Ecological Specialization of Mixotrophic Plankton in a Mixed Water Column

Abstract

In recent years, the population dynamics of plankton in light- or nutrient-limited environments have been studied extensively. Their evolutionary dynamics, however, have received much less attention. Here, we used a modeling approach to study the evolutionary behavior of a population of plankton living in a mixed water column. Initially, the organisms are mixotrophic and thus have both autotrophic and heterotrophic abilities. Through evolution of their trophic preferences, however, they can specialize into separate autotrophs and heterotrophs. It was found that the light intensity gradient enables evolutionary branching and thus may result in the ecological specialization of the mixotrophs. By affecting the gradient, other environmental properties also acquire influence on this evolutionary process. Intermediate mixing intensities, large mixing depths, and high nutrient densities were found to facilitate evolutionary branching and thus specialization. Later results may explain why mixotrophs are often more dominant in oligotrophic systems while specialist strategies are associated with eutrophic systems.

Spatial overlap in lake phytoplankton: Relations with environmental factors and consequences for diversity

“…Empirical observations also support a prediction of phytoplankton species co-existence within very thin layers (Gervais 1998;Olli and Seppälä 2001;Clegg et al 2007). Presumably trade-offs in the use of resources (functional traits) are at work, enabling co-existence (Troost et al 2005;Schwaderer et al 2011).…”

“…Indeed, where spatial overlap is forced through physical properties of lakes, trait differences between species (high functional diversity) may permit them to reduce interaction strengths, promoting co-existence (Troost et al 2005). Recent work has indicated the presence of such trade-offs for spatially co-existing phytoplankton.…”

Determining Selection across Heterogeneous Landscapes: A Perturbation-Based Method and Its Application to Modeling Evolution in Space

“…Adaptive dynamics, in turn, is concerned with mutation-driven evolution and is typically used to determine population-level selection gradients and such phenomena as evolutionary branching. These questions have received very little attention in the setting of spatial adaptive dynamics (but see, e.g., Mizera and Meszéna 2003;Troost et al 2005). In particular, general mathematical expressions describing directional as well as stabilizing or disruptive selection have not yet been developed for reaction-diffusion models in continuous space.…”

Oligomorphic dynamics for analyzing the quantitative genetics of adaptive speciation

“…The latter is expected under frequency-dependent disruptive selection. Such selection can arise from a great variety of ecological processes, including symmetric intraspecific competition (Metz et al 1996;Sasaki 1997;Doebeli 1996aDoebeli , 1996bDieckmann and Doebeli 1999), asymmetric intraspecific competition (Kisdi 1999;Doebeli and Dieckmann 2000;, interspecific competition (Law et al 1997;, resource specialization (Meszéna et al 1997;Geritz et al 1998;Day 2000;Kisdi 2001;Schreiber and Tobiason 2003;Egas et al 2004Egas et al , 2005, temporally fluctuating selection with storage effect (Ellner and Hairston 1994;Sasaki andEllner 1995, 1997;Ellner and Sasaki 1996), ontogenetic niche shifts (Claessen and Dieckmann 2002), mixotrophy (Troost et al 2005), phenotypic plasticity (Sasaki and Ellner 1995;Sasaki and de Jong 1999;Van Dooren and Leimar 2003;Ernande and Dieckmann 2004;Leimar 2005), dispersal evolution (Levin et al 1984;Cohen and Levin 1991;Ludwig and Levin 1991;Doebeli and Ruxton 1997;Johst et al 1999;Parvinen 1999;Mathias et al 2001;Parvinen and Egas 2004), mutation evolution (Haraguchi and Sasaki 1996), mutualism (Doebeli and Dieckmann 2000;…”