Relationships between the density and diversity of floral resources and flower visitor activity in a temperate grassland community

Abstract

1. Does the diversity and abundance of one trophic level affect another? Several studies at the landscape level have found a positive relationship between the diversity of floral resources and the diversity and abundance of pollinators. However, little is known about the relationship between these trophic levels on a smaller spatial scale, and the importance of blossom density relative to plant species richness in predicting abundance and richness of different flower visitor groups.2. This study used a small-scale approach to investigate how, and if, the diversity and abundance of floral resources in study plots affected the visitation activity of different flower visitor groups. During 201 observation periods between late May and midAugust 2003, 3682 visits were observed. Bumblebees (60%), muscoids (17%), syrphids (9%), and beetles (5%) were the most abundant flower visitors.3. Regression analysis was used to investigate the relationship between blossom density and plant species richness with visitation activity, including the probability of presence in plots, the visits within plots, and the visitor richness of the most abundant pollinator groups.4. The activity of beetles, bumblebees, and muscoids was positively predicted by the variation in blossom density, while syrphid activity was better predicted by plant species richness. Overall, the models for beetles and bumblebees explained much more of the variation in activity compared with the models for the dipterans, and blossom density was a better predictor of both flower visitor richness and activity than was plant species richness.

Disruption of a Belowground Mutualism Alters Interactions Between Plants and Their Floral Visitors

“…The importance of plant species richness as a predictor of bee species richness or abundance has been shown in several studies (Potts et al 2003, Hegland and Boeke 2006, Vulliamy et al 2006), but we are unaware of any study demonstrating the importance of evenness of the flowering-plant community for variation in insect-community visitation patterns. Visual inspection of the data suggests that the evenness of number of flowering stems of other species is positively related to the total number of visits received by a particular species.…”

“…The benefits of pollinator services to a plant are influenced by visitation rate (Ashman et al 2004), which can be affected by plant species richness and evenness (Ghazoul 2006), floral density (Moeller 2004, Hegland andBoeke 2006), and floral display and reward sizes (Thompson 2001, Elle andCarney 2003). In addition to influencing the behavior of pollinators that are already present, floral traits can also influence which floral visitors will be present at a given location (Potts et al 2003, Fenster et al 2004.…”

Effects of vegetation structure and human impact on understory honey plant richness: implications for pollinator visitation

“…Therefore, maintaining the pollination services can be achieved by the conservation and management of enough resources for pollinators (Ricketts et al 2008). One important factor for the diversity and abundance of pollinator populations is the composition of floral communities (Hegland and Boeke 2006).…”

História natural e interação flores-besouros em espécies de Cerrado

“…Guilds of flower visitors may respond differently to diversity and abundance of floral resources, and little is still known about the general response of pollinator groups to these variables, especially at a local scale (Steffan-Dewenter & Tscharntke 1999, Potts et al 2003, Hegland & Boeke 2006. Among flower visitors, the guild composed by beetles is responsible for many flower-pollinator relationships in the tropics as well in temperate regions .…”

“…Although plant phenological variation exists at every spatial and temporal scale, we rarely know the degree of phenological difference among patches. At present, we still know remarkably little about how floral visitors respond to spatial and temporal variation in their floral resources at local and regional scales , Hegland & Boeke 2006, and there is no consensus in relation to the density effects in the plant-pollinator systems, indicating complex patterns of density-dependence acting on this interaction . Some studies have discussed that plants with high number of flowers or located in rich floral resource patches can be more visited than the ones in low floral resource availability conditions , Thompson 2001.…”