J Plant Ecol ›› 2017, Vol. 10 ›› Issue (6): 918-926 .DOI: 10.1093/jpe/rtw102

• Research Articles • Previous Articles     Next Articles

Diverse outcomes of species interactions in an invaded annual plant community

Claire E. Wainwright1,*, John M. Dwyer1,2, Richard J. Hobbs3 and Margaret M. Mayfield1   

  1. 1 The Ecology Centre, School of Biological Sciences, Building 8, The University of Queensland, St Lucia, Queensland 4072, Australia; 2 Commonwealth Scientific and Industrial Research Organisation, Land and Water, EcoSciences Precinct, Dutton Park, Queensland 4001, Australia; 3 School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
  • Received:2016-03-16 Accepted:2016-09-20 Published:2017-11-17
  • Contact: Wainwright, Claire

Diverse outcomes of species interactions in an invaded annual plant community

Abstract: Aims Despite acknowledgement that interactions among native and exotic species are important for determining the structure and diversity of novel communities, directed experiments using multiple exotics from the same system are rare. Recent observational studies have highlighted distinct ways that exotic species interface with resident natives across invaded communities. The correlative nature of these studies, however, has provided few details about the mechanisms driving distinct interaction outcomes within the same communities. Our aim was to determine how three exotic annual plant species with distinct relationships with local plant diversity impact the performance of a co-occurring native annual in the York gum–jam woodlands of Western Australia.
Methods We grew species in experimental communities in growth chambers at varying total planting densities to assess how interaction outcomes varied among natives and exotics across a gradient of competition intensity. We measured a variety of performance responses, including survival, biomass and population-level and individual-level reproductive investment.
Important findings Overall, the effects of interspecific versus intraspecific competition on performance varied with the identity and density of exotic competitors. The exploitative exotic grass Bromus madritensis was dominant in polyculture, whereas the diminutive grass Pentameris airoides conferred weak intraspecific competition and interspecific facilitation on native Waitzia nitida. The exotic broadleaf forb, Hypochaeris glabra, suppressed growth and survival of W. nitida, while W. nitida had weakly negative, neutral or positive effects on all exotics. These outcomes highlight the complexity of interactions impacting the diversity, stability and structure of novel plant communities. As few of these communities contain a single exotic species, understanding the competitive dynamics occurring in diverse novel communities is critical for their conservation and restoration.

Key words: annual plants, biotic interactions, competition, invasion, novel ecosystems

摘要:
Aims Despite acknowledgement that interactions among native and exotic species are important for determining the structure and diversity of novel communities, directed experiments using multiple exotics from the same system are rare. Recent observational studies have highlighted distinct ways that exotic species interface with resident natives across invaded communities. The correlative nature of these studies, however, has provided few details about the mechanisms driving distinct interaction outcomes within the same communities. Our aim was to determine how three exotic annual plant species with distinct relationships with local plant diversity impact the performance of a co-occurring native annual in the York gum–jam woodlands of Western Australia.
Methods We grew species in experimental communities in growth chambers at varying total planting densities to assess how interaction outcomes varied among natives and exotics across a gradient of competition intensity. We measured a variety of performance responses, including survival, biomass and population-level and individual-level reproductive investment.
Important findings Overall, the effects of interspecific versus intraspecific competition on performance varied with the identity and density of exotic competitors. The exploitative exotic grass Bromus madritensis was dominant in polyculture, whereas the diminutive grass Pentameris airoides conferred weak intraspecific competition and interspecific facilitation on native Waitzia nitida. The exotic broadleaf forb, Hypochaeris glabra, suppressed growth and survival of W. nitida, while W. nitida had weakly negative, neutral or positive effects on all exotics. These outcomes highlight the complexity of interactions impacting the diversity, stability and structure of novel plant communities. As few of these communities contain a single exotic species, understanding the competitive dynamics occurring in diverse novel communities is critical for their conservation and restoration.