Ecological Entomology (2008), 33, 529–536 DOI: 10.1111/j.1365-2311.2008.01006.x Life-history strategy in an oligophagous tephritid: the tomato fruit fl y, Neoceratitis cyanescens THIERRY BRÉVAULT 1 , PIERRE-FRANÇOIS DUYCK 2,3 a n d S E R G E QUILICI 2 1 CIRAD, UPR Cotton Farming Systems, Montpellier, F-34398, France , 2 UMR « Peuplements Végétaux et Bio-agresseurs en Milieu Tropical », CIRAD, St Pierre, La Réunion, F-97410, France and 3 Department of Entomology, University of California, One Shields Avenue, Davis, CA 95616, U.S.A. Abstract . 1. In phytophagous insects, life-history traits mainly depend on host plant range. Substantial longevity, high fecundity and larval competition are the major traits of polyphagous Tephritidae while species with a restricted host range generally exhibit a lower longevity and fecundity as well as mechanisms to avoid larval competition. Our aim in this study was to investigate the life history of an oligophagous species, the tomato fruit fly, Neoceratitis cyanescens (Bezzi). 2. We determined life tables under laboratory conditions in order to calculate the main demographic parameters of N. cyanescens and studied the influence of larval and adult diet on life-history traits. 3. The mean longevity of N. cyanescens females was 40 days. There was a strong synchronisation of female maturity. Oviposition showed an early peak at 9 – 13 days after a short pre-oviposition period (6 days). The absence of proteins in the adult diet both delayed ovarian maturation and decreased female fecundity. In addition, females originating from tomato fruits produced significantly more eggs than females originating from bugweed or black nightshade, showing that even the larval host plant may strongly affect the subsequent fecundity of adult females. 4. The traits of N. cyanescens are then discussed in the light of those documented for polyphagous and monophagous tephritids. Neoceratitis cyanescens displayed attributes intermediate between those of polyphagous and monophagous tephritids. Its smaller clutch size compared with polyphagous species and its specialisation on the Solanaceae family whose fruits contain toxic compounds may help in reducing intra- and inter- specific competition, respectively. Key words. Demography , fecundity , host range , longevity , Neoceratitis cyanescens , Tephritidae . Introduction Chapman, 1994; Schoonhoven et al. , 1998 ). While a few insect characteristics (e.g. diapause, difference in the structure of The demographic strategies of insects are linked to their eco- mouth parts, body size) have been related to host range ( Bernays logical function in the ecosystem. In phytophagous insects, & Chapman, 1994; Schoonhoven et al. , 1998 ), the relationship these biological traits mainly depend on the host plant range between life-history traits of insects and host range width needs ( Schowalter, 2000 ). Their resource foraging process may be to be further explored. classified into two major strategies: one opportunistic, based on The Tephritidae family contains a large number of polypha- a wide host range including different plant families, the other gous species. Most of these generalist species are widespread in specialist, restricted to one or only a few host plants ( Bernays & tropical and sub-tropical regions of the world and are multivolt- ine ( White & Elson-Harris, 1992 ). One striking example is the Correspondence: S. Quilici, UMR “Peuplements Végétaux et Mediterranean fruit fly Ceratitis capitata (Wiedemann), which Bioagresseurs en Milieu Tropical” (PVBMT), CIRAD Réunion, Pôle de can infest more than 350 fruit species belonging to a range of Protection des Plantes, Laboratoire d’Ecologie Terrestre et de Lutte different plant families ( Liquido et al. , 1991 ). While there are Intégrée, 7 chemin de l’IRAT, 97410 Saint-Pierre, France. E-mail: serge. some differences in life-history traits among these polyphagous [email protected] species, for instance their colonisation and competition abilities © 2008 The Authors Journal compilation © 2008 The Royal Entomological Society 529 530 Thierry Brévault, Pierre-François Duyck and Serge Quilici ( Duyck et al. , 2004 , 2006, 2007), they overall show similar pat- In this study, we have established the life tables of N. cyanes- terns such as high fecundity and intrinsic rate of increase, large cens in laboratory conditions in order to calculate its main de- clutches, as well as high dispersal ability ( Zwölfer, 1982 ). The mographic parameters. In addition, as such factors may strongly adults of these species may fly long distances during the host influence life-history traits, we have also examined the influ- location process as a result of the temporal and spatial unpredicta- ence of the quality of larval and adult diet on female fecundity. bility of resources ( Fletcher, 1987 ). Intra-specific competition, The traits of N. cyanescens are then discussed in the light of associated with a high larval population in fruits, leads to a com- those documented for polyphagous and monophagous tephritids promise between larval survival and adult fitness which may be in order to establish the relationship between the life history and reduced through a decrease in body size, low survival rates and ecology of this oligophagous species. low fecundity ( Krainacker et al. , 1987 ). The Tephritidae family also contains specialist species such as members of the genus Rhagoletis ( White & Elson-Harris, 1992 ) which are monopha- Material and methods gous or stenophagous and univoltine ( Boller & Prokopy, 1976 ). The main challenge these species have to face is adapting to host Insects characteristics such as the fruiting period. Accordingly, seasonal synchrony with their host and the host selection process are their Life-history traits and the influence of adult diet on fecundity key life-history traits. They are generally characterised by lower were conducted on F1 laboratory-reared flies ( Etienne, 1973 ) longevity and fecundity, small clutches (often one or two eggs), stemming from larvae that were collected from tomatoes in the low adult dispersal ability and diapause events ( Fletcher, 1989 ). western part of Reunion Island (LEGTA, Saint-Paul). In most Rhagoletis species, females mark the host fruit with a pheromone immediately after ovipositing, which deters other gravid females ( Boller & Prokopy, 1976 ). This strategy allows Life table experiments for a wider distribution of egg laying and consequently a better exploitation of resources to the progeny. The high intrinsic rate Upon emergence, 30 pairs of flies were isolated into small of increase of polyphagous species enables them to rapidly ex- Plexiglas cages of approximately 1 litre volume, in a climatic ploit unpredictable resources, while the Rhagoletis species are chamber (25 ± 2 °C, 70 ± 20% r.h., and a LD 12:12 h photoperiod). able to better exploit a more stable resource, particularly through The flies were fed ad libitum with sugarcane and enzymatic yeast the limitation of intra-specific competition. hydrolysate (ICN Biomedicals, Costa Mesa, CA), presented sepa- While life histories of species exhibiting these two contrast- rately. Water was made available using damped cotton. Two spheri- ing strategies are well documented within the Tephritidae fam- cal devices of about 3 cm diameter were presented to flies: a small ily, few detailed studies have dealt with the life-history strategies green tomato fruit (susceptible phenological stage) or an agar ball. of species with an intermediate host range. Neoceratitis cyanes- Agar balls were prepared with 7.5 g of agar mixed with 450 ml of cens (Bezzi) infests fruits of several cultivated and wild plants aqueous extract of green tomato (obtained by the filtration of 100 g belonging to the Solanaceae family. This species is classified in of crushed green tomatoes mixed with 500 ml of water) and two the subfamily Dacinae and the tribe Ceratitidini, which includes drops of edible yellow food colorant. After solidification, they were other genera such as Ceratitis and Trirhithrum . The genus covered with Parafilm ® (Pechiney Plastic Packaging, Chicago, IL). Trirhithromyia Hendel, which includes five African species, This laying substrate aimed at avoiding the variability of natural was originally described as a subgenus of Ceratitis before being fruit characteristics. The number of eggs laid was recorded daily considered as a distinct genus by Hancock (1984) . More re- while 100 eggs were collected with a camel brush from the tomato cently, Hancock and White (1997) transferred this species to fruit, placed on humid filter paper and incubated at 25 °C for 4 days the genus Neoceratitis (Hendel), whose host plants belong to to determine hatching proportion. The pairs of flies were monitored the Solanaceae family. This major pest of tomato crops is until females died, while males that died before females were im- widespread throughout the Indian Ocean region, including mediately replaced by another male of the same age. Madagascar, Mauritius, Reunion, and Mayotte islands ( OEPP/ EPPO-CABI, 1997 ). The females usually lay eggs in green fruits, causing serious damage to vegetable crops, particularly Infl uence of adult and larval diets on fecundity tomato ( Lycopersicum esculentum Mill.), but also sweet pepper ( Capsicum annuum L.), egg-plant ( Solanum melongena L.), and The influence on the ovarian development of two diets, a chilli ( C. frutescens L.). Additional wild species such as black complete diet of granulated sugar (sugar) and enzymatic yeast nightshade