Évolution de la coopération au sein d'une population dans un environnement spatial

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Using mathematical modelling to investigate the adaptive divergence of whitefish in Fennoscandia

Modern speciation theory has greatly benefited from a variety of simple mathematical models focusing on the conditions and patterns of speciation and diversification in the presence of gene flow. Unfortunately the application of general theoretical concepts and tools to specific ecological systems remains a challenge. Here we apply modeling tools to better understand adaptive divergence of whitefish during the postglacial period in lakes of northern Fennoscandia. These lakes harbor up to three different morphs associated with the three major lake habitats: littoral, pelagic, and profundal. Using large-scale individual-based simulations, we aim to identify factors required for in situ emergence of the pelagic and profundal morphs in lakes initially colonized by the littoral morph. The importance of some of the factors we identify and study - sufficiently large levels of initial genetic variation, size- and habitat-specific mating, sufficiently large carrying capacity of the new niche - is already well recognized. In addition, our model also points to two other factors that have been largely disregarded in theoretical studies: fitness-dependent dispersal and strong predation in the ancestral niche coupled with the lack of it in the new niche(s). We use our theoretical results to speculate about the process of diversification of whitefish in Fennoscandia and to identify potentially profitable directions for future empirical research.Peer reviewe

Eco-evolution in size-structured ecosystems : simulation case study of rapid morphological changes in alewife

Background: Over the last 300 years, interactions between alewives and zooplankton communities in several lakes in the U.S. have caused the alewives' morphology to transition rapidly from anadromous to landlocked. Lakes with landlocked alewives contain smaller-bodied zooplankton than those without alewives. Landlocked adult alewives display smaller body sizes, narrower gapes, smaller inter-gill-raker spacings, reach maturity at an earlier age, and are less fecund than anadromous alewives. Additionally, landlocked alewives consume pelagic prey exclusively throughout their lives whereas anadromous alewives make an ontogenetic transition from pelagic to littoral prey. These rapid, well-documented changes in the alewives' morphology provide important insights into the morphological evolution of fish. Predicting the morphological evolution of fish is crucial for fisheries and ecosystem management, but the involvement of multiple trophic interactions make predictions difficult. To obtain an improved understanding of rapid morphological change in fish, we developed an individual-based model that simulated rapid changes in the body size and gill-raker count of a fish species in a hypothetical, size-structured prey community. Model parameter values were based mainly on data from empirical studies on alewives. We adopted a functional trait approach; consequently, the model explicitly describes the relationships between prey body size, alewife body size, and alewife gill-raker count. We sought to answer two questions: ( 1) How does the impact of alewife populations on prey feed back to impact alewife size and gill raker number under several alternative scenarios? ( 2) Will the trajectory of the landlocked alewives' morphological evolution change after 150-300 years in freshwater?  Results: Over the first 250 years, the alewives' numbers of gill-rakers only increased when reductions in their body size substantially improved their ability to forage for small prey. Additionally, alewives' gill- raker counts increased more rapidly as the adverse effects of narrow gill- raker spacings on foraging for large prey weremade less severe. For the first150- 250 years, alewives' growth decreased monotonically, and their gill- raker number increased monotonically. After the first 150-250 years, however, the alewives exhibited multiple evolutionary morphological trajectories in different trophic settings. In several of these settings, their evolutionary trajectories even reversed after the first 150-250 years.  Conclusions: Alewives affected the abundance and morphology of their prey, which in turn changed the abundance and morphology of the alewives. Complex low-trophic-level interactions can alter the abundance and characteristics of alewives. This study suggests that the current morphology of recently (similar to 300 years)-landlocked alewives may not represent an evolutionarily stable state

Online data browser

This package contains supplementary material for the paper "How mechanisms of habitat preference evolve and promote divergence with gene flow" in Journal of Evolutionary Biology. An interactive version of this material can also be found at http://xavier.thibert-plante.com/habitatPref . Download this package habPrefSupp.tar.bz2 into a directory of your choice. We will call this directory . Unload the package using for example: tar -xjf habPrefSupp.tar.bz2 (UNIX) http://www.7-zip.org/download.html (MS Windows) Using your favorite web browser "open file": /DIR.bernerThibert-Plante/index.html and you can start browsing the supplementary material