Sobre una interacción tritrófica pobremente conocida: Rhagoletotrypeta pastranai Aczél (Diptera: Tephritidae) y su parasitoide Utetes anastrephae (Viereck) (Hymenoptera: Braconidae) en frutos de Celtis ehrenbergiana (Klotzsch) Liebm. (Rosales: Cannabaceae)RESUMEN. Presentamos información sobre una interacción tritrófica nativa poco conocida constituida por Celtis ehrenbergiana (Klotzsch) Liebm. (Cannabaceae), la mosca de la fruta Rhagoletotrypeta pastranai Aczél (Diptera: Tephritidae), y su parasitoide Utetes anastrephae (Viereck) (Hymenoptera: Braconidae) en Buenos Aires, Argentina. Los insectos fueron colectados a partir de 70 árboles y 950 frutos y la cría de las formas inmaduras se llevó a cabo en laboratorio. La mosca de la fruta representó 41,8% del total de pupas (59 de 141), mientras que el parasitoide representó 32,6% del total de pupas de R. pastranai (46 de 141). Los niveles de infestación por mosca de la fruta variaron entre 0 y 191 pupas/100g de frutos (media = 53,3 ± 55,3 pupas/100 g de frutos), y los porcentajes de infestación variaron entre 0 y 100% (media = 18,2% ± 32,1%). La mayoría de los parasitoides adultos emergieron luego de 1-2 meses, mientras que la mayoría de moscas adultas emergieron luego de un período de diapausa de 12 meses. Nuestros resultados muestras que ambos insectos son comunes y abundantes en el área de estudio, y resaltan la necesidad de estudiar especies poco conocidas, a pesar de no presentar importancia económica, para lograr un mejor entendimiento de la ecología de interacciones bióticas con múltiples interactores. PALABRAS CLAVE. Infestación de frutos. Interacciones planta-insecto. Talares.ABSTRACT. We present information on a poorly known native tritrophic interaction involving Celtis ehrenbergiana (Klotszch) Liebm. (Cannabaceae), the fruit fly Rhagoletotrypeta pastranai Aczél (Diptera: Tephritidae), and its parasitoid Utetes anastrephae (Viereck) (Hymenoptera: Braconidae) from Buenos Aires, Argentina. Insects were collected from 70 trees and 950 fruits and immatures were reared in the laboratory. The fruit fly accounted for 41.8% of all pupae (59 out of 141 pupae), whereas the parasitoid accounted for 32.6% of fruit www.biotaxa.org/RSEA. ISSN 1851-7471 (online) Revista de la Sociedad Entomológica Argentina 78(3): 29-32, 2019
Every organism on Earth must cope with a multitude of species interactions both directly and indirectly throughout its life cycle. However, how selection from multiple species occupying different trophic levels affects diffuse mutualisms has received little attention. As a result, how a given species amalgamates the combined effects of selection from multiple mutualists and antagonists to enhance its own fitness remains little understood. We investigated how multispecies interactions (frugivorous birds, ants, fruit flies and parasitoid wasps) generate selection on fruit traits in a seed dispersal mutualism. We used structural equation models to assess whether seed dispersers (frugivorous birds and ants) exerted phenotypic selection on fruit and seed traits in the spiny hackberry (Celtis ehrenbergiana), a fleshy-fruited tree, and how these selection regimes were influenced by fruit fly infestation and wasp parasitoidism levels. Birds exerted negative correlational selection on the combination of fruit crop size and mean seed weight, favouring either large crops with small seeds or small crops with large seeds. Parasitoids selected plants with higher fruit fly infestation levels, and fruit flies exerted positive directional selection on fruit size, which was positively correlated with seed weight. Therefore, higher parasitoidism indirectly correlated with higher plant fitness through increased bird fruit removal. In addition, ants exerted negative directional selection on mean seed weight. Our results show that strong selection on phenotypic traits may still arise in perceived diffuse species interactions. Overall, we emphasize the need to consider diverse direct and indirect partners to achieve a better understanding of the mechanisms driving phenotypic trait evolution in multispecies interactions.
Worldwide, the areas covered by native forests are declining while those of tree plantations are increasing. This has raised the question of whether tree plantations are able to preserve native forest species. In Argentina, the main native forests of the Pampas region, called talares, are endangered and their disappearance is imminent. Although exotic tree plantations are increasing in this region, their role in maintaining native bird diversity has not been studied in Argentine Pampas. We compared the bird community attributes and vegetation structure of talares native forest with those of tree plantations. Plantations exhibited markedly lower bird richness than talares, up to 80% lower, and all forest-dependent bird species were absent in plantations. Talares and plantations differed also in some aspects of vegetation structure, which usually are key determinants of bird abundance. Given the extreme importance of talares for forest birds, this bird community will be deeply affected if it continues to decline, as nearby plantations do not offer suitable habitat. In order to maintain the bird diversity of talares, and probably the diversity of other unstudied taxa related to them, we recommend management actions that should be applied urgently in these endangered forests of the Argentine Pampas.
The selection of suitable host plants for larval development is critical for most herbivorous insects. In this study, we examined host plant preferences of larvae of the Epistrophus white morpho butterfly, Morpho epistrophus argentinus (H. Fruhstorfer), a specialized butterfly that oviposits on a few plant species. In many species, the selection of host plant species for larvae development is under the control of ovipositing females and the role of larvae in host selection is minimal. Through field observations, we characterized larval host plant use in coastal woodland patches of its southernmost distribution range at eastern Buenos Aires, Argentina. All sampled M.e. argentinus larvaegroups (n = 40) were found on Scutia buxifolia trees, although the number of larval groups did not correlate with cover of this plant at patch scale. To further examine host plant preferences we performed translocation experiments and feeding choice assays. M.e. argentinus larvae translocated to unsuitable host plants had a shorter residence time than those translocated to suitable (i.e. control) hosts. Choice assays also indicated strong feeding preferences of wild larvae for S. buxifolia leaves. Our results highlight the high degree of host specificity of this butterfly, and reveal that host preference of growing larvae matches that of ovipositing females.
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