Competitive ability of native and alien plants: effects of residence time and invasion status

Abstract

Competition is commonly thought to underlie the impact of plant invasions. However, competitive effects of aliens and competitive response of natives may also change over time. Indeed, as with time, the novelty of an invader decreases, the accumulated eco-evolutionary experience of resident species may eventually limit invasion success. We aimed to gain insights on whether directional changes in biotic interactions over time or more general differences between natives and aliens, for instance, resulting from an introduction bias, are relevant in determining competitive ability. We conducted a pairwise competition experiment in a target-neighbour design, using 47 Asteraceae species with residence times between 8 years-12,000 years in Germany. We first tested whether there are differences in performance in intraspecific competition amongst invasion status groups, that is casual and established neophytes, archaeophytes or native species. We then evaluated whether competitive response and effects depend on residence time or invasion status. Lastly, we assessed whether competitive effects influence range sizes. We found only limited evidence that native target species tolerate neighbours with longer potential co-existence times better, whereas differences in competitive ability were mostly better explained by invasion status than residence time. Although casual neophytes produced most biomass in intraspecific competition, they had the weakest per-capita competitive effects on natives. Notably, we did not find differences between established neophytes and natives, both of which ranked highest in interspecific competitive ability. This lack of differences might be explained by a biased selection of highly invasive or rare native species in previous studies or because invasion success may result from mechanisms other than interspecific competitive superiority. Accordingly, interspecific per-capita competitive effects did not influence range sizes. Further studies across a broader range of environmental conditions, involving other biotic interactions that indirectly influence plant-plant interactions, may clarify when eco-evolutionary adaptations to new invaders are a relevant mechanism.

Alien plant fitness is limited by functional trade‐offs rather than a long‐term increase in competitive effects of native communities

“…They found that competitive effects increased with residence time and suggested that this arises from a build‐up of biotic resistance by the native community. Furthermore, in a pairwise competition experiment, Sheppard and Brendel (2021) found that native Asteraceae tended to perform better with Asteraceae neighbors of increasing residence time (consistent with an increase in biotic resistance at the level of individual species), but only under certain soil conditions. However, our finding that naïve communities have similar competitive effects as experienced ones contradicts these findings.…”

“…This experimental study is based on a species‐for‐time approach, for which we chose 40 annual Asteraceae species, including recently introduced neophytes, archaeophytes, and natives that arrived in Germany after the last glacial maximum (10,000–12,000 years before present; see Brendel et al, 2021; Sheppard & Brendel, 2021; Sheppard & Schurr, 2019). Neophytes represent those alien species that were introduced after the discovery of America in 1492 AD (usually rounded to 1500 AD) and archaeophytes were introduced before that date (Pyšek et al, 2004).…”

Alien species revises systematic status: integrative species delimitation of two similar taxa of Symbrenthia Hübner, [1819] (Lepidoptera, Nymphalidae)

“…Competition may occur between native taxa and the invading one, notably when the counter taxa are closely related, where they are expected to share resource requirements ( Zwerschke et al, 2018 ). This kind of scenarios have been well-documented in various organisms, such as ants ( von Aesch & Cherix, 2005 ), birds ( Koenig, 2003 ), molluscs ( Zwerschke et al, 2018 ), plants ( Leger & Espeland, 2010 ; Čuda et al., 2015 ; Sheppard & Brendel, 2021 ), etc ., and even inspired E. O. Wilson to coin in his “taxon cycles” hypothesis ( Wilson, 1961 ). Alternatively, if the involved taxa were previously allopatric populations or subspecies, gene flow may occur between taxa, resulting in changes in the genetic make-up of the local population ( Rhymer & Simberloff, 1996 ).…”

Are species more harmful in their native, neonative or alien range? Insights from a global analysis of bark beetles

“…For instance, neonative populations of Dendroctonus frontalis , whose presence was recorded for the first time in New York and Connecticut in 2014 and 2015, respectively (Dodds et al, 2018, Table 1), are much less harmful than those of Dendroctonus ponderosae (Table 2), a species that was recorded outside of its native range since 1970 (Carroll et al, 2006; Cudmore et al, 2010). Residence time has been frequently used to predict range size (Allen et al, 2013; Desprez‐Loustau et al, 2010; Pyšek et al, 2015), abundance (Hamilton et al, 2005), population growth (Brendel et al, 2021) and even competitive ability (Sheppard & Brendel, 2021) of alien taxa, whereas a possible link between the time since introduction and impact dynamics has received far less attention. The use of residence time as a predictor of environmental impacts seems ripe for further investigations in both bark beetles and other taxonomic groups that have been established as alien or neonative.…”