Date of Completion


Embargo Period



Robert Bagchi, Sarah Knutie

Field of Study

Ecology and Evolutionary Biology


Master of Science

Open Access

Open Access


Interaction networks among plants and animals are important determinants of the stability of ecological communities. Historically, researchers have considered interaction networks in isolation, and characterized the structures of the interactions within such networks, and how these structures can affect community stability. Such studies have identified unique structures attributable to different interactions, such as mutualisms (e.g. pollination) and antagonisms (e.g. herbivory). My thesis explores a tropical system in which all interacting guilds are directly connected. Mutualistic hummingbird-plant pollination networks are connected to antagonistic nectar robbing mite-plant networks, via phoresy. Because phoretic mites must hitchhike on hummingbirds to colonize flowers, we aim to understand whether visiting patterns of hummingbirds to their host plants constrains the structure of interactions between phoretic mites and their host plants. Previous studies suggested that most mites are highly specialized on particular host plant species to increase mate encounters (i.e., the Mating-Rendezvous Hypothesis). Alternatively, mites may use multiple host plants not shared with other species (i.e. Compartments Hypothesis). A third option is that mite-plant interactions will be structured in a similar way to hummingbird-plant interactions (i.e. Mirror Hypothesis). To reconstruct interactions among 23 mite MOTUs and 14 plants, and ten mites and 12 hummingbirds we used DNA CO1 barcodes. To record interactions between hummingbirds and plants we used video cameras. From the data gathered we were able to reconstruct the interaction networks to analyze their structures. The hummingbird-plant network was found to be significantly nested as is typical of mutualistic networks. Similarly, the antagonistic mite-plant network was also found to be significantly nested. We then provide potential mechanisms for the observed network structures by examining host plant use similarities between hummingbirds and mites, and mapping the dispersal routes of mites among host plants. Our findings collectively support our Mirror hypothesis and show that interconnected networks can affect each other’s structure.

Major Advisor

Carlos Garcia-Robledo

Available for download on Wednesday, April 21, 2021