Biology subjects

Ardichvili, A. N.

Publications and source records attributed to Ardichvili, A. N..

5 recordsLinked to original sources

bioRxiv2026

Biodiversity effects on ecosystem functioning: disentangling the roles of biomass and effect trait expression

O_LISpecies diversity potentially has a dual effect on communities: a generally positive effect on overall community biomass, reflecting the expression of species response and interaction traits, and a poorly characterised effect on mass-specific species contribution to ecosystem functions, reflecting the expression of their effect traits. Disentangling the effects of biodiversity on total biomass from those on effect trait expression would help settle a long-standing debate by clarifying how biodiversity relates to both facets of species effects on ecosystem functioning. C_LIO_LIFollowing the classical BEF approach, we calculate expected ecosystem function based on observed functioning in monoculture. We then derive a net biodiversity effect (NBE) and decompose it into four components: the classical complementarity and selection effects on total community biomass, and complementarity and selection effects on effect trait expression. The latter two reflect, respectively, a complementarity or facilitation in how effect traits influence the function, and how species with the highest potential for increasing the function become dominant in the community. C_LIO_LIWe illustrate this NBE decomposition with three ecosystem functions (nitrogen retention capacity, soil hydraulic conductivity improvement, and forage digestibility) measured in assembled communities under controlled experimental conditions of perennial grassland plants. Regarding nitrogen retention, we find a positive complementary effect via total biomass, but a negative biodiversity effect via effect trait expression. For hydraulic conductivity improvement, biodiversity effects are mostly mediated by total biomass. As for forage digestibility, we found a positive complementarity effect on trait expression, outweighed however by a negative selection effect. This analysis reveals how biodiversity may have contrasting effects on ecosystem functions via its impact on biomass and effect trait expression. C_LI SynthesisSeparating between the effect of biodiversity on plant community biomass and on effect trait expression at the community level is one important step towards understanding the pathways by which diverse plant communities drive ecosystem functioning.

ecology↗

bioRxiv2025

Beyond biomass: how interactions shape species' importance for ecosystem functioning

Assessing the functional role of species in a changing world is critical for effectively preserving ecosystems. Intuitively, this role should relate to how the loss of a species ultimately impacts a function. We introduce the notion of a species dynamic contribution, which takes into account biotic interactions as they develop in the community. Contrary to the static contribution --a measure of what a species directly does-- the dynamic contribution captures what the presence of the species causes. Using both model simulations and empirical data from a ciliate microcosm experiment, we demonstrate that dynamic and static contributions of species are generically unrelated. Our novel characterization of species functional contributions reveals that, due to biotic interactions, rare species that do not possess unique functional traits are just as likely as any other species to play an important role for ecosystem functioning.

ecology↗

bioRxiv2024

Spatial context allows the evolution the control of nitrification by plants

Some plant species inhibit or stimulate soil nitrification, the transformation of ammonium into nitrate by microorganisms. The control of nitrification may in turn alter ecosystem productivity and functioning. Given the potential positive impacts of nitrification control on plant fitness, we aim to determine the conditions under which nitrification control is likely to have been selected, and the consequences of that selection on ecosystem functioning. We investigate both the role of the abiotic context (nutrient availability and diffusion) and the role of other plant traits (mortality and dispersal). A first mean-field model shows that when nitrogen pools are shared among individuals within the plant population, the control of nitrification is counter-selected. A tragedy of the commons occurs because the costs of controlling nitrification (ie. of producing root exudates) only affect the controlling individuals while benefits are shared among all individuals. We then assume that the effects of the control of nitrification are spatially restricted to the rhizosphere, and we build a spatially explicit, individual-based model in which mutation of control of nitrification is possible. Plant capacity to control nitrification evolves when the plant environment is sufficiently private and generation time sufficiently long, leading to higher fitness benefits of the construction process. In such cases, plants evolve to inhibit nitrification when losses of nitrate are greater than losses of ammonium and evolve to stimulate nitrification when losses of ammonium are greater than losses of nitrate. Finally, biomass production tends to be maximal at the selected strategy when the diffusion of ammonium and nitrate is low. Our results help predict which strategies should be selected and likely to be found in different plants in different parts of the world.

ecology↗

bioRxiv2024

Diffusion of constructed resources and specialism promotes facilitation in spatial systems

Sessile organisms contend with locally limiting nutrients and neighbours. Increases in nutrient concentration due to niche construction and diffusion of resources change the interaction sign between neighbours usually thought to compete for resources. We investigate conditions under which the positive effect of niche construction outweighs the negative effect of resource consumption. Following the design of facilitation experiments, we model two patches connected by resource flows, and ask whether the presence of a niche constructor in one patch eases the colonisation of the other. Niche constructors positively affect neighbouring organisms when their niches are sufficiently differentiated, and when the constructed resource diffuses more than the non-constructed resource. Our work proposes mechanisms for the emergence of facilitation, which is increasingly recognised as a key process structuring plant and microbial communities. We discuss the implications for the spatial structure of communities and their functioning, including in an agricultural context.

ecology↗

bioRxiv2022

Evolutionary emergence of alternative stable states in shallow lakes

AO_SCPLOWBSTRACTC_SCPLOWEcosystems under stress may respond abruptly and irreversibly through tipping points. Although much is explored on the mechanisms that affect tipping points and alternative stable states, little is known on how ecosystems with alternative stable states could have emerged in the first place. Here, we explore whether evolution by natural selection can lead to the emergence of ecosystems with tipping points using a toy model inspired by shallow lakes. Shallow lakes are the best-known example where a shift from a submersed macrophyte dominated state to a floating macrophyte dominated state in response to excess nutrient loading corresponds to a tipping point between alternative stable states. We model the evolution of the macrophytes living depth in the lake, we identify the conditions under which the ancestor macrophyte population diversifies, and investigate whether alternate stable states dominated by different macrophyte phenotypes occur. Given the trade-off between access to light and nutrient along the water column, we show that asymmetry in competition for light is required for diversification, while alternative stable states require an additional mechanism, an unequal efficiency in nutrient removal. We find that eco-evolutionary dynamics may produce alternative stable states, but only under a restrictive range of conditions. Our analysis suggests that competitive asymmetries along opposing resource gradients may allow alternative stable states to emerge by natural selection.

ecology↗