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  • 1.
    Berggren, Hanna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tinnert, Jon
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Forsman, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Spatial sorting may explain evolutionary dynamics of wing polymorphism in pygmy grasshoppers.2012In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 25, no 10, p. 2126-2138Article in journal (Refereed)
    Abstract [en]

    Wing polymorphism in insects provides a good model system for investigating evolutionary dynamics and population divergence in dispersal-enhancing traits. This study investigates the contribution of divergent selection, trade-offs, behaviour and spatial sorting to the evolutionary dynamics of wing polymorphism in the pygmy grasshopper Tetrix subulata (Tetrigidae: Orthoptera). We use data for > 2800 wild-caught individuals from 13 populations and demonstrate that the incidence of the long-winged (macropterous) morph is higher and changes faster between years in disturbed habitats characterized by succession than in stable habitats. Common garden and mother-offspring resemblance studies indicate that variation among populations and families is genetically determined and not influenced to any important degree by developmental plasticity in response to maternal condition, rearing density or individual growth rate. Performance trials show that only the macropterous morph is capable of flight and that propensity to fly differs according to environment. Markrecapture data reveal no difference in the distance moved between free-ranging long- and short-winged individuals. There is no consistent difference across populations and years in number of hatchlings produced by long- and shorter-winged females. Our findings suggest that the variable frequency of the long-winged morph among and within pygmy grasshopper populations may reflect evolutionary modifications driven by spatial sorting due to phenotype- and habitat typedependent emigration and immigration.

  • 2.
    Tinnert, Jon
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Microevolution in pygmy grasshoppers2017Doctoral 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.

  • 3.
    Tinnert, Jon
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Berggren, Hanna
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Forsman, Anders
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Population-specific effects of interbreeding and admixture on reproductive decisions and offspring quality2016In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 53, no 1-2, p. 55-68Article in journal (Refereed)
    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.

  • 4.
    Tinnert, Jon
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Forsman, Anders
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    The role of dispersal for genetic and phenotypic variation: insights from comparisons of sympatric pygmy grasshoppers2017In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 122, no 1, p. 84-97Article in journal (Refereed)
    Abstract [en]

    Patterns of genetic and phenotypic variation within and among populations are influenced by a complex interplay of ecological and evolutionary processes. Theory posits that gene flow should increase diversity within and reduce differentiation between populations. Evaluating these predictions is potentially complicated by selection, population dynamics and plasticity that may also affect genetic and phenotypic variation. Here, we compare genetic and morphological variation between sympatric populations of two pygmy grasshopper species, Tetrix subulata and T. undulata, that differ in dispersal capacity. We found that genetic differentiation between populations is lower on average in the generally dispersive T. subulata compared with the mostly sedentary T. undulata, suggesting that genetic structure in the latter species has been less influenced by the homogenizing effects of migration. Our results also provided weak support for the hypothesis that neutral genetic diversity within populations should be higher in T. subulata than in T. undulata. We further found that body size varied among populations in both species, but the differences seen in T. subulata did not parallel those seen in T. undulata, indicating that the two species have unique plasticity responses or that they have responded differently to shared selective regimes. Our findings illustrate the utility of the pairwise comparative approach and further highlight that results and conclusions may not be transferrable even between closely related species.

  • 5.
    Tinnert, Jon
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Hellgren, Olof
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Lund University.
    Lindberg, Jenny
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Naturbruksskolan Sotasen.
    Koch-Schmidt, Per
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Forsman, Anders
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Population genetic structure, differentiation, and diversity in Tetrix subulata pygmy grasshoppers: roles of population size and immigration2016In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, no 21, p. 7831-7846Article in journal (Refereed)
    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.

  • 6.
    Yildirim, Yeserin
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Tinnert, Jon
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Forsman, Anders
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Contrasting patterns of neutral and functional genetic diversity in stable and disturbed environments2018In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 8, no 23, p. 12073-12089Article in journal (Refereed)
    Abstract [en]

    Genetic structure among and diversity within natural populations is influenced by acombination of ecological and evolutionary processes. These processes can differentlyinfluence neutral and functional genetic diversity and also vary according toenvironmental settings. To investigate the roles of interacting processes as drivers ofpopulation‐level genetic diversity in the wild, we compared neutral and functionalstructure and diversity between 20 Tetrix undulata pygmy grasshopper populations indisturbed and stable habitats. Genetic differentiation was evident among the differentpopulations, but there was no genetic separation between stable and disturbedenvironments. The incidence of long‐winged phenotypes was higher in disturbedhabitats, indicating that these populations were recently established by flight‐capablecolonizers. Color morph diversity and dispersion of outlier genetic diversity, estimatedusing AFLP markers, were higher in disturbed than in stable environments,likely reflecting that color polymorphism and variation in other functionally importanttraits increase establishment success. Neutral genetic diversity estimated usingAFLP markers was lower in disturbed habitats, indicating stronger eroding effects onneutral diversity of genetic drift associated with founding events in disturbed comparedto stable habitats. Functional diversity and neutral diversity were negativelycorrelated across populations, highlighting the utility of outlier loci in genetics studiesand reinforcing that estimates of genetic diversity based on neutral markers donot infer evolutionary potential and the ability of populations and species to copewith environmental change.

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