dc.description.abstract | The natural variability was researched in natural populations of oaks, (Quercus sp) in the
Cordillera of Talamanca, Costa Rica. In the first chapter the leaves’s morphology was
researched in four species of oaks in natural populations located in Villa Mills (Q.
copeyensis and Q. costaricensis, 2700m), El Empalme (Q. copeyensis and Q. seemannii,
2200m) and Copey de Dota (Q. copeyensis and Q. corrugata, 1800m).The leave’s length
and width and the peciolo’s length were assessed. A variation analysis was carried out for
each site with two species at a time, and for Q. copeyensis in the three sites. Significatives
differences between species in each site and highly significatives differences in all
characters between individuals from each specie were found. For Quercus copeyensis
significative differences between sites and between trees within each population were
obtained. A clinal variation pattern for the characteristics assessed from the decrease of the
foliage dimensions with the increase in altitude was determined . A variance components
analysis for Quercus copeyensis on its peciolo length, the foliage length and the lengthwidth
ratio was performed. The variance among sites presented the highest proportion:
48%, 52%, and 43% for the peciolo length, foliage length and width respectively. For the
foliage width the highest proportion corresponded to the variance among leaves within the
same tree (40%).
The main observed characters for each of the four tree species in the field were
summarized in a table which proposed basic information to recognize them in the field: Q.
copeyensis is recognized mainly because of its white stern and white little terminal
branches. It has ovuled leaves. Q. costaricensis is distinguished because of its dark stern
and being found only in sites above 2400m in elevation. While Q. seemannii has the
longest and thin leaves and a grey stern. Q. corrugata is the only specie with sawed-edge
leaves and a pinky stern.
In conclusion, the observation from the leaves in the researched species allows a right
differentiation of each one. Similar research for other Quercus species in others country
sites is recommended.
In the second chapter were included the trial with electrophoresis and isozymes, based on
seedling samples from the specie Quercus copeyensis and natural population samples from
the species Q. copeyensis, Q. costaricensis, Q. seemannii and Q. corrugata. The enzymes
systems PGM, PGI, 6-PGDH, MDH, IDH, G-6PDH, MNR and SKDH were tested, but
with no acceptable results. | es |