POPULATION VARIATION IN THE ENDEMIC PINUS CULMINICOLA DETECTED BY RAPD

Resumen

Pinus culminicola, the dwarf pinyon,
is an endangered species endemic to
northeastern Mexico, where it grows
at the highest altitude of any of the
Cembroides group. In order to determine
the degree of genetic isolation between
populations of P. culminicola and the
amount of gene flow between them,
samples were obtained from Cerro El
Potosi and Sierra La Viga, two localities
within its restricted area of distribution in
the Sierra Madre Oriental, and analyzed
using random amplified polymorphic DNA
(RAPD). The five primers tested for the
analysis showed banding patterns with
very high reproducibility and clear band
resolution. These five primers produced
a total of 72 distinct bands, 52 of which
were polymorphic across the whole
sample. The genetic diversity in the two
populations was high with a percentage
of polymorphism of 53.7% and degree of
diversity measured by the Shannon index
of 56%. The total variation found between
the two populations was 5.98% (P =
0.0001). Most of the variation was found
within populations (94.02%). Contrary to
expectations, the level of genetic variation
found in the two isolated populations was
high but differentiation between them low.
This suggests that even though this treeline pine has a restricted and fragmented
distribution through the Sierra Madre
Oriental, gene flow between populations
has been sufficient to prevent a dramatic
loss of genetic variation and genetic drift.