Genetic Structure in Peregrine Falcons (Falco peregrinus): An Assessment Using Multiple Markers
Caballero, Isabel C.
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The Peregrine Falcon (Falco peregrinus) is a bird of prey with one of the largest natural distributions of any avian species. This thesis explores its mating system, effects of reintroductions, and worldwide population structure. Research questions are focused on different spatial and geographical scales, making use of nuclear and mitochondrial data to address these questions. The use of the pesticide DDT had negative impacts on Peregrine populations causing extirpation or sharp reduction in numbers. On a local level, I investigate the breeding and dispersal patterns in urban- dwelling reintroduced Midwestern Peregrine Falcons. Data was gathered from a total of 282 chicks and 68 additional birds with most extensive sampling from Chicago. I found high nest site fidelity, long-term mate fidelity, and two instances of extra-pair paternity. My results are in accordance with previous findings for other raptors that genetic monogamy is the rule and nest site fidelity is frequent. On a regional level, I focused on historical changes in Midwestern populations as well as effects of management practices in Western and Midwestern Peregrines. For the historical aspect, I detected differences in levels of genetic diversity in extirpated and reintroduced Peregrines. Bayesian clustering analysis of microsatellite data revealed a genotypic shift between historical and contemporary populations. The cause of this shift is likely the result of the use of non-native stock in the recovery process. For the regional comparison of reintroduced birds, Western management practices involved the use of remnant birds while in the Midwestern non-native stock was used. Analyses were carried out on 192 birds, 112 individuals representing recovered Western US populations and 80 individuals from the Midwest. I found genetic differentiation among populations, and similar levels of genetic diversity across regions. Microsatellite data separate Western Peregrines into three distinct genetic clusters: (i) Channel Islands and Southern California; ii) Northern California and Oregon; and iii) Washington. These genetic patterns were concordant with previous ecological modeling studies. My results do not support the hypothesis that different management techniques have left an imprint on these recovered populations, but there is genetic structure consistent with the original groups on which management plans were focused. On a global level, worldwide Peregrines exhibit regional differences in behavior, morphology, and demographic history. A mix of migratory and resident breeding populations occurs in the northern hemisphere while exclusively resident breeding populations occur in the southern hemisphere where northern migrants come to winter. To understand how Peregrines evolved such a wide-ranging distribution I compared two alternative hypotheses of range expansion: Isolation by Distance, and Suspension of Migration. Genetic results show low to medium degrees of genetic differentiation among northern hemisphere Peregrines while significant differentiation was observed between northern migrants and southern residents in both the Old and New World. Mitochondrial data reveals a similar picture with lack of differentiation between northern Peregrines and significant differentiation between northern and southern populations. Worldwide genetic patterns derived from multiple type of analysis supported the Isolation by Distance hypothesis. Contiguous populations were less differentiated than far distant ones. Even though Suspension of Migration was not supported, mitochondrial DNA migration analysis detected a west to east historical gene flow in northern migrants, and a south to north direction of gene flow for Old World Peregrines.
Isolation by Distance