Genetic diversity and the mating system of a rare Mexican pinon, Pinus pinceana, and a comparison with Pinus maximartinezii (Pinaceae)

Weeping$pi\tilde {n}on$(Pinus pinceana) has a restricted and fragmented range, trees are widely scattered within populations, and reproduction is limited. Nevertheless, genetic diversity was high; based on 27 isozyme loci in 18 enzyme systems, unbiased expected heterozygosity averaged 0.174. Differe...

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Bibliographic Details
Published in:American journal of botany 2001-11, Vol.88 (11), p.1977-1987
Main Authors: Ledig, F. Thomas, Capo-Arteaga, Miguel A, Hodgskiss, Paul D, Sbay, Hassan, Flores-Lopez, Celestino, Thompson Conkle, M, Bermejo-Velazquez, Basilio
Format: Article
Language:English
Subjects:
Alleles
Arroyos
Bajadas
Endangered & extinct species
endangered species
fitness
fragmentation
Genetic distance
Genetic diversity
Genetic loci
genetic structure
Genetics
Inbreeding
Inbreeding coefficient
isozymes
Mating systems
Pinus maximartinezii
Pinus pinceana
Plant reproduction
Pollen
pollen allele frequencies
Population Biology
Population genetics
selfing
Trees
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Summary:Weeping$pi\tilde {n}on$(Pinus pinceana) has a restricted and fragmented range, trees are widely scattered within populations, and reproduction is limited. Nevertheless, genetic diversity was high; based on 27 isozyme loci in 18 enzyme systems, unbiased expected heterozygosity averaged 0.174. Differentiation also was high (FST= 0.152), reflecting isolation between southern, central, and northern fragments of the range. Among populations in the northern fragment, FSTwas only 0.056, and the number of migrants per generation (Nm) was 4.21, which should preclude fixation. Nm between central and southern populations or between them and populations in the northern fragment was lower, 0.99-1.66, indicating a degree of genetic isolation. Multilocus outcrossing rates (tm) ranged from 0.836 in the south to 0.897 in the north. Therefore, selfing is low but statistically significant. The equilibrium inbreeding coefficient (Fe) calculated from tmwas in good agreement with observed inbreeding coefficients, suggesting that weeping$pi\tilde {n}on$may be near equilibrium with respect to inbreeding and selection against selfed trees. Weeping$pi\tilde {n}on$on was variable at all loci polymorphic in$maxipi\tilde {n}on$(Pinus maximartinezii) and, therefore, qualifies as a possible progenitor of$maxipi\tilde {n}on$. Because of the high level of diversity, reasonable levels of gene flow within the northern fragment of weeping$pi\tilde {n}on's$range, high rates of outcrossing, and, perhaps, only weak selection against inbred trees, protection in reserves would be a viable option for conservation.
ISSN:0002-9122
1537-2197
DOI:10.2307/3558425