ABSTRACT
Land-use alteration and climate seasonality have profound effects on bee species diversity by influencing the availability of nesting and floral resources. Here, using twelve sites embedded in an agriculture-forest mosaic in the tropical highlands of Guatemala, we investigated the relative effects of climate seasonality and landscape heterogeneity on bee and floral-resource community structure and on their mutualistic network architecture. We found that climate seasonality affected bee diversity, which was higher in the wet season and associated positively with the availability of floral resources across both seasons. Bee community composition also differed between seasons and it was mainly driven by floral-resource richness and the proportion of agricultural, semi-natural and forest cover. In addition to the effects on bee diversity, climate seasonality also affected flower-bee visitation networks. We documented higher relative (null model corrected) nestedness in the dry season compared to the wet season. Niche partitioning as a result of competition for scarce resources in the dry season could be the process driving the differences in the network structure between seasons. Furthermore, relative nestedness was consistently smaller than zero, and relative modularity and specialization were consistently larger than zero in both seasons, suggesting the existence of isolated groups of interacting partners in all our flower-bee visitation networks. Our results highlight the effect of climatic seasonality and the importance of preserving local floral resources and natural heterogeneous habitats for the conservation of bee communities and their pollination services in tropical highlands.
Subject(s)
Ecosystem , Pollination , Agriculture , Animals , Bees , Flowers , SeasonsABSTRACT
Se compararon tres categorías de paisaje: bosque continuo, bosque fragmentado y áreas agrícolas o de cultivo, en Sacatepéquez y Chimaltenango, Guatemala. Los sitios de estudio fueron definidos sobre la base de su grado de fragmentación y tipos de uso del suelo, durante las estaciones seca y lluviosa del año 2012. Se buscó observar patrones de variación entre la diversidad de abejas en las distintas categorías, e identificar cambios en la composición de las comunidades. Los resultados señalan hacia dos situaciones generales: (1) Se observó diferencia en la diversidad de abejas en los distintos tipos de vegetación, siendo esta más alta en los sitios que correspondían a la categoría fragmentada. Esta categoría está caracterizada por una composición heterogénea de áreas perturbadas y remanentes de bosque. Por otra parte, la categoría bosque presentó mayor abundancia de individuos, tanto en la estación seca como lluviosa. (2) Se observó algún grado de agrupamiento de los sitios de muestreo, pero parece responder más a la cercanía geográfica entre ellos que al uso del suelo. Adicionalmente, se reporta las frecuencias de visitas florales realizadas por las abejas a distintas familias botánicas. Se recomienda incentivar la protección de los remanentes boscosos, tanto fragmentados como continuos, para asegurar la conservación de la diversidad de abejas silvestres y la continuidad del servicio de polinización que proporcionan a los sistemas naturales y agrícolas de la zona.
Comparison was raised in three landscape categories (continuous forest, fragmented forest and agricultural or farming areas) in Sacatepéquez and Chimaltenango, Guatemala; defined on the basis of their degree of fragmentation and types of land use, during the dry and rainy seasons of 2012. It sought to determine patterns of bee diversity variation among the three landscape categories, and identify changes in community composition. The results point towards two general situations: (1) Difference in bee diversity was observed in different types of vegetation, this being highest at sites corresponding to the fragmented forest category. This category has a greater heterogeneity in landscape configuration, composed of fragmented forest and agricultural areas. In addition, the continuous forest category had higher abundance of individuals, both in the dry and rainy seasons. (2) Some degree of clustering of the sampling sites was observed, but it seems to respond to geographical closeness among them rather than to differences in land use. Also, frequency of floral visits made by bees to different botanical families are reported. The protection of forest remnants, both fragmented and continuous, is highly recommended in order to preserve pollination services given by native bees to natural and agricultural systems in the study area.