Intraspecific phenotypic variation in life history traits of Daphnia galeata populations in response to fish kairomones

Abstract

Phenotypic plasticity is the ability of a genotype to produce different phenotypes depending on the environment. It has an influence on the adaptive potential to environmental change and the capability to adapt locally. Adaptation to environmental change happens at the population level, thereby contributing to genotypic and phenotypic variation within a species. Predation is an important ecological factor structuring communities and maintaining species diversity. Prey developed different strategies to reduce their vulnerability to predators by changing their behavior, their morphology or their life history. Predator-induced life history responses in Daphnia have been investigated for decades, but intra population variability was rarely addressed explicitly. We addressed this issue by conducting a common garden experiment with four EuropeanDaphnia galeata populations, each represented by six genotypes. We recorded life history traits in the absence and presence of fish kairomones. Additionally, we looked at the shape of experimental individuals by conducting a geometric morphometric analysis, thus assessing predator-induced morphometric changes. Our data revealed high intraspecific phenotypic variation within and between all four D. galeata populations, the potential to locally adapt to a vertebrate predator regime as well as an effect of the fish kairomones on morphology of D. galeata. 10 Phenotypic plasticity is the ability of a genotype to produce different phenotypes depending on 11 the environment. It has an influence on the adaptive potential to environmental change and 12 the capability to adapt locally. Adaptation to environmental change happens at the population 13 level, thereby contributing to genotypic and phenotypic variation within a species. Predation is 14 an important ecological factor structuring communities and maintaining species diversity. Prey 81 conclusions based on single genotypes. The relative importance of the intra and inter-82 population variation was thus rarely measured. In our experimental design we specifically 83 considered the population level by using six genotypes per population. All of our genotypes 84 stem from lakes with different fish predation pressures, and we therefore expect the 85 populations to be locally adapted, which translates into a population specific response. The 86 ability of Daphnia to locally adapt to different stressors has been demonstrated e.g. for 87 vertebrate predators (Boersma et al. 1998;Cousyn et al. 2001;Declerck and Weber 2003) and 88 pesticides . 90In the present study, we assess the intraspecific phenotypic variation among four (Table S1)

Intrapopulation variability in a functional trait: Susceptibility ofDaphniato limitation by dietary fatty acids

“…The outcome of intraspecific competition in natural Daphnia assemblages can depend on several other traits, such as susceptibility to parasites, predation or toxic cyanobacteria, for which intraspecific variability has been reported previously (e.g. Chislock et al., 2013; Duffy & Sivars‐Becker, 2007; Tams et al, 2018). Nevertheless, seasonal changes in Daphnia assemblage composition (in terms of genotype frequencies) are frequently associated with seasonal changes in phytoplankton food quality (e.g.…”

“…Similarly, in the presence/absence of fish kairomones, D. hyalina × galeata hybrid clones displayed differences in numerous life‐history traits, such as size or age at maturity and habitat use (De Meester & Weider, 1999). Tams et al (2018) detected substantial intraspecific variability in life history traits in four populations of D. galeata when subjected to predation risk. Several studies reported clonal variation of Daphnia in their sensitivity to the toxic cyanobacterium Microcystis sp.…”

Insights into the genetic basis of predator‐induced response in Daphnia galeata

“…This lake is inhabited permanently by a diverse fish population (Fischereiamt Berlin, 2013). A previous study involving 24 genotypes (clonal lines) from four different lakes revealed that the variation for some life‐history traits increased for genotypes exposed to fish kairomones within the Müggelsee population (Tams et al., 2018), meaning a broader range of phenotypes were displayed for that life‐history trait. We chose the genotypes M6 and M9 which differed in all of their life‐history traits and were at the contrasting ends of the phenotypic range exhibited by D .…”

“…Reaction norms of selected life‐history traits of experimental genotypes (mea n ± SE) from a previous experiment (Tams et al. 2018) emphasizing the opposing environmental effect on life‐history traits for the two genotypes. (a) Age at first reproduction in days.…”

“…Our goal is to investigate the genetic basis of life‐history shifts in response to vertebrate predation risk. Daphnia galeata is the ideal candidate species to address this question, since this species does not show diel vertical migration behavior (Stich & Lampert, 1981) or severe morphological changes in the presence of vertebrate predator cues even after long exposure, but strong phenotypic variation of life‐history traits under vertebrate predation risk (Tams et al., 2018). With a combined approach, we aim to understand the complexity of responses to environmental changes such as those induced by predators, which are known to vary across Daphnia species.…”