Host utilization by the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

DIEGO F. SEGURA; MARÍA T. VERA; JORGE L. CLADERA

Proceedings of the 6th International Fruit Fly Symposium

Isteg scientific Publications

Lugar: Irene, Sudáfrica; Año: 2004; p. 83 - 90

Host utilization by fruit flies has traditionally been studied using data on infestation levels found in different hosts. This analysis does not allow any comparison among hosts, because the variables are affected by the carrying capacity (i.e. maximum number of pupae/kilogram of fruit) of each host. Also, the data from different hosts species cannot be pooled to obtain a global measure of the degree of exploitation of available resources. In this study, host utilization was determined by defining a new variable, percent of exploited resource (PER), which relates the extracted pupae in a host with the maximum quantity of pupae extractable in the same host, in order to: 1) compare host utilization with host availability (globally and for each host species); 2) compare host utilization among fruit species; and 3) analyse the effect of environmental variables on the capacity of the C. capitata population to exploit this resource during the reproductive season.. The results showed that PER values reached by any host species was never higher than 60%, and that the maximum PER value obtained by pooling all species together in a given sample was below 35%, suggesting that host availability is not a limiting resource in this system. However, PER was not constant over time, probably indicating periods in which competition becomes more intense. These fluctuations were associated with biotic and abiotic factors, which in turn determine to fluctuations in the activity and abundance of adults. No association was found between global PER and global availability of hosts, probably due to the lack of synchrony between C. capitata population levels and host availability. For each species, PER usually showed a gradual growth that ended sharply when the host disappeared, while the host availability grew, reached a maximum and then dropped gradually. Apparently, during this gradual reduction in hosts availability fruit fly infestation are confined to the few available fruits of the same species, instead of using other host species with higher abundance. Significant differences were found comparing PER among hosts species. In most cases, the host species with a high PER were those with a high carrying capacity, indicating that C. capitata was preferentially exploiting the hosts with better yield. This behaviour probably tends to improve the fitness of the females.