Changing species interaction networks

cheetahs_impalaGlobal change drivers are profoundly impacting species’ abiotic and biotic environments. These impacts threaten the capacity of ecosystems to sustain biological diversity and ecosystem functions that are important to people. To understand the feedbacks that govern community responses to global change, ecologists must work toward a deeper understanding of the tangled web of species interactions that govern the dynamics of complex ecological communities. By studying anthropogenically altered communities and the impacts of global drivers, my research addresses a major predictive challenge for ecology in an era of global environmental change, to forecast how novel interactions, altered interactions, and interaction extinction drive ecological and evolutionary change.

My research seeks to explain variation among species in their responses to altered species interactions. Theory on species coexistence and evolutionary ecology is critical for making these links because it explains why species vary in their ecological roles and how traits of species reflect these differences. Knowledge of the links between traits and the strategies most affected by global change can help predict winners and losers under anthropogenic change. I am pursuing these interests with research on the consequences of defaunation following the introduction of the invasive brown treesnake on Guam with Haldre Rogers, with field projects identifying the plant traits that mediate interactions with antagonists in Panama, and with synthesis of global mutualistic interaction and trait databases to understand the species most vulnerable to mutualism disruption. This research works to improve predictions for plant migration under climate change, persistence of animal-dispersed tree species important for tropical forest carbon storage, and regeneration of deforested areas and secondary forest.


The seed dispersal mutualism

PrintMutualistic interactions between plants and their seed dispersers generate and sustain
plant diversity, and mutualisms provide compelling systems to understand the evolution of nature’s impressive diversity of plant and animal traits. My research in this area has focused on the breadth of mechanisms by which frugivores benefit plants, the ecological contexts where these benefits occur, and variation among species in the magnitude of these benefits. These projects have focused on detailed studies of wild chilies with Josh Tewksbury and Doug Levey and community-scale studies of dispersal benefits in the Mariana Islands working with Haldre Rogers. In particular, I am interested in the reasons why species vary in their demographic dependence on seed dispersal and how diversifying processes cause differentiation in mutualistic strategies among species.

Mutualistic network approaches offer useful tools for understanding the dynamics of mutualistic communities. The promise of this approach is its capacity to use simple interaction data to understand the assembly and disassembly of mutualistic communities. My ongoing work suggests that including other axes of variation among species—in addition to interaction frequency data—can reorient our understanding of the stability of mutualistic networks and their responses to change.


Maintenance of species and trait diversity

IMG_1699Understanding the processes that allow species to coexist is a central goal of ecology, and species interactions are at the core of the diversity-maintaining processes that shape ecological communities. A key coexistence mechanism caused by interactions between plants and their predators and pathogens is conspecific negative density dependence. My research has addressed the role of conspecific density dependence in tropical forest dynamics, working to identify the agents that cause this phenomenon and to assess how variation in the strength of density dependence influences species abundance and diversity.

My research also focuses on the causes and consequences of variation in traits among and within species. Recent interest among ecologists has focused on links between functional traits and coexistence, particularly with coexistence mechanisms involving competitive interactions among plants. Extending these concepts to interactions with mutualists and antagonists, my ongoing projects assess how physical and chemical defense traits influence interactions with antagonists, how traits of mutualists determine the diversity and identity of their partners, and how tradeoffs operating within species underlie intraspecific trait variation. These projects point toward a broader importance of traits for plant coexistence: traits mediate differentiation among plant species in their interactions with the abiotic environment, competitors, natural enemies, and mutualists. My major collaborators on these projects include Joe Wright for work on Barro Colorado Island and Haldre Rogers in the Mariana Islands.


This work supported by: