Depression and dementia are the most frequently occurring psychiatric syndromes in elderly populations (Blazer and Williams 1980; Caine et al., 1994). The two disorders often coexist. There are ...multiple streams of evidence for a relationship between affective and cognitive symptoms and syndromes in elderly persons. However, our understanding of the pathophysiology and possible common pathways of both disorders is limited.
Vascular dementia (VaD) is the second most common type of dementia following Alzheimer’s disease (AD) and accounts for 10 to 20% of dementia cases (1,2). VaD is commonly associated with behavioral ...disturbances that impair overall functioning and often require active intervention (3). However, unlike AD, where there is an extensive literature describing the phenomenology and management of behavioral and psychological symptoms, the neuropsychiatric features of VaD have received less clinical and scientific attention.
Clinical depression in the elderly is associated with striking medical and psychosocial consequences. These include more frequent visits to physicians’ offices, absenteeism, use of tranquilizers, and ...suicide attempts. Amplification of associated medical and cognitive difficulties together with a substantial decline in overall productivity are also hallmarks of mood disorders in late life (Lavretsky and Kumar, 2002; Lebowitz et al., 1997). While major depressive disorder (MOD) is the best recognized and characterized depressive syndrome in the elderly, other depressive syndromes and subsyndromal disorders are also associated with significant functional impairment and disability (Beck and Koenig, 1996; Beekman 1997; Geiselmann and Bauer, 2000; Judd et al., 1996; Koenig et al., 1997). These clinical categories have received minimal attention in the psychiatric literature.
Along with manipulating habitat, the direct release of domesticated individuals into the wild is a practice used worldwide to augment wildlife populations. We test between possible outcomes of ...human‐mediated secondary contact using genomic techniques at both historical and contemporary timescales for two iconic duck species. First, we sequence several thousand ddRAD‐seq loci for contemporary mallards (Anas platyrhynchos) throughout North America and two domestic mallard types (i.e., known game‐farm mallards and feral Khaki Campbell's). We show that North American mallards may well be becoming a hybrid swarm due to interbreeding with domesticated game‐farm mallards released for hunting. Next, to attain a historical perspective, we applied a bait‐capture array targeting thousands of loci in century‐old (1842–1915) and contemporary (2009–2010) mallard and American black duck (Anas rubripes) specimens. We conclude that American black ducks and mallards have always been closely related, with a divergence time of ~600,000 years before present, and likely evolved through prolonged isolation followed by limited bouts of gene flow (i.e., secondary contact). They continue to maintain genetic separation, a finding that overturns decades of prior research and speculation suggesting the genetic extinction of the American black duck due to contemporary interbreeding with mallards. Thus, despite having high rates of hybridization, actual gene flow is limited between mallards and American black ducks. Conversely, our historical and contemporary data confirm that the intensive stocking of game‐farm mallards during the last ~100 years has fundamentally changed the genetic integrity of North America's wild mallard population, especially in the east. It thus becomes of great interest to ask whether the iconic North American mallard is declining in the wild due to introgression of maladaptive traits from domesticated forms. Moreover, we hypothesize that differential gene flow from domestic game‐farm mallards into the wild mallard population may explain the overall temporal increase in differentiation between wild black ducks and mallards, as well as the uncoupling of genetic diversity and effective population size estimates across time in our results. Finally, our findings highlight how genomic methods can recover complex population histories by capturing DNA preserved in traditional museum specimens.
