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Searching for food in complex environments: Integrating processes at multiple spatial scales
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0003-0130-6485
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Resources are often unevenly distributed through the environment, resulting in a challenging task for insects to locate food, mates and oviposition sites. Consequently, there is an ongoing need to unravel how insects rely on behavioural and sensory traits while searching for resources in heterogeneous environments. In the first part of this thesis, I addressed this issue by studying how neighbouring resources can affect the likelihood of insects finding their preferred host resources. These effects of neighbouring resources are commonly referred to as associational effects, and are expected to result from limitations in the sensory physiology of insects. Such limitations constrain the insect’s ability to correctly evaluate resource quality at the different steps involved in insect search behaviour. Furthermore, I determined whether the physiological state of an insect, and sensory experiences made during larval stages, can affect host search behaviour in heterogeneous environments.

By comparing the behaviour of Drosophila melanogaster in environments with single and multiple resources, I found that the presence of neighbouring recourses increased the selection rates for attractive resources, while it decreased the selection rates for less attractive resources. These effects are referred to as associational susceptibility and associational resistance respectively. Furthermore, by studying oviposition behaviour, I found that during these small-scale behavioural decisions, associational effects are mainly governed by gustatory mediated selection and less by olfactory mediated selection. The oviposition assay eliminated potential misinterpretations of resource quality along the different steps of search behaviour, hence the results suggested that associational effects rely on distinctive selection behaviour between resource types rather than on sensory constraints.

In the second part of this thesis I determined whether natal experiences can be used by insects as sensory shortcuts to find host resources, and whether this leads to better larval performance on those selected host resources. For this purpose, I studied the interactions between the larval parasitoid Asecodes lucens and the oligophagous leaf beetle Galerucella sagittariae. The results showed that the relationship between oviposition preference and larval performance, of both insect species, depends on an interactive effect between the insects’ natal origin and the quality of the different host resources. Moreover, I found that the natal origin was a better predictor for the adult host preference, rather than for larval performance. This suggests that, aside from the actual quality of the host resources, locating any suitable host might be even more limiting for the female’s fitness. 

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University , 2017. , 34 p.
Keyword [en]
Associational effects, Natal experiences, Olfaction, Oviposition
National Category
Ecology
Research subject
Plant Ecology
Identifiers
URN: urn:nbn:se:su:diva-141762ISBN: 978-91-7649-784-5 (print)ISBN: 978-91-7649-785-2 (electronic)OAI: oai:DiVA.org:su-141762DiVA: diva2:1088815
Public defence
2017-06-02, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, 09:30 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Submitted.

Available from: 2017-05-10 Created: 2017-04-16 Last updated: 2017-05-15Bibliographically approved
List of papers
1. Disentangling associational effects: both resource density and resource frequency affect search behaviour in complex environments
Open this publication in new window or tab >>Disentangling associational effects: both resource density and resource frequency affect search behaviour in complex environments
2016 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 30, no 11, 1826-1833 p.Article in journal (Refereed) Published
Abstract [en]

Neighbouring resources have been found to either decrease or increase the likelihood that a consumer organism attacks a focal resource. These phenomena are referred to as associational resistance (AR) and associational susceptibility (AS), respectively. While associational effects have been observed in various field studies, little is known on how resource heterogeneity can cause associational effects. We used a laboratory approach in which we studied the effects of resource density and frequency in the search behaviour of Drosophila melanogaster as a model organism for olfactory-guided behaviour in insects. We first determined whether D.melanogaster could discriminate between odour sources that differ quantitatively. Secondly, we determined what the effect of resource density and frequency was on the search behaviour of D.melanogaster by combining these resources into various patch arrangements. Finally, we used the outcome of our experiments to disentangle the role of resource density and frequency in associational effects. We found that D.melanogaster has the ability to discriminate between quantitatively different resources, but that the attraction to resource density is constrained by an optimum after which attraction decreases. Furthermore, in heterogeneous environments, flies showed a strong preference towards the more apparent resource, leading to AS for the more apparent resources and AR for the less apparent resource. The strength of this interaction increased with a decreasing frequency of the more apparent resource. These results imply that D.melanogaster mainly selects patches at the level of individual resources. Consequently, when a patch contains qualitatively different resources, the more apparent resource will attract a higher number of flies than the less apparent resource irrespective of the frequency of the apparent resource within the patch. Our study shows that associational effects can be explained by determining the hierarchical level at which a consumer selects its resources. When a consumer selects resources at the individual level rather than at the patch level, our results can be used to explain the population dynamics of host plants and their associated consumers under field conditions.

Keyword
associational effects, attraction behaviour, complex environments, Drosophila melanogaster, frequency dependence, insect olfaction, neighbourhood effects, wind tunnel
National Category
Biological Sciences
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-136924 (URN)10.1111/1365-2435.12670 (DOI)000387362600010 ()
Available from: 2017-01-03 Created: 2016-12-19 Last updated: 2017-04-27Bibliographically approved
2. Mating affects resource selection and modulates associational effects between neighbouring resources
Open this publication in new window or tab >>Mating affects resource selection and modulates associational effects between neighbouring resources
(English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706Article in journal (Refereed) Accepted
National Category
Ecology
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-141760 (URN)
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2017-04-27Bibliographically approved
3. Sensory mutations in Drosophila melanogaster influence associational effects between resources during oviposition
Open this publication in new window or tab >>Sensory mutations in Drosophila melanogaster influence associational effects between resources during oviposition
2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, 9352Article in journal (Refereed) Published
Abstract [en]

Neighboring resources can affect insect oviposition behavior when the complexity of sensory information obscures information about host resource availability in heterogeneous resource patches. These effects are referred to as associational effects and are hypothesized to occur through constraints in the sensory processing of the insect during host search, resulting into suboptimal resource use. Because the possibilities to study these constraints on naturally occurring animals are limited, we instead used sensory mutants of Drosophila melanogaster to determine the importance of sensory information in the occurrence of associational effects. We found that oviposition was mainly governed by non-volatile chemical cues and less by volatile cues. Moreover, the loss of gustatory sensilla resulted in random resource selection and eliminated associational effects. In conclusion, our study shows that associational effects do not necessarily depend on constraints in the sensory evaluation of resource quality, but may instead be a direct consequence of distinctive selection behavior between different resources at small scales.

National Category
Ecology
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-141761 (URN)10.1038/s41598-017-09728-7 (DOI)000408441600076 ()
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2017-09-18Bibliographically approved
4. Natal origin affects host preference and larval performance relationships in a tritrophic system
Open this publication in new window or tab >>Natal origin affects host preference and larval performance relationships in a tritrophic system
Show others...
2017 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 7, 2079-2090 p.Article in journal (Refereed) Published
Abstract [en]

Many insects face the challenge to select oviposition sites in heterogeneous environments where biotic and abiotic factors can change over time. One way to deal with this complexity is to use sensory experiences made during developmental stages to locate similar habitats or hosts in which larval development can be maximized. While various studies have investigated oviposition preference and larval performance relationships in insects, they have largely overlooked that sensory experiences made during the larval stage can affect such relationships. We addressed this issue by determining the role of natal experience on oviposition preference and larval performance relationships in a tritrophic system consisting of Galerucella sagittariae, feeding on the two host plants Potentilla palustris and Lysimachia thyrsiflora, and its larval parasitoid Asecodes lucens. We firstly determined whether differences in host-derived olfactory information could lead to divergent host selection, and secondly, whether host preference could result in higher larval performance based on the natal origin of the insects. Our results showed that the natal origin and the quality of the current host are both important aspects in oviposition preference and larval performance relationships. While we found a positive relationship between preference and performance of natal Lysimachia beetles, natal Potentilla larvae showed no such relationship and developed better on L. thyrsiflora. Additionally, the host selection by the parasitoid was mainly affected by the natal origin, while its performance was higher on Lysimachia larvae. With this study we showed that the relationship between oviposition preference and larval performance depends on the interplay between the natal origin of the female and the quality of the current host. However, without incorporating the full tritrophic context of these interactions, their implication in insect fitness and potential adaptation cannot be fully understood.

Keyword
Asecodes lucens, Galerucella sagittariae, larval performance, natal experience, oviposition preference, tritrophic interactions
National Category
Ecology
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-141758 (URN)10.1002/ece3.2826 (DOI)000399738700007 ()
Available from: 2017-04-15 Created: 2017-04-15 Last updated: 2017-06-19Bibliographically approved

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