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Microevolution in pygmy grasshoppers
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Evolutionary ecology)
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Knowledge of how spatiotemporal environmental variation impacts ecological and evolutionary processes and contributes to genetic and phenotypic diversity of natural populations is key to understanding and protecting biological diversity. In this thesis I used pygmy grasshoppers to study how environmental conditions, population dynamics, dispersal and admixture may influence genetic structure and diversity, and to evaluate how functionally important variation may affect the ability of populations to cope with novel and changing habitats.

Analyses of AFLP (Amplified Fragment Length Polymorphism) markers in Tetrix subulata individuals from 20 sampling locations in Sweden showed significant genetic structure and restricted gene flow among populations. Genetic diversity increased with population size and proportion of long-winged dispersive phenotypes on the island of Öland, but not on the mainland.

A contrasting environment comparative approach (CECA) applied to 20 T. undulata populations suggested that processes associated with environmental change differently influence functional and neutral diversity. Long-winged phenotypes were more common in disturbed than in stable habitats, indicative of recent establishment. Color morph diversity was higher in disturbed environments consistent with the notion that polymorphism promotes establishment success. Conversely, neutral diversity (AFLP) was lower in disturbed habitats, pointing to a stronger eroding effect of genetic drift in disturbed compared to stable habitats.

I compared genetic and morphological variation between sympatric populations of the two species. Populations of the generally dispersive T. subulata were genetically less differentiated compared with the more sedentary T. undulata, suggesting that the latter species has been less influenced by the homogenizing effects of gene flow. Non-parallel body size differences pointed to species-specific drivers of morphological change.

Finally, comparisons of reproductive output of T. subulata females that had been experimentally mated with males from the same or from a different population suggested that responses to interbreeding and genetic admixture can differ in direction and magnitude even between populations within a species, and thus influence whether dispersal translates into gene flow.

My thesis emphasizes the complexity of microevolution and illustrates how the effects of different ecological and evolutionary processes can vary according to disturbance regimes and geographic areas, and differ between closely related sympatric species.

Place, publisher, year, edition, pages
Växsjö: Linnaeus University Press, 2017.
Series
Linnaeus University Dissertations ; 295
National Category
Evolutionary Biology
Research subject
Ecology, Evolutionary Biology
Identifiers
URN: urn:nbn:se:lnu:diva-67729ISBN: 978-91-88357-87-8 (print)OAI: oai:DiVA.org:lnu-67729DiVA, id: diva2:1138309
Public defence
2017-09-22, 18:14 (English)
Opponent
Supervisors
Available from: 2017-09-05 Created: 2017-09-04 Last updated: 2017-09-05Bibliographically approved
List of papers
1. Population genetic structure, differentiation, and diversity in Tetrix subulata pygmy grasshoppers: roles of population size and immigration
Open this publication in new window or tab >>Population genetic structure, differentiation, and diversity in Tetrix subulata pygmy grasshoppers: roles of population size and immigration
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2016 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, no 21, p. 7831-7846Article in journal (Refereed) Published
Abstract [en]

Genetic diversity within and among populations and species is influenced by complex demographic and evolutionary processes. Despite extensive research, there is no consensus regarding how landscape structure, spatial distribution, gene flow, and population dynamics impact genetic composition of natural populations. Here, we used amplified fragment length polymorphisms (AFLPs) to investigate effects of population size, geographic isolation, immigration, and gene flow on genetic structure, divergence, and diversity in populations of Tetrix subulata pygmy grasshoppers (Orthoptera: Tetrigidae) from 20 sampling locations in southern Sweden. Analyses of 1564 AFLP markers revealed low to moderate levels of genetic diversity (PPL=59.5-90.1; Hj=0.23-0.32) within and significant divergence among sampling localities. This suggests that evolution of functional traits in response to divergent selection is possible and that gene flow is restricted. Genetic diversity increased with population size and with increasing proportion of long-winged phenotypes (a proxy of recent immigration) across populations on the island of oland, but not on the mainland. Our data further suggested that the open water separating oland from the mainland acts as a dispersal barrier that restricts migration and leads to genetic divergence among regions. Isolation by distance was evident for short interpopulation distances on the mainland, but gradually disappeared as populations separated by longer distances were included. Results illustrate that integrating ecological and molecular data is key to identifying drivers of population genetic structure in natural populations. Our findings also underscore the importance of landscape structure and spatial sampling scheme for conclusions regarding the role of gene flow and isolation by distance.

Keywords
dispersal, evolution, gene flow, Orthoptera, polymorphism, population divergence, Tetrix subulata
National Category
Ecology Evolutionary Biology
Research subject
Ecology, Evolutionary Biology
Identifiers
urn:nbn:se:lnu:diva-59010 (URN)10.1002/ece3.2520 (DOI)000387120800024 ()2-s2.0-84990964599 (Scopus ID)
Available from: 2016-12-15 Created: 2016-12-14 Last updated: 2018-10-24Bibliographically approved
2. Population-specific effects of interbreeding and admixture on reproductive decisions and offspring quality
Open this publication in new window or tab >>Population-specific effects of interbreeding and admixture on reproductive decisions and offspring quality
2016 (English)In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 53, no 1-2, p. 55-68Article in journal (Refereed) Published
Abstract [en]

We investigated interbreeding and admixture in Tetrix subulata grasshoppers from two maternal origin populations that differed in life-history and dispersal traits. We compared reproductive output of females that had been experimentally mated with males from the same or from a different population. Interbreeding affected clutch size and number of clutches; in one population females in the admixed treatment produced smaller clutches, in the other population females in the admixed treatment produced more clutches. Behavioral observations indicated that individuals can discriminate scents emitted by individuals from different populations; such that females might adjust reproductive allocation depending on male origin. However, hatchability of eggs and survival of nymphs were not affected by the mating treatment. Admixture influenced the production of viable offspring in the F2 generation, but the effect was opposite in the two populations of maternal origin. Results suggested that responses to interbreeding and admixture can differ between populations within a species.

National Category
Ecology Evolutionary Biology
Research subject
Ecology, Evolutionary Biology
Identifiers
urn:nbn:se:lnu:diva-51998 (URN)10.5735/086.053.0205 (DOI)000374707600005 ()2-s2.0-84965082807 (Scopus ID)
Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2018-10-24Bibliographically approved

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Doctoral Thesis (Extended Summary)(3200 kB)116 downloads
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