Photo by: Basant Giri
SUSMA GIRI
- PhD in Ecology -
Interactive effects of temperature and parasites in bees
I collected native bumblebees across elevations from three mountains in Wyoming and two native honeybee species from Annapurna Conservation Area, Nepal. Part of the honeybee sample has been submitted for PCR analysis of Crithidia spp., Nosema spp., Acarapis woodii, and conopid fly larvae. I will analyze the quantities of lipids, glycogen and sugars, which form major metabolic substrates, in another subsample of these honeybees. I am currently dissecting the bumblebees to count the loads of above-mentioned parasites in an individual and will use the remaining body tissue to compare the amounts of three metabolic substrates mentioned above.
Fig 1: UFA: SFA across altitude for bumblebees
Fig 2: UFA: SFA across the growing season for bumblebees
DISSERTATION RESEARCH:
My dissertation research focuses on understanding the physiological impacts of warming environmental temperatures in organisms. I take advantage of the temperature gradient across altitudes and seasons to address my research questions.
Homeoviscous adapation across altitude and season in bees
In this project, I studied how fatty acid composition changes across altitude and season (manuscript in prep.). Fatty acids are important energy resources in organisms and make up cell membranes. Environmental temperature can strongly affect the structure and function of fatty acids, but organisms can adjust fatty acid composition, thereby altering fatty acid fluidity in part, to maintain function in the face of changing temperatures, a hypothesis termed 'homeoviscous adaptation' (Sinensky, 1974). Fatty acid composition can be measured as the ratio of unsaturated to saturated fatty acids (UFA: SFA). I compared UFA: SFA in four native bee genera (Andrena, Bombus, Megachile & Osmia) collected throughout the growing season (May through September) across two altitudinal gradients in Wyoming. I found that UFA: SFA in the bees was significantly higher at higher altitudes than at lower altitudes and during early spring than in late summer when environmental temperatures are relatively low (Figure 1 and 2 show UFA: SFA across altitude and season for bumblebees). I am following-up this experiment by conducting a lab experiment to understand the relative effects of temperature and diet in fatty acid composition.
Photo by: Achyut Aryal
UNDERGRADUATE RESEARCH:
Diet composition of Himalayan Serow
I studied the distribution of serow (Capricornis sumatraensis), a near-threatened species, and its feeding ecology in the Annapurna Conservation Area (ACA), Nepal. It is distributed across the lower belt of ACA spanning four districts of the conservation area. Microhistological analyses of plant remains in its fecal samples collected at an elevation of 2,310 m asl showed that serow is a generalist herbivore. A total of thirty four plant species were identified, with Arundinaria spp being the most prevalent component (9.4%). Two important challenges for the conservation of serow were identified: i. Competition for resources with the local people, who rely on many of the plants that comprise the diet of serow, including the important Arundinaria spp for medicines, foods and sources of structural materials, and ii. Populations are becoming isolated as a result of habitat fragmentation caused due to human settlements.
Himalayan Serow, photo taken by Achyut Aryal, co-advisor for the project
Effects of temperature on fatty acid composition and thermal tolerance in bees
The composition of fatty acids, as determined by the ratio of UFA: SFA can have impact the range of environmental temperatures organisms can tolerate ("breadth of thermoal tolerance"). I, in collaboration with another graduate student in Dillon lab, measured critical thermal mimimun and maximum, and revival temperatures in bees collected across altitudes, and also from lab-reared hives exposed to varying temperatures. Critical thermal minimum and critical thermal maximum temperatures represent the low and high temperatures respectively, below or above which organisms lose coordination. Revival temperature is the temperature at which organisms regain consciousness after entering chill-coma. I have determined the fatty acid composition in these bees and am currently analyzing the data.