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The genetic diversity of small populations is greatly influenced by local dispersal patterns and genetic connectivity among populations, with pollen dispersal being the major component of gene flow in many plants species. Patterns of pollen dispersal, mating system parameters and spatial genetic structure were investigated in a small isolated population of the emblematic palm Phoenix canariensis in Gran Canaria island (Canary Islands). All adult palms present in the study population (n ¼ 182), as well as 616 seeds collected from 22 female palms, were mapped and genotyped at 8 microsatellite loci. Mating system analysis revealed an average of 5.8 effective pollen donors (N ep ) per female. There was strong variation in correlated paternity rates across maternal progenies (ranging from null to 0.9) that could not be explained by the location and density of local males around focal females. Paternity analysis revealed a mean effective pollen dispersal distance of B71 m, with B70% of effective pollen originating from a distance of o75 m, and 90% from o200 m. A spatially explicit mating model indicated a leptokurtic pollen dispersal kernel, significant pollen immigration (12%) from external palm groves and a directional pollen dispersal pattern that seems consistent with local altitudinal air movement. No evidence of inbreeding or genetic diversity erosion was found, but spatial genetic structure was detected in the small palm population. Overall, the results suggest substantial pollen dispersal over the studied population, genetic connectivity among different palm groves and some resilience to neutral genetic erosion and subsequently to fragmentation.

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Goat grazing management is a powerful ecological force structuring plant communities which effects are highly different depending on factors such as climatic conditions, grazing intensity, type of plant community, etc. Pastures in the Canary Islands have important heritage, socioeconomic and landscape values because they are the remains of traditional livestock management and a key element of local economy. An experimental study of goat grazing exclusion has been carried out in an area of La Gomera Island to determine the main effects of grazing abandonment on species richness and species composition. The species composition of La Gomera pastures is more sensitive to grazing than to climatic variability, though effects in the species richness in relation to grazing were not detected. Because the pasture origin in this area involved artificial, removing of non useful plants in order to provide land for agriculture more than 300 years ago, and using it for pastures around 80 years ago, the sustainable use has maintained this rich plant community. Grazing abandonment can have a negative effect on the pastures' diversity, as grazing has been a strong force in the maintenance of certain species. Public promotion of this primary activity is suggested to allow the continuation with minimal effects on the vegetation composition. This will help to conserve the high diversity of this area and the promotion of natural values as well as traditional and sustainable human activities.Additional key words: detrended correspondence analysis; plant community; rarefaction; sustainability. Resumen Efectos a largo plazo del abandono del pastoreo de cabras en la composición y riqueza de especies en los pastizales de La Gomera, Islas CanariasEl pastoreo caprino es una importante fuerza estructurante de las comunidades de plantas, con efectos altamente dependientes de factores como las condiciones climáticas, la intensidad de pastoreo y el tipo de comunidad entre otros. Los pastizales de las Islas Canarias tienen valores culturales, socioeconómicos y paisajísticos importantes, puesto que son remanentes de actividades tradicionales y elementos clave de la economía local. Se ha llevado a cabo un estudio de exclusión del ramoneo de cabras en la isla de La Gomera para determinar los efectos del abandono del pastoreo en la riqueza y composición de especies de sus pastizales. La composición de especies de los pastizales está más influenciada por el pastoreo que por la variabilidad climática, aunque no se detectaron efectos en la riqueza de especies entre áreas pastoreadas y no pastoreadas. La explotación sostenible de estos ecosistemas para fines agrícolas desde hace más de 300 años y como pasto desde hace aproximadamente 80 años, ha mantenido su alta riqueza de especies. El abandono del pastoreo puede afectar negativamente a la diversidad de los pastizales, al haber sido una importante fuerza para el mantenimiento de ciertas especies. Se sugiere la promoción pública de esta actividad para asegurar su continuación con mínimos efectos...

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