Population genetic structure and breeding philopatric behavior of Cackling Canada Geese
I studied patterns of genetic differentiation in breeding Cackling Canada Geese (Branta canadensis minima) at multiple scales and sought to link reproductive consequences of philopatry with subsequent patterns.
I first examined large-scale patterns of structure in breeding Cackling Canada Geese using different types of molecular markers. I showed that there was significant differentiation among groups of females at maternally inherited genes (mtDNA) but less differentiation using biparentally inherited markers (microsatellites). This suggests a restriction in mtDNA gene flow through philopatry of females, but increased gene flow at microsatellite loci promoted by dispersal of males.
Next, I examined differentiation at a finer-scale (<5 km) not commonly resolved in larger-scale studies. There were strong patterns of relatedness among females using different types of markers. Neighbors were more likely to have similar mtDNA haplotypes and exhibited higher levels of relatedness at microsatellite loci than expected. Given this pattern of relatedness, I then investigated breeding philopatry and the effects of relatedness on nesting success. Using microsatellite genotypes to identify individuals, I showed that philopatry was influenced by previous success and to a lesser extent, by the relatedness of neighbors. Philopatry in turn affected future success of females while relatedness of neighbors had a small positive influence on success.
Lastly, I investigated relatedness and nesting dispersion in another species, Pacific Greater White-fronted Geese (Anser albifrons frontalis ). White-fronted Geese nest in clusters of females and I investigated whether these groups were comprised of related females. Given their behavioral characteristics, White-fronted Geese have the potential to be highly structured. However, females in clusters were not more related than expected, suggesting that the benefits of nesting near kin were not the only determinants for clustering.
My dissertation illustrates the value of considering both large and small-spatial scale patterns in analyses of population differentiation. Moreover, by examining the effects of individual behavior, such as philopatry, on reproductive success and subsequent patterns of relatedness, I can provide deeper insight into the behavioral mechanisms lead to and maintain such patterns of differentiation.