The Causes and Consequences of Variation in Dispersal Distance

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Like people, wild animals and plants can spend their lives close to where they were born or move away. Scientists call these lifetime movements "dispersal". While short-distance dispersal is common, long-distance dispersal is rare. Long-distance dispersal, however, plays an important role in nature -- it can help species survive when their habitat is destroyed, and can spread genes that they need to adapt to new conditions. Long-distance dispersal can also allow invasive species to spread quickly, leading to significant management costs and threatening native species. Scientists do not fully understand the factors that cause differences in dispersal distance, in part because it is difficult to track long-distance dispersers. This research will help people understand the causes and consequences of differences in dispersal distance by focusing on a salamander that lives in small, mountain streams. Because salamanders disperse along streams, and because even long-distance dispersers don't go very far (less than 500 meters), it is possible to collect information on dispersal (distance, timing, conditions before and after) that would be difficult and expensive to collect in other species. With this information, scientists and managers can better promote dispersal by native species, or prevent dispersal by invasive species. This research will test whether dispersal distance affects individual performance (survival and growth), and how environmental factors (habitat stability and predation) influence those effects. The researcher will then test whether individual performance consequences predict population-level variation in dispersal distances (i.e., dispersal kernels), associated morphological, behavioral, and physiological phenotypes, and emergent patterns of population connectivity and range expansion. Because the research questions center on fundamental performance consequences, scaling relationships, and biogeographic processes, results will be informative across taxa. In particular, this work will help bridge plant and animal studies of dispersal by filling a common gap in our understanding of the scaling of dispersal data -- from individual traits to population-level dispersal distributions, and further to landscape and biogeographic consequences.