Invasive plants in Minnesota are “joining the locals”: A trait‐based analysis

Abstract

Questions:Predicting which newly arrived species will establish and become invasive is a problem that has long vexed researchers. In a study of cold temperate oak forest stands, we examined two contrasting hypotheses regarding plant functional traits to explain the success of certain non-native species. Under the "join the locals" hypothesis, successful invaders are expected to share traits with resident species because they employ successful growth strategies under light-limited understorey conditions. Instead, under the "try harder" hypothesis, successful invaders are expected to have traits different from native species in order to take advantage of unused niche space.Location: Minnesota, USA. Methods:We examined these two theories using 109 native and 11 non-native plants in 68 oak forest stands. We focused on traits related to plant establishment and growth, including specific leaf area (SLA), leaf carbon-to-nitrogen ratio (C:N), wood density, plant maximum height, mycorrhizal type, seed mass and growth form.We compared traits of native and non-native species using ordinations in multidimensional trait space and compared community-weighted mean (CWM) trait values across sites. Results:We found few differences between trait spaces occupied by native and nonnative species. Non-native species occupied smaller areas of trait space than natives, yet were within that of the native species, indicating similar growth strategies. We observed a higher proportion of non-native species in sites with higher native woody species CWM SLA and lower CWM C:N. Higher woody CWM SLA was observed in sites with higher soil pH, while lower CWM C:N was found in sites with higher light levels.Conclusions: Non-native plants in this system have functional traits similar to natives and are therefore "joining the locals." However, non-native plants may possess traits toward the acquisitive end of the native plant trait range, as evidenced by higher nonnative plant abundance in high-resource environments. K E Y W O R D SAlliaria petiolata, community-weighted mean, functional trait, invasive species, ordination, Rhamnus cathartica, specific leaf area, temperate forest, wood density | 747 Journal of Vegetation ScienceLODGE Et aL.

Alien species affect the abundance and richness of native species in tropical forests: The role of adaptive strategies

“…Within moist forests and wet‐rainforests, alien species mostly share strategies deployed by successful native species. As a result, both natives and aliens should have the same probability of establishing persistent populations that thrive under local environmental conditions (Dalle Fratte et al, 2019; Lodge et al, 2018; Tecco et al, 2010), with local‐scale to broad‐scale disturbances (which characterize the disturbance regimes of many Caribbean forests), decreasing the benefits to natives derived from priority effects (Fukami, 2015).…”

“…This agrees with previous studies suggesting that invasive aliens are successful because they generally have growth and survival strategies that allow them to perform better than native species (Lamarque et al, 2011; Maron & Marler, 2008; van Kleunen et al, 2010). The “try harder” hypothesis could also be viewed as a “try differently” hypothesis, indicating that successful alien species may have traits that are simply different from those of native species (Lodge et al, 2018). Caribbean dry forests are highly degraded and fragmented ecosystems, characterized by high levels of anthropogenic disturbance, marked seasonality, water stress, and nutrient limitation.…”

“…According to this theory, environmental filters, such as local climate, nutrient availability, or disturbance regimes, may limit the number of alien species that can successfully establish in a particular community. Under this theory, successful invaders should have similar traits to those of the local native species, especially the dominant ones (Leishman et al, 2007; Lodge et al, 2018; Tecco et al, 2010). Conversely, the “try harder” theory, which derives from the concept of limiting similarity (Crawley et al, 1996; Keddy & Weiher, 1999).…”

Trait divergence and opposite above- and below-ground strategies facilitate moso bamboo invasion into subtropical evergreen broadleaf forest

“…The community-weighted mean trait value (CWM) was used to measure the functional composition of the community ( Lodge et al., 2018 ; Sodhi et al., 2019 ). In this study, a community is referred to as a sampling plot.…”

“…Regarding trait values, two opposing hypotheses have been put forward to explain successful invasion for invasive species. The “phenotypic convergence hypothesis” suggests that successful invaders possess traits similar to coexisting natives due to habitat filtering ( Cornwell et al., 2006 ), facilitating invasive species preadaption to the local environment and thus invading native habitats more easily ( Fridley and Sax, 2014 ), which has been supported by substantial evidence ( Leishman et al., 2010 ; Lemoine et al., 2015 ; Lodge et al., 2018 ; Sodhi et al., 2019 ). Conversely, the “phenotypic divergence hypothesis”, based on limiting similarity, argues that successful invaders have distinct traits from coexisting natives, enabling them to occupy vacant niches ( Ordonez, 2014 ).…”