Long term effects of habitat fragmentation on mating patterns and gene flow of a tropical dry forest [6].
Study area:
Undisturbed trees were located at the Chamela-Cuixmala Biosphere Reserve while the disturbed tree were outside the reserve at Arroyo Seco, Programa and Boca de Iguanas. Methods: The experiment was done over a period of 4 years from 2000 to 2003 on the species Ceiba Aesculifolia (Malvaceae: Bombacoideae), whose flowers are pollinated by two species of bats, on the coast of Jalisco, Mexico. Two areas with the selected species were used in the experiment to determine what effect fragmentation has on gene flow, either undisturbed or disturbed. Areas that were considered disturbed were composed of a small group of trees that were considered isolated (if they was surrounded by pastures), while the other larger group of trees that were surrounded by forest were considered undisturbed. Fruit was gathered from the two selected groups and from each fruit, five seeds would be taken and studied, to see if fragmentation was affecting genetic composition. Six loci were used from these seeds to test pollen donors, genetic structure, relatedness between the fruits, and lastly outcrossing rates. Results: Ceiba Aesculifolia had suffered a lower gene flow in the disturbed isolated trees than their undisturbed counterparts. The amount of pollen available in both categories was generally the same, only varying in genetic structure throughout the years. The only difference was that the amount of sources to sire seeds was much lower in the fragmented areas. This shows that fragmentation lowers genetic diversity and increases relatedness among the fragmented trees due to limiting pollen movement among the trees.This also caused the fruits of the fragmented trees to be more related than the fruits of the undisturbed trees, as well as the seeds. |
Conservation:
This study shows that forest fragmentation has a clear effect on genetic diversity. While some areas such as the reserves do help with stopping fragmentation, human agricultural techniques such as slash and burn will constantly be a problem. There needs to be increased management of land usage and more education on the dangers of irresponsible land management. More studies also need to be done in order to gather more data, which could be used to determine the fitness of the disturbed trees.
Isolation caused by fragmentation is a serious conservation issue. Especially in an ecosystem with such a high percentage of endemism, fragmentation is a serious threat to diversity. Areas that are relatively small and genetically isolated are much more susceptible to genetic drift. This puts those areas at an increased risk of developing deleterious traits, which can easily lead to competitive exclusion in the area. When this occurs, species richness and diversity decreases, and in the case of endemic species, extinction may even occur, decreasing global diversity.
This study shows that forest fragmentation has a clear effect on genetic diversity. While some areas such as the reserves do help with stopping fragmentation, human agricultural techniques such as slash and burn will constantly be a problem. There needs to be increased management of land usage and more education on the dangers of irresponsible land management. More studies also need to be done in order to gather more data, which could be used to determine the fitness of the disturbed trees.
Isolation caused by fragmentation is a serious conservation issue. Especially in an ecosystem with such a high percentage of endemism, fragmentation is a serious threat to diversity. Areas that are relatively small and genetically isolated are much more susceptible to genetic drift. This puts those areas at an increased risk of developing deleterious traits, which can easily lead to competitive exclusion in the area. When this occurs, species richness and diversity decreases, and in the case of endemic species, extinction may even occur, decreasing global diversity.