Abstract
The question of why variation is maintained in personality traits is an evolutionary puzzle. According to the condition‐dependence hypothesis, such traits depend on condition, which limits the behavioral choices available to individuals. Because condition is affected by many genes, it can effectively be manipulated by inbreeding, which exposes the effects of deleterious recessive mutations. Here, I compared two personality traits, boldness and tendency to explore, of male guppies (Poecilia reticulata) from first‐generation inbred and outbred treatments. Boldness in guppies is associated with increased sexual attractiveness and is thus expected to affect fitness. Therefore, I hypothesized that the personality traits would be negatively affected by inbreeding. However, the results indicated that inbred guppies did not differ in either personality trait from their outbred counterparts. This finding suggests that mechanisms other than condition dependence are maintaining personality variation in the guppy.
Highlights
Less attention has been devoted to a second scenario, which assumes that high‐fitness personalities are only available to individ‐ uals in good condition, whereas poor condition individuals are con‐ strained to express low‐fitness personalities (Lewis, 2015; Luttbeg & Sih, 2010; Rands, Cowlishaw, Pettifor, Rowcliffe, & Johnstone, 2003)
One of the hypotheses explaining consistent differences in personali‐ ties, that is, individually consistent behavioral traits, poses that the ex‐ pression of costly behavioral traits is dependent on condition (Lewis, (a)
If the personality traits I investigated were condition‐dependent, I expected them to show the effects of inbreeding depression, to what was reported for traits important for individual fitness (DeRose & Roff, 1999)
Summary
Reports have accumulated for a wide range of taxa on the presence of behaviors that differ within populations and/or among individuals but are individually stable. In the population studied here, under laboratory conditions, I found a positive association between males' boldness and their competi‐ tive reproductive success (Herdegen‐Radwan, in preparation) These personality traits seem to be important components of indi‐ vidual fitness and good candidates for being condition‐dependent. If variation in guppies' personality traits is maintained due to their condition dependence, I predicted personality traits to be negatively affected by inbreeding This is because inbreeding is expected to dete‐ riorate guppies' overall condition due to the exposure of slightly delete‐ rious recessive mutations in many genes. This would result in a shift in mean population trait values toward lower fitness. In which inbreed‐ ing depression has previously been demonstrated (Mariette, Kelley, Brooks, & Evans, 2006; van Oosterhout et al, 2003), and which was shown to be condition‐dependent (Nicoletto, 1993), was measured as a control for the effectiveness of the inbreeding treatment
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