Agapostemon

Abstract: The relative efficiencies of native bees and honey bees in pollinating sunflower were compared with male sterile and male fertile lines. Wild bees as a group and some oligolectic females were more effective in pollinating florets than were the apids (hon ey bees and bumble bees). In comparisons of the fidelity of bee visitation to either sterile or pollen varieties, apids preferred male sterile rows, some wild bee species were evenly distributed be tween sterile and pollen rows, and other wild bees preferred pollen rows. In comparisons of the amount of pollen carried on a bee body, oligolectic sunflower bees carried more pollen than did other kinds of bees. Few researchers have examined the role of bees in the production of sunflower seed since this plant has become an important oil seed crop (Car ter, 1978). In fact, so little is known concerning the diversity of bee species and their relative efficiency as pollinators of this crop that most commercial sunflower producers use self-fertile varieties (Fick and Rehder, 1977). Some researchers have suggested the use of honey bees, Apis mellifera L., as pollinators, but the recommended numbers of colonies vary from 1 to 51 hectare (McGregor, 1976). The sunflower is a native North American crop species with which many native bee species have probably co-evolved (Hurd et al., 1980). Many species of native bees are commonly observed associated with commercial plantings of sunflower, but their role in seed production has not been in vestigated. Parker (1980) found that sunflower oligoleges (bees restricted in pollen utilization to sunflower or closely related composites) carried more pollen on their body hairs than did sunflower polyleges (bees that visit many crop species including sunflower). However, relative effectiveness of these groups as sunflower pollinators was not determined in his study. This study was conducted 1) to compare different species of native bees with honey bees as pollinators of sunflowers, and 2) to compare the fidelity of bee species to male fertile or male sterile lines (most commercial self-fertile Received for publication 24 May 1980. This content downloaded from 40.77.167.48 on Thu, 15 Dec 2016 04:57:19 UTC All use subject to http://about.jstor.org/terms 62 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY varieties are produced by hybridization of male sterile and male fertile lines, and bees are the mechanism of pollen transfer). Methods and Materials plots: Sunflower was grown at the North Farm at Logan, Utah in Mill ville silt loam. Northrup King Co., Woodland, California, supplied 6 male sterile lines (SW 504, 506, 509, 517, 526) and 1 male fertile line (RW 637). Twenty-four rows (.7-m apart and 16-m long) were planted. Rows 1, 2, 9, 16, 23, and 24 were sown with the male fertile line and the remaining 3 blocks (rows 3-8, 10-15, and 17-22) were divided in half and sown with the 6 male sterile lines. counts: Bloom began on August 13 and ended on September 4. Polli nators were counted and changes in abundance and diversity of pollinators noted on early blooming heads 3 times daily (9:00 am, 11:00 am, and 1:00 pm) on Mondays, Wednesdays, and Fridays to determine any changes in abundance and diversity of pollinators during the day. Just prior to bloom, 20 randomly chosen plants of each variety were bagged with cheesecloth to exclude insect visitors; when these heads were in full bloom, the bags were removed to allow bee visitation. After one bee visit/head, the bag was re placed to prevent additional visits. During each visit, a sketch of the flower and the route taken by the bee on the florets was made (Fig. 1). To determine if pollen was accidentally transferred with the bagging technique, we treated 10 heads as above except that no bees were allowed to land before the flower was rebagged. Any male fertile plants in the sterile plots were rogued. However, the actual number of heads used was 86; some heads were un visited and others were fertile instead of male sterile. Data on single visits/ head were lumped because of inconsistent bee visitation/variety and simi larities among varieties in percentage seed set when open-pollinated. harvesting: In October, we collected all bagged heads and recorded the number and pattern of mature seed set by opening the seed. Mature (pollinated) seed was easily distinguished by size from immature (unpolli nated) seed (Fig. 2). We determined seed yield/head of unbagged heads by sampling 12 heads/variety. Each head was sampled by removal of 6 arcs (a single row of seed from the outer edge of a head to the center) of seed at the 2, 4, 6, 8, 10, and 12 o'clock positions (Fig. 3). The number, per centage, and weight of the mature seed in each arc were recorded. An additional 102 heads (17/row) sampled randomly from each plot were used to estimate yield/hectare. pollen: To estimate the amount of pollen carried on a bee body, we collected samples of bees from male sterile and male fertile lines by catching a single bee in a long tube, adding distilled water, vigorously shaking the vial up and down until no more pollen could be seen on the bee, and then removing the bee. Only one female (Megachile parallela Smith) died when This content downloaded from 40.77.167.48 on Thu, 15 Dec 2016 04:57:19 UTC All use subject to http://about.jstor.org/terms VOLUME 54, NUMBER 1 63 Figs. 1-3 1. Pattern of bee visit on male sterile sunflower. 2. Male sterile sunflower head showing large, mature seeds at bottom. 3. Male sterile sunflower head with 6 arcs (rows) of seed removed (arrows), illustrating sampling method. This content downloaded from 40.77.167.48 on Thu, 15 Dec 2016 04:57:19 UTC All use subject to http://about.jstor.org/terms 64 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Table 1. Average number of sunflower seeds produced per bee visit on male sterile lines of sunflower. Logan, Utah, 1979. Species and sex Observations x number of seeds Range Control Bombus 9 Apis 9 Agapostemon Melissodes 6 Andrena 9 Melissodes 9 10 6 22 13 14 5 5 0.00 0.83 2.55 3.15 7.21 12.60 27.80 (0-2) (0-23) (0-15) (0-57) (6-15) (6-70) treated in this manner. After the bees dried sufficiently, they flew off, and many treated bees were seen a short time later gathering nectar from sun flower heads. The washed pollen was centrifuged in the vial, and the number of pollen grains/insect was counted with a hemocytometer.

Abstract: Native bees (Hymenoptera: Anthophila) were sampled using bee bowls in two states to determine biodiversity in commercial cotton fields of the southern United States. In both states, native bee communities found in cotton fields were dominated by generalist pollinators in the genera Agapostemon, Augochloropsis, Halictus, and Lasioglossum (Hymenoptera: Halictidae), and Melissodes (Hymenoptera: Apidae). Melissodes tepaneca (Cresson) was the most abundant species found in cotton fields in both states. Some species collected are known specialists on other plant taxa, suggesting they may be tourist species. Here we provide a baseline species list of native bees found in cotton. Ordination indicated separation between the communities found in the two states when pooled by genus, but these differences were not significant. While cotton is grown in highly managed and disturbed landscapes, our data suggest that a community of common generalist native pollinators persists. Many of these species are also found in other cropping systems across North America.

Abstract: The large, yellow, bowl-shaped flowers ofOpuntia lindheimeri, O. discata, O. phaeacantha major, andO. compressa in Texas are visited by various species of beetles and bees. The beetles and small bees (Perdita, Dialictus) are pollen thieves. The pollinators are the medium-sized and larger bees (Melissodes, Diadasia, Lithurge, Megachile, Agapostemon, etc.). Different species of theOpuntia lindheimeri group have the same pollination system and there is no evidence of any floral isolation between them. The pollination system of these species ofOpuntia in Texas is essentially the same as that ofEchinocereus fasciculatus andFerocactus wislizeni in Arizona.