have led to morphological and reproductive differentiation in Polaskia chichipe, but neutral genetic markers show only slight differences.
- Despite long-term use and management, genetic diversity remains largely intact and homogenized across populations, likely due to gene flow.
- Conservation strategies should consider the subtle genetic distinctions and potential impacts of ongoing human interaction on this species.