Item – Thèses Canada

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Numéro d'OCLC
1019473879
Lien(s) vers le texte intégral
Exemplaire de BAC
Auteur
Daoust, Simon P.
Titre
Impacts de l'intensification agricole et de la structure du paysage sur les relations tri -- trophiques entre un oiseau hote, des mouches ectoparasites et leur parasitoides.
Diplôme
Thèse (Ph. D.)--Université de Montréal, 2011.
Éditeur
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, 2013.
Description
1 online resource.
Notes
Comprend des réf. bibliogr.
Résumé
<?Pub Inc> Landscape fragmentation and homogenization are considered to be the main causes of the worldwide decline in biological diversity. The degradation of habitat quality is mainly caused by the expansion and intensification of human land-use activities, primarily for agricultural purposes. Many studies documented the impact of landscape fragmentation and agricultural intensification on the overall fitness of animals across various taxa, but few works have studied this phenomenon in relation to trophic interactions. Here, we investigated the effects of landscape structure on the tri-trophic interactions between a bird host (the Tree Swallow 'Tachycineta bicolor' (Vieillot)), its blowfly ectoparasites ('Protocalliphora' Hough), and their parasitoid wasps ('Nasonia' Walker) along a gradient of agricultural intensification covering 10, 200 km2 in southern Québec, Canada. The first objective was to describe the assemblages of 'Protocalliphora ' and 'Nasonia' species found in Tree Swallow nests within our system. The prevalence of nest infestation by 'Protocalliphora ' was of 70.8% in 2008 and 34.6% in 2009. The percentage of nests containing 'Protocalliphora' pupae parasitized by Nasonia spp. was of 85.3 % in 2008 and 67.2% in 2009. Three species of 'Protocalliphora ' were collected ('P. sialia, P. bennetti' and ' P. metallica') and two species of 'Nasonia' (' N. vitripennis' and 'N. giraulti'). Secondly, I evaluated the impact of landscape structure and agricultural intensification on the number of Tree Swallow fledglings, number of 'Protocalliphora' per nest and the level of hyperparasitism by 'Nasonia'. Our results revealed that organisms from different trophic levels perceived the landscape at distinctive spatial extents. This perception, however, differed based on whether the proportions of intensive or extensive culture in the landscape were considered. Furthermore, the number of Tree Swallow fledglings, the abundance of 'P. sialia' and the level of hyperparasitism by 'N. vitripennis' all decreased with an increase in the proportion of intensive culture in the landscape. 'Protocalliphora' and ' Nasonia' were more susceptible to extinction within highly intensive landscapes as they are confronted with both the direct effect of habitat degradation on their populations and the indirect effect of habitat degradation on their host populations. The last objective was to investigate how parasitoid wasps respond to environmental variability. We showed that the size of the ' P. sialia' pupae hosts decreased in more intensive landscapes. Wasps clutch size was shown to increase within increasing host size and the sex ratio of offspring produced by 'N. vitripennis' became more male biased as the proportion of intensive culture increased in the landscape. In addition, both female and male size was influenced by resource availability (size of host and number of competitors). Our data indicate that by producing smaller male biased clutches in the smaller hosts within intensive landscapes, females were able to respond to poor environments and maximize the size of their offspring. To conclude, this work highlights the importance of considering the landscape context of trophic interactions, as these interactions dictate local biodiversity and ecosystem function. Key-words: agricultural intensification, functional spatial scale, trophic interactions, clutch size, sex ratio, Tree Swallow, 'Protocalliphora, Nasonia.'
ISBN
9780494835111
0494835117
9780494835111