Recherche

Hodapp, Dorothee; Borer, Elizabeth T.; Harpole, W. Stanley; Lind, Eric M.; Seabloom, Eric W.; Adler, Peter B.; Alberti, Juan; Arnillas, Carlos A.; Bakker, Jonathan D.; Biederman, Lori; Cadotte, Marc; Cleland, Elsa E.; Collins, Scott; Fay, Philip A.; Firn, Jennifer; Hagenah, Nicole; Hautier, Yann; Iribarne, Oscar; Knops, Johannes M.H.; McCulley, Rebecca L.; MacDougall, Andrew; Moore, Joslin L.; Morgan, John W.; Mortensen, Brent; La Pierre, Kimberly J.; Risch, Anita C.; Schuetz, Martin; Peri, Pablo; Stevens, Carly J.; Wright, Justin; Hillebrand, Helmut; Knops, Johannes M. H. — 2019-05-24 Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta-diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change – fertilization and herbivore loss – are affected by species pool size and spatial compositional heterogeneity. Fertilization led to higher rates of local extinction whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.

Livingstone, Stuart; Smith, Sandy; Bourchier, Robert; Ryan, Kathleen; Roberto, Adriano; Cadotte, Marc — 2020-08-06 <p>1. Pre-release testing for biological control agents is focused primarily on assessment of host-range specificity and safety of potential agents. Agent impact is considered pre-release, however the ultimate assessment of an agent must occur following release in the field under the target population levels and conditions of the invaded ecosystems. The invasive Eurasian vine, Vincetoxicum rossicum, has spread aggressively through its invaded range of eastern North America since its initial introduction in the late 1800’s. In laboratory tests, the Eurasian moth Hypena opulenta has shown great promise as a potential control agent for V. rossicum.</p> <p>2. We were interested in the defoliating ability of H. opulenta and its subsequent effect on the seed production of V. rossicum under field conditions. To examine this, we established a field site near Kirkfield, Ontario that consisted of meadow and forest understory plots, both of which were highly invaded by V. rossicum.</p> <p>3. We report highly significant feeding by H. opulenta in both light conditions. Unexpectedly, we observed a significant increase in seed production following folivory in shade conditions. We observed no significant effect of larval folivory on seed production under sun conditions, where V. rossicum seed production is greater by a factor of ten as compared to shade conditions.</p> <p>4. Synthesis and application: It is unclear how continuous exposure to folivory by H. opulenta will affect mature V. rossicum stands, although it might be expected that such populations would invest in defenses to herbivory, possibly at the expense of reproductive output. In order to better understand if V. rossicum populations in either light condition could exhibit longer-term compensatory growth in response to folivory, further experimental work is needed that examines inter-annual variability in V. rossicum reproduction at variable H. opulenta densities.</p> https://creativecommons.org/publicdomain/zero/1.0/

Potgieter, Luke; Shrestha, Namrata; Cadotte, Marc — 2022-01-03 <p>1. Invasive alien plant species (IAPs) in urban areas can have detrimental effects on biodiversity, ecosystem services and human well-being. Urban areas are complex social management mosaics with high land-use diversity, complex land tenure patterns, and many different stakeholder groups, some of which derive benefits from invading species. Urban conservation practitioners face complex decisions about which IAPs require management. Yet most IAPs prioritization frameworks have been designed for and implemented in natural or rural areas and are generally inadequate for guiding effective and sustainable interventions in urbanized areas.</p> <p>2. We modified an existing prioritization scheme to develop a framework for prioritizing terrestrial IAPs in urban areas which applies evidence-based (data-driven) and stakeholder-based (local knowledge) assessments to score and rank alien plant species in terms of their priority for management using an objective set of criteria.</p> <p>3. The framework consists of forty-six criteria, grouped into eight modules which assess invasion status, habitat requirements, biological characteristics, dispersal ability, distribution, impact (positive and negative), and potential for control for each alien plant species under consideration.</p> <p>4. We use the city of Toronto, Canada as a case study to test our framework – a list of 50 IAPs were effectively scored and ranked in order of high to low priority for control. Species with the highest <i>total prioritization scores</i> were <i>Vincetoxicum</i> <i>rossicum</i> (Dog Strangling Vine), <i>Convolvulus</i> <i>arvensis</i> (Field Bindweed) and <i>Taraxacum</i> <i>officinale</i> (Common Dandelion) (ranked 1, 2 and 3, respectively).</p> <p>5. Many of the identified high priority species align with the those previously flagged as of management concern by conservation practitioners, but also include those that are not actively managed due to their perceived lower ecological impacts. These species still require high resource investment for other objectives such as aesthetics. This highlights the complexity of alien plant species management in urban areas.</p> <p>6.<i> Synthesis and applications. </i>Prioritizing invasive alien plants for management in urban areas is particularly challenging due to often conflicting ecological, economic, and social objectives. We use available evidence and local stakeholder knowledge to develop an objective and systematic prioritization tool which can assist conservation practitioners in selecting priority species for management action in complex urban landscapes.</p>

Cadotte, Marc — 2022-11-05 <p>Plant species invasion represents one of the major drivers of biodiversity change globally, yet there is confusion about the nature of non-indigenous species (NIS) impact. This stems from differing notions of what constitutes invasive species impact and the scales at which it should be assessed. At local scales, the mechanisms of impact on local competitors can be classified into four scenarios: 1) minimal impact from NIS inhabiting unique niches; 2) neutral impact spread across the community and proportional to NIS abundance; 3) targeted impact on a small number of competitors with overlapping niches; and 4) pervasive impact that is disproportionate to NIS abundance and caused by modifications that filter out other species. I developed a statistical test to distinguish these four mechanism scenarios based on plant community rank-abundance curves and then created a scale-independent standardized impact score. Using an example long-term dataset, that has high native plant diversity and an abundance gradient of the invasive vine, <em>Vincetoxicum rossicum</em>, I show that impact resulted in either targeted or pervasive extirpations. Regardless of whether NIS impact is neutral, targeted, or pervasive, the net outcome will be the homogenization of ecosystems and reduced biodiversity at larger scales, perhaps reducing ecosystem resilience. The framework and statistical evaluation of impact presented in this paper provide researchers and managers with an objective approach to quantifying NIS impact and prioritizing species for further management actions.</p>