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)

Variations in gut microbiota associated with changes in life-history traits of Daphnia galeata induced by fish kairomones

“…Prey species demonstrate diverse adaptations to predation, including alterations in life history, behavior, and morphological and physiological traits (Lima, 1998). Consistent with previous studies (Tams et al, 2018;Choi et al, 2023b), the presence of fish kairomones significantly affected variations in life-history traits related to reproduction and growth of the examined genotype of D. galeata (Figure 1). The KB5 genotype exhibited defensive strategies by improving fertility to sustain generations, producing a substantial number of offspring, and minimizing their "Body Length" (Figure 1).…”

“…The experimental design and procedures were based on a previous study (Choi et al, 2023b). To minimize interindividual variances, D. galeata was bred for two generations in a kairomone-free medium (control group) and a fish kairomone medium (experimental group) before the experiment (Tams et al, 2018). The D. galeata individuals used in this experiment are the same age.…”

“…The "Somatic Growth Rate" of D. galeata was determined by dividing the difference in body length between the neonates at the start (t0) and the adults at the end (t21) of the experiment by the total experimental duration. Body length of D. galeata was measured from the top of the head, through the middle of the eye, to the base of the spine excluding the spine itself (Tams et al, 2018). The individuals were observed with the CX22LED microscope (Olympus, Japan) and photographed with the eXcope T500 microscope camera (DIXI Science, Korea).…”

“…Among the Daphnia species, Daphnia galeata is a relatively large zooplankton found throughout the northern hemisphere and has been identified as a dominant plankton species in the Han River, Korea (Choi et al, 2023a). The freshwater crustacean D. galeata, which has a short life cycle, a rapid response to environmental stress, convenient clonal reproduction under laboratory conditions, and typical defense mechanisms induced by predators in life-history traits, is an appropriate organism for research in this field (Tams et al, 2018;Choi et al, 2023b).…”

Contrasting patterns of divergence at the regulatory and sequence level in European Daphnia galeata natural populations

“…Additionally, numerous studies on life history traits in Daphnia also report very high intrapopulation variability (Beckerman, Rodgers, & Dennis, ; Castro, Consciência, & Gonçalves, ; Cousyn et al, ; Macháček, ). A common garden experiment conducted on the very same clonal lines also showed a higher phenotypic variability within populations than among populations (Tams, Luneburg, Seddar, Detampel, & Cordellier, ). Finally, the observed relative homogeneity in the gene expression profiles might be the consequence of high selective pressure on transcription regulation or canalization (Waddington, ).…”