Browsing by Author "Ramirez, Claudio C."

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    Harbouring the secondary endosymbiont Regiella insecticola increases predation risk and reproduction in the cereal aphid Sitobion avenae
    (2019) Ramirez-Caceres, Guillermo E.; Moya-Hernandez, Mario G.; Quilodran, Manuel; Nespolo, Roberto F.; Ceballos, Ricardo; Villagra, Cristian A.; Ramirez, Claudio C.
    Symbiosis in insects has been recognized as contributing to their ecological and evolutionary success. In the case of agricultural pests, endosymbionts may help insects colonize and expand their niches, allowing them to use different crops and to confront climatic variation. Moreover, endosymbionts provide improved defences against pathogens, predators, and parasitoids. In aphids, facultative endosymbionts have been found capable of generating these characteristics. However, evidence for this has been gathered from only a few model organisms. Here, we studied the effect of the facultative endosymbiont Regiella insecticola on the predation of Sitobion avenae clones by the ladybird Hippodamia variegata. In the laboratory, we assessed the predation rate of this coccinellid and the concomitant anti-predator behaviour of S. avenae with and without R. insecticola. We also evaluated the effect of the presence of this endosymbiont on the constitutive levels of E--farnesene, on the metabolic rate, and on the reproductive performance of S. avenae. All these traits were studied on two common alternative crops: wheat and barley. We found that R. insecticola-infected aphids were more predated irrespective of host plants and did not improve defences against coccinellid predators or metabolic rates on any host plants. Levels of E--farnesene were higher on wheat plants, irrespective of the presence of R. insecticola. Interestingly, R. insecticola-infected aphids had increased performance on wheat, while the opposite was true on barley. We discuss our findings based on the importance of secondary symbionts as providers of traits allowing aphids to be very invasive crop pests worldwide.
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    Phylogeographical Analysis of Neotropical Rhagoletis (Diptera: Tephritidae): Did the Andes Uplift Contribute to Current Morphological Differences?
    (2008) Ramirez, Claudio C.; Salazar, Marcela; Eduardo Palma, R.; Cordero, Cecilia; Meza-Basso, Luis
    Neotropical Rhagoletis species are arranged in four groups: nova, psalida, striatella and ferruginea, which include 18 species. On both sides of the Andes, the evolution of morphological differences among these groups has been suggested to be related to the Andes uplift process. In order to test this hypothesis, a phylogenetic analysis of morphological and molecular data was performed. The results suggest that: 1) Neotropical species of Rhagoletis constitute a separate group from Paleartic and North American species, with the only exception being a member of the striatella group having a certain association with the northern species. 2) Neotropical species seem to form a monophyletic clade, although statistical support for this is weak. 3) The split of South American Rhagoletis from other groups was dated at 4.333 million years ago, which is before the emergence of a continuous landbridge between Central and South America. 4) Within species distributed in South America, morphological and molecular data were coincident, placing species of the ferruginea group separate from the other Neotropical Rhagoletis. 5) The divergence of the ferruginea group from the other groups was dated at 3.882 million years ago, which is before the last uplift of the Andes. These results suggest that diversification of the ferruginea, psalida and nova groups, on each side of the Andes, was the result of a vicariant separation followed by dispersal and isolation processes. Thus, these results support the hypothesis that the Andes uplift has played an important role in Neotropical Rhagoletis diversification.