Abstract

Neighboring plants may have dual roles in relation to focal plants, being both competitors, and mediators of associational resistance (AR), or associational susceptibility (AS) to herbivores. Even though these two roles are played out simultaneously in nature, they have traditionally been studied separately. We conducted a two-by-two factorial experiment by manipulating the occurrence of neighbors (meadowsweet, Filipendula ulmaria) and shared mammal herbivores (moose, Alces alces) to investigate how the two simultaneously affect the performance of focal fireweed (Chamerion angustifolium) plants.We found that interactions between mammal herbivory and neighbors had significant effects on fireweed performance. These effects were explained by two counteracting mechanisms. First, when mammal herbivores were present, fireweed experienced AR such that plants growing outside of meadowsweet patches had an almost tripled risk of being browsed compared to plants growing among meadowsweet, resulting in reduced fireweed reproduction and growth. Second, when mammals were excluded, the association with meadowsweet had a direct negative effect on fireweed growth rates - mainly due to competition for light. Additionally, for the first time, we show that association with neighbors affected mammal-induced branching in fireweed.This study demonstrates that AR mediated by mammal herbivores can flip plant-plant interactions from competitive (-) to facilitative (+), and affect plant architecture. As AR and competition are probably simultaneously co-occurring forces, interactions between the two are likely common and thus of fundamental importance for populations and communities.

Keywords

Associational herbivory; Apparent competition; Tolerance; Branching; Moose; Alces alces; Altica; Epilobium angustifolium

Published in

Basic and Applied Ecology
2014, Volume: 15, number: 1, pages: 10-17
Publisher: ELSEVIER GMBH, URBAN & FISCHER VERLAG

SLU Authors

• Axelsson, Petter

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Stenberg, Johan A.

  • Department of Ecology, Swedish University of Agricultural Sciences
    

Associated SLU-program

SLU Plant Protection Network


UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1016/j.baae.2013.12.003

Permanent link to this page (URI)

https://res.slu.se/id/publ/60484