Phenotypic responses of zooplankton to variable conditions
Lee, Marcus LU
(2021)
- Abstract
- Organisms are continually challenged by multiple threats in the environment, and such threats are seldom constant in either time or space. Therefore, organisms must maintain physiological, behavioural, morphological and life- history adaptations across environments to prevent reductions in fitness. Freshwater ecosystems are particularly variable environments, and so organisms inhabiting lakes and ponds exhibit a range of different adaptations in order to survive and propagate. Despite this, the energetic constraints and potentially divergent responses required towards multiple threats creates the necessity to make trade-offs in their phenotypic repertoire. The outcomes of such phenotypic compromises are often difficult to predict and... (More)
- Organisms are continually challenged by multiple threats in the environment, and such threats are seldom constant in either time or space. Therefore, organisms must maintain physiological, behavioural, morphological and life- history adaptations across environments to prevent reductions in fitness. Freshwater ecosystems are particularly variable environments, and so organisms inhabiting lakes and ponds exhibit a range of different adaptations in order to survive and propagate. Despite this, the energetic constraints and potentially divergent responses required towards multiple threats creates the necessity to make trade-offs in their phenotypic repertoire. The outcomes of such phenotypic compromises are often difficult to predict and requires both a mechanistic understanding of the threats and responses involved, as well as insights into the resulting fitness consequences. Although this is relatively well understood with regards to some threats like predation for example, other biotic and abiotic stressors are less well studied. In this thesis I identify phenotypic compromises in behavioural, morphological and life-history traits of zooplankton with regards to variable environments.
Behaviour is often considered one of the most labile traits and consequently it may provide a quick and inexpensive response to infrequent or rapidly changing contexts. Using 3D tracking, I focused on swimming behaviour of Daphnia magna in response to social context and found that females avoid males in a way that resembles a predation event. In a separate experiment I investigated how the presence of a high-density food patch altered the response to the abiotic threat ultraviolet radiation (UVR). Here I found that despite the potential fitness consequences of UVR the foraging opportunity reduced the avoidance response that has been classically described in Daphnia.
UVR is a substantial threat in aquatic systems with documented physiological, behavioural, morphological and life- history responses. It is also a particularly variable stressor as it is absent during night and varies in intensity over the seasons. Despite its variable nature, studies have typically only addressed the presence or absence and not fluctuating UVR stress. I addressed this gap in the knowledge by tracking the survival, reproduction and behavioural response to both fluctuating and stable exposure of UVR. Simply by varying the scheduling but not the quantity of UVR stress, I identified fitness costs that appeared to be linked to the cost of the behavioural avoidance.
In high-latitude environments, where phenotypic plasticity is promoted due to seasonal variability, copepods increase pigmentation in response to increased UVR but only in the absence of fish. I tested whether this response is ubiquitous at lower latitudes that experience less seasonality and have evolved with different predation regimes. Copepods from fishless environments had higher pigmentation than those with visually hunting predators. I also found that plasticity towards UVR removal was minor, but plasticity towards predation was mostly idiosyncratic. This suggests that plasticity does exist for the threats that are most variable and constitutive responses may have evolved towards ever present danger. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/aa267026-8784-4791-bcca-bad496d1df42
- author
- Lee, Marcus
LU
- opponent
-
- Professor Walsh, Matthew, University of Texas at Arlington, USA
- organization
- publishing date
- 2021
- type
- Thesis
- publication status
- published
- subject
- keywords
- Multiple threats, Plasticity, Risk-Spreading, sexual conflict, ultraviolet radiation, Daphnia, Copepods
- pages
- 123 pages
- publisher
- Lund University
- defense location
- The Blue Hall, Ecology Building, Sölvegatan 37, Lund
- defense date
- 2022-01-14 09:30:00
- ISBN
- 978-91-8039-098-9
- 978-91-8039-097-2
- language
- English
- LU publication?
- yes
- id
- aa267026-8784-4791-bcca-bad496d1df42
- date added to LUP
- 2021-11-30 13:28:01
- date last changed
- 2023-09-06 10:04:04
@phdthesis{aa267026-8784-4791-bcca-bad496d1df42,
abstract = {{Organisms are continually challenged by multiple threats in the environment, and such threats are seldom constant in either time or space. Therefore, organisms must maintain physiological, behavioural, morphological and life- history adaptations across environments to prevent reductions in fitness. Freshwater ecosystems are particularly variable environments, and so organisms inhabiting lakes and ponds exhibit a range of different adaptations in order to survive and propagate. Despite this, the energetic constraints and potentially divergent responses required towards multiple threats creates the necessity to make trade-offs in their phenotypic repertoire. The outcomes of such phenotypic compromises are often difficult to predict and requires both a mechanistic understanding of the threats and responses involved, as well as insights into the resulting fitness consequences. Although this is relatively well understood with regards to some threats like predation for example, other biotic and abiotic stressors are less well studied. In this thesis I identify phenotypic compromises in behavioural, morphological and life-history traits of zooplankton with regards to variable environments.<br/>Behaviour is often considered one of the most labile traits and consequently it may provide a quick and inexpensive response to infrequent or rapidly changing contexts. Using 3D tracking, I focused on swimming behaviour of <i>Daphnia magna</i> in response to social context and found that females avoid males in a way that resembles a predation event. In a separate experiment I investigated how the presence of a high-density food patch altered the response to the abiotic threat ultraviolet radiation (UVR). Here I found that despite the potential fitness consequences of UVR the foraging opportunity reduced the avoidance response that has been classically described in <i>Daphnia</i>.<br/>UVR is a substantial threat in aquatic systems with documented physiological, behavioural, morphological and life- history responses. It is also a particularly variable stressor as it is absent during night and varies in intensity over the seasons. Despite its variable nature, studies have typically only addressed the presence or absence and not fluctuating UVR stress. I addressed this gap in the knowledge by tracking the survival, reproduction and behavioural response to both fluctuating and stable exposure of UVR. Simply by varying the scheduling but not the quantity of UVR stress, I identified fitness costs that appeared to be linked to the cost of the behavioural avoidance.<br/>In high-latitude environments, where phenotypic plasticity is promoted due to seasonal variability, copepods increase pigmentation in response to increased UVR but only in the absence of fish. I tested whether this response is ubiquitous at lower latitudes that experience less seasonality and have evolved with different predation regimes. Copepods from fishless environments had higher pigmentation than those with visually hunting predators. I also found that plasticity towards UVR removal was minor, but plasticity towards predation was mostly idiosyncratic. This suggests that plasticity does exist for the threats that are most variable and constitutive responses may have evolved towards ever present danger.}},
author = {{Lee, Marcus}},
isbn = {{978-91-8039-098-9}},
keywords = {{Multiple threats; Plasticity; Risk-Spreading; sexual conflict; ultraviolet radiation; Daphnia; Copepods}},
language = {{eng}},
publisher = {{Lund University}},
school = {{Lund University}},
title = {{Phenotypic responses of zooplankton to variable conditions}},
url = {{https://lup.lub.lu.se/search/files/110428263/Marcus_Lee_Thesis.pdf}},
year = {{2021}},
}