Variación natural en cuatro especies de roble, Quercus spp. en la Cordilera de Talamanca, Costa Rica

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.