Segundo R. Nuñez-Campero

Inter-specific competition and competition-free space in the tephritid parasitoids Utetes anastrephae and Doryctobracon areolatus (Hymenoptera: Braconidae: Opiinae)

Utetes anastrephae (Viereck) and Doryctobracon areolatus (Szépligeti) are common, native, Neotropical braconid parasitoids of tephritid fruit flies that are sympatric and often found attacking the same host. The coexistence of the two species may be due in part to the longer ovipositor of D. areolatus that permits it to attack larvae in larger fruit than can U. anastrephae. This increases its potential host range and provides ‘competitor‐free space’. The capacity of U. anastrephae to persist in smaller fruit, exploitable by D. areolatus, suggested that it was a superior competitor in multiparasitised hosts. As predicted U. anastrephae had a competitive advantage over D. areolatus and this advantage occurred regardless of the order in which the two parasitoids attacked. Although we could not identify the precise mechanisms used for elimination of competitors, a possible cause is suggested by the formidable mandibles of the first‐instar U. anastrephae. However, D. areolatus survival increased significantly if eggs had been deposited 24 h prior to exposure to U. anastrephae. Older D. areolatus larvae might be more competitive after a period of development. Utetes anastrephae females were less likely to oviposit into hosts previously attacked by D. areolatus than vice versa. This was a second case of the relatively rare phenomenon of inter‐specific discrimination of a previously exploited host within the opiine braconid parasitoids of frugivorous tephritids.

Natural Ocurrence of Hymenopterous Parasitoids Associated with Anastrepha fraterculus (Diptera: Tephritidae) in Myrtaceae Species in Entre Rios, Northeastern Argentina

Abstract Parasitoids of Anastrepha fraterculus (Wiedemann) were monitored on ripe fruit of 3 native and 1 exotic, wild Myrtaceae species in the Province of Entre Rios, NE Argentina, between Jan and Mar 1993 and 1994 with the aim of identifying indigenous parasitoid species and determining natural parasitization rates and fruit infestation levels. The fruit species surveyed were Psidium guajava L. (common guava), Feijoa sellowiana (O. Berg) O. Berg (feijoa), Eugenia uniflora L. (Surinam cherry), and Myrcianthes pungens (Berg) Legrand (mato). Altogether 2,186 tephritid puparia were obtained, 95% of which were A. fraterculus and 5% of which were Ceratitis capitata (Wiedemann). Of 1,667 adult insects that emerged from these puparia, 1,378 were A. fraterculus, 89 C. capitata, and 200 larval-pupal parasitoids, representing 4 species of 2 Hymenoptera families: Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), Utetes anastrephae (Viereck) (all Braconidae, Opiinae), and Aganaspis pelleranoi (Brèthes) (Figitidae, Eucoilinae). All these parasitoid species are new reports for Entre Rios. Moreover, these records represent the southernmost natural distribution range in the Americas for these species. Doryctobracon areolatus and A. pelleranoi were recovered from all of the Myrtaceae species sampled, and they were the most abundant parasitoid species. Infestation patterns by A. fraterculus in mato, Surinam cherry, guava, and feijoa varied from 15.2 to 41.8, 21.3 to 49.4, 34.1 to 109.2, and 78.9 to 140.6 larvae per kg of fruit, respectively. Highest levels of parasitism were recorded in P. guajava, whereas M. pungens had the lowest parasitization rates. However, overall mean parasitism levels (i.e., considering all parasitoid species) did not appear to have great differences when comparing Myrtaceae species, collection sites, and years. The relative abundance and parasitization rates data of the recovered parasitoids in the 4 Myrtaceae species suggest some degree of host plant preference by U. anastrephae and D. brasiliensis.

The effect of four fruit species on the parasitization rate of Anastrepha fraterculus (Diptera: Tephritidae, Trypetinae) by Diachasmimorpha longicaudata (Hymenoptera: Braconidae, Opiinae) under laboratory rearing conditions

Abstract In the laboratory, the effect of host fruit species Citrus paradisi, C. aurantium, Prunus persica, and Psidium guajava on A. fraterculus parasitism by Diachasmimorpha longicaudata was studied. The number of ovipositor-probing events and the probing-time were documented to evaluate the role of fruit chemistry, and epicarp and mesocarp thickness, respectively. The relationship between the parasitization rate and fruit size in particular plant species was analyzed by applying a simple regression. Results showed that guava and peach yielded significantly more parasitoids than both Citrus spp. Probably, the parasitization rate of D. longicaudata on A. fraterculus would be influenced in part by chemical and physical factors from fruit species.

A Survey of Hymenopterous Larval-Pupal Parasitoids Associated with Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae) Infesting Wild Guava (Psidium guajava) and Peach (Prunus persica) in the Southernmost Section of the Bolivian Yungas Forest

ABSTRACT Parasitoids of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) infesting wild guava (Psidium guajava L.) and peach (Prunus persica (L.) Batsch) fruits in the southernmost extension of the Bolivian Yungas forest, in the Province of Tarija, were surveyed in Dec (early summer), Feb (mid summer) and Mar (late summer) 1999 and 2000. The abundance patterns and diversity of fruit fly larval-pupal parasitoid species were similar to previously published data for the southern and northern Yungas forests of Argentina. A total of 1,600 guavas and 800 peaches, weighing 57.713 kg and 24.544 kg, respectively, were collected yielding 13,080 tephritid puparia, 78.4% of which were A. fraterculus and 21.6% Ceratitis capitata (Wiedemann). We reared 712 larval-pupal parasitoids of the following species: Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), D. crawfordi (Viereck), Opius bellus Gahan, Utetes anastrephae (Viereck) (all Braconidae, Opiinae), Aganaspis pelleranoi (Brèthes) Odontosema anastrephae Borgmeier, and Lopheucoila anastrephae (Rohwer) (all Figitidae, Eucoilinae). Utetes anastrephae, O. anastrephae, and L. anastrephae are new fruit fly parasitoid reports for Bolivia, as well as O. anastrephae in the South American Yungas forest. A thorough sampling of other C. capitata and Anastrepha host plants, mostly native fruit species, will be necessary in the Yungas forest of Bolivia before further conclusions on abundance and composition of all fruit fly parasitoids can be reached.

Occurrence of Ceratitis capitata and Anastrepha fraterculus (Diptera: Tephritidae) on cultivated, exotic fruit species in the highland valleys of Tucuman in Northwest Argentina.

ABSTRACT Fruits from 6 exotic, cultivated fruit species were collected in the Tafí and Calchaquí valleys between Jan 2000 and Jan 2002 to determine the occurrence of Ceratitis capitata (Wiedemann) and Anastrepha fraterculus (Wiedemann) and the corresponding fruit infestation levels. The valleys are situated in the western semiarid highlands of Tucumán province (NW Argentina) and the altitude ranges from 1,800 to 2,014 m above sea level. The fruit species surveyed were Cydonia oblonga Miller, Malus domestica Borkh., Prunus armeniaca L., P. domestica L., P. persica (L.) Batsch, and Pyrus communis L. (Rosaceae). Out of a total of 2,129 puparia recovered from infested fruit, 2,112 (98.8%) were C. capitata and only 27 (1.2%) A. fraterculus. Ceratitis capitata was recovered from all fruit species and it was the dominant species. Anastrepha fraterculus was only recovered from C. oblonga, P. persica and P. domestica. All Prunus species and P. communis were the host plants that were infested most by C. capitata. The infestation data of C. oblonga, P. communis and M. domestica demonstrated that these 3 fruit species were acceptable host plants for C. capitata in Tucumán. This study provides the first record of both C. capitata and A. fraterculus infesting fruit species in semiarid highland valleys in Tucumán, and it also expands the altitudinal range of distribution of these two tephritid species to 2,014 m within the Tucumán province.

Biomechanical evidence suggests extensive eggshell thinning during incubation in the Sanagasta titanosaur dinosaurs

The reproduction of titanosaur dinosaurs is still a complex and debated topic. Their Late Cretaceous nesting sites are distributed worldwide and their eggs display substantial morphological variations according to the parent species. In contrast to the typical 1.3–2.0 mm thick shells common to eggs of most titanosaur species (e.g., those that nested in Auca Mahuevo, Tama, Toteşti or Boseong), the Cretaceous Sanagasta eggs of Argentina display an unusual shell thickness of up to 7.9 mm. Their oviposition was synchronous with a palaeogeothermal process, leading to the hypothesis that their extra thick eggshell was an adaptation to this particular nesting environment. Although this hypothesis has already been supported indirectly through several investigations, the mechanical implications of developing such thick shells and how this might have affected the success of hatching remains untested. Finite element analyses estimate that the breaking point of the thick-shelled Sanagasta eggs is 14–45 times higher than for other smaller and equally sized titanosaur eggs. The considerable energetic disadvantage for piping through these thick eggshells suggests that their dissolution during incubation would have been paramount for a successful hatching.