Intraspecific Larval Competition in the Olive Fruit Fly (Diptera: Tephritidae)

Abstract

Olive fruit flies [Bactrocera oleae (Gmelin)] occur at densities in California that can result in intraspecific larval competition within infested fruit. Larval B. oleae densities tracked in the field at six location were found to be highly variable and related to the proportion of fruit infested and adult densities. Egg and larval distribution within the field was generally aggregated early in the season and trended toward random and uniform as the season progressed. To determine whether B. oleae experienced fitness consequences at a range of larval densities observed in the field, olive fruits were infested with one, two, four, and six eggs, and larval and pupal developmental time, pupal weight, and pupal yield were compared. At the highest egg density, all measures of performance were negatively impacted, resulting in fewer and lighter pupae that took longer to pupate and emerge as adults, and even when only two larvae was present per olive, resulting pupae were significantly smaller. Density did not impact the sex ratio of the resulting flies or survive to adults. As field surveys showed, larval densities ranged from 1 to 11 B. oleae per fruit at some sites, and our results suggest that, at high densities, B. oleae do experience competition for larval resources. The impact of intraspecific larval competition North American in field populations of B. oleae is unknown, but the potential for competition is present.

Insect oviposition plasticity in response to host availability: the case of the tephritid fruit fly Bactrocera dorsalis

“…As demonstrated in Fig. Because larval competition in tephritids is strong in small fruits (Dukas et al, 2001;Burrack et al, 2009), females that tended to adaptively increase oviposition activity also tended to generally lay small egg clutches and broaden their egg distribution; however, when hosts were less available, survival chances could be increased if the egg clutch size was enlarged (Fig. Because larval competition in tephritids is strong in small fruits (Dukas et al, 2001;Burrack et al, 2009), females that tended to adaptively increase oviposition activity also tended to generally lay small egg clutches and broaden their egg distribution; however, when hosts were less available, survival chances could be increased if the egg clutch size was enlarged (Fig.…”

“…2, the proportion of hosts used significantly declined with increasing host densities. Because larval competition in tephritids is strong in small fruits (Dukas et al, 2001;Burrack et al, 2009), females that tended to adaptively increase oviposition activity also tended to generally lay small egg clutches and broaden their egg distribution; however, when hosts were less available, survival chances could be increased if the egg clutch size was enlarged (Fig. 2).…”

Control of the olive fruit fly using genetics-enhanced sterile insect technique

“…Females typically lay a single egg per olive [1], injected into the fruit through the female's ovipositor. The developing larva tunnels through the olive, feeding on the fleshy mesocarp.…”

Olive Fruit Fly (Diptera: Tephritidae) in California: Longevity, Oviposition, and Development in Canning Olives in the Laboratory and Greenhouse

“…Although larval density may affect size (Burrack et al 2009), the effect should be proportionate among instars in the same fruit. Larval food may also affect size and we observed wide variation in individual length within the instars during growth.…”

“…Within the fruit, Burrack et al (2009) found that high egg and larval densities negatively impacted resultant pupal numbers and size as well as adult emergence. Although large fruit size supported infestation, the size of the infestation limited olive fruit ßy immature development.…”