Adaptive and non-adaptive responses to toxin-producing cyanobacteria in water fleas
Author
Summary, in English
Here, I first investigate the scope and efficacy of maternal (Paper I) and transgenerational (Paper II) effects in this system. Secondly, I examined how the overall fitness, and tolerance to the cyanotoxin microcystin in particular, changes across the season in a natural lake environment (Paper III and IV). Finally, I attempted to link variation in growth, reproductive output and survival to changes in the diversity and composition of the gut microbiome (Paper II and IV), one possible mechanism that enable cumulative transgenerational adaptive change in response to a toxic diet.
In agreement with previous studies, I find that exposure to toxin-producing cyanobacteria consistently reduces fitness in Daphnia, both in terms of reproductive output and survival. The ability of mothers to transfer tolerance to their offspring was limited (Paper I), and there was little evidence that these positive effects accumulate across several generations (Paper II). These results fit well with studies of natural seasonal variation in how microcystin-producing cyanobacteria affected fitness, which provided no robust evidence for an increase in tolerance following blooms (Paper III and IV). Instead, the fitness of Daphnia declined steadily over the season in both experiments, an effect that could partly be attributed to natural exposure to microcystin-producing cyanobacteria (Paper III).
The gut microbiome was strongly influenced by seasonal changes in a lake environment (Paper IV). The microbiome was also affected by different cyanobacteria environments in the laboratory (Paper II), but these effects were only weakly correlated with the ability to tolerate microcystin-producing cyanobacteria.
In summary, this work shows that there are both adaptive and non-adaptive responses to toxin-producing cyanobacteria in Daphnia. The adaptive value of transgenerational effects in this system was consistently small, and does not support the existence of a dedicated machinery to transfer information between generations. This probably also means that induced changes in tolerance within a season have a limited influence on the dynamics of Daphnia populations, even in populations that are recurrently exposed to toxic algal blooms.
Department/s
- Evolutionary ecology
- Evolutionary Biology
Publishing year
2020
Language
English
Full text
Document type
Dissertation
Publisher
Lund University
Topic
- Biological Sciences
Status
Published
Research group
- Evolutionary Biology
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-7895-675-3
- ISBN: 978-91-7895-674-6
Defence date
27 November 2020
Defence time
09:00
Defence place
Blå hallen, Ekologihuset, Sölvegatan 37, Lund. Join via zoom: https://lu-se.zoom.us/j/64691238024?pwd=bkZWNHFzWDlmRjV5WHhSOXg1NFNEdz09 Passcode: 210316
Opponent
- Blake Matthews (Dr.)