Summer Grant Progress Report for Dr. C. Bennington and Dr. P. May: A Comparison of Pollinator Diversity and Dynamics Between Natural and Restored Sandhill Ecosystems
Documented widespread declines in native pollinator abundance and diversity have been attributed, at least in part, to habitat loss. Fragments of natural habitat in urban settings, like the Volusia Sandhill Ecosystem Teaching Landscape can maintain diverse wildflower assemblages, and may be important for maintaining viable populations of a diversity of pollinating species. One of the main objectives of this study was to quantify pollinator diversity and visitation rates at two common sandhill plants (Bidens alba and Chamaecrista fasciculata) and compare them between a natural sandhill habitat (Heart Island Conservation Area) and the on-campus sandhill restoration site, the Volusia Sandhill Ecosystem Teaching Landscape (hereafter referred to as Volusia Sandhill). We requested a full summer grant to be split between us to support this research, but were awarded a half-grant instead. Despite this reduced level of support, we were able to successfully complete most of the research objectives; we anticipate completion of the remaining components during the current academic year.
The research we proposed marked the initiation of a multi-year assessment of pollinator abundance and diversity in the Volusia Sandhill, with four main goals. Below we list each of the goals of our Summer Grant research and describe the way in which these goals were met through our work.
1. Goal: To quantify the abundance and diversity of insect pollinators on all summer-flowering plants in the Volusia Sandhill, creating both photographic and specimen collections.
Outcome: We began the long-term project of obtaining and curating a voucher collection of pollinating insects from both sites. We collected, identified, and mounted 94 insect specimens representing more than 30 different species of beetles, flies, wasps, bees and butterflies, displaying them in museum cases housed in the Rinker Environmental Learning Center. We obtained high-quality photographs of 26 species of pollinating insects. These photographs, along with a description of the results of our research, will soon be incorporated into a new page on the Volusia Sandhill Ecosystem website (http://www.stetson.edu/other/gillespie- museum/vse/research.php). Representative photographs of some pollinators can be found in Appendix I.
2. Goal: To compare pollinator visitation rates and pollinator species composition on two abundant species in the Volusia Sandhill with those in a mature sandhill community in Heart Island Conservation Area. We originally proposed to collect data from a natural sandhill in Ocala National Forest, but found the equally suitable sandhill ecosystem at Heart Island to be more accessible and convenient.
Outcome: In nearly 30 hours of direct floral observations collected on 22 field days over an eleven-week period (May 31 – August 11) we observed more than 1300 insect visitors. Our findings suggest that urban habitat fragments like the Volusia Sandhill can support diverse pollinator populations.
We found that the inflorescences of Spanish needles (Bidens alba), for example, were visited by bees, wasps, flies, butterflies, and beetles at both sites. However, although the sandhill habitat at Heart Island Conservation area is part of a more than 14,000 acre site encompassing several major ecosystems with high species diversity, bee visitation rate (number of visitors/inflorescence/minute) on Spanish needles was significantly lower there than in the Volusia Sandhill (Fig. 1, Appendix II), perhaps because the density of flowers is higher in the more 1 cultivated Volusia Sandhill landscape. In contrast, butterfly visitation to Bidens alba was slightly, though not significantly, higher at Heart Island than Volusia Sandhill (Fig. 2, Appendix II). While additional data are required to confirm this conclusion, this difference may be due to the very specific host plant preferences of many butterfly larvae. We suspect that the higher abundance of butterflies at Heart Island is a function of higher total plant diversity and a greater variety of larval host plants for the butterflies. Bees and wasps, on the other hand, are more generalized foragers and can maintain viable populations in a greater range of habitats.
3. Goal: To develop educational materials, in collaboration with Dr. Karen Cole, Director of the Gillespie Museum, to highlight the pollinators that frequent flowers in the teaching landscape and to educate museum visitors about the importance of pollinators in native ecosystems.
Outcome: The Volusia Sandhill Pollinator Project will become a permanent outreach program through the Gillespie Museum’s programming: (1) The pollinator count will provide an additional activity in the museum’s K-12 educational programs, specifically in the Florida Ecosystems Outdoor Classroom) track (along with soil profile, leaf transpiration and native plant scavenger hunt ) (http://www.stetson.edu/other/gillespie-museum/educational-programs.php ). (2) As an established field study site, with a data set, it will offer another laboratory experience on the museum grounds for Stetson University faculty and undergraduate research (http://www.stetson.edu/other/gillespie-museum/vse/research.php ). And (3) as an ongoing citizen scientist opportunity, museum visitors may choose to monitor, describe, and record native pollinator activity in designated quadrants in the landscape.
For the 2016-17 academic year, there will be a station in the Gillespie Museum’s Collector’s Gallery (Appendix III), with the pollinator collection boxes, photographs, microscopes, and field study logs. During Science Saturdays and during regular visits, museum goers will have the opportunity to participate in the pollinator count, extending the data set for pollinators in the Volusia Sandhill Ecosystem.
4. Goal: To initiate new avenues of undergraduate research in the Volusia Sandhill.
Outcome: This fall (2016), the results of our summer data collection were incorporated into a new Plant Ecology (BIOL 450) lab investigating pollination biology (Appendix IV). In addition, a senior Environmental Science major (BA track) will be creating an educational activity and associated assessment tool related to pollinators for her senior research project (Fall 2016). In Spring 2017, when junior Biology majors choose a Senior research topic, both PM and CB will offer pollination research as a potential area for student engagement.
In summary, we were able to complete the main objectives of our proposed research, though as in any long-term ecological project, the data from one field season are inadequate to fully answer the questions posed. Of particular interest to us was the finding that pollinator diversity and visitation rates for some taxa at the restored Volusia Sandhill ecosystem is actually equal to or greater than that at the intact sandhill ecosystem of Heart Island Conservation Area.
However, because of significant between-year variability in many aspects of ecosystem function, any one year’s data are but a brief snapshot of the ecological process being studied. Systematic study of these types of questions demands a multi-year commitment to document the extent and effect of this between- year variability. The results of our research to date will establish the baseline for a multi-year project that will fully explore between-year variability in pollinator dynamics of sandhill ecosystems.
2 Appendix I: Representative photographs of some pollinators of Bidens alba and Chamaecrista fasciculata
Female Agapostemon splendens (Halictidae) nectaring at Bidens alba
Thread-waisted wasp (Ammophila sp., Sphecidae)
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Honeybee (Apis mellifera, Apidae)
Sand wasp (Bembix americana, Crabronidae)
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Weevil wasp (Cerceris bicornutus, Crabronidae)
Leafcutter Cuckoo Bee (Coelioxys slossoni, Megachilidae)
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Ectemnius sp, Crabronidae
Halictus sp., Halictidae
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Zebra longwing (Heliconius charithonius, Heliconiidae)
Ceraunus blue (Hemiargus ceraunus, Lycaenidae)
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Fiery skipper (Hylephila phileus, Hesperiidae)
Beefly (Lepidophora sp., Bombyliidae)
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Cassius blue (Leptotes cassius, Lycaenidae)
Leafcutter bee (Megachile sp., Megachilidae)
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Long-horned bee (Melissodes sp., Apidae)
Beefly (Poecilanthrax sp., Bombyliidae)
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Scolia nobilitata (Scoliidae)
Bumblebee (Bombus sp., Apidae). This was the only pollinator that frequently visited partridge pea (Chamaecrista fasciculata)
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Appendix II: Results of preliminary data analysis, suggesting some interesting differences in pollinator abundance between the Volusia Sandhill and Heart Island Conservation Area.
0.1
0.08 HI 0.06 VS 0.04
0.02
#Visitors/ lower/minute 0 Bidens Chamaecrista Species
Fig. 1. Visitation rates by native bees (European honeybees were excluded from analysis) on Bidens alba and Chamaecrista fasciculata at the Volusia Sandhill Ecosystem (VS) and Heart Island Conservation Area (HI). Both species received more bee visitors in the Volusia Sandhill than at Heart Island, and this difference was greatest for Bidens alba.
0.06
0.05
0.04
0.03
0.02
0.01
##Visitors/ lower/minute 0 HI VS -0.01 Location
Fig. 2. Visitation rates by butterflies and moths at Heart Island Conservation Area (HI) and the Volusia Sandhill Ecosystem (VS). The difference between sites is interesting, but not statistically significant (p = 0.15).
12 Appendix III.
Adrian Fonseca, Gillespie Museum staff, and Emmy Stamey, Volusia Sandhill Intern, setting up the Pollinator Project in the museum's Collections Gallery.
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Appendix IV. Description of new laboratory exercise introduced into Plant Ecology (BIOL 450) in Fall 2016. Photos from the first week of the exercise are included.
Pollination Abundance and Diversity
Background Information
Because the majority of flowering plants depend upon animal pollinators to reproduce, the documented widespread declines in pollinator abundance have raised concerns for the future of agriculture, human health, and the conservation of native plants. The importance of urban assemblages of wildflowers for maintaining diverse pollinator communities is receiving increased attention given that declines in native habitat have been cited as a major factor contributing to pollinator declines.
The Volusia Sandhill Ecosystem Teaching Landscape is an ongoing, small-scale (1 acre), restoration of the historic longleaf pine forests that once dominated much of the southeastern United States. With more than 80 trees and 350 flowering plants representing nearly 50 different understory plant species, the site is small but diverse. This pocket of high diversity, however is surrounded by manicured campus to the north, dense residential neighborhoods to the east and west, and downtown Deland to the south. Data on pollinator visitation rates and pollinator diversity were collected in both the Volusia Sandhill and in a more mature sandhill community (Heart Island Conservation Area) beginning in early June and continuing into August 2016. In this lab, you will use the same methodology employed earlier this summer to collect additional data on pollinator visitation rates.
Your research will address three main questions: 1. How does the species composition of the two sites compare? You will create a list of floral visitors at each site. 2. How do visitation rates (#visitors/plant/min) differ between Heart Island and the Volusia sandhill for partridge pea (Chamaecrista fasciculata), a species that depends upon specialist pollinators (bees) for successful fertilization? 3. How do visitation rates (#visitors/plant/min) differ between Heart Island and the Volusia sandhill for Spanish needles (Bidens alba), a species that attracts a variety of generalist pollinators?
Methods
Week 1, Volusia Sandhill - Working in groups of 2 – 3 students you will observe a minimum of three Bidens and three Chamaecrista plants for 5 minutes each, recording the number of flowers visited by each species of insect visitor.
Week 2, Heart Island Conservation Area - Working in groups of 2 – 3 students you will observe a minimum of three Bidens and three Chamaecrista plants for 5 minutes each, recording the number of flowers visited by each species of insect visitor.
Data Summary
Question 1 – Compiling data from all members of the class you will create a species list for each plant species (Bidens and Chamaecrista) in each site. There are no statistics associated with these data.
14 Questions 2 and 3 - Compiling data from all members of the class and using each plant as a replicate, you will use a t-test to compare pollinator visitation rates between the two sites for each species.
September 2, 2016 - Students in Plant Ecology (BIOL 450) collected data on pollinator visitation to Spanish needles (Bidens alba) and partridge pea (Chamaecrista fasciculata). They collected the same kind of data at Heart Island in the following week.
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