Appraisal of the consequences of the DDT‐induced bottleneck on the level and geographic distribution of neutral genetic variation in Canadian peregrine falcons,Falco peregrinus

Abstract

Peregrine falcon populations underwent devastating declines in the mid-20th century due to the bioaccumulation of organochlorine contaminants, becoming essentially extirpated east of the Great Plains and significantly reduced elsewhere in North America. Extensive re-introduction programs and restrictions on pesticide use in Canada and the United States have returned many populations to predecline sizes. A proper population genetic appraisal of the consequences of this decline requires an appropriate context defined by (i) meaningful demographic entities; and (ii) suitable reference populations. Here we explore the validity of currently recognized subspecies designations using data from the mitochondrial control region and 11 polymorphic microsatellite loci taken from 184 contemporary individuals from across the breeding range, and compare patterns of population genetic structure with historical patterns inferred from 95 museum specimens. Of the three North American subspecies, the west coast marine subspecies Falco peregrinus pealei is well differentiated genetically in both time periods using nuclear loci. In contrast, the partitioning of continental Falco peregrinus anatum and arctic Falco peregrinus tundrius subspecies is not substantiated, as individuals from these subspecies are historically indistinguishable genetically. Bayesian clustering analyses demonstrate that contemporary genetic differentiation between these two subspecies is mainly due to changes within F. p. anatum (specifically the southern F. p. anatum populations). Despite expectations and a variety of tests, no genetic bottleneck signature is found in the identified populations; in fact, many contemporary indices of diversity are higher than historical values. These results are rationalized by the promptness of the recovery and the possible introduction of new genetic material.

Back to the future: museum specimens in population genetics

“…Such 'ghost alleles' have subsequently been reported in several bottlenecked animal populations. By contrast, other studies have reported stable genetic diversity despite declines in population size [24][25][26]. For example, no obvious loss of genetic diversity was detected among Canadian peregrine falcons (Falco peregrinus) despite a DDT induced bottleneck [25].…”

The Use of Genetics for the Management of a Recovering Population: Temporal Assessment of Migratory Peregrine Falcons in North America

“…All samples were kept frozen, and DNA extractions were performed using methods described elsewhere [34]. An additional 349 samples were obtained from the contemporary northern breeding distribution of peregrine falcons throughout Alaska, Canada and western Greenland, of which 168 samples were used in a previous study [35]. The samples collected from breeding territories were included in this study to verify the degree of population subdivision throughout their northern breeding distribution from which the Padre Island migrants likely originated.…”

Museum collections reveal that Buff-breasted Sandpipers (Calidris subruficollis) maintained mtDNA variability despite large population declines during the past 135 years

“…While we expected to see a signal of declining genetic variation, other studies have also found mtDNA variation to be stable in species with declining populations (Brown et al 2007;Kuro-o et al 2010;Reding et al 2010). In these species, high levels of mtDNA variation were likely maintained because historical populations had high genetic variation or large effective population sizes prior to declines and because populations recovered or stabilized quickly once these species were managed.…”