450 



Nim-nallve Species — Our Living Resources 



^1 Rocky Mountain Alpine 

 ^1 Rocky Mountain Subalpine Conifer 

 ^1 Rocky Mountain Cornier Forest 

 ^1 Great Basin Conifer Woodland 

 ^1 Madrean Evergreen Woodland 

 H Mogollon Interior Chaparral 

 ^1 Rocky Mountain Subalpine Forest 

 ^1 Plains and Desert Grassland 

 [ I Semidesert Grassland 

 I I Mo|ave Desertscrub 

 ^1 Cfiihuatiuan Desertscrub 

 I I Sonoran Desertscrub Arizona Lowland 

 H Sonoran Desertscrub Anzona Upland 

 • Domestic honeybee colonies 

 •^^Africanized honeybee colonies 



Fig. 3. Known honeybee locations in Arizona displayed 

 with vegetation classes; derived from Brown et al. ( 1979). 



One observational and manipulative compe- 

 tition study between honeybees, bumblebees, 

 solitary bees, and ants was at midelevations in 

 the Santa Catalina Mountains in the Sonoran 

 Desert near Tucson. Arizona (Schaffer et al. 

 1983). Dramatic shifts in abundance of ants and 

 bumblebees were detected when honeybees 

 were present (introduced) or sealed inside their 

 hives. The researchers suggested that direct 

 competition between introduced honeybees and 

 native hymenopteran tloral visitors was caused 

 by honeybees numerically dominating the site. 

 Initial evidence seems to indicate that honey- 

 bees seek out and preempt the most profitable 

 habitats and partially exclude native bees indi- 

 rectly by rapidly reducing the standing crop of 

 plant nectar and pollen {Agave in this study). 



Both species of non-native bees forage vast 

 expanses of tenitory containing native and non- 

 native floral resources. Estimates of the amount 

 of terrain foraged annually by an average-sized 

 honeybee colony in New York hardwood forests 

 (Visscher and Seeley 1982) are 80-100 km- 

 (30-40 mi-). Forage area estimates for AHB 

 colonies living in lowland Panamanian rain 

 forests (Roubik 1989) are 200-300 km- (75-1 15 



mi-), although 90% of these foraging flights are 

 completed within 5 km (3 mi) of the nest 

 (Visscher and Seeley 1982). Even given this 

 restrictive caveat, the amount of "bee pasture" 

 grazed by these aerial herbivores is immense. 



In studying honeybee colonies foraging in 

 temperate forests in New York State, Visscher 

 and Seeley (1982) found that these cold-hardy 

 EHB colonies amassed 15-30 kg (33-66 lb) of 

 pollen and 60-80 kg ( 1 32- 1 76 lb) of honey each 

 year. To collect this amount of food, a colony 

 must dispatch tens of thousands of foragers on 

 many millions of foraging bouts with the bees 

 Hying 20-30 million km (12-19 million mi) 

 overall. Similar studies of AHBs in Panama 

 (Roubik 1989) determined that AHBs placed 

 more emphasis on pollen collection. The 

 Sonoran Desert of northern Mexico and south- 

 ern Arizona is perhaps one of the richest areas 

 in the world in floral resources because of the 

 relative high plant diversity and the many fair- 

 weather days for worker-bee foraging. 



Many important nectar- and pollen-produc- 

 ing plants visited by AHBs bloom at night and 

 arc pollinated by bats. Africanized honeybees 

 find and exploit these rich flowers at first light, 

 and we predict that saguaros and other colum- 

 nar cacti will be heavily used as food plants for 

 AHBs in Arizona. Early Arizona data for AHB 

 colonies illustrate that most AHB colonies have 

 been found in the subtropical climate zones in 

 Sonoran desertscrub. 



Determining which plants are used primari- 

 ly for nectar versus pollen, or both, depends on 

 direct observations of bees on flowers or indi- 

 rectly by identifying pollen grains in stored nest 

 samples of honey. In Panama, Roubik (1989) 

 found that AHB colonies harvested pollen from 

 at least 142-204 flowering plant species in a for- 

 est containing about 800-1,000 species. 

 European honeybees collected pollen or nectar 

 from about 1 85 plant species from a secondary 

 forest and agricultural area in Mexico 

 (Villanueva 1984). These studies suggest that 

 honeybees are using about 25% of the local 

 flora, but intensively use far fewer species at 

 any given time (Roubik 1989). In Arizona 

 EHBs will often harvest pollen from more than 

 60 species annually, but of these, only 10-15 are 

 harvested heavily and consistently from year to 

 year (Buchmann et al. 1992). Because of their 

 pollen herbivory and reproductive contact with 

 so many plants, there can be serious long-temi 

 ecological and evolutionary consequences of 

 these interactions that we simply do not yet 

 understand. 



Ecological Monitoring 



Although we have made a case for potential 

 serious, competitive displacement of food 



