Scale-dependent shifts in the species composition of flower visitors with changing floral density

Online Resource 3: Study design and supplementary floral visitation data

Carla J. Essenberg

University of California, Riverside

Phone: 951-250-3012, Fax: 951-827-4286, Email:

Tables

Table 1: Pearson’s product-moment correlations between independent variables and interaction terms used in analyses of effects of H. virgata floral density on visitation rates. Temp. = temperature in °C. Other abbreviations are the same as in Table 1 in the main text.

Site Density / Site Extent / Day / Temp. / Site Diversity / Patch Density x Site Density / Patch Density x Site Extent
Patch Density / 0.50*** / 0.23* / 0.16 / 0.07 / -0.24** / -0.04 / 0.04
Site Density / 0.29** / 0.40*** / -0.002 / -0.39*** / 0.15 / 0.04
Site Extent / 0.03 / -0.04 / -0.23* / 0.05 / 0.03
Day / -0.34*** / -0.15 / 0.28** / 0.13
Temperature / -0.25*** / -0.01 / -0.05
Site Diversity / 0.01 / 0.16
Patch Density x Site Density / 0.50***

* p < 0.05, ** p < 0.01, *** p < 0.001

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Table 2: Flower visitors observed during this study.

Taxon / Number of visits / Percentage of total visits
BEES (Hymenoptera):
Large sweat bees (Halictidae: Halictus ligatus, Lasioglossum titusi) / 1,640 / 30.6
Melissodes lupina (Anthophoridae) / 1,401 / 26.1
Honeybees (Apidae: Apis mellifera) / 804 / 15.0
Small sweat bees (Halictidae: Dialictus sp., Halictus tripartitus) / 228 / 4.3
Tetraloniella pomonae (Anthophoridae) / 95 / 1.8
Other/unidentified bees (including Megachilidae: Ashmeadiella, Megachile) / 327 / 6.1
FLIES (Diptera):
Large beeflies (Bombyliidae: Exoprosopa, Paravilla, Villa) / 284 / 5.3
Hoverflies (Syrphidae: Eristalis, Eupeodes, Toxomerus) / 195 / 3.6
Small beeflies (Bombyliidae: Geron, Phthiria) / 161 / 3.0
OTHER
Other/unidentified (including Lepidoptera: Noctuidae: Heliothodes; Hymenoptera: Braconidae) / 231 / 4.3


Table 3: Estimated standard deviations of the random effects site and sampling event in the analyses of the effects of H. virgata floral density on per-flowerhead visitation rates. The fixed effects and further information about the analyses are presented in Table 1 in the main text.

Site / Sampling event, nested within site
All visitors combined / 0.27 / 0.059
Long-horned bees (M. lupina) / 1.2 x 10-5 / 0.14
Honeybees (A. mellifera) / 0.082 / 0.11
Large sweat bees (H. ligatus and L. titusi) / 0.14 / 0.11


Figures

Figure 1: Study design. The upper-left image shows the study species: Holocarpha virgata. The locations of the eight sites are shown with white circles in the upper-right image. The middle image shows the boundaries of a representative site, and the bottom-left image shows the H. virgata patch used for pollinator observations at that site. Source of aerial photographs: USDA Farm Service Agency - National Agriculture Imagery Program 2005. The other photographs were taken by the author

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