| 1. |
- Reinikainen, Marko, et al.
(författare)
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Resurrected past-century Ceriodaphnia quadrangula highlight differences between pheno- and genotypic expressions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The hatching of cladoceran ephippia from a 15 cm long sediment core was investigated, and Ceriodaphnia quadrangula -clones were isolated from different sediment layers. Bosmina-microfossil data were also analyzed, and compared with the corresponding data from a Pb210-dated core, which allowed us to infer the age of the sediment-layers. Using changes in Bosmina-microfossil morphologies, we were furthermore able to infer the presence of different regimes of fish-predation. C. quadrangula was found to hatch in layers with an inferred age of approximately a century. Newly hatched individuals had smaller eye-size in sediment layers corresponding to high predation by young-of-the-year perch. Newly hatched individuals also generally had a marked neck-spine. In contrast, morphological characters of C. quadrangula -clones reared in the laboratory over several generations showed no variation in relation to predation regime, indicating the absence of fixed genotype-level changes. Furthermore, the laboratory-grown clones only rarely produced a neck-spine. The results suggest phenotypic variation in response to the regime under which ephippia were produced.
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| 2. |
- Rova, Emma, 1978-, et al.
(författare)
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An experimental study on the interaction between inbreeding and assortative mating in the process of speciation : Assortative mating and inbreeding
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In the process of speciation, assortative mating and its costs in terms of possible inbreeding depression play a central and sometimes critical role. Despite this fact, given the numerous models on assortative mating, and the rich theory and empirical data on inbreeding at hand, studies of the interaction between the two are essentially missing. This study experimentally explores the interaction of inbreeding and assortative mating in the process of speciation. We show that in small populations of the bean weevil, Callosobruchus maculatus, signs of inbreeding depression, such as reduced female fecundity, decreased juvenile hatching success, changed hatched offspring sex ratio, and extinction develop in relation to assortative mating. We also show that in these inbred populations, the mating system changes in terms of a reduced tendency to mate assortatively.
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| 3. |
- Moksnes, Per-Olav, et al.
(författare)
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Larval behavior and dispersal mechanisms in shore crab larvae : Local adaptations to different tidal environments?
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies indicate that local adaptations may occur in marine populations over relatively small geographic areas despite high dispersal potential if strong environmental gradients are present. Here we assess if local adaptations in larval behavior can develop in response to tidal gradients by studying the shore crab Carcinus maenas in the North Sea area using a combination of empirical and model studies. Specific aims of the study was to assess if shore crab larvae from different tidal environments have different swimming behaviors, and if these behaviors affect connectivity and recruitment success of the larvae. Field and laboratory studies demonstrated that newly hatched shore crab larvae from mesotidal Danish Wadden Sea displayed an inherited vertical migration rhythm with a circatidal periodicity, and that postlarvae swam in surface water almost exclusively during flood tides, suggesting that larvae use selective tidal stream transport to control the dispersal process. In contrast, shore crab larvae from microtidal Skagerrak displayed a nocturnal vertical migration behavior that switched to a diurnal behavior at the end of the larval phase, indicating an adaptation to avoid visual predators and to use wind-driven transport to reach shallow settlement areas. Results from a biophysical model showed that larval swimming behavior had a dominant role for the dispersal process and the recruitment success in the study area, and demonstrated that modeled tidal-migrating larvae in Wadden Sea had 2x higher recruitment success than larvae with a diel behavior. However, in microtidal Skagerrak no differences in recruitment success was found between the two larval behaviors. Lower fitness is suggested for tidal-migrating larvae in microtidal regions due to a predicted higher predation mortality. Consistent with recent population genetic studies, connectivity analyses indicated an oceanographic dispersal barrier in Eastern Wadden Sea that will restrict gene-flow between the two areas, and allow local adaptations in larval behavior.
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| 4. |
- Söderlind, Lina, 1982-, et al.
(författare)
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When mother does not know best : Contrasting host plant choice across life stages in individuals of the comma butterfly
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Since host plant choice is often crucial for the fitness of herbivorous insects we investigated if individual variation in such decisions is consistent throughout life. In the comma butterfly, Polygonia c-album, (Nymphalidae, Nymphalini) newly hatched larvae and adult females have been found to rank hosts plants similarly, suggesting that the host plant recognition mechanisms could be preserved through metamorphosis. We measured preference for Urtica dioica relative to Salix cinerea when the plants were encountered by the same individuals in the two different life stages, finding no relationship between the two measurements. This was however found when we instead measured acceptance of a suboptimal host: First instar larvae were placed on the suboptimal S. cinerea, and were scored as to whether they accepted this host or if they instead moved to feed on the generally more preferred host U. dioica. The same individuals were then tested once more as ovipositing females, in a cage setup arranged so that females would encounter the low-ranked hosts S. cinerea and Betula pubescens more often than the high-ranked host U. dioica.Individuals that chose to abandon S. cinerea as larvae differed in oviposition behaviour later in life from those that accepted this low-ranked host, but did so by laying a higher proportion eggs on the low-ranked hosts as adults. We interpret this initially unexpected result as a result of possible genetic correlation between female host-plant specificity and larval acceptance for the plant chosen by their mother: Offspring of ‘choosy’ specialist mothers have a strong tendency to remain on their original host, whereas less discriminating generalist mothers beget larvae with lower acceptance for their original plant when it is suboptimal. Ecologically, this presents a further explanation for how a generalist oviposition strategy can be sustained since larval mobility to some extent compensates for poor female choice.
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