Ceanothus

Does Resource Partitioning occur between Apis and Bombus on Ceanothus Thyrsiflorus flowers?: 

Does Resource Partitioning occur between Apis and Bombus on Ceanothus Thyrsiflorus flowers? Rudy Borowczak & Darren Yondorf Pollination Biology 2007

Introduction:: 

Introduction: Ceanothus Thyrsiflorus plant- shrub up to 6 m tall, evergreen perennial, native to western CA and OR, Flowers- 1-2 cm diameter, complete and perfect, Major pollinators- Bombus, Apis, solitary bees Resources: Pollen and Nectar (observed)

Slide4: 

Questions from primary observations Multiple species of bees observed foraging on Ceanothus Abundance of Bombus noticed compared to Apis Why are there less Apis when the hive is nearby, and Ceanothus has a broad array of flowers? Hypothesis: interspecific competition for resources driving spatial/temporal resource partitioning between Apis and Bombus. What resource? Presumed proximate & ultimate mechanisms Null Hypothesis: Competition (and resource partitioning) not influencing prevalence of Bombus. Introduction:

Methods: 

Methods Determine resource (nectar) quality/avaliability at different times during the course of a day. Observe pollinators on marked inflorescences for simultaneous times: Temporal/spatial distribution Is competition occurring? What type? Determine correlation between species present and resource. Record environmental conditions. Local averages for temperature, humidity, weather.

Slide6: 

Table 1: Average abundance of bees for each time, averaged from multiple sample days. Proportions are shown to illustrate the prevalence of Bombus at all times. Average temperature at sampling times is also shown to correlate with the presence of Apis. Complications in sampling nectar led to inconclusive data, and we were forced to throw it out. But that’s ok. Results & Discussion

Slide7: 

Fig 1: Shows temporal distribution of Apis & Bombus. Based on averages from multiple days. Fig 2: Average temperature throughout sampling period. Results & Discussion

Slide8: 

Nectar data inconclusive. Bee distribution is likely unrelated to competition anyway. Presence of Apis limited: Very low amounts of nectar probable. Temperature dependent foraging: Bombus able to exploit early morning and evening. Results & Discussion

Slide9: 

Our results indicate that resources on Ceanothus are not competed for between Apis and Bombus enough to drive partitioning. This means that our hypothesis is incorrect: abiotic factors (temperature), and the lack of Apis recruitment to the resource lead to the prevalence of Bombus, not competition. Though Bombus has the opportunity to exploit the resource through adaption to the colder crepuscular temperatures, Apis is uninterested. Results & Discussion

Slide10: 

Questions for Future Study Does resource partitioning occur on a community level?