Takeshima, Noel2025-11-122025-11-12https://hdl.handle.net/1885/733794076Plant-pollinator communities play an important role in the functioning of mountain ecosystems, which are notably threatened by rapid climate change impacts. I investigated trends in the thermal tolerance (CTmin), body pollen composition, and genetic diversity in these communities by sampling 96 reed bees (Exoneura) at 7 sites along an elevational gradient ranging from 920m to 1850m. Reed bees underwent genome sequencing to test for genetic diversity, which revealed two clades, Exoneura c.f. robusta and Exoneura c.f. bicolor. I found that E. c.f.robusta, mostly present up until 1600m, was the more abundant clade up until 1450m, whereas E. c.f. bicolor, present at 6 out of 7 elevations, became more abundant above 1450m. Considering all bees, high-elevation bees were more tolerant to low temperatures than low-elevation bees (p = 0.002). However, there was an interaction between the effect of elevation and clade on CTmin, such that while CTmin was greater at higher elevations in E. c.f. bicolor, the effect was weaker in E. c.f. robusta. Pollen composition analysis showed that, on any given bee, the most abundant pollen type accounted for 86.5% (population mean) of their total body pollen. Therefore, our analysis focused on the identity of the most abundant pollen type found on bees. At elevations 920m to 1600m, the pollen family that both reed bee clades foraged from the most was Myrtaceae. However, at the highest elevation (1850m), where only E. c.f. bicolor was present, Asteraceae was foraged from the most as shown by 7 of 13 bees. Overall, my findings indicate that the nature of reed bee distribution is complex and interwoven with climatic variables. Despite exhibiting a broader range of CTmin across elevations, reed bees in the E. c.f. bicolor clade are more likely to be vulnerable to climate change-induced temperature increases than those in the E. c.f. robusta clade. A process which may drive this change is the potential upward range expansion of E. c.f. robusta populations, introducing competitive pressures at higher elevations. Additionally, my findings indicate that reed bees consistently forage from a single plant family at a time, regardless of elevation, while also demonstrating a capacity to forage from a variety of plant species. This foraging behaviour highlights reed bees' important role as pollinators, supporting plant reproduction in mountain ecosystems.en-AU202410.25911/CJ40-RW02