Genetic structure and rabies spread potential in raccoons: the role of landscape barriers and sex‐biased dispersal

Abstract

Identifying natural barriers to movements of hosts associated with infectious diseases is essential for developing effective control strategies. Raccoon rabies variant (RRV) is a zoonosis of concern for humans because its main vector, the raccoon (Procyon lotor), is found near residential areas. In Québec, Canada, all cases of RRV found in raccoons since 2006 were detected on the eastern side of the Richelieu River, suggesting that this river acts as a barrier to gene flow and thus the potential for RRV to spread. The objectives of this study were to characterize the genetic structure of raccoon populations and assess the effect of the Richelieu River on the population structure in southern Québec, Canada. We also evaluated whether RRV spread potential differed between sex and at a larger spatial scale. Our analyses revealed a weak signal of genetic differentiation among individuals located on each side of the Richelieu River. At a larger spatial scale, genetic structuring was weak. Our results suggest that rivers might not always efficiently restrain raccoon movements and spread of RRV. We suggest that the difference in genetic structure found between sexes can be partly explained by male movements during the breeding season in winter, when ice bridges allow passage over most rivers in Québec.

Lack of Genetic Structure and Female-Specific Effect of Dispersal Barriers in a Rabies Vector, the Striped Skunk (Mephitis mephitis)

“…In comparison with average distances traveled by similar-size mesocarnivores, skunks can be regarded as relatively sedentary [56]. We also predicted that large rivers (physical barriers) and roads (behavioural avoidance and sources of mortality) would limit gene flow in skunks, as previously reported in other mesocarnivores (raccoons [24], [35] and badgers, Meles meles [10]). Finally, we hypothesized that males are more likely to disperse than females and thus, that sex-biased dispersal could be detected indirectly through differences in observed patterns of pairwise genetic relatedness in each sex.…”

Modelling the dispersal of the two main hosts of the raccoon rabies variant in heterogeneous environments with landscape genetics

“…Microsatellite polymorphism was assessed at ten loci developed for raccoons (see Côté et al. for the list of loci used and PCR protocols) and at nine loci developed for skunks (see Talbot et al. ).…”

“…Previous work in the study area (south‐eastern Québec) has shown very little genetic structuring in resident raccoons and skunks, with highways and rivers generally generating a rather weak effect on patterns of genetic differentiation (Côté et al. ; Talbot et al. ).…”

Isolation of peripheral populations of Canada lynx (Lynx canadensis)

“…Rivers have been shown to impede dispersal and gene flow of a diversity of terrestrial species, including reptiles (lizards: Lamborot et al 2003), birds (Hayes and Sewlal 2004;Voelker et al 2013), and mammals (mustelids: Garroway et al 2011;primates: Ayres and Clutton-Brock 1992;Peres et al 1996). There are also examples of rivers that do not act as barriers (Patton et al 1994;Fairley et al 2002;Lougheed et al 1999;Côté et al 2012). Equivocal support for the riverine barrier hypothesis might be a function of the ecology and dispersal abilities of the focal species in relation to the width and flow rate of the river in question (Haffer 1997).…”