Dissertation

Bees, Trees, and Floral Interactions: Studies in Anthecology From Temperate Farms to Tropical Canopies

Aldercotte, Andrew Hudson

2025

Overview

Plant-pollinator mutualisms play a central role in the ecology and evolution of terrestrial ecosystems. Nonetheless, and despite a long history of study, major knowledge gaps persist. There is still much to learn regarding how plant-pollinator relationships are responding to a changing world, and how they function in understudied systems, particularly in the tropics and in the forest canopy. This dissertation draws on two long-term monitoring datasets that were generously shared with me—one from New Jersey and one from Indonesian Borneo— as well as original fieldwork I conducted in the canopy of a tropical peat swamp forest, to explore questions relating to temporal trends in the abundances of pollinators, the flowering phenology of tropical trees, and the structure of interactions between plants and pollinators in the forest canopy.Between 2005 and 2012, the Winfree lab group conducted multiple studies on bee visitation and pollination in watermelon fields in New Jersey and Pennsylvania. Soon after joining the lab in 2020, it occurred to me to use the data from those studies to conduct a longitudinal analysis of trends in bee abundance. Little is known about the population dynamics of bees, especially in the context of agricultural environments where they provide critical pollination services to crop plants. In Chapter 1, we show that bee abundances declined sharply over the 8-year period but also fluctuated wildly from year to year. To differentiate trends from noise, we applied a permutational model that allowed for stochastic variation in bee populations between years. Results of the permutational tests were non-significant, highlighting the importance of accounting for typical annual fluctuations in pollinator abundance when describing long-term trends, as well as the need for more long-term monitoring of pollinator communities.In 2021, I decided that I wanted to conduct research on pollination and pollinators at the Tuanan Research Center, a Rutgers affiliated facility in Central Kalimantan, Indonesia. Unfortunately, Indonesia’s borders were shut to foreign researchers due to the COVID-19 pandemic. Consequently, I turned to existing long-term phenology monitoring data from Tuanan for Chapter 2, which investigates patterns of asynchronous flowering and their implications in tropical rainforest trees. Asynchronous flowering can result in temporal mate restriction, which under certain conditions can lower effective population sizes, reduce genetic diversity, and lead to inbreeding. Tropical peat swamp trees may be among the most asynchronously flowering plant communities known, yet studies of intra-population variation in phenology are lacking for these tree species. Using 18 years of phenology data for 24 tree species, we found that the same conspecific trees tend to flower together across flowering events, but did not find patterns that would lead to lifetime restriction of parental pairings. Taken together with a lack of spatial autocorrelation in phenology, these results do not suggest that temporal mate restriction is likely to have a substantial impact on the genetic structure and genetic health of these tree populations.In 2022 Indonesia opened its borders to foreign researchers, and I was finally able to collect my own data in the field. I travelled to Tuanan on a Fulbright scholarship, where I spent 10 months observing floral interactions in the canopies of 15 species of trees and shrubs in the genus Syzygium. Syzygium is one of the most diverse tree genera in the world, and one of the least understood. In Chapter 3, we provide the first thorough description of pollination mutualisms in Bornean Syzygium and identify relationships between visitor attraction and floral traits in the genus. Communities of Syzygium visitors at Tuanan were similar to those described elsewhere, but we also encountered some unexpected differences, including a few predominantly beetle-visited species, a lack of honeybees, and low rates of nocturnal visitation.A feature of the floral morphology of Syzygium is that it is easy to determine whether visitors are foraging on nectar, pollen, or both during their visits. In Chapter 4, we take advantage of this to build parallel networks of visitation, pollen-use, and nectar-use, and then compare estimates of foraging specialization across the three networks. We found that the community of animals visiting Syzygium flowers was more specialized in their use of nectar as a resource than pollen, contrary to general expectations for specialization in anthophilous animals. Furthermore, the visitation network did not accurately represent resource specialization by flower visiting taxa, an important consideration given the widespread use of visitation-based plant-pollinator networks in current research on pollination mutualisms.These chapters represent a broad range of systems, questions, and methodologies. Yet each one addresses a currently relevant topic in anthecology where substantial knowledge gaps persist, where analytical methods are frequently misapplied, or both.

• Publisher: ProQuest Dissertations & Theses
• Subject: Ecology / Evolution & development / Evolution and Development
• ISBN: 9798297635500