Interspecific competition of Dacus cucurbitae Coq. and Dacus ciliatus Loew in mixed infestation of cucurbits¹

Abstract

The studies on interspecific competition of melon fly, Dacus cucurbitae Coq, and Ethiopian melon fly D. ciliatus Loew were carried out in the laboratory at 27±2±C and 65±5% R. H. The results on the superimposed restricted or unrestricted oviposition indicated that Ethiopian melon fly drastically suppressed the population of melon fly. The placement of equal number of eggs of both the species in the same fruit also indicated that Ethiopian melon fly larvae suppressed the development of melon fly larvae. Furthermore, lesser preoviposition and incubation periods and more reproductive potential of Ethiopian melon fly contributed towards the suppression of melon fly. It was concluded that the competition between Ethiopian melon fly and melon fly occurred in the larval stage. Zusammenfassung Interspezifische Konkurrenz zwischen Dacus cucurbitae Coq. und Dacus ciliatus Loew bei gleichzeitigem Befall von Kürbisfrüchten Die Untersuchungen zur interspezifischen Konkurrenz zwischen Dacus cucurbitae und D. ciliatus wurden im Labor bei 27 ± 2°C, 65 ± 5% R. H. durchgeführt. Wie die Ergebnisse einer uneingeschränkten bzw. einer eingeschränkten Eiablage beider Dacus‐Arten in jeweils gleiche Früchte zeigten, unterdrückt D. ciliatus sehr deutlich die Entwicklung von D. cucurbitae. Dies konnte auch durch die Übertragung einer gleichen Anzahl von Eiern beider Arten in eine Frucht gezeigt werden. Weiterhin ergibt sich aus der kürzeren Entwicklungszeit vor und nach der Eiablage sowie eines größeren Reproduktionsvermögens von D. ciliatus eine Überlegenheit gegenüber D. cucurbitae. Es wird angenommen, daß die Konkurrenz zwischen den beiden Arten im Larvenstadium auftritt.

Mechanisms contributing to the competitive success of the invasive fruit fly Bactrocera invadens over the indigenous mango fruit fly, Ceratitis cosyra: the role of temperature and resource pre‐emption

“…The observed pattern in our study also suggests a competitive pre‐emption of resources among species, i.e., the first larvae to develop benefit from more resources than the later ones (Qureshi et al., 1987; Blanckenhorn, 1999; Krijger et al., 2001; Duyck et al., 2006). When two groups of differently sized and aged juvenile insects are reared together, the smaller and younger cohort is more likely to suffer from increased mortality and reduced size if resources are limiting (Averill & Prokopy, 1987; Edgerly & Livdahl, 1992; Dukas et al., 2001; Cameron et al., 2007).…”

“…Shortly after eclosion, 20 newly emerged larvae of each species of fruit fly were collected from the dish and gently introduced with a moistened fine camel’s hair brush into each of 20 holes for control fruit, or 40 holes (20 holes per fruit fly species) for co‐infested fruit perforated with an entomological pin on the surface of a single large ripe mango (220–250 g) with the aid of a binocular microscope. This density of larval infestation has previously been used in interspecific interaction studies of Tephritidae (Keiser et al., 1974; Fitt, 1986; Krainacker et al., 1987; Qureshi et al., 1987; Duyck et al., 2006) and is comparable to observed larval densities from field collected mango samples (I. Rwomushana, unpubl.). Each hole was ca.…”

Watermelon-infesting Tephritidae fruit fly guild and parasitism by Psyttalia phaeostigma (Hymenoptera: Braconidae)

“…Possibly, an interspecific competition occurs between Z. cucurbitae and D. ciliatus, hence, the increase of the former coincided with a reduction of the latter, yet the competitive superiority among species is yet to be disclosed, since conflicting results have been obtained. Studies conducted in Pakistan showed that D. ciliatus overcame the population of Z. cucurbitae by suppressing its larval development in interspecific competition (Quereshi et al 1987), while in Reunion Islands, Z. cucurbitae outcompeted D. ciliatus (Vayssières et al 2008). It is often stated that D. ciliatus is the major competitor of Z. cucurbitae in Africa (Vayssières et al 2008;Mwatawala et al 2010); yet, here we observed that, D. vertebratus also competed with Z. cucurbitae in at least on watermelon.…”

A review of relationships between interspecific competition and invasions in fruit flies (Diptera: Tephritidae)

“…Whatever the mechanism, the first larvae to hatch in a given fruit will have an advantage over subsequent larvae (Fitt, 1989). The impact of cross‐infestation on larva development has been demonstrated in two species that live on the Cucurbitaceae B. cucurbitae and Dacus ciliatus Loew (Qureshi et al ., 1987), and in Ceratitis capitata and Bactrocera dorsalis (Keiser et al ., 1974). These experiments have shown that the competitive advantage observed in the wild can partly be predicted by a better survival of larvae in laboratory conditions.…”