Starvation resistance is a trait often associated with longevity. Animals with increased longevity frequently show elevated starvation resistance and vice versa. Consequently, both life-history traits are thought to share genetic and physiological mechanisms, such as increased fat content and lowered metabolic rate. Here, we present results from 20 generations of selection on Drosophila melanogaster for increased starvation resistance at the time of adult eclosion. We observe that starvation resistance can be the result of more than one mechanism, all associated with an increase in fat resources. In general, metabolic rate is lowered under starved conditions relative to fed conditions. Metabolic rate in the starvation resistant lines is generally higher than in control lines under starved conditions. Starvation resistant flies are able to sustain a higher metabolic rate for a longer period of time when food is unavailable. This implies depletion of the increased fat reserves. However, longevity was not consistently affected by selection for increased starvation resistance. Similarly, paraquat resistance differed between selection lines and did not associate with starvation resistance, but rather with longevity. The results are discussed in relation to previous reported results on starvation resistance and its relation with mechanisms of aging and longevity.

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Abstract. Starvation resistance is a trait often associated with longevity. Animals with increased longevity frequently show elevated starvation resistance and vice versa. Consequently, both life-history traits are thought to share genetic and physiological mechanisms, such as increased fat content and lowered metabolic rate. Here, we present results from 20 generations of selection on Drosophila melanogaster for increased starvation resistance at the time of adult eclosion. We observe that starvation resistance can be the result of more than one mechanism, all associated with an increase in fat resources. In general, metabolic rate is lowered under starved conditions relative to fed conditions. Metabolic rate in the starvation resistant lines is generally higher than in control lines under starved conditions. Starvation resistant flies are able to sustain a higher metabolic rate for a longer period of time when food is unavailable. This implies depletion of the increased fat reserves. However, longevity was not consistently affected by selection for increased starvation resistance. Similarly, paraquat resistance differed between selection lines and did not associate with starvation resistance, but rather with longevity. The results are discussed in relation to previous reported results on starvation resistance and its relation with mechanisms of aging and longevity. Increased stress resistance is often observed in Drosophila melanogaster lines selected for increased longevity (Service et al. 1985;Service 1987;Leroi et al. 1994;Force et al. 1995;Harshman et al. 1999a), in mutants (Lin et al. 1998), and in phenotypic manipulation experiments (e.g., Zwaan et al. 1991;Bouletreau-Merle and Fouillet 2002). This association also holds in other species such as mice and nematodes (Longo and Fabrizio 2002). Similarly, selection for increased adult starvation resistance has been shown to increase longevity (Rose et al. 1992;Chippindale et al. 1996; but see Bubliy and Loeschcke 2005). Selection on shorter longevity also results in decreased starvation resistance (Zwaan et al. 1995a). These results strongly suggest that starvation resistance shares, at least in part, genetic regulatory mechanisms with longevity. Moreover, the selection experiments indicate the presence of standing genetic (co)variation in natural populations. There are strong positive correlations between starvation resistance and longevity as opposed to the negative correlations both traits display with reproductive output. This indicates the presence of a trade-off between maintenance and reproduction, or between the soma and the germ line as has been proposed in the disposable soma theory (Kirkwood 1977;Kirkwood and Holliday 1979). This theory overlaps with the theory of antagonistic pleiotropy (Williams 1957), in which advantages of early life traits are considered to be disadvantageous later in life (Kirkwood and Rose 1991). In pursuit of the validity of this latter theory, reproduction late in life was found to increase longevity considerably (Rose 19...