No abstract

Land-use intensification for agricultural purposes modifies the structure of natural environments in various ways and at different spatial scales. These modifications can affect ecological processes and the community structure of multi-environment users such as solitary bees and wasps. Understanding the role of distinct habitat descriptors in promoting such changes is one of the major challenges of empirical studies. In this study, we use a multi-scale approach to evaluate how landscape compositional and configurational heterogeneity, vegetation structural complexity, and the proportion of agricultural landscape composition affect communities of bees and wasps that nest in pre-existing cavities in remnants of native vegetation bordering agroecosystems. We selected 25 sampling points along a gradient of amount of surrounding agriculture and landscape diversity within natural physiognomies located in Chapada Diamantina, Bahia, Brazil. Through model selection using Akaike's information criterion, we verified the complementary roles of landscape heterogeneity and local vegetation in structuring these hymenopteran communities. Abundance in the groups showed different tendencies depending on the descriptors employed, pointing to the importance of evaluating within-group specificity. Furthermore, bees and wasps presented differential responses to landscape composition, but they did not differ in relation to configurational complexity. In more heterogeneous landscapes or sites with more complex local vegetation, the proportion of agriculture had a positive influence on the response evaluated. Efficient management of agricultural landscapes therefore requires increased landscape heterogeneity and conservation or restoration of native vegetation remnants at the local scale.

Studies in crop plants analyzing floral biology in conjunction with effectiveness and efficiency of pollinators on pollen transfer and fruit formation are not common, although they are essential to provide better management actions. On this base, we selected a farm in Bahia, Brazil, to study pollination on coffee plants (Coffea arabica L.). Specifically, we want to analyze if nectar traits influence visitor's performance throughout flower lifetime and if honeybees (Apis mellifera scutellata Lepeletier, 1836) are effective and efficient for coffee pollination comparing fertilization and fructification among four experimental treatments: open (OP), wind (WP), cross (HCP), and single-visit bee pollination (SVBP). We found that honeybees collect both nectar and pollen from coffee flowers and transfer pollen on stigmas even after one visit. No differences were found among treatments regarding the number of pollen grains transferred on the stigmas (effectiveness). OP flowers showed a comparative lower efficiency (pollen tubes and fruit set) probably due to pollination failure as those flowers have a higher variability on the number of deposited pollen grains. Two of the treatments (HCP and SVBP) showed higher fertilization (measuring tubes until the end of the style). Pollen loads seem to be limited by a peak of pollen transference by pollinators, followed by the stabilization in the number of pollen grains deposited per stigma. Thus, reproduction of the coffee can be limited by the quality of pollen grains moved by pollinators instead of quantity. Management strategies should focus on monitoring bee density on plants for increasing pollen quality transfer on flowers trough maintaining the adequate proportions of seminatural habitats and/or the number of hives on agricultural fields according to the flowering of the crop.

Pachira aquatica is a Neotropical tree of economic importance for local communities, although little is known about its flower biology especially flower rewards. This study aimed to analyze some aspects of flower biology of this species, focusing on nectar production dynamics We measured nectar production and analyzed the effect of nectar removal and cross-pollination on sugar production and standing crop (the amount of nectar present in a flower exposed to pollination at a given moment). We found that P. aquatica has large, brush-type, perfect flowers, with white colored petals, red stamens and a strong floral scent. Flowers are protandrous and dichogamous. Pollen viability is about 96%. Anthesis is nocturnal and asynchronous. The nectar is relatively abundant (99.8 ± 118.5 μL) and diluted (15.2 ± 4.7% p/p) and its production increases in the morning period. Neither nectar removal nor cross-pollination affected sugar production. Standing crop was not significantly different from the control, indicating that there is probably a low visitation rate. Both flower and nectar production characteristics indicate that this species has the potential to be visited by different flower visitors, especially bats, birds and bees.