Tracking large-scale range expansion and colonization of American white pelicans using multiple intrinsic markers

Background/Question/Methods   Changes in global climate and land-use practices are drastically altering the environment, resulting in large-scale demographic changes in many animal populations. These environmental changes have led to both range expansions and contractions, yet developing effective tools to track animal movements has remained a major challenge. To develop such predictions requires in-depth study of populations that are expanding or contracting in the face of global change. Recently, new American white pelican colonies have become established across their continental range, including attempted breeding on an island off Akimiski Strait, James Bay (Ontario and Nunavut, Canada) – 500km from the previously reported easternmost breeding population. Our objectives were to 1) create a genetic and biogeochemical “map” of the breeding range of American white pelicans and 2) examine the genetic and biogeochemical profiles of colonizers to determine their provenance.

Results/Conclusions   To track the movement patterns of American white pelicans and delineate the provenance of new colonizers, we used microsatellite and mtDNA markers, stable-isotopes, and trace-element analysis to characterize potential source colonies and assign new colonizers to source populations. Blood and tissue samples from 333 nestlings from 19 colonies spanning the continent, from California to Ontario, were used for microsatellite and mtDNA analysis. Our genetic analyses indicated complete panmixia across the entire range of American white pelicans, suggesting low utility of genetic data for tracking movement or assigning colonizers to source populations. Stable-isotope analysis of 221 individuals from 22 colonies spanning the same range as our genetic data indicated a high level of within-colony variation, supporting the idea that low site fidelity and high rates of dispersal likely led to the lack of range-wide genetic differentiation. However, despite high levels of within-site variation, among-site patterns of variation were high enough to allow us to create an isotopic “map” to which we were able to assign new colonizers from two newly established colonies to potential source populations. New colonies of American white pelicans appear to be composed of individuals that molted across a wide range of locations and habitats and these new colonies were not merely assemblages of individuals from nearby colonies. Though a multiple-isotope approach using H, C, and N provided moderate resolution at a broad spatial scale, we also present preliminary evidence that suggests trace-element analysis will provide high resolution at a fine (colony-level) spatial scale.