Experimental infection magnifies inbreeding depression in house mice

Abstract

It is often assumed that inbreeding reduces resistance to pathogens, yet there are few experimental tests of this idea in vertebrates, and no tests for the effects of moderate levels of inbreeding more commonly found in nature. We mated wild‐derived mice with siblings or first cousins and compared the resistance of their offspring to Salmonella infection with outbred controls under laboratory and seminatural conditions. In the laboratory, full‐sib inbreeding reduced resistance to Salmonella and survivorship, whereas first‐cousin inbreeding had no detectable effects. In competitive population enclosures, we found that first‐cousin inbreeding reduced male fitness by 57% in infected vs. only 34% in noninfected control populations. Our study provides experimental evidence that inbreeding reduces resistance and ability to survive pathogenic infection, and moreover, it shows that even moderate inbreeding can cause significant fitness declines under naturalistic conditions of social stress, and especially with exposure to infectious agents.

Fitness Assays Reveal Incomplete Functional Redundancy of the HoxA1 and HoxB1 Paralogs of Mice

“…It is possible that the natural stressors present within OPAs could exacerbate embryonic or early neonatal death or reproductive impairment, as has been seen with caloric restriction, territorial instability, and increased exposure to pathogens, all of which are elevated within OPAs relative to standard breeding cages (Bruce 1959;Rivers and Crawford 1974;Ilmonen et al 2008).…”

“…Mouse fitness is largely based upon intraspecific competition and can be measured directly in terms of reproductive success or indirectly through key fitness components such as survival and competitive ability. OPAs have previously been used to detect and quantify fitness costs of both cousin-and sibling-level inbreeding, the cost of bearing a selfish genetic element (t complex), and health consequences of added sugar consumption and pharmaceutical exposure (Meagher et al 2000;Carroll et al 2004;Ilmonen et al 2008;Ruff et al 2013Ruff et al , 2015Gaukler et al 2015). In all cases, OPAs revealed major fitness deficiencies that analyses with conventional, laboratory-based methods failed to detect.…”

Condition, innate immunity and disease mortality of inbred crows

“…Empirical evidence for disease costs of inbreeding has been documented in captive settings (e.g. Spielman et al 2004;Hawley et al 2005;Ross-Gillespie et al 2007;Charpentier et al 2008;Ilmonen et al 2008) as well as in an array of free-living taxa, including California sea lions (Zalophus californianus; Acevedo- Whitehouse et al 2003), Mediterranean striped dolphins (Stenella coeruleoalba; Valsecchi et al 2004), Galapagos hawks (Buteo galapagoensis; Whiteman et al 2006), Soay sheep (Ovis aries; Coltman et al 1999), harbour seals (Phoca vitulina; Rijks et al 2008) and American crows (Corvus brachyrhynchos; Townsend et al 2009a). In some studies, however, the relationship between inbreeding and disease is unclear (e.g.…”

Inbred decorated crickets exhibit higher measures of macroparasitic immunity than outbred individuals

“…The ability to draw on a large pool of genetic variation allows hosts to respond adaptively to such challenges and thus inbreeding places populations at a competitive disadvantage by depriving them of their ability to co-evolve defenses against pathogenic invaders (Stow and Beattie, 2008). Moreover, inbreeding can have negative effects on overall health as genetic drift allows disadvantageous traits to reach fixation (Reid et al, 2003;Calleri et al, 2006;Ilmonen et al, 2008). Consequently, inbred individuals may have poorly adapted or disabled immune pathways or fewer resources available with which to respond to novel parasites and pathogens (Rantala and Roff, 2007).…”