Interspecific competition between entomopathogenic nematodes Steinernema is modified by their bacterial symbionts XenorhabdusReportar como inadecuado

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BMC Evolutionary Biology

, 6:68

First Online: 05 September 2006Received: 17 May 2006Accepted: 05 September 2006


BackgroundSymbioses between invertebrates and prokaryotes are biological systems of particular interest in order to study the evolution of mutualism. The symbioses between the entomopathogenic nematodes Steinernema and their bacterial symbiont Xenorhabdus are very tractable model systems. Previous studies demonstrated i a highly specialized relationship between each strain of nematodes and its naturally associated bacterial strain and ii that mutualism plays a role in several important life history traits of each partner such as access to insect host resources, dispersal and protection against various biotic and abiotic factors. The goal of the present study was to address the question of the impact of Xenorhabdus symbionts on the progression and outcome of interspecific competition between individuals belonging to different Steinernema species. For this, we monitored experimental interspecific competition between i two nematode species: S. carpocapsae and S. scapterisci and ii their respective symbionts: X. nematophila and X. innexi within an experimental insect-host Galleria mellonella. Three conditions of competition between nematodes were tested: i infection of insects with aposymbiotic IJs i.e. without symbiont of both species ii infection of insects with aposymbiotic IJs of both species in presence of variable proportion of their two Xenorhabdus symbionts and iii infection of insects with symbiotic IJs i.e. naturally associated with their symbionts of both species.

ResultsWe found that both the progression and the outcome of interspecific competition between entomopathogenic nematodes were influenced by their bacterial symbionts. Thus, the results obtained with aposymbiotic nematodes were totally opposite to those obtained with symbiotic nematodes. Moreover, the experimental introduction of different ratios of Xenorhabdus symbionts in the insect-host during competition between Steinernema modified the proportion of each species in the adults and in the global offspring.

ConclusionWe showed that Xenorhabdus symbionts modified the competition between their Steinernema associates. This suggests that Xenorhabdus not only provides Steinernema with access to food sources but also furnishes new abilities to deal with biotic parameters such as competitors.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2148-6-68 contains supplementary material, which is available to authorized users.

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Autor: Mathieu Sicard - Julie Hinsinger - Nathalie Le Brun - Sylvie Pages - Noël Boemare - Catherine Moulia


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