Individual-based model of Chironomus riparius population dynamics over several generations to explore adaptation following exposure to uranium-spiked sediments

Abstract

Natural populations are chronically exposed to various pollutants over many generations. It is thus crucial to understand and quantify adaptive dynamics of stressed populations in order to increase the relevance of ecotoxicological risk assessment. However, long-term consequences to population exposure are not much studied yet. The present study investigated evolutionary responses of Chironomus riparius populations exposed to uranium (heavy metal pollutant) and to assess the underlying mechanisms. To fulfil our objective, we produced data with organisms exposed to four relevant concentrations of uranium through eight successive generations. We built an individual-based (IBM) model of C. riparius population dynamics to analyse these data and to test several assumptions about the mechanisms involved in the phenotypic changes. The IBM was based on a dynamic energy budget (DEB) model for C. riparius by Pery et al. (2002). DEB models account mathematically for the acquisition and use of energy to describe and predict growth, maintenance, development and reproduction of living organisms. The IBM accounted for the influence of the test conditions on the observations over eight generations and highlighted some trait evolution such as time to emergence and adult size in control conditions. The model was then used to analyse the exposed population data. Our results showed that exposure to uranium led to a phenotypic selection via a differential survival characterised by longer time to emergence and smaller larval maximal size. As a general conclusion, IBMs based on DEB-based modelling developed to analyse multi-generation experiments are very promising for understanding and quantifying long term selection and tolerance mechanisms in a population under toxic stress.

Consequences of a multi-generation exposure to uranium on Caenorhabditis elegans life parameters and sensitivity

“…Moreover, they showed a similar trend in growth reduction for exposed organisms and for unexposed organisms originated from adult males and females exposed to uranium during their immature life stages. Beaudouin et al (2012) showed effects of uranium on both growth and reproduction of Chironomus riparius and also showed that exposure to uranium during eight generations led to a phenotypic selection via a differential survival characterized by longer time to emergence and smaller larval maximal size. They estimated a longterm No Effect Concentration (NEC) of 28.3 µg g −1 dry weight of sediment.…”

A bioenergetics model of the entire life cycle of the three‐spined stickleback,gasterosteus aculeatus

“…For this, the DEB model of G. aculeatus will be combined with an individual‐based model. DEB‐IBM models have already used to others species and have demonstrated their abilities to extrapolate from ecotoxicological data measured on organisms in laboratory conditions to biological endpoints convenient (Beaudouin et al., , ; Martin et al., ). Moreover, data on population obtained in our mesocosm (De Kermoysan et al., ) could be used to improve the DEB model by giving information on the energy budget in male after maturity and during the reproduction season.…”

“…Mathematical models are increasingly used in ecological risk assessment, due to the rise in demand for ecological realism in regulatory risk assessment (Forbes et al., ). Models are conveniently used to upscale from individual level to population level (Beaudouin, Dias, Bonzom, & Péry, ; Beaudouin et al., ; Goussen et al., ; Martin et al., ). However, their development requires a large amount of data on the life cycle of the organisms (Beaudouin et al., ; Goussen et al., ; Péry, Ducrot, Mons, & Garric, ).…”

“…energy resources, temperature) offer a realistic description of the life cycle of individuals (growth, reproduction, survival, etc.). They can also contribute to reduce the data necessary to develop a model of population dynamics when they explicitly link feeding, growth and reproduction (Beaudouin et al., ). Accounting for energy in population models also allows to assess how energy is shared between different species competing for the same resource, for instance stickleback and economically valuable species (Hovel et al., ).…”

Energy-based modelling to assess effects of chemicals on Caenorhabditis elegans: A case study on uranium

“…DEB modelling can also be adapted to other types of analysis. Thereby, individual based model (IBM) based on DEB modelling can permit to analyse population level data, especially multi-generation studies (Beaudouin et al, 2012;Martin et al, 2013).…”