| 1. |
- Braga, Mariana Pires, 1988-
(författare)
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Evolution of host repertoires and the diversification of butterflies
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- All herbivorous insects are specialized to some extent to their host plants, but the level of specialization varies greatly. Insect-plant coevolution is often invoked to explain the large diversity of herbivorous insects, but the role of specialization during diversification is still controversial. Although well-studied, our understanding of the evolution of species interactions is still improving, and recent theoretical developments have highlighted the role of generalization (via colonization of new hosts) on diversification. In this thesis, various approaches are combined for a detailed study of the origins of macroevolutionary patterns of host use and butterfly diversity. Chapter I provides a mechanistic basis for such patterns through simulations of lineages evolved in silico. By separating the effects of the number of hosts used by a parasite lineage and the diversity of resources they encompass, we found that resource diversity, rather than host range per se, was the main driver of parasite species richness in both simulated and empirical systems. In Chapter II, we combined network and phylogenetic analyses to quantify support for the two main hypothesized drivers of diversification of herbivorous insects. Based on analyses of two butterfly families, Nymphalidae and Pieridae, we found that variability in host use is essential for diversification, while radiation following the colonization of a new host is rare but can produce high diversity. We then reconciled the two alternative hypotheses into a unified process of host-associated diversification where continuous probing of new hosts and retention of the ability to use hosts colonized in the past are the main factors shaping butterfly-plant networks. While network analysis is a powerful tool for investigating patterns of interaction, other methods are necessary to directly test the mechanisms generating the observed patterns. Therefore, in Chapter III we describe a model of host repertoire evolution we developed for Bayesian inference of evolution of host-parasite interactions. The approach was validated with both simulated and empirical data sets. Finally, in Chapter IV we used the method described in Chapter III to explicitly test the predictions made in Chapter II about the evolution of butterfly-plant networks. We found direct evidence for the role of expansion of fundamental host repertoire and phylogenetic conservatism as important drivers of host repertoire evolution. Thus, using three different approaches, we found overall support for the idea that variation in host use accumulated over evolutionary time is essential for butterfly diversification.
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| 2. |
- Audusseau, Hélène, 1986-
(författare)
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Effect of climate and land use on niche utilization and distribution of nettle-feeding butterflies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anthropogenic changes in climate and land use are causing a dramatic erosion of biodiversity. To understand this erosion, and predict future transformations of biodiversity, we need to understand better species’ response to these changes at different spatial and temporal scales. Modeling studies have identified correlations between physical parameters of the environment and species’ distribution at large spatial scales. However, this does not accurately characterize the response of a specific species, since this does not account for the constraints arising from the biology of the species. This thesis shall combine knowledge on the biology of species obtained from laboratory experiments with modeling studies. This will allow us (i) to identify life history traits and biotic interactions that influence species’ adaptive potential, and hence, explain possible differences in species’ distribution, and (ii) to consider, not only the ecological but also the evolutionary aspects of species’ response to changes. This integrative approach is likely to improve our predictions on species’ population dynamic in a changing environment.I focus on a community of butterflies in Sweden (Vanessa cardui, Polygonia c-album, Aglais urticae, Aglais io, Araschnia levana) that feeds on the stinging nettle (Urtica dioica). The available knowledge on the biology of these species and their short life cycles, which allow investigations of their response to changes on a short-time scale, make them a good system to study. Among three of these species, I showed great differences in organisms’ response to variation in food nutrient content. This is a potentially important finding considering the increased use of chemical fertilizers. These differences are to a large extent explained by differences among species in their degree of host plant specialization and voltinism (paper II). Thus, life history traits determine the response of species to environmental changes, but are themselves likely to evolve in response to such changes. Climate change, for instance, may alter the phenological synchrony between plant-feeding insects and their host plants, making it necessary for the insects to evolve their host plant range in order to ensure the availability of resources during larval development (paper I & III). The biology of a species, including biotic interactions, helps to explain the observed shift in a species’ distribution and environmental niche that result from climate change. I have shown that the recent establishment of A. levana in southern Sweden has modified the niche of the resident species, A. urticae and A. io (Paper IV). Niche partitioning in this community is likely mediated by parasite-driven apparent competition.
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| 3. |
- Yahya, Saleh A.S. 1972-
(författare)
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Habitat structure, degradation and management effects on coral reef fish communities
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coral reefs are among the most diverse and productive ecosystems on earth, and are critical to the survival of tropical marine ecosystems and sustenance of local human populations. However, coral reefs are quite vulnerable to disturbances, both natural and anthropogenic. This thesis looks at how coral reef communities have responded to climactic disturbances, particularly the 1997-98 El Niño Southern Oscillation (ENSO) and subsequent coral bleaching and mortality that affected much of the Indian Ocean, including the coastal waters of Tanzania, where the study was conducted. In particular, it investigates the effects of coral bleaching, habitat degradation and reef spatial arrangement on reef fish assemblages. Habitat structural complexity and spatial arrangement of reefs had an effect on reef fish communities. Fish communities showed patterns in distribution among habitats and between patch and continuous reefs. Fishes preferred live to bleached/dead or eroded coral, but trophic groups reacted differently to patch and continuous reefs. There were slight changes in fish abundance and significant changes in fish diversity on experimental, bleached branching Acropora coral plots over a period of one year. While fish abundance on one site increased shortly after a bleaching event, 6 years later fish abundance had decreased significantly. Conversely, coral reef communities in northern Tanzania had changed little over an 8-year period, with minor changes associated with the 1997-98 ENSO and the presence or absence of fisheries management. The coral reefs in the region were found to show high variability in community structure and responses of associated fish and invertebrate communities. The findings of this thesis indicate the importance of habitat structure and spatial arrangement of reefs, the detrimental effects of coral bleaching, and the possibility that some reefs and some (generalist) reef fish taxa may exhibit resilience to climate change.
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| 4. |
- Andersson, Mathias H., 1976-
(författare)
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Offshore wind farms - ecological effects of noise and habitat alteration on fish
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are large gaps in our understanding how fish populations are affected by the anthropogenic noise and the alteration of habitat caused by the construction and operation of offshore wind farms. These issues are of great importance as the construction of offshore wind farms will increase all over the world in the near future. This thesis studies these effects with a focus on fish. The wind turbine foundations function as artificial reefs and are colonized by invertebrates, algae and fish. The epibenthic assemblages are influenced by factors such as hydrographical parameters, time of submergence, distance to natural hard bottom, material and texture (PAPER I, II). Once an epibenthic assemblage has been developed, fish utilize it for different ecosystem services such as food, shelter, and spawning and nursery area. Benthic and semi-pelagic species show a stronger response to the introduced foundation than pelagic species, as it is the bottom habitat that has mainly been altered (PAPER I, II). Pelagic species could be positively affected by the increased food availability - but it takes time and the effect is local. Construction noise like pile driving creates high levels of sound pressure and acoustic particle motion in the water and seabed. This noise induces behavioural reactions in cod (Gadus morhua) and sole (Solea solea). These reactions could occur up to tens of kilometres distance from the source (PAPER III). During power production, the wind turbines generate a broadband noise with a few dominating tones (PAPER IV, V), which are detectable by sound pressure sensitive fish at a distance of several kilometres even though intense shipping occurs in the area. Motion sensitive species will only detect the turbine noise at around a ten meter distance. Sound levels are only high enough to possibly cause a behavioural reaction within meters from a turbine (PAPER IV, V).
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| 5. |
- Lindestad, Olle, 1988-
(författare)
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Geographic variation in life cycles : Local adaptation and ecological genetics in a temperate butterfly
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Conditions in nature change with the seasons, necessitating seasonal adaptations that synchronize the life cycles of organisms with their surroundings. Such regulatory adaptations must vary between populations to track local variation in climate and seasonality; this local adaptation is facilitated by locally specific seasonal cues, but may be hampered by gene flow and genetic history. For populations of temperate insects, two central features of adaptation to local climate are voltinism, the yearly number of generations; and diapause, the state of arrested development and suppressed metabolism in which most temperate insects spend winter. Delaying diapause allows for an additional generation to be produced within the same year, but this is only adaptive if the season is sufficiently long to safely accommodate such a life cycle. Hence, selection to express a locally adaptive voltinism should drive divergence between populations in diapause regulation and associated life history traits. In this thesis, I investigate variation in voltinism and life cycle regulation in a set of populations of the butterfly Pararge aegeria. Population-level variation in seasonal plasticity was tested in two sets of experiments. The first (Paper I) focused on photoperiodic plasticity during the growing season, and revealed considerable differences between populations in diapause induction and developmental reaction norms. Mechanistic modeling based on the laboratory results indicated that differences in voltinism are actively maintained by these genetic differences. Next, I tested the idea that shorter diapause may help populations achieve higher voltinism through earlier emergence in the spring (Paper II). This idea was not supported; instead, populations differed in a manner that suggests that diapause duration is selected upon by the need to avoid premature development under warm autumn conditions. The genetic background of seasonal adaptation in these populations was also explored. Phylogeographic structures inferred from genome-wide data put the results of the laboratory experiments into a historic context, and were used as the basis for a scan for genetic loci showing signs of differential selection (Paper III). The scan revealed novel variation in two circadian genes that have been shown to be linked to diapause control in P. aegeria, including a large deletion in the gene timeless. Finally, a test of two previously described circadian mutations (Paper IV) showed that, while these mutations may affect photoperiodic plasticity on a between-population level, they seemingly have no effect within a single population located at intermediate latitudes. Closer inspection revealed novel, locally unique mutations in the same genes, possibly compensating for the effect of diapause-delaying variants in a setting where an attempted second generation is not adaptive. I have shown that voltinism variation in P. aegeria is enabled by population differences in seasonal plasticity, with population differences playing a greater role during some parts of the year than others. These results present voltinism as a complex trait resulting from plasticity acting at different levels of geographic specificity. Although much of the genetic variation enabling the observed local adaptation remains uncharacterized, the considerably variable circadian genes seen in these populations provide an intriguing target for future investigation.
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| 6. |
- Neethiraj, Ramprasad, 1989-
(författare)
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Advances in studying the role of genetic divergence and recombination in adaptation in non-model species
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the role of genetic divergence and recombination in adaptation is crucial to understanding the evolutionary potential of species since they can directly affect the levels of genetic variation present within populations or species. Genetic variation in the functional parts of the genome such as exons or regulatory regions is the raw material for evolution, because natural selection can only operate on phenotypic variation already present in the population. When natural selection acts on a phenotype, it usually results in reduction in the levels of genetic variation at the causal loci, and the surrounding linked loci, due to recombination dynamics (i.e. linkage); the degree to which natural selection influences the genetic differentiation in the linked regions depends on the local recombination rates.Studies investigating the role of genetic divergence and recombination are common in model species such as Drosophila melanogaster. Only recently have genomic tools allowed us to start investigating their role in shaping genetic variation in non-model species. This thesis adds to the growing research in that domain. In this thesis, I have asked a diverse set of questions to understand the role of genetic divergence and recombination in adaptation in non-model species, with a focus on Lepidoptera.First, how do we identify causal genetic variation causing adaptive phenotypes? This question is fundamental to evolutionary biology and addressing it requires a well-assembled genome, the generation of which is a cost, labor, and time intensive task. In paper I, I present a tool, MESPA, that stitches together exonic sequences in fragmented assemblies to produce high-quality gene models. These high-quality gene models can be used by researchers in the downstream analyses, providing genomic insights for a fraction of cost of a high quality genome. Second, what does the pattern of recombination rate look like in chromosomes that lack centromeres (i.e.holocentric chromosomes)? In paper II, I compare the recombination landscape and the patterns of nucleotide diversity in three Lepidotera with holocentric chromosomes, Pieris napi, Bombyx mandarina, and Bombyx mori, with a monocentric species. Our results show that on average these three Lepidoptera have high rates of recombination across the vast majority of their genome. Our results also suggest that given similar effective population sizes, these species are likely to harbor more genetic diversity compared to monocentric species, which has important evolutionary consequences for these species.Third, what is the potential for parallelism at the genetic level in convergent melanic phenotypes? In paper III, I investigated the genetic basis of the female-limited melanic phenotype in the green-veined white (Pieris napi) butterfly, and found a 20kb region, approximately 50kb from the gene cortex, associated with this trait. This gene has been implicated in melanic phenotypes in other Lepidoptera that diverged from Pieris approximately 100my, indicating very high predictability for this trait.Finally, what is the role of cis-regulatory variation in local adaptation? In paper IV, I analyzed the relationship between allele specific expression (ASE) and genetic divergence (FST) in the F1 hybrids of Pieris napi napi and Pieris napi adalwinda. I show that intersecting results from ASE with FST is a powerful approach to identify genes involved in local adaptation.
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| 7. |
- Weingartner, Elisabet, 1969-
(författare)
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Phylogenetic perspective on host plant use, colonization and speciation in butterflies
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we have studied speciation in three butterfly genera Polygonia (Nymphalidae, Nymphalini), Pararge (Nymphalidae, Satyrinae) and Celastrina (Lycaenidae: Polyommatinae). In the first paper a dated phylogeny, based on molecular data, of Polygonia was constructed. We found strong conflict between the nDNA and mtDNA datasets. Possibly this can be explained by ancestral and recent hybridizations between contemporary taxa. The results point to the importance in using different markers when we try to resolve evolution of taxa. In the second paper a sister group comparison was made in order to discover whether host plant range has had an effect on species diversity in Polygonia. Our result indicated higher diversification rates in clades which included species with larvae feeding on different, or additional, plants compared to the ”urticalean rosids” specialists. In the third paper our focus was on the colonization abilities in polyphagous butterflies. The haplotype structures of the mtDNA cytochromeoxidase I (COI) within the Nearctic species of Celastrina as well as within P. c-album and P. faunus were analysed in a network. We found little variation in Celastrina and P. c-album. This results imply that the genera have expanded recently and rapidly. There are indications of differentiation in COI in Celastrina and, possibly, host plant use is involved. However, in P. faunus we found structure among the haplotypes. We believe that several different haplotypes of this species have been preserved during glaciations in the Nearctic. In the fourth paper the evolution of the grassfeeding Pararge was analysed. The phylogeny was based on the mtDNA COI and the nDNA wingless (wgl) and times of divergences were calculated. We found a deep divergence between the European and Moroccan populations of P. aegeria which indicates the importance of the Mediterranean as a barrier for gene flow.
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| 8. |
- Andersson, Mathias H., 1976-
(författare)
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Man-made structures as habitat for marine faunal assemblages
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial reefs are structures placed in the sea to promote marine life. Although constructions such as oil-rigs, wind farms, bridges and pier pilings are built for other purposes, they could be regarded as artificial reefs as they add new surfaces in the oceans, susceptible to colonization by marine organism. One of the most common constructions in the oceans is cylindrical structures of different materials. Most research of artificial reefs has been conducted in tropical and temperate water and experience and conclusions cannot always be applied to colder waters. Man-made constructions are common in northern European seas, however, few studies are presented in the scientific literature on their impact on the marine ecosystem. The aim of this thesis was to study cylindrical structures of different scale and materials, in order to determine their effect on local fish, algae and sessile invertebrate assemblages. These structures were offshore wind turbines, and pillars of different materials (concrete and steel), situated at the Swedish east and west coast, respectively. They add vertical surfaces into the otherwise empty water column, increasing the probability for fish and invertebrate larvae as well as algae spores and propagules to encounter these high structures, compared to low profile natural or other artificial reefs. Fish species usually associated with rocky reefs and algae communities, i.e. the two spotted goby and the goldsinny-wrasse, showed an increase in abundance around the introduced cylindrical structures. Similar effect on fish species were found on both the Swedish east and west coast. The observed increase in fish densities seemed to be caused by added habitat since the pillars and wind turbines provide shelter from predators as well as increased food availability. The latter was either due to the fouling assemblage or change in water movement. The environment created by the introduced structures functions both as nursery and spawning areas since juveniles, adults and gravid fish were recorded in close association with the structures. The fouling community on the vertical surfaces did not resemble the natural assemblages and a difference in recruitment and succession on the pillars of different materials were observed. Further, dissimilar fouling assemblages were observed with other species dominating the assemblages on a fifty year old light-house foundation compared to the seven year old wind turbines, both located in the same area. The sessile filter feeding invertebrates located on the foundations have an advantage in food accessibility towards individuals at the seabed, as the organisms on the foundations are constantly susceptible to the water passing by. In addition, by adding offshore structures in areas previously lacking hard surfaces, non-indigenous species could find new available habitat or the foundations can function as stepping stones into new geographical regions.
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| 9. |
- Löwenborg Di Marino, Kristin, 1985-
(författare)
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Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The onset of agriculture about 12,000 years ago has had a major influence on the biodiversity of plants and animals. Unfortunately, the rapid changes in agricultural practices that has occurred in recent times has negatively affected many farmland species. One such species is the grass snake (Natrix natrix), which has been reported to decline in many parts of Europe, including Sweden. The grass snake is unique, not only in that it is the most northerly distributed oviparous reptile in the world, but also because of its habit of using anthropogenic heat sources such as manure heaps and composts as nesting-sites. Unfortunately changes in manure management and abandonment of farmlands have resulted in a decline and fragmentation of these environments. This may pose a threat for the northernmost populations of the grass snake, because natural nests in these areas may not provide sufficient heat for the eggs to hatch. The eggs and embryos of reptiles are highly sensitive to incubation temperatures, which can influence not only hatching success but also many phenotypic traits in the hatchlings. In this thesis I used a series of laboratory and field experiments to investigate the importance of anthropogenic heat sources for the reproductive ecology of cold-climate populations of grass snakes. More specifically, I aimed to investigate thermal regimes of nests and how they influence embryonic development and offspring traits associated with survival and fitness. The results showed that manure heaps and composts are significantly warmer than potential natural nests and that natural nests do not provide sufficient heat to sustain embryonic development. Further, manure heaps were warmer and more constant in temperature than composts, resulting in higher hatching success and earlier hatching in manure heaps. The higher thermal variability in composts increased the frequency of abnormalities that are likely to negatively affect survival and fitness. In conclusion, this thesis shows that the use of anthropogenic heat sources has enabled grass snakes to expand their range farther north than any other oviparous reptile and that the thermal dichotomy in the primary nesting environments used by grass snakes contribute to important life-history variation in this species. These findings have important implications for conservation of reptile populations in general and grass snakes in particular.
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| 10. |
- Söderlind, Lina, 1982-
(författare)
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Life-history consequenses of host plant choice in the comma butterfly
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is much evidence that herbivory is a key innovation for the tremendous success of insect. In this thesis I have investigated different aspects of host plant utilization and phenotypic plasticity using the polyphagous comma butterfly, Polygonia c-album. Even though external conditions affect a phenotypic plastic response, the outcome is often influenced by a genetic background which may differ among populations. In Paper I we suspected the genetic background to seasonal polymorphism to be X-linked. However, results from interspecific hybridization between two populations suggested that diapause response is instead inherited in a mainly autosomally additive fashion, with a possible influence of sexual antagonism on males. In Paper II we showed that female oviposition preference is not a plastic response influenced by larval experience, but has a genetic background coupled to host plant suitability. Further, there is a strong individual correlation between larval host plant acceptance and female host plant specificity (Paper III). We believe this to be a larval feed-back genetically linked to female host specificity: offspring to ‘choosy’ specialist mothers benefit by remaining on the original host while offspring to less discriminating generalist mothers should risk inspecting the surroundings, thus compensating for potential poor female choice. In the larval mid-gut, genes are differentially expressed depending on host plant diet (Paper IV). Therefore, we expected to find fitness consequences of host plant switch. However, although growth rate was affected in a few treatments, larvae were generally surprisingly good at adjusting to new diets (Paper V). To conclude, host plant choice in both female and larval life stage is connected to performance. Combined with increased understanding about the plastic response to diet intake and seasonal polymorphism we have gained further insights into the processes of local adaptations and speciation in the Lepidoptera.
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