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Long Term Studies of Insect Abundances in Temporary Wetlands in Relation to Hydrology, Predation and Bti
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]

Long-term insect abundances have been studied to investigate factors structuring the insect communities of the temporary wetlands around the River Dalälven floodplain. In the wet meadows and swamps in the River Dalälven floodplains recurrent floods are the ultimate prerequisite for high production of floodwater mosquitoes. In the larval stages these make up a superabundant potential prey for aquatic predatory insects while as adults they become nuisance for people and animals. Mosquito control with Bacillus thuringiensis israelensis (Bti) has been carried out in parts of the floodplain wetlands since 2002. This study investigate potential long-term effects of Bti on non-target insects in general, and non-biting midges (Diptera: Chironomidae) and aquatic predator insects in special in 10 temporary wetlands. Diving-beetles (Coleoptera: Dytiscidae) were the most common aquatic predatory insects in temporary flooded wetlands, and we found no indications that diving-beetles were negatively affected by mosquito larvae reduction with Bti-treatments. Non-target Bti-effects on the insect community in general, measured as increase or decrease of insect abundances, in general showed no effects of Bti except for Coleoptera. The non-biting midges were studied on species level, since this taxon previously has been associated with negative Bti non-target effects in the short-term. We found no reduced production of chironomids at neither family, nor subfamily level in Bti-treated as compared to untreated wetlands. We conclude that other factors than the occasional Bti-treatments dominate in structuring the chironomids fauna. For example, hydrology measured as floods and hydroperiod had substantial impact on insect emergence Increased hydroperiod was associated with lower insect emergence for the majority of the studied taxa, indicating an insect fauna adapted more to terrestrial conditions. In the final study, we developed and applied a molecular method to study interspecific predator – prey relationships between medium-sized diving beetles and floodwater mosquito larvae. Gut content analyses showed that floodwater mosquito larvae are a regular, but limited, part of the diet of medium-sized diving beetles. This thesis is one of the first long-term studies of insects of temporary wetlands in relation to mosquito control actions. The results indicate that hydrology is one of the major factors influencing and structuring the insect communities of the temporary flooded wetlands in the River Dalälven floodplains, and that mosquito control actions with Bti only have marginal effect on insect abundances.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 48 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1080
Keyword [en]
floodwater mosquitoes, mosquito control, predation, aquatic insects
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-207841ISBN: 978-91-554-8762-1 (print)OAI: oai:DiVA.org:uu-207841DiVA: diva2:650611
Public defence
2013-11-08, Lindahlsalen, Evolutionsbiologiskt Centrum, Norbyvägen 18 B, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-10-18 Created: 2013-09-19 Last updated: 2014-01-23
List of papers
1. Diving beetle assemblages of flooded wetlands in relation to time, wetland type and Bti-based mosquito control
Open this publication in new window or tab >>Diving beetle assemblages of flooded wetlands in relation to time, wetland type and Bti-based mosquito control
2009 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 635, no 1, 189-203 p.Article in journal (Refereed) Published
Abstract [en]

We investigated the abundance and taxonomic composition of the aquatic predatory insect fauna, with focus on adult diving beetles (Coleoptera: Dytiscidae), in eight temporary flooded wet meadows and two alder swamps in the River Dalalven flood-plains, central Sweden from 2002 to 2006. Diving beetles are generalist predators and often abundant in various waters, including temporary wetlands. In the River Dalalven floodplains, recurrent floods induce massive hatching of flood-water mosquitoes (Diptera: Culicidae), which constitute a superabundant patchy and irregular food resource for aquatic predatory insects. Our aims were (1) to characterize the assemblage of adult diving beetles occurring in the wetlands during floods in relation to time and wetland type and (2) to evaluate the effect on the aquatic predator assemblage of strongly reducing the abundance of a potential prey, flood-water mosquito larvae with Bacillus thuringiensis var. israelensis (Bti) during floods. We found diving beetles to be the dominating aquatic predatory insect taxa in all 10 wetlands. There was a difference in Dytiscidae species richness but not in diversity between wet meadows and alder swamps after rarefaction. The cluster analysis based on dytiscid species and abundances showed very high similarities between the wetlands. The variance component analysis was unable to distinguish any factor that could explain more than 7.4% of the variation in the dytiscid species assemblages. The only effect of Bti-treatment against flood-water mosquito larvae, potential food for the predatory dytiscids, was a slight increase in abundance of the medium-sized dytiscid species. Our results are in accordance with previous studies, suggesting that irregular and recurrent flood dynamic structure the dytiscid fauna more than food limitations and environmental factors.

Keyword
Diving beetles, Aquatic predatory insects, Flood-water mosquitoes, Temporary wetlands, Bti
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-127480 (URN)10.1007/s10750-009-9911-9 (DOI)000270652200018 ()
Available from: 2010-07-15 Created: 2010-07-13 Last updated: 2014-01-23Bibliographically approved
2. A six-year study of insect emergence from temporary flooded wetlands in central Sweden, with and without Bti-based mosquito control
Open this publication in new window or tab >>A six-year study of insect emergence from temporary flooded wetlands in central Sweden, with and without Bti-based mosquito control
Show others...
2010 (English)In: Bulletin of entomological research, ISSN 0007-4853, E-ISSN 1475-2670, Vol. 100, no 6, 715-725 p.Article in journal (Refereed) Published
Abstract [en]

In temporary wetlands in the River Dalalven floodplains, recurrent but irregular floods induce massive hatching of the flood-water mosquito Aedes sticticus, which causes enormous nuisance. Flood-water mosquito control using the biological larvicide Bacillus thuringiensis var. israelensis (Bti) was commenced in parts of the floodplains during 2002, and here we report the first six years of full-season monitoring of general insect emergence from temporary wetlands with and without treatment. Emergence traps, which were emptied weekly, were used from May to September each year. A total of 137,153 insects of 13 taxonomic orders were collected. Diptera was highly dominating and especially the sub-order Nematocera with 18 families was a very prominent taxon. Bti-treatment effects were analysed by taxonomic order, by sub-order in Diptera and Hemiptera, and by family for Nematocera and Coleoptera for the whole study period. We found no significant negative effects of Bti treatments on the production of insects by taxonomic order, with the exception of Coleoptera in the long term. However, no significant negative effects were found for the Coleoptera families, neither in the short term nor in the long term. There was no significant negative treatment effect on Nematocera production, neither when analyzed for the whole sub-order nor when analyzed by family. However, abundance of Ceratopogonidae was significantly higher in experimental than in reference wetlands. We conclude that Bti-treatment effects on insect production may be minute in comparison to other environmental factors structuring the insect fauna of the temporary wetlands studied.

Keyword
wetland insects, insect production, Bti, temporary wetlands
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-135365 (URN)10.1017/S0007485310000076 (DOI)000284012200010 ()
Available from: 2010-12-07 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
3. Production of wetland Chironomidae (Diptera) and the effects of using Bacillus thuringiensis israelensis for mosquito control
Open this publication in new window or tab >>Production of wetland Chironomidae (Diptera) and the effects of using Bacillus thuringiensis israelensis for mosquito control
Show others...
2010 (English)In: Bulletin of entomological research, ISSN 0007-4853, E-ISSN 1475-2670, Vol. 100, no 1, 117-125 p.Article in journal (Refereed) Published
Abstract [en]

Massive mosquito nuisance problems, caused by the flood-water mosquito Aedes sticticus, occur after floods in the flood plains of the River Dalalven, central Sweden. Since 2002, the biological mosquito larvicide Bacillus thuringiensis var. israelensis (Bti) has been used to control these mosquitoes. Here, we report results from the first six years of monitoring Chironomidae, the most Susceptible non-target organisms, in three wetlands with Bti-treatment against mosquitoes and in three wetlands without treatment. Emergence traps were used for continuous insect sampling from May to September each year, 2002-2007, and were emptied once a week. A total of 21,394 chironomids of 135 species were collected, and the Subfamily Orthocladiinae dominated the fauna followed by Chironominae and Tanypodinae. The annual chironomid production in the wetlands was low, with ail average of 1.91.7 individuals per m(2) and 42 g ash-free dry weight per m(2) We found no reduced production of chironomids at neither family, nor subfamily level, in Bti-treated as compared to untreated wetlands. This is the first long-term follow-up study of the possible effects of Bti-based mosquito larval control oil chironomid species production. In the short-term view, one species had higher production in treated areas. In the long-term view, four species had higher and one species had lower production in treated areas. We conclude that the B3ti-based control of floodwater mosquitoes does not cause and, major direct negative effects on chironomid production, and therefore does not seem to induce any risk for indirect negative effects on birds, bats or any other predators feeding on chironomids.

Keyword
Chironomidae, Chironominae, Bti, non-target organisms, mosquito control
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-138044 (URN)10.1017/S0007485309990137 (DOI)000274270500013 ()19497137 (PubMedID)
Available from: 2010-12-16 Created: 2010-12-16 Last updated: 2017-12-11Bibliographically approved
4. Insect emergence in relation to floods in wet meadows and swamps in the River Dalälven floodplain
Open this publication in new window or tab >>Insect emergence in relation to floods in wet meadows and swamps in the River Dalälven floodplain
2014 (English)In: Bulletin of entomological research, ISSN 0007-4853, E-ISSN 1475-2670, Vol. 104, no 4, 453-461 p.Article in journal (Refereed) Published
National Category
Zoology
Identifiers
urn:nbn:se:uu:diva-207209 (URN)10.1017/S0007485314000078 (DOI)000338105900005 ()
Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2017-12-06Bibliographically approved
5. Specific detection of the floodwater mosquitoes Aedes sticticus and Aedes vexans DNA in predatory diving beetles
Open this publication in new window or tab >>Specific detection of the floodwater mosquitoes Aedes sticticus and Aedes vexans DNA in predatory diving beetles
2015 (English)In: Insect Science, ISSN 1672-9609, E-ISSN 1744-7917, Vol. 22, no 4, 549-559 p.Article in journal (Refereed) Published
National Category
Ecology Genetics
Identifiers
urn:nbn:se:uu:diva-207839 (URN)10.1111/1744-7917.12146 (DOI)000358380600008 ()24895318 (PubMedID)
Note

Funding: Swedish Environmental Protection Agency

Available from: 2013-09-23 Created: 2013-09-19 Last updated: 2017-12-06Bibliographically approved

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