BACKGROUND AND RATIONALE

Transcription

1 Proposal for Shipley- Skinner Reserve Riverside County Endowment: Temporal variation and effects of drought in coastal sage scrub plant- pollinator mutualisms Principal Investigator: C. Sheena Sidhu (Postdoctoral Researcher), co- Principal Investigator: Erin E. Wilson Rankin (Assistant Professor), Department of Entomology, UC Riverside RESEARCH AIMS AND SIGNIFICANCE This research will examine and characterize plant- pollinator interactions and pollination requirements for the successful promotion and conservation of native and rare plants of Riverside County. The 2014 Shipley- Skinner award provided us the opportunity to begin critical work examining plant- pollinator relationships in the unique Riverside coastal sage scrub habitat. The 2015 Shipley- Skinner award will allow us to leverage our work to- date in sage scrub habitat, and combine it with our experience studying rare and federally listed plants from related projects, and embark on a long- term study of the coastal sage scrub pollinator community. With the baseline data attained from the first year contributing to the experimental framework, we will complement field surveys with manipulative pollination experiments to further investigate the pollination ecology of this threatened ecosystem. We propose to: 1) Identify the plant- pollinator community of the coastal sage scrub habitat through continued sampling and expansion of study site locations to (a) examine the effects of drought on pollinator populations, and (b) capture temporal variation in plant and pollinator phenology 2) Quantify the pollination requirements of selected plants of the coastal sage scrub community via both (a) field experiments and (b) manipulative greenhouse experiments This project will provide critical data aligned with the Metropolitan Water District (MWD) of Southern California s objectives. In particular, we will conduct quantitative assessments of plant- pollinator relationships to monitor the status of plant and pollinator populations in this habitat, and conduct manipulative greenhouse experiments to quantify pollination requirements necessary for successful reproduction and propagation of key plant taxa. Moreover, collecting multi- season data from multiple reserves in Riverside County will be vital for the detection and prediction of changes in the plant- pollinator community. Collectively, this project will help fill in the missing links in our understanding of mutualisms between native plant communities and their pollinators and will contribute to restoration and conservation efforts in this unique habitat. BACKGROUND AND RATIONALE The Riverside County coastal sage scrub ecosystem is a unique habitat that is threatened by increasing agriculture and urbanization (Minnich & Dezzani 1998). In order to protect and manage this habitat, which includes many rare plant species, as evidenced by the Multiple Species Habitat Conservation plan (MSHCP 2003), it is necessary to consider pollinators and their relationships with plants. Insect pollinators are critical for Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 1

2 the successful reproduction of many flowering plants (Waser & Ollerton 2006), but pollinator populations are threatened by increasing habitat fragmentation as are the rare plants they pollinate (Committee on the Status of Pollinators in North America 2007). Plant- pollinator relationships are critical to maintaining any healthy ecosystem, and special consideration should be directed to threatened, fragile ecosystems where healthy populations are necessary to maintain viability in the face of stressors. Another serious threat to both plants and pollinators is drought. This is a particularly pressing issue in Riverside County. Drought can have severe consequences on ecosystems as well as plant and pollinator health (Cayan et al. 2008). Several studies have examined the effects on plants and long- living animals, but few have examined short- lived insects (Minckley et al. 2013). And while drought has been demonstrated to directly impact plant populations and phenology (Penuelas et al. 2004), and some evidence suggests drought impacts pollinator populations (Minkley et al. 2013), few studies consider the impact of drought on the combined plant- pollinator mutualism. Studies examining the long- term affects of climate change on plant- pollinator relationships suggest a negative impact on pollination due to phenological mismatching of floral blooms and bee emergence caused by varied response to abiotic cues (Gilman et al. 2012, Bartomeus et al. 2013). This can be especially threatening to rare plants with small populations in the case where their pollinators may have emerged too early or too late to synchronize with their bloom period. It is possible that drought may cause plants and pollinators to respond irregularly to rainfall cues and negatively impact the plant- pollinator mutualism that both groups of organisms rely on. The 2014 Shipley- Skinner award allowed the Rankin Lab to begin examining the plant- pollinator relationships present in the Riverside coastal sage scrub habitat, and incidentally also recognize potential impacts of drought on the community. The conclusions of our initial year of research identified the pollinator community present in the inland coastal sage scrub community at Motte Rimrock Reserve, in Perris, CA, via pollinator surveys (Table 1). The data also suggest a phenological mismatch of overall floral availability relative to pollinator abundance over time (Figure 1). Further work is required to parse out if there is a phenological mismatch and/or if this follows typical and predictive population fluctuations. For this reason, a multi- year study of these native vegetation areas, and additional sampling sites would be beneficial to elucidate these trends and potential negative impacts. Expanding our survey sites to additional areas in Riverside County will provide increase sampling effort to identify the plant- pollinator communities present in the county and allow for comparison of plant- pollinator networks across reserves. Collectively, this information can be used to predict population fluctuations of plant and pollinator species of the coastal sage scrub community. Table 1: Motte Rimrock species list and abundances, 2015 (abbreviated list) Hymenoptera (bees & wasps) Adrena spp 19 Agapostemon spp 21 Apis mellifera 87 Anthidium sp 1 Bombus spp 24 Colletidae 4 Diadasia spp 6 Halictidae (large) 29 Halictidae (small) 46 Lasioglossum spp 62 Melissodes spp 9 Xylocopa spp 14 Vespid 7 unknown bee spp 15 Diptera (flies) Muscidae sp1 7 Muscidae sp2 2 Syrphidae sp1 9 Syrphidae sp2 2 unknown fly sp 1 Lepidoptera (butterflies) Sphingidae 4 Vanessa sp 2 Unknown moth spp 4 Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 2

3 Figure 1: Possible phenological mismatch due to overall pollinator abundance peaking prior to maximal floral availability (displayed proportionally) at Motte Rimrock Reserve. To quantify the plant- pollinator relationship, our previous research supplemented the pollinator survey with measures of pollinator effectiveness. To do this, we presented the pollinator community with pollinator- excluded (bagged) and pollinator- accessible flowers (unbagged) flowers to measure pollination requirements and seed set of select flower species in the community. However, in 2015, drought negatively impacted insect activity and longevity of floral display (extreme heat reduced both). This made it difficult to observe plant- pollinator interactions and directly measure pollination efficiency (i.e. amount of pollen transferred by pollinators and amount required for adequate seed set). To overcome this obstacle, we propose future, field experiments be supplemented with controlled greenhouse experiments of the same plant species and pollen transfer can be manipulated to measure efficiency (Kearns & Inouye 1993). Building upon our current research, we aim to gain a deeper understanding of the plant and pollinator community of the coastal sage scrub to benefit and support support conservation. To achieve this, we propose to complete the following research objectives: Objective 1: Identifying the plant- pollinator community of the coastal sage scrub habitat through continued sampling and expansion of study site locations to (a) examine the effects of drought on pollinator populations, and (b) capture temporal variation in plant and pollinator phenology. Objective 2: Quantify the pollination requirements of selected plants of the coastal sage scrub community via both (a) field experiments and (b) manipulative greenhouse experiments. RESEARCH PLAN Objective 1: Identifying the plant- pollinator community of the Riverside coastal sage scrub habitat through continued and expanded sampling to (a) examine the effects of drought on pollinator populations, and (b) capture temporal variation in plant and pollinator phenology. Pollinators will be surveyed at each site utilizing vane traps that are designed to attract and collect insects (Rao et al. 2011). We will continue surveys at Motte Rimrock Reserve in Perris, CA in the typical winter/rain season, spanning December to April. Replicating methods from our previous season, we will place vane traps in nine plots throughout the reserve for one week approximately every 3 weeks. Each plot will identified by a dominant plant species (Table 2), and presence and abundance of all flowering plant species will be recorded for each time point. In addition, we will set up vane traps at two additional reserves: Box Springs Reserve and Shipley- Skinner Reserve. At least five plots will be designated based on known populations of rare plants and key species of the coastal sage scrub ecosystem that compliment the species examined at Motte Rimrock Reserve. While final selection will be Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 3

4 based on location and abundance of plant population (MSHCP 2013)., possible species include: Eschscholzia californica, Chorizanthe spp., Allium spp. and Dudley spp. Collected pollinators will be brought back to the lab to be mounted and identified. At the termination of the project, the samples will be deposited at the UC Riverside Entomology Research Museum, where they will be entered in an electronic database and publicly available for reference in any future research. Repeated sampling throughout the season will allow us to capture temporal changes in the community throughout the season, and compare change across the two years, and across sites, (with effort to continue this research in subsequent years). Pollinator community composition in relation to blooming plants will be analyzed using principal components analyses to identify plant- pollinator associations. Table 2: List of sites by dominant plant species (Motte Rimrock Reserve) Site name CA broom patch Annual patch Buckwheat Gully Cactus patch Goldfield site Hilltop site Poppy field Sage site Squash patch Dominant plant species Acmispon glaber Calandrinia ciliata, Cryptantha sp. Eriogonum fasciculatum Opuntia parryi Lasthenia californica Phacelia minor, Solanum xanti Eschscholzia californica Salvia mellifera Cucurbita palmate Objective 2: Quantify the pollination requirements of selected plants of the coastal sage scrub community via both (a) field experiments and (b) manipulative greenhouse experiments. We will measure pollination of coastal sage scrub plants in the field by bagging flowers to exclude pollinators, and comparing seed set of bagged flowers to unbagged flowers are left to be pollinator accessible (Kearns and Inouye 1993). Ten soon- to- flower buds of select plants will be bagged with fine- meshed drawstring bags during peak bloom period. Ten corresponding buds at the same growth stage will be marked as the unbagged, control flowers. Upon seed set, fruit will be brought back to the Rankin lab where seeds will be counted and compared between the bagged and unbagged flowers. To complement the field manipulation, we will also conduct an additional greenhouse manipulation to further investigate pollination requirements of plants. We will grow common and rare plants of the coastal sage scrub community from seed in the greenhouse and hand- pollinate flowers to measure pollination requirements (Kearns & Inouye 1993). Seeds will be obtained from UC reserve population, with appropriate permission, or commercial vendors. The Rankin Lab has experience collective and growing native and rare endemic plants in greenhouses for related projects. Flowers will be individually pollinated using a fine sable brush to touch and transfer pollen between flowers, and the approximate number of pollen grains transferred will be estimated. Flowers will be hand- pollinated with low, medium, or high amount of touches to simulate low, medium, or high pollinator visitation (the actual amount of touches will vary among flower species dependent on flower size and pollen transfer). After pollination, flowers will be bagged and allowed to set seed, in addition to flowers bagged without any manipulation (control). Seeds will be counted and compared to estimate the amount pollen Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 4

5 required for corresponding seed set. The complementary greenhouse experiment will allow us to model and estimate the pollinator activity required for natural seed set in controlled conditions independent of drought and other stressors. Seed set can be compared to field seed counts of common plants for model validation. The greenhouse experiment also has the advantages of allowing manipulative experimentation on rare taxa with no risk to wild populations of rare species. Project Duration: July 1, 2015 to June 30, BUDGET Personnel Postdoctoral Researcher (C. Sheena Sidhu) at 30% for 6 months $9500 Laboratory technician (Sarah Barney) at 10% for 6 months $1800 Work- study student technician (Chien Yu) at 20% for 6 months/ 2 quarters $1500 Equipment Field supplies & greenhouse supplies $1200 Travel Mileage reimbursement (approx miles at $0.56/mile) $740 Total $14, 740 BUDGET NARRATIVE We request funding to cover postdoctoral researcher, a laboratory technician, and a work- study student to carry out this project. We request partial funding for a postdoctoral researcher (Dr. Sheena Sidhu) for 6 months plus 37. fringe is $5550. Dr. Sidhu conducted the first year of field work and has experience with experimental manipulation of rare and federally listed plants. She will continue field work and oversee greenhouse experiments. Partial funding for laboratory technician for 6 months at 54% fringe is $1800. Technician Sarah Barney is experienced in manage greenhouse plants, assist with field experiments and laboratory duties. During the academic year, one student technician will be hired for 20% time with 2.5% fringe, which is $1550 for each quarter. Current student technician, Chien Yu, is trained in sorting and pinning insects, basic identification, and database management. Field and greenhouse equipment required for this project is estimated to cost $1200 in total. Most field material was purchased in the previous year and will be reused this year (eg. Vane traps, sample vials, and nets), and we will allocate $100 for any replacement supplies. Greenhouse materials include seeds, pots and soil (approximately $400) plus greenhouse rental ($100/mo for 4 months). Additional material includes supplies for preparing and storing collected pollinator specimens, and dissection and measuring tools for quantifying seed set ($300). Travel to Shipley- Skinner Reserve is 100 miles round trip from UC Riverside campus, and travel to Motte Rimrock is 30 miles round trip from UCR campus, and travel to Box Springs Reserve, a minimal distance behind campus, will be combined into trips to other reserves. We estimate 6 trips to Shipley- Skinner Reserve and 24 trips to Motte Rimrock. Mileage reimbursement for personal car use is estimated for 1320 miles at $0.56 per mile reimbursement (UCR Travel Policy), which is $740. Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 5

6 Literature Cited Bartomeus I, J.S. Ascher, J. Gibbs, B.N. Danforth, D. L. Wagner, S.M. Hedtke, R. Winfree (2013). Historical changes in northeastern U.S. bee pollinators related to shared ecological trails. PNAS 110: Cayan, D. R., E. P. Maurer, M. D. Dettinger, M. Tyree, and K. Hayhoe (2008) Climate change scenarios for the California region. Climatic Change 87: Committee on the Status of Pollinators in North America NRC (2007) Status of Pollinators in North America. National Academy Press. Gilman, R. T., N. S. Fabina, K. C. Abbott, and N. E. Rafferty (2012) Evolution of plantpollinator mutualisms in response to climate change. Evolutionary Applications 5: Kearns C.A., and D.W. Inouye (1993) Techniques for Pollination Biologists. University of Texas Press. Minckley, R.L., T.H. Roulston, and N.M. Williams (2013) Resource assurance predicts specialist and generalist bee activity in drought. Proc R Soc B 280: Minnich, R.A., and R.J. Dezzani (1998) Historical decline of coastal sage scrub in the Riverside- Perris Plain, California. Western Birds 29: MSHCP WRC (2003) Multiple Species Habitat Conservation Plan. MSHCP WRC (2013) Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP). Western Riverside County Regional Conservation Authority. Penuelas, J., C. Gordon, L. Llorens, T. Nielsen, A. Tietema, C. Beier, P. Bruna, B. Emmett, M. Estiarte, and A. Gorissen (2004) Nonintrusive field experiments show different plant responses to warming and drought among sites, seasons, and species in a north-south European gradient. Ecosystems 7: Waser N.M., and J. Ollerton (2006) The Ecological Consequences of Complex Topology and NEsted Structure in Pollinator Webs (NM Waser, J Ollerton, Eds,). University Of Chicago Press. Sidhu & Rankin Proposal: Shipley- Skinner Reserve Riverside County Endowment 6