Low genetic variation but high population differentiation in a common tropical forest tree species

Genetic variation and population differentiation were studied in an abundant, outcrossing tropical tree species, Pentaclethra macrolaba, in Costa Rica. Population differentiation was analyzed on two spatial scales by collecting leaf material from 7 locations within a 1800-ha biological reserve and f...

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Bibliographic Details
Published in:Conservation biology 1994-06, Vol.8 (2), p.471-482
Main Authors: Hall, Pamela, Chase, Michael R., Bawa, Kamaljit S.
Format: Article
Language:English
Subjects:
AGE
ALLELES
Animal, plant and microbial ecology
Applied ecology
ARBOLES
ARBRE
Biological and medical sciences
BOSQUE TROPICAL
Conservation biology
Conservation, protection and management of environment and wildlife
COSTA RICA
DEBOISEMENT
DEFORESTACION
DEFORESTATION
DIVERSITY
EDAD
FORET TROPICALE
Fundamental and applied biological sciences. Psychology
GENE
GENES
Genetic diversity
Genetic loci
GENETIC VARIATION
LEGUMINOSAE
Parks, reserves, wildlife conservation. Endangered species: population survey and restocking
PENTACLETHRA MACROLOBA
PLANTULAS
PLANTULE
Population genetics
Population geography
Population mean
SEEDLINGS
Species
TREES
TROPICAL FORESTS
VARIACION GENETICA
VARIATION GENETIQUE
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Summary:Genetic variation and population differentiation were studied in an abundant, outcrossing tropical tree species, Pentaclethra macrolaba, in Costa Rica. Population differentiation was analyzed on two spatial scales by collecting leaf material from 7 locations within a 1800-ha biological reserve and from 11 additional sites up to 70 km from the reserve. Genetic differences between age classes were investigated by collecting leaves from adults and seedlings at six locations within the reserve. Measures of genetic variation were determined using protein electrphoresis of leaf material. Five polymorphic and nine monomorphic loci were identified. The mean heterozygosity of P. macroloba populations was 0.074. Heterozygosity varied among populations, ranging from 0.045 to 0.135, with the lowest value found in the reserve and the highest in a distant population. Low variation in the reserve was largely due to fixation at two loci that were polymorphic outside the reserve. Within the reserve, seedling populations were less differentiated than adult populations, with multilocus Fst values of 0.0189 and 0.0384, respectively. On larger geographic scales, however, population differentiation accounted for 21.9% of the total genetic variation. Nm, calculated from multilocus Fst, was negatively correlated with geographic distance among pairs of populations within the reserve (r = 0.53) and among populations throughout Costa Rica (r= -0.47). In combination, these results suggest that while P. macroloba may be panmitic within the reserve, gene flow is relatively restricted among sites that are scattered over a deforested landscape. Furthermore, in spite of the abundance of this species, genetic neighborhoods may be small due to asynchronous reproduction and isolation by distance. Allelic diversity is higher outside the reserve, and continuing deforestation may result in loss of genetic diversity, greater genetic differentiation, and genetic isolation of these populations.
ISSN:0888-8892
1523-1739
DOI:10.1046/j.1523-1739.1994.08020471.x