Below and aboveground mutualisms and the invasion by Australian acacias: relevance on invasive dynamics and consequences for native ecosystems - MUTUALNET.
Coordinator - Susana Rodríguez Echeverría
Programme - PTDC/BIA-BEC/103507/2008
Execution dates - 2010-01-01 - 2012-12-31 (36 Months)
Funding Entity - FCT
Total Funding - 170 €
Proponent Institution -
Participating Institutions
Faculdade de Ciências e Tecnologia da Universidade de Coimbra (FCT/UC)
Fundação da Faculdade de Ciências e Tecnologia (FFCT/FCT/UNL)
University of Wollongong, NSW, Australia

Biological invasions are nowadays a major threat to biodiversity and ecosystem functioning worldwide. Invasive species can reduce local plant biodiversity, modify ecohydrological and nutrient cycles, alter the genetic integrity of native species and change native ecological interactions that have arisen over evolutionary timescales. Several hypotheses, based either on the characteristics of the invaded ecosystem or the biology of the invasive species, have been proposed to explain the success of exotic species in colonizing new areas. Nevertheless, in spite of the research effort developed in the last years to explain biological invasions by exotic species, this is a process still not well understood that offers challenging opportunities in ecological research.
The establishment of successful key mutualisms in the invaded ecosystem has been recently suggested as an essential non-explored mechanism for the survival, spread and establishment of invasive exotic plants. Plants are involved in many forms of mutualisms, for nutrient acquisition, pollination, seed dispersal, which are critical to their ecological success and, therefore, might be crucial for the invasion of new areas. Plants introduced to new geographical regions can forge totally novel combinations by plugging into the native mutualist networks, or associating with other exotic species. In some cases, exotic plants only become invasive after the introduction of mutualists from their native range. Any of these possibilities have profound implications for the behaviour of the introduced plant in the new environment and unknown evolutionary consequences. Theoretically, plants that are involved in very specific mutualisms should fail to colonize new habitats where those organisms are absent. Nevertheless, the increasing degradation of ecosystems worldwide leads to an increasing abundance of generalist mutualistic partners that can trigger the invasion by exotic species. The current lack of information on this topic hinders our ability to predict and understand invasions and their ecological and evolutionary impact on the native communities.
Taking into account the area occupied, aggressiveness and impact on the native ecosystems, three woody Australian species can be considered as the most problematic and widespread invasive exotic plants in Portugal. These species are, in order of aggressiveness, Acacia dealbata Link, Acacia longifolia (Andr.) Willd. and Acacia saligna (Labill.) H. Wendl. (family Leguminosae, subfamily Mimosoideae). In spite of their fast expansion and ecological impacts in the invaded areas, little is known about the invasive dynamics of these Australian acacias in Portugal. Enemy release might partially explain their invasive expansion, but acacias are involved in other biotic interactions essential for the colonization of new areas and long-term establishment of viable populations. Previous research developed in the CFE suggests that belowground mutualisms are crucial in the expansion of Australian acacias. This project proposal aims at expanding this research to other relevant biological processes within the general framework of mutualisms.
The objective of this project is to determine the role of below and aboveground mutualisms in the invasive expansion of A. dealbata, A. longifolia and A. saligna. Our general working hypotheses are a) the Australian acacias need to find compatible mutualists in the invaded range in order to establish permanent viable populations, and b) the invasion by Australian acacias will disrupt native plant-mutualist networks leading to ecosystem degradation and therefore facilitating the progress of invasion.