Ecological application of biotic resistance to control the invasion of an invasive plant, Ageratina altissima

Abstract

Biotic resistance is the ability of species in a community to limit the invasion of other species. However, biotic resistance is not widely used to control invasive plants. Experimental, functional, and modeling approaches were combined to investigate the processes of invasion by Ageratina altissima (white snakeroot), a model invasive species in South Korea. We hypothesized that (1) functional group identity would be a good predictor of biotic resistance to A. altissima, whereas a species identity effect would be redundant within a functional group, and (2) mixtures of species would be more resistant to invasion than monocultures. We classified 37 species of native plants into three functional groups based on seven functional traits. The classification of functional groups was based primarily on differences in life longevity and woodiness. A competition experiment was conducted based on an additive competition design with A. altissima and monocultures or mixtures of resident plants. As an indicator of biotic resistance, we calculated a relative competition index (RCI avg) based on the average performance of A. altissima in a competition treatment compared with that of the control where only seeds of A. altissima were sown. To further explain the effect of diversity, we tested several diversity–interaction models. In monoculture treatments, RCI avg of resident plants was significantly different among functional groups but not within each functional group. Fast‐growing annuals (FG1) had the highest RCI avg, suggesting priority effects (niche pre‐emption). RCI avg of resident plants was significantly greater in a mixture than in a monoculture. According to the diversity–interaction models, species interaction patterns in mixtures were best described by interactions between functional groups, which implied niche partitioning. Functional group identity and diversity of resident plant communities were good indicators of biotic resistance to invasion by introduced A. altissima, with the underlying mechanisms likely niche pre‐emption and niche partitioning. This method has most potential in assisted restoration contexts, where there is a desire to reintroduce natives or boost their population size due to some previous level of degradation.

Using limiting similarity to enhance invasion resistance: Theoretical and practical concerns

“…woodiness, height, presence of taproot; Byun & Lee, ; von Holle, ) and/or in physiology (e.g. specific leaf area, relative growth rate, leaf dry‐matter content; Byun & Lee, ). The findings from most studies do not support limiting similarity as an efficient, robust way to limit early establishment of invasive species.…”

“…Competitive hierarchies have been shown to occur within functional groups (Turnbull, Coomes, Hector, & Rees, ; Turnbull et al, ; Wedin & Tilman, ), contrary to the within‐group equivalence predicted by limiting similarity (Hubbell, ). Accordingly, specific trait values—not necessarily similar to those of the target invader—such as high specific root length (Daneshgar & Jose, ; Funk & Wolf, ), large size or height (Byun & Lee, ), high growth rate (Symstad, ), or early access to limiting resources (Longo et al, ) have been linked to increased invasion resistance (Drenovsky & James, ). Moreover, competition can be intense between functionally distant species (e.g.…”

“…Different groups based on similarities in growth form or other morphological or phenological trait similarities have been defined, assuming that species from the same group should have greater niche overlap and compete more intensively than species from different groups (Johansson & Keddy, 1991;MacArthur & Levins, 1967). However, most studies found no or very limited support for limiting similarity in invasion resistance (Abella, Craig, Smith, & Newton, 2012;Byun & Lee, 2017;Cleland, Larios, & Suding, 2013;Daneshgar & Jose, 2009;Emery, 2007;Eriksson, Wikström, Eriksson, & Lindborg, 2006;Fargione, Brown, & Tilman, 2003;Funk & Wolf, 2016;Larson et al, 2013;Longo, Seidler, Garibaldi, Tognetti, & Chaneton, 2013;Öster & Eriksson, 2012;Prieur-Richard, Lavorel, Grigulis, & Dos Santos, 2000;Turnbull et al, 2005;von Holle, 2005;Yannelli, Karrer, Hall, Kollmann, & Heger, 2018). While such failures do not necessarily invalidate the limiting similarity theory, they are probably due to an inability to reach the domain of validity of this theory.…”

“…annuals, perennials, early or late seasonal plants; Abella et al, 2012;Cleland et al, 2013;Larson et al, 2013), in morphology (e.g. woodiness, height, presence of taproot; Byun & Lee, 2017;von Holle, 2005) and/or in physiology (e.g. specific leaf area, relative growth rate, leaf dry-matter content; Byun & Lee, 2017).…”

“…Invasive species are a key driver of biodiversity loss world‐wide (MacGeoch et al, ). Controlling them (as a conservation objective) is a central topic of both applied (Byun & Lee, ; Clements, Larsen, & Grenz, ; Clewley, Eschen, Shaw, & Wright, ; Connolly et al, ) and theoretical research (Catford, Jansson, & Nilsson, ; Davis, Grime, & Thompson, ; Hallett, ; Shea & Chesson, ; Tilman, ). Many studies suggest that more resources are invested in post‐invasion control and impact reduction than in prevention or early intervention (Simberloff et al, ).…”