The role of behavior in the range expansion of an invasive colonial orbweaver spider, Cyrtophora citricola
Given the ecological and economic costs of invasive species, increasing incidences of species introductions have highlighted the importance of understanding the dynamics of their range expansion. Individuals at the front of an ongoing range expansion are often the first to encounter novel environmental conditions; thus, they are often exposed to a different set of selection pressures compared to conspecifics at the core of the range. Identifying phenotypic trait differences between individuals at the leading edge and core may provide valuable insight on the driving factors of both range establishment and spread that might be applied in limiting invasion events. Previous research documenting phenotypic shifts across species ranges have focused on morphological changes and life history shifts, but the role of behavior in the success of animal invasions remains a largely unexplored frontier of research.
I am interested in the variation of behavioral types (AKA behavioral syndromes, personalities, etc.) within populations of the invasive colonial tentweb orbweaver, Cyrtophora citricola. It has Old World origins, with descriptions in Asia, Europe, and Africa, but has been increasingly introduced in the Americas as of the last 20 years. Originally reported in Florida in 2000, C. citricola initially occupied a narrow range south of Miami. In my recently completed field season, I established that its range in Florida now spans over 150 miles north, suggesting an ongoing range expansion process. Cyrtophora citricola is an uncommon spider due to its colonial tendencies. Some spiders are found in large colonies consisting of a network of connected webs, whereas others remain in solitary webs. Due to this variation in social grouping, I am interested in whether a suite of behavioral traits, including social tendency, can explain certain spatial patterns of occurrence of individuals across a range. I hypothesize that certain behavioral types, such as individuals with high dispersal or low social tendencies, may accumulate at invasion fronts and promote range expansion.
Risks of biological invasions associated with the global shipping routes
The shipping industry is an important unintentional pathway for novel species introductions, and is responsible for some of the largest invasions in history (e.g., rats). Understanding the patterns of species movement through shipping routes will provide vital information for preventing future invasions. Yet surprisingly few studies have attempted to model these introductions using empirical shipping networks, and none have attempted to do so with terrestrial species. My collaborators and I seek to create a mathematical model that predicts how shipping networks move both terrestrial and marine species across the globe. Using shipment data from actual cargo routes, this model will visualize the system as a network, where major harbors are represented as nodes and ship movements as edges between them. We will then weigh these edges by quantifying the probabilities that a given species will board the ship, survive the journey, and become established in a new ecosystem. The equilibrium distribution of the weighted network will provide information about the species’ global distribution over time. This will identify the ports most susceptible to specific invasive species, and allow us to make predictions about how changes in trade routes will impact future invasions. Conversely, our proposed model may also identify sources of invaders by tracing their current patterns of distribution back to an original port. This model is therefore of both applied and theoretical relevance; it has the potential to inform management decisions to optimize cargo sterilizations and searches, supply risk assessments of routes and ports, and provide insight on the historical biogeography of invasive species associated with the shipping industry.
This collaborative project spawned a Summer Research Experience for undergraduates in 2015, resulting in the visualization of the domestic transportation of commodities in the U.S. through the interactive website, ComFlo. A model was also created to simulate the risks of invasion, shown here.
The three undergraduates on this project, Ashish Gauli, Nathan Wikle, and Ryan Yan, have recently won a student competition and have been invited to present their project at the NatureServe EcoInformatics Workshop in Washington, DC, in December 2015!