Abstract
Inbreeding can threaten population persistence by reducing disease resistance through the accelerated loss of gene diversity (i.e. heterozygosity). Such inbreeding depression can affect many different fitness-related traits, including survival, reproductive success, and parasite susceptibility. Empirically quantifying the effects of inbreeding on parasite resistance is therefore important for ex-situ conservation of vertebrates. The present study evaluates the disease susceptibility of individuals bred under three different breeding regimes (inbred, crossed with full siblings; control, randomly crossed mating; and fully outbred). Specifically, we examined the relationship between inbreeding coefficient (F-coefficient) and susceptibility to Gyrodactylus turnbulli infection in a live bearing vertebrate, the guppy Poecilia reticulata. Host-breeding regime significantly affected the trajectories of parasite population growth on individual fish. Inbred fish showed significantly higher mean parasite intensity than fish from the control and outbred breeding regimes, and in addition, inbred fish were slower in purging their gyrodactylid infections. We discuss the role of inbreeding on the various arms of the immune system, and argue that the increased disease susceptibility of inbred individuals could contribute to the extinction vortex. This is one of the first studies to quantify the effects of inbreeding and breeding regime on disease susceptibility in a captive bred vertebrate of wild origin, and it highlights the risks faced by small (captive-bred) populations when exposed to their native parasites.
Highlights
Small and isolated populations are vulnerable to environmental and demographic stochasticity, which can result in the loss of genetic variation due to random genetic drift (Keller and Waller, 2002)
Genetic diversity has been negatively associated with susceptibility to parasitism in many animals, including insects (e.g. Whitehorn et al, 2011), birds (e.g. MacDougallShackleton et al, 2005; Ortego et al, 2007), mammals (e.g. Roelke et al, 1993; Rijks et al, 2008) and fish (e.g. Arkush et al, 2002; Consuegra and de Leaniz, 2008; Ellison et al, 2011; Eszterbauer et al, 2015)
This study examines the relationship between the level of inbreeding and susceptibility to Gyrodactylus turnbulli infection in the live bearing guppy under controlled laboratory conditions
Summary
Small and isolated populations are vulnerable to environmental and demographic stochasticity, which can result in the loss of genetic variation due to random genetic drift (Keller and Waller, 2002). Both drift and inbreeding tend to accelerate the loss. Inbreeding depression can affect many different fitness-related traits (Saccheri et al, 1998; van Oosterhout et al, 2000a; Keller and Waller, 2002), including survival (Coltman et al, 1998), reproductive success (Spielman et al, 2004), sexual ornamentation and courtship behaviour (van Oosterhout et al, 2003), and parasite susceptibility (MacDougall-Shackleton et al, 2005; Rijks et al, 2008). Genetic diversity has been negatively associated with susceptibility to parasitism in many animals, including insects (e.g. Whitehorn et al, 2011), birds (e.g. MacDougallShackleton et al, 2005; Ortego et al, 2007), mammals (e.g. Roelke et al, 1993; Rijks et al, 2008) and fish (e.g. Arkush et al, 2002; Consuegra and de Leaniz, 2008; Ellison et al, 2011; Eszterbauer et al, 2015)
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