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Sex in Murky Waters: Anthropogenic Disturbance of Sexual Selection in Pipefish
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Animals experience variation in their environment because of natural changes. However, due to anthropogenic disturbance, the speed and severity of these changes have recently increased. This thesis investigates how reproductive behaviours may be affected by human induced environmental change. In specific, I investigate how visual and chemical changes in the aquatic environment, caused by eutrophication, affect mating systems and sexual selection in fish. Broad-nosed- and straight-nosed pipefish, which both have been studied in detail for a long period, were used as model organisms. These two species are particularly suitable model organisms since they perform complex courtship behaviours, including the advertisement of ornaments and a nuptial dance. Further, two distinct populations were studied, one on the Swedish west coast and one in the Baltic Sea, as these two locations vary in the degree and extent of environmental disturbance, in particular turbidity. I found that changes in the visual environment had no impact on the development of female sexual ornaments in these sex-role reversed pipefishes, but it hampered adaptive mate choice. Turbidity also had a negative effect on reproductive success in the Baltic Sea population. Changes in the chemical environment in the form of increased pH reduced the probability to mate, while hypoxia did not alter mating propensity. However, hypoxic water delayed the onset of both courting and mating. Hence, human induced change in aquatic environments may alter the processes of sexual selection and population dynamics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 35 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1022
Keyword [en]
Mating system, Mate choice, Courtship, Eutrophication, Turbidity, Hypoxia, Ocean acidification, Syngnathidae
National Category
Natural Sciences
Research subject
Biology with specialization in Animal Ecology
Identifiers
URN: urn:nbn:se:uu:diva-195861ISBN: 978-91-554-8603-7 (print)OAI: oai:DiVA.org:uu-195861DiVA: diva2:608504
Public defence
2013-04-19, Zootissalen, EBC, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-03-21 Created: 2013-02-27 Last updated: 2013-04-02Bibliographically approved
List of papers
1. Turbidity hampers mate choice in a pipefish
Open this publication in new window or tab >>Turbidity hampers mate choice in a pipefish
2010 (English)In: Ethology, ISSN 0179-1613, E-ISSN 1439-0310, Vol. 116, no 8, 713-721 p.Article in journal (Refereed) Published
Abstract [en]

European coastal waters have in recent years become more turbid as algal growth has increased, probably due to eutrophication, global warming and changes in fish communities. Turbidity reduces visibility, and such changes may in turn affect animal behaviour as well as evolutionary processes that are dependent on visual stimuli. In this study we experimentally manipulated water visibility and olfactory cues to investigate mate choice using the sex role-reversed broad-nosed pipefish Syngnathus typhle as our study organism. We show that males spent significantly longer time assessing females when they had access to full visual cues, compared to when visibility was reduced. Presence or absence of olfactory cues from females did not affect mate choice, suggesting that the possible use of smell could not make up for a reduction in visibility. This implies that mate choice is environmentally dependent and that an increased turbidity may affect processes of sexual selection through an impaired possibility for visually based mate choice.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-132342 (URN)10.1111/j.1439-0310.2010.01787.x (DOI)000279443000004 ()
Available from: 2010-10-18 Created: 2010-10-18 Last updated: 2017-12-12Bibliographically approved
2. Human induced turbidity alters reproductive success and the stength of sexual selection in a pipefish
Open this publication in new window or tab >>Human induced turbidity alters reproductive success and the stength of sexual selection in a pipefish
(English)Manuscript (preprint) (Other academic)
Abstract [en]

 Human induced environmental change has the potential to alter species interactions, population dynamics and evolutionary processes. One such environmental change is algal induced turbidity, caused by eutrophication. While changes in mate choice and sexual selection due to turbidity has been demonstrated, the possible impact on mating systems remains to be explored. In this study we investigated the impact of algal turbidity on reproductive success, mating system and sexual selection using two populations of the broad-nosed pipefish, Syngnathus typhle, one from the Swedish west coast and one from the Baltic Sea. Under natural conditions, both populations practise a polygynandrous mating system with males as well as females having several partners. However, in a population from the Venice lagoon, where turbidity levels are high, the male mating system is shifted towards polyandry, with most males mating with one female only. In an experimental setting we tested whether this shift in mating system could be driven by turbidity alone. Contrary to our expectations, we found no effect of turbidity on the male mating system in terms of a general shift towards genetic polyandry. However, a positive relationship between male body length and number of mates was stronger in turbid environments for the Baltic Sea population. This indicates that although turbidity did not seem to affect the number of females a male mated with it has the potential to affect the strength of sexual selection. Further, for this population the turbid environment resulted in lower reproductive success.

Keyword
Eutrophication, Mating system, Mate choice, Syngnathidae
National Category
Ecology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-195087 (URN)
Available from: 2013-02-27 Created: 2013-02-20 Last updated: 2013-03-22
3. Male mate choice, but not female ornamentation, is impaired by turbidity in the straight-nosed pipefish
Open this publication in new window or tab >>Male mate choice, but not female ornamentation, is impaired by turbidity in the straight-nosed pipefish
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Sexual ornaments are used both in intra- and intersexual contexts, and these signals have evolved to function in the particular habitat the animal is adapted to. Habitat characteristics may change rapidly due to anthropogenic effects, sometimes at rates too fast for many organisms to adaptively respond. In aquatic ecosystems, eutrophication and overfishing is currently changing chemical as well as visual properties of the environment. Algae blooms increase water turbidity, and the reduction of water transparency has the potential to alter visual ornaments and their perception. Here we found that male mate choice, but not the development of female sexual ornaments, was affected by turbidity in the straight-nosed pipefish, Nerophis ophidion. In a laboratory mate choice experiment, males preferred females with larger ornaments in clear water, while mate choice became random under turbid conditions. Female ornamentation, courtship and fecundity, on the other hand, seemed unaffected by turbidity, as no effect was found even though we investigated long-term turbidity effects. Thus, we show that water turbidity had no affect on signal expression but did hamper ornament perception and consequently altered mate choice.

Keyword
Eutrophication, Intersexual selection, Syngnathidae, Status signals
National Category
Ecology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-195089 (URN)
Available from: 2013-02-27 Created: 2013-02-20 Last updated: 2013-03-22
4. Altered oceanic pH impairs mating propensity in a pipefish
Open this publication in new window or tab >>Altered oceanic pH impairs mating propensity in a pipefish
2013 (English)In: Ethology, ISSN 0179-1613, E-ISSN 1439-0310, Vol. 119, no 1, 86-93 p.Article in journal (Refereed) Published
Abstract [en]

Anthropogenic disturbance is currently altering the environment of terrestrial as well as aquatic organisms. Those changes affect a variety of animal behaviours, which in turn may cause changes in species interactions, population dynamics and evolutionary processes. In marine ecosystems, nutrient enrichment may elevate pH, while it is reduced by carbon dioxide-induced ocean acidification. These two processes are not expected to balance one another but rather to affect the environment at different times and scales. We here show experimentally that an increase in water pH has a negative effect on mating propensity in the broad-nosed pipefish Syngnathus typhle, whereas lowered pH did not elicit the same detrimental effect. This study provides, to our knowledge, the first evidence that mating propensity is impaired by an increase in pH, suggesting that anthropogenic nutrient enrichment in aquatic ecosystems may change the processes of sexual selection and population dynamics solely on the basis of altered water pH.

National Category
Ecology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-191484 (URN)10.1111/eth.12039 (DOI)
Available from: 2013-01-10 Created: 2013-01-10 Last updated: 2017-12-06Bibliographically approved
5. Hypoxia delay mating in the broad-nosed pipefish
Open this publication in new window or tab >>Hypoxia delay mating in the broad-nosed pipefish
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Courtship is often an important part of the reproductive process with functions such as ensuring reproductive compatibility, reducing hostility between the potential partners, and conveying individual quality. Except for the importance of the courtship behaviours themselves, latency until courting and mating is a key factor of the mating process. One factor in aquatic environments that has the potential to influence courtship behaviours is the level of dissolved oxygen, and hypoxic areas are currently spreading due to human activities, such as eutrophication. In this study we used the well-studied broad-nosed pipefish, Syngnathus typhle, to investigate the impact of hypoxia on reproductive behaviours preceding mating, on the latency until these behaviours occurred, and on the probability to mate. We found that time spent courting as well as probability to mate was unaffected by the oxygen treatment. Interestingly, we found that latency until courting and mating was prolonged in the oxygen-deprived environment. These results suggest that levels of low oxygen due to human activities can have implications for important aspects of reproductive behaviours.

Keyword
Latency, Courtship behaviours, Syngnathus, Dissolved oxygen, Sex role reversed, Climate change
National Category
Ecology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-194676 (URN)
Available from: 2013-02-27 Created: 2013-02-18 Last updated: 2013-03-22

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