KSEF RDE: Social Networks and the Dynamics of Species Invasions: Range Expansion of the Invasive Western Mosquitofish in Kentucky

The western mosquitofish (Gambusia affinis) is on the list of top 100 invasive species worldwide, Global Invasive Species Database. Native to North America, this fish has been widely introduced outside its native range in North America, South America, Europe, Asia and Africa for mosquito control. Unfortunately, this species eats the larvae of native fishes and amphibians, and has had a major impact on the communities to which it has been introduced. In addition, western mosquitofish have been expanding their range naturally up the Mississippi River drainage. They are native to western Kentucky, and over the last 50 years have expanded their range eastward throughout the entire Commonwealth. My lab studies the ecological and social determinants of microhabitat choice, dispersal and range expansion in this species. Predation, body size, sexual conflict, and personality of the focal fish and its shoal mates are all known to contribute to microhabitat choice and dispersal in western mosquitofish. Now, I am adding an exciting new approach to this research, social network theory. Social network analysis requires marking individuals in an experimental population, repeatedly sampling them over time, and noting their locations and proximity to other marked individuals. Out of these analyses emerge nonrandom association patterns among individuals, and I seek to understand how these association patterns determine dispersal. Two specific hypotheses, which are not mutually exclusive, will be tested: 1. Individual dispersal: Predation and social conflict disrupt social networks in the short term and cause fish to alter their microhabitat choice or to disperse. 2. Group dispersal: These fish often move about in shoals, and shoals of mosquitofish account for much of their dispersal. Experiments will be conducted in stock tanks and artificial streams at the University of Kentucky's Ecological Research Facility. Social network data will be obtained using burst-mode digital photography and high-definition videography of individually marked fish, and will be analyzed using UCINET software.