Clutch size in frugivorous insects as a function of host firmness: the case of the tephritid fly Anastrepha ludens

Abstract

Abstract. 1. Optimal clutch size theory predicts that individuals will oviposit the number of eggs that increases their fitness. In Anastrepha ludens Loew (Diptera: Tephritidae), females oviposit larger clutches in unripe (firm) fruits than in ripe (soft) fruits. The following hypotheses were tested: (1) Using fruit firmness as an indicator of fruit quality, A. ludens females vary the number of eggs per clutch every time they reach an oviposition decision. (2) Maximising offspring survival with respect to either unripe or ripe fruit requires placing large clutches in firm fruit and smaller clutches in soft fruit. 2. Agar spheres were used as artificial hosts. Three agar concentrations resulted in three degrees of firmness. Mango fruits Mangifera indica L. served as natural hosts. Ripe and unripe fruits were used to test soft and firm host conditions respectively. Females laid significantly larger clutches in the firmer artificial hosts than in the softer hosts. They also laid significantly more eggs in artificial hosts without sugar than in hosts with sugar. Firm (unripe) mangoes also received significantly larger clutches than soft (ripe) mangoes. 3. When an individual female was first presented with a firm artificial host, it laid a large clutch. If subsequently offered a soft host, the female laid a significantly smaller clutch. Finally, if again offered a firm host, clutch size was increased significantly. 4. Possible trade‐offs in offspring fitness were explored in ripe and unripe mangoes by measuring offspring egg‐to‐adult survival, pupal weight, mean adult longevity, and fecundity. Despite the fact that larval survival was greater in soft fruit than in firm fruit, parameters such as pupal weight, mean longevity, and fecundity of adults stemming from both fruit types did not differ significantly. 5. A probable trade‐off between high offspring mortality caused by host unsuitability and low offspring and adult mortality caused by parasitism and predation is discussed as the reason for the exploitation of sub‐optimal hosts.

Selection of oviposition sites by wild Anastrepha obliqua (Macquart) (Diptera: Tephritidae) based on the nutritional composition

“…Aluja et al (2001) observed that the presence of hosts and their volatile substances are important for ovarian maturation of A. obliqua. In addition, the presence of ripe fruits also influences the females' oviposition decision, probably due to the sugar content (Fernandes-da-Silva & Zucoloto 1997, Díaz-Fleischer & Aluja 2003. So, according to our results, the protein is the nutrient that most stimulates oviposition.…”

“…We believe that the discussion presented by Díaz-Fleischer and Aluja (2003) regarding the oviposition behavior of Anastrepha ludens (Loew) is also applicable to what was observed for A. obliqua. Ripe fruits, with higher sugar content, are more attractive and susceptible to predation by vertebrates, occasionally leading to larva's death.…”

“…Therefore, when insects lay eggs on lower sugar content fruits (unripe fruits), despite the higher toxicity, it is possible that more larvae survive in this toxic environment than when vulnerable to predators. These aspects must be subjects of further research in order to analyze whether or not there is an adaptive relation between the amount of laid eggs both on unripe and ripe fruits and the offspring success (Díaz-Fleischer & Aluja 2003).…”

Selection of artificial hosts for oviposition by wild Anastrepha obliqua (Macquart) (Diptera, Tephritidae): influence of adult food and effect of experience

“…Thus, a polyphagous insect with high behavioral adaptability, as A. obliqua, may keep a large number of hosts. Several authors (Carey et al 1986;Prokopy & Reynolds 1998;Díaz-Fleischer & Aluja 2003a, 2003b) and the present study have reported the plasticity of fruit flies concerning their oviposition behavior strategies. In this sense, further investigations on the factors related to this behavior are needed.…”

Influence of fruit traits on the infestation of Dacus persicus in two fruit morphs of Calotropis procera

“…In phytophagous insects that lay eggs in discrete packets of food, there is a tendency to select resources of adequate quality to ensure larval development (Diaz-Fleischer and Aluja 2003a). A wide variety of factors seem to influence host selection by fruit flies (Balagawi et al 2005).…”