Short Communication |
Corresponding author: Victor H. Gonzalez ( victorgonzab@gmail.com ) Academic editor: Jack Neff
© 2016 Victor H. Gonzalez, Kristen E. Park, Ibrahim Çakmak, John M. Hranitz, John F. Barthell.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gonzalez VH, Park KE, Çakmak I, Hranitz JM, Barthell JF (2016) Pan traps and bee body size in unmanaged urban habitats. Journal of Hymenoptera Research 51: 241-247. https://doi.org/10.3897/jhr.51.9353
|
Pan traps are among the most popular methods employed to survey bees and changes in some functional traits, such as body size, are increasingly used to understand how bee communities and species respond to landscape changes. Herein we assess body size differences between bees captured at ground-level and elevated (70 cm) pan traps in unmanaged urban habitats in northwestern Turkey. We compare body size at the community level as well as for the sweat bee Lasioglossum malachurum (Kirby) (Halictidae: Halictini), the most abundant species. We also compare the diversity, richness and abundance of bees sampled at both heights. A total of 31 species (13 genera of three families) were captured. We did not find significant differences in the abundance nor in the species richness between heights, and Simpson’s indices were similar. At the community level, average intertegular distance was significantly greater in bees collected at the elevated traps than on the ground. Intertegular distances in L. malachurum did not differ between elevated and ground-level pan traps. Our results show an effect of pan trap height on bee body size in the urban habitat surveyed, thus suggesting that assessing bee body size from samples collected with either ground-level or elevated pan traps alone might result in biased estimates of this functional trait.
Anthophila , Halictidae , intertegular distance, sampling bias, urban ecology
Pan traps of different colors placed at different heights have been successfully used as complementary methods in monitoring bee communities across a number of habitats and landscapes of both tropical and temperate environments (e.g.,
Body size affects bee foraging behavior (
This study was conducted at two unmanaged areas separated by 900 m in the Görükle Campus of Uludağ University in Bursa, Turkey (40°13'35"N, 28°52'13"E, 56m). In addition to grasses, these sites were dominated by wild carrots (Daucus carota L., Apiaceae), whose primary umbels occasionally reached up to 2 m in height; Heracleum platytaenium Boiss (Apiaceae), Echinops microcephalus Sm. (Asteraceae), Sonchus asper (L.) Hill (Asteraceae), and Cota tinctoria (L.) J. Gay ex Guss (Asteraceae) were also common in both sites. On each site we set up two parallel transects of pan traps 1 m apart. Each stratified pair, one on the ground and one elevated, was 2 m apart, for a total of 10 pairs per transect. Each elevated pan trap was placed 70 cm above the pan trap on the ground. Pan traps consisted of plastic bowls spray-painted fluorescent yellow (Solo® plastics Soufflé Cup, 3.25 oz.) and half filled with soapy water. This color was chosen because preliminary observations suggest that it is the most effective color to capture bees at the study area. We built the elevated pan traps using a white PVC tube (2 cm in diameter, 86 cm in length) and the upper one-third of a transparent 0.5 L plastic bottle. The tube’s lower end was cut at a diagonal with a pipe cutter so that it was easily inserted into the ground. At the upper end we placed the screw cap of a cut plastic bottle, which served as a support for the plastic bowl; the latter was secured to the bottle with clear adhesive tape. The PVC tube was inserted into the ground until the bottom of the bowl was 70 cm above the ground, a height that exceeded the minimum height of D. carota, the tallest surrounding flowering plant. We collected bees and refilled the pan traps with soapy water every two days from July 19 to July 24, 2015. We pinned all specimens and estimated their body size by measuring the minimum intertegular distance (
We used a Chi-square analysis to test for differences in abundance and species richness of bees collected at different heights. We also calculated the Simpson (1-D) and Sørensen indices to estimate the diversity and similarity between the samples and used a two-sample t-test to detect differences in body size between the community of bees collected at the ground and elevated traps, as well as between specimens of Lasioglossum malachurum collected at both heights. Averages are given with standard errors.
We collected 154 specimens representing a total of 31 species belonging to 13 genera and three families. Similar counts of individuals and species were captured at both heights (Abundance: X2 (1, n = 154) = 0.234, p = 0.629; Richness: X2 (1, n = 40) = 0.90, p = 0.343). Nine species were collected at both heights and, according to the Sørensen index (0.45), these communities moderately overlap; similar Simpson’s indices were also obtained at both heights (Table
Average intertegular distance and number of specimens of each bee species collected from pan traps placed on the ground and at 70 cm above ground. Supraspecific classification follows
Bee taxa | Intertegular distance (mm) | Ground | Elevated |
---|---|---|---|
Family Apidae | |||
Amegilla sp. | 3.50 | 0 | 1 |
Apis mellifera L. | 2.83 | 1 | 5 |
Ceratina sp. 1 | 1.27 | 4 | 1 |
Eucera sp. 1 | 2.60 | 0 | 1 |
Eucera sp. 2 | 3.05 | 0 | 1 |
Eucera sp. 3 | 3.50 | 0 | 1 |
Xylocopa iris (Christ) | 4.28 | 0 | 3 |
Xylocopa violacea (L.) | 6.03 | 0 | 3 |
Family Halictidae | |||
Halictus (Seladonia) sp. | 1.22 | 1 | 6 |
Halictus scabiosae (Rossi) | 3.10 | 0 | 2 |
Halictus sp. 1 | 1.91 | 0 | 3 |
Halictus sp. 2 | 1.60 | 2 | 0 |
Halictus sp. 3 | 1.11 | 0 | 2 |
Lasioglossum malachurum (Kirby) | 1.40 | 22 | 25 |
Lasioglossum (Evylaeus) sp. 1 | 1.53 | 1 | 3 |
Lasioglossum (Evylaeus) sp. 2 | 1.23 | 0 | 2 |
Lasioglossum (Evylaeus) sp. 3 | 1.23 | 1 | 0 |
Lasioglossum (Dialictus) sp.1 | 1.49 | 1 | 2 |
Lasioglossum (Dialictus) sp. 2 | 1.25 | 1 | 0 |
Lasioglossum (Dialictus) sp. 3 | 1.06 | 0 | 3 |
Lasioglossum (Dialictus) sp. 4 | 0.83 | 1 | 0 |
Lasioglossum (Dialictus) sp. 5 | 1.02 | 2 | 1 |
Lasioglossum (s. str) sp. 1 | 2.00 | 24 | 11 |
Lasioglossum (s. str) sp. 2 | 2.10 | 0 | 1 |
Family Megachilidae | |||
Anthidium florentinum (Fabricius) | 3.75 | 0 | 1 |
Hoplitis sp. | 2.35 | 3 | 0 |
Hoplosmia sp. | 1.46 | 3 | 0 |
Lithurgus chrysurus Fonscolombe | 2.90 | 1 | 1 |
Osmia erythrogastra Ferton | 1.57 | 5 | 0 |
Osmia bidentata Morawitz | 1.63 | 1 | 0 |
Pseudoanthidium lituratum (Panzer) | 2.03 | 0 | 1 |
Total specimens | 74 | 80 | |
Total species | 17 | 23 | |
Simpson’s Index | 0.80 | 0.87 |
We showed that, on average, larger bees are captured more often with elevated pan traps than with ground-level traps in the urban environments surveyed. As in previous studies, large-bodied bees such as Xylocopa, Eucera and Anthidium were captured exclusively or, in the case of honey bees, more frequently in elevated traps than at ground-level traps. Species of these groups were often seen either flying across the field or foraging at taller inflorescences, and had been previously collected at the same area with aerial nets only. Pan traps located at a height that exceeds the minimum height of the tallest surrounding flowering plants, as in our study, might act as beacons given that bees and other pollinators are naturally attracted to flowers or inflorescences of taller plants (e.g.,
Differences in foraging behavior associated with intraspecific variations in body size have been documented in social species, such as bumble bees (e.g.,
We are indebted to Daphne Mayes, Mariano Lucia, Jason Gibbs, and Jack Neff for comments and suggestions that improved this manuscript. This work was supported by the National Science Foundation’s REU program (DBI 1263327).