Genetic factors associated with population size may increase extinction risks and decrease colonization potential in a keystone tropical pine

Rafael F. del Castillo

doi:10.1111/j.1752-4571.2010.00177.x

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Genetic factors associated with population size may increase extinction risks and decrease colonization potential in a keystone tropical pine

2010-12-22

Rafael F. del Castillo *

Sonia Trujillo‐Argueta

Nahúm M. Sánchez-Vargas

Adrian C. Newton

DOI：10.1111/j.1752-4571.2010.00177.x

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Abstract

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Pioneer species are essential for forest regeneration and ecosystem resilience. Pinus chiapensis is an endangered pioneer key species for tropical montane cloud forest regeneration in Mesoamerica. Human activities have severely reduced some P. chiapensis populations, which exhibited a small or null colonization potential suggesting the involvement of genetic factors associated with small populations. We explored the relationships between (i) population genetic diversity (allozymes) and population size, including sampling size effects, (ii) fitness estimates associated with colonization potential (seed viability and seedling performance) in a common environment and population size, and (iii) fitness estimates and observed heterozygosity in populations with sizes spanning five orders of magnitude. All the estimates of genetic diversity and fitness increased significantly with population size. Low fitness was detected in progenies of small populations of disturbed and undisturbed habitats. Progenies with the lowest observed heterozygosity displayed the lowest fitness estimates, which, in turn, increased with heterozygosity, but seed viability peaked at intermediate heterozygosity values suggesting inbreeding and outbreeding depression. Inbreeding depression appears to be the most immediate genetic factor in population decline. Conservation efforts should try to maintain large and genetically diverse populations, enhance gene flow by restoring connectivity between adjacent populations, and avoid genetically distant individuals.

Keywords:

colonization

conservation

fitness

genetic variation

inbreeding depression

outbreeding depression

Pinus chiapensis

population size

restoration

tropical montane cloud forest