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Are modified areas accessible to pollinators?: analysis of the foraging pattern of Melipona quadrifasciata as an indicator of functional connectivity

Grant number: 12/10727-2
Support type:Scholarships in Brazil - Master
Effective date (Start): November 01, 2012
Effective date (End): February 28, 2014
Field of knowledge:Biological Sciences - Ecology
Principal Investigator:Danilo Boscolo
Grantee:Tatiana Machado de Souza
Home Institution: Pró-Reitoria de Pós-Graduação e Pesquisa. Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Environmental change can transform landscapes, breaking existing environments into a group of small, isolated patches of natural vegetation, interspersed with different types of land use and occupation. This process interferes with gene flow between populations of plants through pollinators, what is directly linked to functional connectivity and accessibility of the remaining environments. This happens because pollinators must consider the costs and benefits of moving between patches of different environments, as expected by the theory of optimal foraging. In the Chapada Diamantina (BA) there is a great diversity of natural habitats and extensive agricultural lands, such as the agricultural hub of Mucuge/Ibicoara, which has highly heterogeneous environments, a very interesting situation for researches on foraging patterns of pollinators and functional connectivity. Within this framework, the bee Melipona quadrifasciata is appropriate for studies of foraging because it is easy to handle and has been successfully used in pollination experiments in the study area. Thus, the aim of this study was to estimate the accessibility of natural and cultivated environments of the study area for the species M. quadrifasciata by analyzing their pollen foraging patterns in different spatial contexts, in order to infer about the preferences of the species in different landscape contexts (more or less anthropized), in order to estimate the functional connectivity of these landscapes. For this, we allocated 15 artificial nests of M. quadrifasciata within different landscape contexts. Three colonies were allocated adjacent to flowering crops to serve as control colonies, while the others were placed in natural areas between 500m to 2000m away from the crops surrounded by different degrees of human made environments to assess in what situations bees would fly preferentially to the crop or stay foraging in natural areas. We also made transects around the colonies to estimate available resources by collecting pollen and herbarium specimens from natural and agricultural areas. We also collected pollen directly from the bee's pollen baskets to know this resource foraging pattern by this species. Pollen sampled from the bees was then quantitatively analysed. The foraging pattern of the bees demonstrates that the diversity of pollens collected by the bees was largely dependent on the distances between the observed colonies and flowering crops. Bee collected pollen diversity was also influenced by the association between distance to crops and diversity of environments around each colony. Considering the data obtained and the foraging strategy of the M. quadrifasciata, it is possible to derive an indirect measure of the functional connectivity of the study area for these pollinators, what have direct influence on their movement possibilities and hence efficiency as a vector of pollen exchange in semi-natural environments. Thus, maintaining healthy natural areas close to the crops may be a way to keep the pollination system running in the long term, as this would ensure that natural and crop areas around the colony are accessible enough to provide a fairly stable resources availability throughout the whole life of the native colonies. (AU)