Abstract
Reproductive success is a critical fitness attribute that is directly influenced by resource availability. Here, we investigate the effects of diet-based resource availability on three interrelated aspects of reproductive success: a change in mating system based on mate availability, consequent inbreeding depression, and the deterioration of reproductive efficiency with age (senescence). We employed a factorial experimental design using 22 full-sib families of the hermaphroditic freshwater snail Physa acuta to explore these interactions. Individual snails were reared in one of two mate-availability treatments (isolated [selfing] or occasionally paired [outcrossing]) and one of two diet treatments (boiled lettuce or Spirulina, an algae that is rich in protein, vitamins, and minerals). Spirulina-fed snails initiated reproduction at a 13% earlier age and 7% larger size than lettuce-fed snails. Spirulina also resulted in a 30% reduction in the time delay before selfing. Compared to lettuce, a diet of Spirulina increased inbreeding depression by 52% for egg hatching rate and 64% for posthatching juvenile survival. Furthermore, Spirulina led to a 15-fold increase in the rate of reproductive senescence compared with a diet of lettuce. These transgenerational, interactive effects of diet on inbreeding depression and reproductive senescence are discussed in the context of diet-induced phenotypic plasticity.
Highlights
Diet-based resource availability is one of the most important environmental factors influencing life history and fitness-related traits
Resource availability may affect the expression of a variety of other fitness attributes such as adaptive phenotypic plasticity, inbreeding depression and the expression of senescence, and the interactions between resource availability, and these important fitness attributes are increasingly attracting the attention of researchers (e.g., Chippindale et al 1997; Lee et al 2008; Zajitschek et al 2012; Harwood et al 2013)
As reproductive success was measured on each individual at multiple points in time, we examined the effects of maternal age on offspring survival
Summary
Diet-based resource availability is one of the most important environmental factors influencing life history and fitness-related traits. When resources are limiting, organisms face allocation trade-offs that can affect the timing of reproduction, growth, and the amount of resources allocated to reproduction (van Noordwijk and de Jong 1986; Stearns 1992; Roff 2002). Consistent with the disposable soma theory, moderate resource limitation (i.e., dietary restriction) has been theoretically and empirically shown to alter life history expression and extend life span (Shanley and Kirkwood 2000; Kirkwood and Shanley 2005; Partridge et al 2005). The initiation of reproduction is one of the most important transitions that an organism undergoes. Individuals may delay the initiation of reproduction for a variety of reasons, such as low food availability or a lack of available/desirable mates. Previous theoretical (Tsitrone et al 2003a) and empirical (Tsitrone et al 2003b; Escobar et al 2011; Ramm et al 2012) work has revealed a widespread pattern of delayed selfing by reproductively mature, preferentially outcrossing individ-
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