Direct and indirect effects of predation on the genetic structure of a Daphnia population

Hembre, Leif K.; Megard, Robert O.

doi:10.1093/plankt/fbl043

Cited by 9 publications

(13 citation statements)

References 46 publications

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“…It has been suggested that fish predation induces sexual reproduction in Daphnia magna (Slusarczyk, 1999) and therefore indirectly enhances genotypic diversity (Hembre & Megard, 2006). Turnover rates (number of genotypes found only once) were clearly correlated with predation pressure in 2007 when predation pressure increased slowly as juvenile fish were growing.…”

Section: Discussionmentioning

confidence: 99%

Clonal diversity and turnover in an overwinteringDaphnia pulexpopulation, and the effect of fish predation

Lampert¹,

Regmi

Wathne

et al. 2014

Freshwater Biology

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Summary Daphnia are key species in lake ecosystems and are a model system in ecology. Their ecological success is very much due to their dual reproductive mode: females reproduce parthenogenetically when environmental conditions are favourable but switch to sexual reproduction and resting egg production in unfavourable conditions such as winter. Phases of clonal reproduction lower the overall genotypic diversity of Daphnia populations due to the random loss of genotypes. During phases of sexual reproduction, new genotypes enhance the genotypic variability of the population and compensate for the loss of clonal lineages. We hypothesised that clonal diversity should be low during the winter months due to high mortality rates (clonal erosion) but will be restored in the spring most likely from the resting egg bank. To test this hypothesis, we investigated the clonal composition of a Daphnia pulex population in a small mesotrophic lake in Norway. Daphnia were sampled every month from September 2007 to September 2010, and c. 60 individuals per month were genotyped using 11 microsatellite markers. Marker resolution was high, and 582 different genotypes could be detected in the 936 individuals analysed. An unexpected complication for the study was the illegal introduction of planktivorous fish into the lake between autumn 2006 and spring 2007. This led to significant predation pressure on the D. pulex population and shifted the cladoceran community to smaller species. However, while the D. pulex population density declined severely over the study years, the overall genotypic variability increased. We observed very high turnover rates, with many clones being present for only a single month. Nevertheless, and as expected, genotypic diversity was higher during summer and lower during winter, and some parthenogenetic individuals seemed to be able to survive the winter. The large majority of new genotypes came from the resting egg bank. We conclude that, due to the new predation pressure, the resting egg bank has become much more important in restocking genotypic diversity as well as for D. pulex abundance. However, despite the buffering capacities of the resting egg bank, the predation pressure will most likely lead to the extinction of D. pulex in Lake Myravatn.

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Section: Discussionmentioning

confidence: 99%

Clonal diversity and turnover in an overwinteringDaphnia pulexpopulation, and the effect of fish predation

Lampert¹,

Regmi

Wathne

et al. 2014

Freshwater Biology

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“…Cladocerans, particularly members of the genus Daphnia, are known to exhibit a remarkable ability to adapt morphologically, physiologically and/or behaviorally to environmental change (e.g. Grant and Bayly, 1981;Kreuger and Dodson, 1981;Hebert and Grewe, 1985;Ranta and Tjossem, 1987;Hembre and Megard, 2006;Hülsmann and Wagner, 2007;Vanoverbeke et al, 2007). This functional flexibility, in combination with their parthenogenetic reproduction and ease of laboratory culture, has resulted in their emergence as model organisms for many scientific fields, prime among them ecotoxicology and toxicogenomics (e.g.…”

Section: Introductionmentioning

confidence: 99%

Histaminergic signaling in the central nervous system of Daphnia and a role for it in the control of phototactic behavior

McCoole

Baer

Christie

2011

Journal of Experimental Biology

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2007). Regardless of origin, stressors that negatively impact phototaxis are likely to have a major influence on the fitness of individual daphnids, rendering them susceptible to both increased UV damage and increased predation (Lampert, 1993 Among the many assays used for determining the effects of environmental and anthropogenic stressors on these animals is monitoring for changes in their phototactic behavior. In most arthropods, histamine has been shown to play a key role in the visual system. Currently, nothing is known about histaminergic signaling in either D. magna or D. pulex. Here, a combination of immunohistochemistry and genome mining was used to identify and characterize the histaminergic systems in these daphnids. In addition, a behavioral assay was used to assess the role of histamine in their phototactic response to ultraviolet (UV) light exposure. An extensive network of histaminergic somata, axons and neuropil was identified via immunohistochemistry within the central nervous system of both daphnids, including labeling of putative photoreceptors in the compound eye and projections from these cells to the brain. Mining of the D. pulex genome using known Drosophila melanogaster proteins identified a putative ortholog of histidine decarboxylase (the rate-limiting biosynthetic enzyme for histamine), as well as two putative histamine-gated chloride channels (hclA and hclB orthologs). Exposure of D. magna to cimetidine, an H2 receptor antagonist known to block both hclA and hclB in D. melanogaster, inhibited their negative phototactic response to UV exposure in a reversible, time-dependent manner. Taken collectively, our results show that an extensive histaminergic system is present in Daphnia species, including the visual system, and that this amine is involved in the control of phototaxis in these animals.

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“…There is some evidence for such changes in the genetic population structure, correlated with changes in predation pressure, habitat availability, or competition strength (Geedey et al 1996; Hembre and Megard 2006). However, there has been no direct empirical evidence for the role of food quality in the seasonal succession of clones within the population of a given species.…”

Section: Discussionmentioning

confidence: 99%

The role of food quality in clonal succession in Daphnia: an experimental test

2010

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A high genetic variation and recurrent changes in the genetic structure have been found in many pelagic populations. However, evidence that directly links these changes to differences in the ecological performance of particular genotypes is scarce. We hypothesized that within Daphnia, the specialization of clones occurring in a particular season to the food quality specific for that time of the year is responsible for the observed changes in the genetic structure of a population. This hypothesis was tested by comparing the fitness of spring and summer clones of the Daphnia longispina group, given food of biochemical quality relevant to these seasons. We identified significant intraspecific differences between clones of Daphnia that are specific for particular seasons, but there was no evidence that clones are adapted to the food quality available at the respective times of year. Summer clones reproduce at smaller size, and have a lower juvenile specific growth rate as compared to spring clones, irrespective of food quality. Spring clones invest more energy in somatic growth at the cost of reproduction, whereas summer clones invest more energy in reproduction at the cost of somatic growth. On the basis of the observed differences between spring and summer clones in their patterns of energy allocation, we suggest that other factors, most likely predation, are the major forces driving phenotypic and genetic diversity in the investigated Daphnia population of a large lake.

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Direct and indirect effects of predation on the genetic structure of a Daphnia population

Cited by 9 publications

References 46 publications

Clonal diversity and turnover in an overwinteringDaphnia pulexpopulation, and the effect of fish predation

Clonal diversity and turnover in an overwinteringDaphnia pulexpopulation, and the effect of fish predation

Histaminergic signaling in the central nervous system of Daphnia and a role for it in the control of phototactic behavior

The role of food quality in clonal succession in Daphnia: an experimental test

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