Fundamental and realized niches of two chrysomelid competitors on two Salix host species

Sammanfattning: The fundamental and realized niches of phytophagous insects constitute an important topic in contemporary ecology. Hutchinson (1965) formulized the concept of the fundamental and realized niche with regards to species responses to interspecific competition; and for the herbivore insects’ community the consequence of interspecific competition is a debatable and questionable from the very beginning to till now. This study investigated the fundamental and the realized niche of two willow leaf beetles, Galerucella lineola and Phratora vulgatissima, on two different Salix host species, S. viminalis and S. dasyclados; and how plant species affect the fundamental and realized niches of these beetle species. To achieve the objective of this study, I focused on the egg-laying preference and placement of Phratora and Galerucella eggs in monospecific and mixed conditions. The results indicate that the fundamental niches of both beetle species are dissimilar to each other and that plant species affect their fundamental niches. The two leaf beetles affect each other’s realized niche. One mechanism behind the results may be that the beetles induce changes in their shared host plants, leading to indirect interactions between the two beetles. Females could adjust their egg-laying behavior to different host plant species as well as to the presence of the opposite beetle species while ovipositing.