Condition-dependent effects of mating on longevity and fecundity of female Medflies: the interplay between nutrition and age of mating

Abstract

Background: In various species mating exerts direct and indirect effects on female demographic traits ranging from life span shortening to behavioural shifts. A wealth of data regarding effects of nutrition on longevity and reproduction output also exists. Nonetheless, little is known regarding the interaction between the age of mating and nutrition on female fitness.

Methodology: We studied, the effects of protein deprivation and age of mating on female fitness traits, using a wild population of the Mediterranean fruit fly (medfly). We tested the hypotheses that (a) protein availability increases female lifespan and fecundity, (b) female longevity and egg production are independent of mating and the age of mating, and (c) female mating behaviour is independent of their age and nutritional status. Thus, we recorded the mating success and the copulation characteristics, as well as the egg production and survival of females mated at young or at old age and fed a full or a protein-deprived diet.

Results: Mating boosts egg production and reduces longevity of protein-fed females. On the contrary, mating increases the longevity of protein-deprived females. Mortality responses (negative or positive) to mating are expressed after a long lag phase. Old females are more receptive and less selective than young females regardless of the food regime.

Conclusions: Our findings suggest that condition (nutritional status and age) defines the positive or negative output of mating in female medflies. These results contribute towards understanding the effects of mating, aging, resource allocation and their interactions on survival and female reproduction.

Figure 1. Copulation success of females fed a full (left) and a protein-deprived (right) diet, at a young (15 days) and an old (40 days) age.

The percentage of the females that had initiated egg production one day before the mating test is given in parenthesis. Asterisks (*) indicate significant differences (P<0.05).

Figure 2. Copulation duration (A) and latency time (B) of females fed a full (left) and a protein-deprived (right) diet.

Asterisks (*) indicate significant differences (t-test, P<0.05).

Figure 3. Survivorship of control females fed a full (continuous line) and a protein-deprived (dotted line) diet.

Control females were not given the opportunity to mate and were kept virgin throughout lifespan.

Figure 4. Smoothed mortality rates with 95% confidence intervals of females fed a full diet that mated (continuous line) or remained unmated (dotted line) at t = 15 (A) and t = 40 (B) days.

Figure 5. Smoothed mortality rates with 95% confidence intervals of females fed a protein-deprived diet that mated (continuous line) or remained unmated (dotted line) at t = 15 (A) and t = 40 (B) days old.

Figure 6. Average number of eggs (±SE) laid by mated and unmated females fed a full or a protein-deprived diet when subjected to mating tests at 15 (A) and 40 (B) days of age.

Asterisks (*) indicate significant differences (P<0.05).

Figure 7. Smoothed proportion of fecundity rates (age specific fecundity of treatment/age specific fecundity of control) with 95% confidence intervals of females fed a full diet that mated (continuous line) or remained unmated (dotted line) at t = 15 (A) and t = 40 (B) days.

Figure 8. Smoothed proportion of fecundity rates (age specific fecundity of treatment/age specific fecundity of control) with 95% confidence intervals of females fed a protein-deprived diet that mated (continuous line) or remained unmated (dotted line) at t = 15 (A) and t = 40 (B) days old.