The growing establishment of invasive species contributes heavily to the loss in global biodiversity. Elaeagnus umbellata, or Autumn Olive, has established in the E.S. George Reserve in Livingston County, Michigan; however, it is currently unknown by what mechanism it persists in the novel environment. We tested two alternate hypotheses using data collected on leaf traits of the existing woody plant community occurring at the site: 1) a suite of traits has been pre-adapted which allow the species to exploit unused niche space in the community, or 2) the species exhibits varying traits which allow it to persist in a wide variety of conditions, making it a generalist able to utilize most available habitat, but not to outcompete native species per se. Specific leaf area (SLA), leaf area, leaf dry matter content (LDMC), and morphometric data we used to test these hypotheses. Size class, diameter at breast height, and the light environment of individuals were gathered from all common native tree and shrub species.
Results/Conclusions
On average E. umbellata has a specific leaf area of 316.50 cm2/g and a leaf dry matter content of 0.2627. These traits are consistent with shade-intolerant strategy; nonetheless, the species persists in the understory of the forest. With regard to other shrubs and saplings of understory trees (the sapling class), E. umbellata shows high overlap of SLA distribution with other shrub and understory species, comparable to that among native species in the same functional groups. Mean overlap of all species in the shrub/understory class is 0.492. However, its species mean is among the highest observed at the site. Thus, E. umbellata is not overlapped at the high end of the SLA distribution, perhaps allowing it to exploit unfilled niche space; nonetheless, this is the “high light” end of the spectrum, suggesting limitations to the ability of an understory species to exploit the niche space. However, many of its other characteristics suggest E. umbellata is capable of persisting from a release in native controls and an ability to exclude native plants from its colonized area. Coordinating functional traits of invasive species and the mechanism by which the species has established will allow increased understanding of the coexistence mechanisms of this invasive species within this temperate forest.
