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Native Bees Along Elevation Gradients
as Bioindicators of Climate Change
Scott
1
Daniels ,
Dave
2
Smith ,
Neil
3
Cobb
1. Cesar Chavez High School, Laveen, Arizona; 2. U.S. Fish and Wildlife Service; 3. Merriam-Powell Center for Environmental Research, Northern Arizona University
Abstract
Results
In this study, we examined species abundance, richness, and diversity at three life
zones along an elevation gradient of the San Francisco Peaks north of Flagstaff,
Arizona. Three colors of pollinator traps were placed at each of three life zones:
high desert, pinyon-juniper, and mixed conifer (figure 1). We found no significant
differences in species richness between the three sites. However, abundance in
the desert was significantly different from the pinyon-juniper and mixed conifer
sites. Species diversity increased with an increase in elevation. The broader goal
of this project was to develop monitoring program plans using pollinators as
bioindicators of global change. This includes land use change impacts as well as
climate change.
Introduction
It is well understood that climate change affects plant and animal biodiversity.
Changes in climate can disrupt the phenology of both plants and animals and these
changes could lead to plant–pollinator interaction mismatches and therefore
changes in ecological communities (Root et. al 2005). We can understand how
species may change with global warming in the future by examining their
distribution along elevation gradients in the present.
Discussion
A total of 144 of the samples collected contained bees and 1484 bees were
collected. There were 88 different species of bees.
Differences in species abundance were significant among the three sites
( F=12.431, p<.0001). The desert habitat had the greatest abundance and was
dominated by two species (Diadasia ochracea and Melissodes sp.), representing
63% of the desert abundance (table 1).
Species richness was highest at both the pinyon-juniper and the mixed conifer
sites with 42 species collected. However, species richness was not significantly
different among the three different life zones (F=.055, p=.946) (table1).
Diversity and evenness were highest at the mixed-confer site (E=0.810) and
lowest in the desert (E=0.550) (table 1).
ShannonWiener
Life Zone
Species
Species
Abundance Richness Diversity
Index
Desert
Pinyonjuniper
Mixed
Conifer
As a dominant pollinator, bees play a major role in maintaining plant communities.
Although there seems to be evidence that pollinator populations are declining
around the world, the status of most wild pollinators in North America is not known
(Committee on the Status of Pollinators in North America 2007).
With both climate change and native pollinator decline being such significant
issues, it is crucial we improve our understanding of the role of native bees as
pollinators.
846
392
29
42
1.851
2.754
246
42
3.027
Bee abundance was significantly higher in the high desert than at the other two
sites. However, this higher abundance could be the result of a sampling bias.
Bees in the desert may be more attracted to the pollinator cups because few
flowers are present. In one previous study, capture rates in pollinator traps were
lowest when flowering plant richness was highest (Wilson et al. 2008).
Although there was no significant difference in species richness between the three
sites, the three communities did show differences in species diversity. Species
diversity increased with elevation. This increase was expected because plant
diversity along the San Francisco Peaks is highest at the mixed conifer site and
lowest in the desert.
22 species, including all those in the genus Bombus, were found only at the mixed
conifer site. Such species would most likely be impacted by global warming.
Nine species were found throughout the elevation gradient (e.g. Diadasia
diminuta, Mellisodes spp.) and therefore might be least impacted by global
change.
Acknowledgements
Table 1. Species Abundance, richness, and diversity
This study is part of a larger project which will collect baseline information on native
pollinators in five different life zones. These baseline data will be used to assist in
future monitoring of the effects of climate change along an elevation gradient. This
study investigated differences in species abundance, richness, and diversity of
native bees in three of those life zones.
Life Zones
Percentage of
Species Overlap
Desert/
Pinyon-juniper
24%
Pinyon-juniper /
Mixed Conifer
17%
Desert/
Mixed Conifer
10%
Table 2. Species overlap between life zones
We would like to thank Jacob Higgins for his patience and assistance with the
statistical analysis.
Literature Cited
Figure 2. Sampling sites: Great Basin Desert,
Pinyon-juniper, and Mixed- Conifer.
a.
b.
c.
Figure 1. a. Desert b. Pinyon-juniper c. Mixed Conifer
Methods
Biodiversity and abundance of native bees were established for three different life
zones along an elevation gradient. These three life zones (figure 2) consisted of high
desert (1556 m), pinyon-juniper (2020 m), and mixed conifer (2620 m).
Thirty pollinator traps were placed at each of the three sites. Traps were left for one
week. Specimens were identified to the lowest taxonomic level possible.
One-Way ANOVA in SPSS statistics 17.0 was used to test for differences in species
richness and abundance between the three sites. To determine diversity, the ShannonWiener index value was calculated for each.
Nine species (10.2%) were collected at all
three sites.
44 of the 88 species were collected at only one
site.
7 species were found only in the desert,
15 species were found only in the pinyonjuniper, and 22 species were found only in the
mixed conifer (figure 3).
Committee on the Status of Pollinators in North America, National Research
Council. 2007. Status of Pollinators in North America. The National
Academies Press. Washington, D.C. pp. 203-207, 293-297.
Hannah, L., T. Lovejoy, and S.H. Schneider. 2005. Biodiversity and climate
change in context. In: Climate Change and Biodiversity (T.E. Lovejoy and
L Hannah, editors), Yale University Press, New Haven, pp.3-14.
Figure 3. Percentage of species unique to
one life zone.
Root, T.L., and L. Hughes. 2005. Present and future phenological changes in wild plants
and animals. In: Climate Change and Biodiversity (T.E. Lovejoy and L Hannah,
editors), Yale University Press, New Haven, pp.61-69.
Wilson, J.S., T. Griswold, and O.J. Messinger. 2008. Sampling bee communities
(Hymenoptera: Apiformes) in a desert landscape: Are pan traps sufficient? J.
Kans. Entomol. Soc. 81(3): 288-300.
Cesar Chavez
High School