Seasonal fluctuation on infestation of several hosts by the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae) in Buenos Aires Province

Se realizó un relevamiento de 11 especies frutales hospedadoras de Ceratitis capitata presentes en un área experimental de San Pedro (Buenos Aires, Argentina), con una extensión aproximada de 115 ha. Se comparó la abundancia de la población de insectos adultos y el nivel de infestación de las especies frutales (inferido a partir del porcentaje de fruta infestada y del número de puparios/kg de fruta) a lo largo de una temporada cálida, y se analizó el efecto de algunas variables bióticas y abióticas sobre las fluctuaciones poblacionales. El estudio comprendió muestreos quincenales realizados entre noviembre de 1999 y mayo de 2000. En los mismos se recolectaron frutos maduros de 20 plantas tomadas al azar. Los periodos de fructificación de las especies presentes ocurrieron en forma escalonada a lo largo de la temporada reproductiva, asegurando a los individuos un suministro de recurso casi ininterrumpido. No obstante, la disponibilidad global de hospedadores no estuvo asociada con las fluctuaciones poblacionales. Probablemente el efecto restrictivo de las bajas temperaturas de invierno impide que la población alcance los niveles necesarios para explotar el recurso en forma proporcional a su disponibilidad. Se encontró un alto grado de asociación entre la abundancia de adultos y los niveles de infestación. En el área de estudio, el único factor climático que parece tener un efecto sobre estas variables es la temperatura. Las correlaciones de la abundancia de adultos y de los niveles de infestación con la temperatura del perIodo precedente resultaron más altas que con las temperaturas del período corriente, indicando que este factor climático probablemente afecta en forma más intensa a los estadios inmaduros que a los adultos.Seasonal fluctuation on infestation of several hosts by the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae) in Buenos Aires Province: A survey of 11 host species of Ceratitis capitata was carried out in an experimental area of San Pedro (Buenos Aires, Argentina) with an approximate extension of 115 ha. The abundance of adult flies was compared with the infestation level (inferred from the percentage of infested fruit and from the number of puparia/kg of fruit) along the reproductive season. Also, the effect of some biotic and abiotic factors on the population fluctuations was analyzed. The study included 12 fortnightly samplings carried out between November 1999 and May 2000. In each sampling, mature fruits of 20 plants were taken at random. For each fruit, the number of puparia of Ceratitis capitata was recorded. The fruiting periods of the host species present in the area were staggered along the reproductive season, assuring to the flies a continuous supply of hosts. Nonetheless, population fluctuations were not related to the availability of hosts. The restrictive effect of low winter temperatures probably prevents population from reaching levels required to exploit the resource in proportion to its availability. There was a high association between the abundance of adult flies and infestation levels. In the study area, temperature was the only climatic factor showing significant association with the abundance of Ceratitis capitata and infestation levels. Correlations of the abundance of adult flies and of the infestation levels with the temperature of the previous period were higher than the correlation with the temperature of the current period, probably indicating that this climatic factor has a stronger effect on the immature stages than on the adults

Relación entre tiempo de desarrollo larvario y fecundidad de la hembra en Ceratitis capitata (Diptera:Tephritidae) Relationship between time of larval development and fecundity in the female of Ceratitis capitata (Diptera: Tephritidae)

Se estudió la relación entre tiempo de desarrollo larvario y fecundidad en la hembra de Ceratitis capitata Wiedemann, comparando individuos de una cepa salvaje, con individuos de una cepa portadora de la mutación sw , la cual provoca atrasos en el desarrollo larvario. Se observaron caracteres de la morfología del ovario y su herencia entre los segregantes, para «tiempo de desarrollo» en la progenie del cruzamiento entre mutante y silvestre. El estudio mostró que las hembras sw (-) que quedan muy retrasadas en su desarrollo, tienen menos ovariolas y una distribución de tamaños de óvulos menos homogénea que las que se desarrollan antes. Se encontró asimismo que entre las larvas de tipo salvaje, las más retrasadas también producen hembras con menor número de ovariolas y menos huevos totalmente desarrollados, que las que se desarrollan antes. Tanto en las hembras sw (-) como en las sw(+) , los atrasos del desarrollo obran en desmedro de la postura de huevos de las hembras que se desarrollan más tarde, efecto que se manifiesta en el número menor de ovariolas y en las diferencias del ritmo de maduración del ovario. Bajo condiciones apropiadas de cría, las hembras mutantes para sw son capaces de alcanzar la misma fecundidad que las normales.We studied the relationship between the development time in the larva stage and the resulting female fecundity, in Ceratitis capitata Wiedemann wild-type individuals compared to mutant individuals showing slow development (sw). We observed the morphology of the ovaries in the progenies of the crossing between mutant and wild-type strains, comparing females segregating by «development time». This study showed that sw(-) females developing later have got less ovarioles, and a more heterogeneous distribution of ovules, than females developing earlier. It was also found that the wild type females developing late also produce lower numbers both of ovarioles and fully developed ova, than those developing earlier. In sw females as well as in wildtype females, delays in development reduce the fecundity of the females, which is expressed as lower number of ovarioles and slower maturation of the ovary. When the rearing conditions are appropriate, the sw females are as fertile as wild-type ones

When the Past Lives in the Present. Agrarian Landscapes and Historical Social Dynamics in the Southern Andes (Quebrada de Humahuaca, Jujuy, Argentina)

This article examines the agrarian landscape in one part of the southern Andes (Quebrada of Humahuaca, Jujuy, Argentina). The region possesses extensive and well-preserved archaeological remains of agricultural systems, which stretch back to pre-Hispanic times. In this study, we employ an interdisciplinary approach in our analysis of the components that structure the agrarian landscape, especially those historical processes that intervened in its formation. The creation of a cartographic base, built from remote sensing and fieldwork data, allowed for the identification of four principal components of the landscape, each of which correspond to distinct phases or periods that mark the region’s history. Our study shows that, in contrast to what is observed in many other rural areas, the successive productive dynamics that developed in the area did not result in the destruction of previous productive structures. Rather, the agrarian landscape in the study area presents a multi-temporal agglutinating combination or composition, which transcends historical discontinuities in the productive matrix. This is owing to the partial reutilisation of previous structures in each period; however, religious and cultural factors play an important role. The agrarian landscape we studied is not only a passive result of human activity, but also a force influencing the productive and lifestyle decisions of the peasant populations that live there today. Our research amplifies the understanding of agrarian landscapes in the Andes and shows how past temporalities are articulated with the present through a dialectical process

Producción masiva y simultánea de machos de Ceratitis capitata (Diptera: Tephritidae) y parasitoides Dichasmimorpha longicaudata (Hymenoptera: Braconidae) Massive and simultaneous production of Ceratitis capitata (Diptera: Tephritidae) males and Diachasmimorpha longicaudata (Hymenoptera: Braconidae) parasitoids

En la línea de sexado genético «Cast191» las hembras de Ceratitis capitata son homocigotas para el gen slow , lo que reduce su velocidad de desarrollo; los machos son heterocigotas y muestran una velocidad de desarrollo normal. Esta característica permitió producir, con Cast191, machos estériles por un lado, y parasitoides criados sobre las larvas remanentes por el otro. Nuestro objetivo con este trabajo fue producir ambos insumos simultáneamente y a una escala mayor que hasta ahora. Además, bajo estas condiciones, y en un intento por aumentar la separación entre sexos, se aplicó a las larvas del primer estadío un pulso de 15º C, durante 1 ó 2 días, luego del cual se las mantuvo a 20º C ó 25º C, hasta que entraron al estado de pupa, luego se mantuvo todo el material a 25º C. La mejor separación de sexos, lograda con el tratamiento a 20º C sin pulso de frío, se usó para comparar la calidad del parasitoide Diachasmimorpha longicaudata, criado sobre las larvas obtenidas tras la separación de los machos, con aquellos criados sobre la línea salvaje. Para ello, este tratamiento de separación fue aplicado en la cría de la mosca, y el material remanente de dieta con larvas fue expuesto al parasitoide. La tasa de parasitismo obtenida fue semejante a la hallada sobre la línea salvaje, y la tasa sexual de la F 1 del parasitoide presentó un sesgo hacia las hembras aún mayor. Se discute la factibilidad de utilizar la línea Cast191 de C. Capitata, para la producción a mayor escala de machos de mosca y para la cría masiva del parasitoide D. longicaudata.<br>In the genetic sexing strain «Cast191», the females of Ceratitis capitata are homozygous for the mutation slow , slowing down their rate of development, and the males are heterozygous, having a normal rate of development. This feature made Cast191 capable of producing sterile males, on one hand, and parasitoids that are reared on the remaining larvae, on the other. The objective of the present work was to do this two thing simultaneously and at a larger scale than previously. Besides, in an attempt to improve malefemale separation under this conditions, a pulse of 15ºC was applied to first stage larva during 1 or 2 days; these larvae were later held either at 20ºC or, at 25ºC until pupation, both groups of pupae being then kept at 25ºC . The best separation between male and female, achieved rearing larvae at 20ºC without any pulse of 15ºC , was then used to evaluate the quality of the parasitoids Diachasmimorpha longicaudata reared on the larvae remaining after male separation. These larvae were exposed to the parasitoid under standard conditions. The rate of parasitism obtained was similar to the one found when parasitoids are exposed to wild strain, and the F1 sex rate was even more biased toward females. The potential use at larger scale of the Cast191 strain of C. capitata for producing sterile males and D. longicaudata parasitoids is discussed

Coexistence between two fruit fly species is supported by the different strength of intra- and interspecific competition

Unravelling the strength and modes of interspecific interactions betweenresident and introduced species is necessary in order to understand the basis of their coexistence or the displacement of the former by the latter. In Argentina, the indigenous Tephritidae fly Anastrepha fraterculus overlaps its distribution and host fruit with the introduced species Ceratitis capitata.2. This study focused on the relative strength of intra- and interspecific competition during the larval stage as a potential factor supporting coexistence. Classical competition experiments (addition and substitution) were conducted between larvae of the two species reared in artificial larval diet. The study evaluated whether a temporal separation between oviposition events affects the outcome of the competition.3. When both species started to consume the resource at the same time, A. fraterculus experienced a negative effect in larval survival, pupal weight and duration of larval stage, while for C. capitata, pupal weight decreased. When A. fraterculus started feeding 1 day earlier than C. capitata, the negative effects became milder, and when the temporal separation increased, these effects were reversed. Substitution experiments showed an increase in pupal weight when larvae had to share the resource with heterospecific larvae, and showed negative effects suffered for both species when they shared the resource with conspecific individuals.4. These results suggest that intraspecific competition is stronger than interspecific competition, and a differential oviposition preference could generate an asynchrony of these species in nature. Such mechanisms could favour coexistence between A. fraterculus and C. capitata in an environment previously occupied only by the former.Fil: Liendo, María Clara. Universidad Nacional de Tucumán; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo | Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo.; ArgentinaFil: Parreño, Maria Alejandra. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo | Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo.; Argentina. Universitat Zurich; SuizaFil: Cladera, Jorge L.. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo | Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo.; ArgentinaFil: Vera, María Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán; ArgentinaFil: Segura, Diego Fernando. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo | Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo.; Argentin

Patterns of resource distribution among conspecific larvae in two fruit fly species : Anastrepha fraterculus and Ceratitis capitata (Diptera : Tephritidae)

Anastrepha fraterculus (Diptera: Tephritidae) and Ceratitis capitata (Diptera: Tephritidae) are fruit fly pests whose larvae are frequently found sharing the same fruit with conspecifics. Because larvae are incapable of leaving the fruit in search of non-infested fruit, they are forced to share nutritional resources and eventually compete with other larvae for these. In the present study, we investigated the effect of intraspecific competition on the development of A. fraterculus and C. capitata larvae, and compared the strategies adopted by these species. To this end, newly-hatched larvae were transferred into a container with a fixed amount of larval diet at increasing larval densities and several developmental parameters were measured. The two species showed similarities and differences in the way in which they responded to an increasing density. In A. fraterculus, pupal weight and the duration of the larval stage decreased as the competition levels increased. Larvae of C. capitata showed a consistent reduction in pupal weight and larval survival as the larval density increased. In A. fraterculus, the reduction in pupal weight was heterogeneous, with most pupae showing a marked decrease in weight and only few pupae showing slight negative effects or no effect at all, whereas, in C. capitata, the reduction was similar for all pupae. The differences in the way in which these species responded to competition suggest that there are different patterns of resource distribution among conspecific larvae. The implications of these findings for oviposition behaviour and the life history of the two species are discussed.8 page(s

Innate Host Habitat Preference in the Parasitoid Diachasmimorpha longicaudata: Functional Significance and Modifications through Learning.

Parasitoids searching for polyphagous herbivores can find their hosts in a variety of habitats. Under this scenario, chemical cues from the host habitat (not related to the host) represent poor indicators of host location. Hence, it is unlikely that naïve females show a strong response to host habitat cues, which would become important only if the parasitoids learn to associate such cues to the host presence. This concept does not consider that habitats can vary in profitability or host nutritional quality, which according to the optimal foraging theory and the preference-performance hypothesis (respectively) could shape the way in which parasitoids make use of chemical cues from the host habitat. We assessed innate preference in the fruit fly parasitoid Diachasmimorpha longicaudata among chemical cues from four host habitats (apple, fig, orange and peach) using a Y-tube olfactometer. Contrary to what was predicted, we found a hierarchic pattern of preference. The parasitism rate realized on these fruit species and the weight of the host correlates positively, to some extent, with the preference pattern, whereas preference did not correlate with survival and fecundity of the progeny. As expected for a parasitoid foraging for generalist hosts, habitat preference changed markedly depending on their previous experience and the abundance of hosts. These findings suggest that the pattern of preference for host habitats is attributable to differences in encounter rate and host quality. Host habitat preference seems to be, however, quite plastic and easily modified according to the information obtained during foraging