Abstract
Invasive plant species are hypothesized as being more efficient at resource acquisition and use, resulting in faster growth than co-occurring non-invasive plant species. Nonetheless, some findings suggest that trait differences between invasive and non-invasive species are context dependent. In this study, two forms of an invasive vine species,Dolichandraunguis-cati, were used to test the context-dependent hypothesis.Dolichandraunguis-catiis a weed of national significance in Australia with two different forms: the ‘long pod’ (LP) and ‘short pod’ (SP). The two forms have different levels of distribution on the eastern Seaboard of the continent, with the SP form occurring extensively in both States of Queensland and New South Wales while the LP form is found only in isolated sites in South-East Queensland. This study examines whether differences in eco-physiological performance could be responsible for differential success of the two forms. A partially factorial experiment was set up in controlled conditions where potted plants of both forms were grown under two levels of light, water and nutrient resources (high and low) for 15 months. We measured several traits that are known to correlate with plant performance and resource use efficiency (RUE). The SP form exhibited higher values of carbon assimilation, RUE, number of subterranean tubers and leaf nitrogen than the LP form. However, the LP form produced greater biomass than the SP form, with the difference driven mainly by high resource conditions. The LP form displayed significantly higher phenotypic integration (number of traits significantly correlated) than the SP form in response to all treatments while the SP form exhibited higher phenotypic integration than the LP form in response to high resource conditions only. The SP form displayed traits that are well suited for successful colonization, possibly explaining its increased success in Australia, while the LP form possessed traits of opportunistic plants. Overall, we find that the two forms of the weedy vine deploy different carbon economies in response to resource conditions, which is evidence of the context-dependent trait hypothesis.
Highlights
A key component of invasion ecology is to understand traits that enable introduced species to colonize and thrive in novel environments (Richardson and Pyšek 2006; Reichmann et al 2016)
Amount of nutrient and water supplied to the plants all had significant effects on all biomass allocation traits of the two forms (F1, 7 = 12.195, Phigher A with abundant water and nitrogen (HWHN)>HLLN>LWHN>LLHN>L LLN=LWLN (Table 2)
As the two forms clearly separated along the 2nd axis in the ordination space of a principal components analysis (PCA), our study shows that the two forms have varying patterns of resource acquisition, biomass allocation and carbon assimilation in response to treatments
Summary
A key component of invasion ecology is to understand traits that enable introduced species to colonize and thrive in novel environments (Richardson and Pyšek 2006; Reichmann et al 2016). Several pairwise studies found that invasive and non-invasive species had comparable traits under similar environmental conditions (Meiners 2007; Palacio‐López and Gianoli 2011; Jo et al 2016). While there may be differences between some invasive and congeneric non-invasive species, this pattern is not universal (Leishman et al 2010; Parker et al 2013). These conflicting outcomes of trait-based pairwise studies may indicate contextdependence of trait differences (Leishman et al 2010; Leffler et al 2014; Li et al 2016). Comparisons of multiple forms/varieties of an introduced species that both occupy similar niches but exhibiting different levels of invasion success could yield informative insights into invasion success (Kolar and Lodge 2001)
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