Biologia

Crude and refined hazelnut oils from different countries were characterised by major and minor compounds. Fatty acids, triacylglycerides, waxes, sterols, methyl-sterols, terpenic and aliphatic alcohols, tocopherols, tocotrienols and hydrocarbons were identified and quantified by gas chromatography and high-performance liquid chromatography. The levels of these chemical compounds in hazelnut oils together with the equivalent carbon numbers and triacylglyceride carbon numbers, were compared with the results of analyses of samples of other vegetable oils. The statistical procedure of cluster analysis was used to characterise hazelnut oils versus other edible oils.

In recent years the coastal dune vegetation of the state of Yucatan, Mexico has become highly fragmented due to clearing for development. We evaluated patterns of genetic differentiation and genetic variability among orchid populations (Myrmecophila christinae var christinae) in eight habitat fragments along a west-to-east disturbance gradient in which sites located on the western end began experiencing fragmentation earlier than those in the east. Leaf samples from adult individuals and juvenile plants were collected from all eight populations, and analyzed using starch-gel electrophoresis in a lithium buffer system. Per population estimates of genetic diversity, proportion of polymorphic loci at 95 percent, mean number of alleles per locus, allelic richness, and population structure were calculated, as well as estimate comparisons between generations. Genetic diversity at the loci analyzed did not show significant differences among the eight populations. Based on the results, the model of isolation by distance does not fit the M. christinae populations under study; in some cases, populations close to one another apparently experienced very little genetic exchange. Thus, we propose that so far, fragmentation has not led to significant genetic differences between populations subject to different historical backgrounds of disturbance (i.e., time since onset of disturbance), as well as between generations within each of the M. christinae study populations. Nevertheless, the genetic characteristics of some remnant populations might change over time due to a future decrease in the opportunities for genetic exchange with other populations.En años recientes en la vegetación de duna costera del estado de Yucatán se ha venido dando un proceso de fragmentación del habitat y desmonte debido al desarrollo turístico. Para conocer el efecto de este desmonte sobre la vegetación natural, se evaluó el patrón de diferenciación y variabilidad genética entre ocho poblaciones remanentes de la orquídea Myrmecophila christinae que tienen un patrón oeste – este de perturbación. Se tomaron muestras de tejido foliar de plantas adultas y platulas con las cuales se llevaron acabo análisis con electroforesis de geles de almidón en un sistema de buffer de litio. Se estimaron, la diversidad genética, la proporción de loci polimórficos al 95 por ciento, la riqueza alélica, el número promedio de alelos por locus, así como la estructura genética de las poblaciones bajo estudio. Apartir de los resultados obtenidos se observó que la diversidad genética en todos los loci no fue notablemente diferente entre generaciones o entre las ocho poblaciones. El modelo de aislamiento por distancia mostró un ajuste muy pobre; en algunos casos poblaciones cercanas muestran aparentemente poco intercambio genético. Nosotros vemos que no se han detectado efectos significativos entre las poblaciones que tienen diferentes historias de perturbación (timepo desde que comenzó el disturbio) o entre generaciones en la variabilidad genética ni en la diferenciación. Sin embargo, nuestros resultados igualmente muestran que las características genéticas de algunas poblaciones remanentes, en términos de las frecuencias alélicas, pueden cambiar en el tiempo debido un intercambio restringido de genes con otras poblaciones.