Jorge Luis P. Oliveira-Costa¹, Rui F. Figueiredo² and Vânia R. Pivello³
¹Doctoral researcher/Department of Geography of the University of Coimbra, Portugal
²Department of Geography/Faculty of Letters of the University of Coimbra, Portugal
³Department of Ecology/Institute of Biosciences of the University of São Paulo, Brazil
An unresolved problem in the invasibility study of the Australian Acacia longifolia species is that many of its invaded ranges are characterized by coastal environment systems occuring in the boundaries between continents with a long history of human presence which are classified as ‘temperate zones’ when they are functionally a mix of specific climate conditions (oceanic, humid, subtropical, mediterranean, and other different types). More problematically, this climate zone is widely regarded as the ecological niche of Acacia longifolia‘s invasive species distribution, because (i) the two Acacia longifolia species (A. longifolia subsp. longifolia and A. longifolia subsp. sophorae) occur predominantly in areas of coastal dunes with poor soils and ecosystems historically modified, and (ii) the temperate Australian regions where many of these species occur can also climatically support both native and non-native distributions of A. longifolia.
Here, we examine multiple lines of evidence to disentangle this issue on how ecological similarity is determined between different invaded ranges in order to explain the susceptibility to invasion by Acacia longifolia. First, to understand the invasibility of A. longifolia‘s, what is the best climate resolution of analysis? Evidence in several studies established that the invasive A. longifolia taxa, most likely A. longifolia subsp. longifolia, is distributed in the Mediterranean and Humid Subtropical climates. Species occurrences further suggest that A. longifolia’s prevalence increases from the coastlines to the inlands, expressing a non-human influence in the establishment and spread of A. longifolia in this scale of analysis. Second, what current/potential distribution in native range should we consider? Distribution patterns analysis established that, in Australia, ‘Acacia longifolia’ fall within well-established bioclimatic envelopes but little is known about A. longifolia patterns of distribution ranges onother continents. Third, at the taxonomic scale, how much do we gain considering the subspecies level? Taxonomic differences of Acacia longifolia species from multiple invaded sites across the world are clearly distinguishable. Specifically, ‘A. longifolia subsp. longifolia’ is distributed in a higher covered area, with wide eco-geographical conditions, and have significantly more available plant trait information than ‘A. longifolia subsp. sophorae’. Critically, the habitat susceptibility to invasion by Acacia longifolia species seems to occur much more frequently for A. longifolia subsp. longifolia. All these evidence are consistent with expected invasibility differences between invaded ranges by A. longifolia. Fourth, to tackle susceptibility without losing detail: Are these evidences able to tackle the habitat susceptibility by A. longifolia invasions at global scales?
All these reflections will be used to produce a detailed conceptual model to contextualize the susceptibility of invasion by Acacia longifolia in subtropical climatic regions and help to distinguish the different patterns that we encounter.