The thesis deals with variation in age and size at maturation in Saduria entomon and Pontoporeia affinis along a depth gradient in the Gulf of Bothnia, Sweden. I have analysed at what sizes and ages animals should mature in relation to growth and mortality conditions. The thesis also deals with predator-prey interactions within and between the two species. The isopod Saduria entomon matured during winter at an age of three years at 5 m depth in the Norrby archipelago (63° 30'N, 19° 50'E). Males matured eariier and at larger sizes (27-48 mm) than females (23-36 mm). The offspring were released in early summer. The adult size increased with increasing depth. Outside the archipelago, at 125 m depth, the sexes reached a size of 84 and 54 mm respectively. No evidence for temporal restriction in the release of the young was found at the deep area. The species was shown to have a high capacity for cannibalism on small conspecifics, although the small ones have the potential to avoid aggregations of large conspecifics. The number of small conspecifics eaten was related both to the absolute and relative densities of the alternative prey Pontoporeia affinis. The cannibalistic behaviour have the potential to act as a stabilizing mechanism in the Saduria-Pontoporeia system. Fourhom sculpin (Myoxocephalus quadricornis) was the fish species of utmost importance as a predator on S.entomon, and it mainly preferred large specimens. The amphipod Pontoporeia affinis matured at an age of two years in the littoral zone and at a very deep (210 m) locality. Between these depths it mainly reached maturation at an age of three years. In some years in densely populated areas, they delayed reproduction another year and reproduced as four year old. The variation in age at maturation in P.affinis in relation to depth could be quantitatively predicted by maximizing fitness in the Euler-Lotka equation. The size variation at maturation in S.entomon could be qualitatively predicted by maximizing fitness in the Euler-Lotka equation. The general condition for a smaller size at maturity to be adaptive at high temperatures (i.e. shallow areas) is that mortality rate should increase faster than growth rate with increasing temperature. When mortality is higher in young stages than in older and larger ones the pattern is also predicted when growth increases faster than mortality. Small animals may prefer warmer habitats than large ones, because of the presence of a size dependent trade-off between temperature induced growth and mortality. More exactly, the optimum solution of the trade-off between growth and mortality in hazardous environments was suggested to approach maximization of the expression s(W+g)/W, where s is survival rate, W is body weight, and g is growth rate. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1990, härtill 6 uppsatser</p> / digitalisering@umu

[Truncated abstract] Early psychosocial stress is conjectured to place individuals on a developmental trajectory leading to earlier pubertal maturation, earlier initiation of sexual activity and earlier reproduction than those with less early psychosocial stress. This may have an adaptive function to minimise the chances of lineage extinction, which is more likely in environments of high risk and uncertainty. Previous studies have examined the relationship between early psychosocial stress and life history stages (e.g., age at puberty, age at first sex and age at first birth). However, these studies are limited in that they either examined only a few early psychosocial stressors, examined psychosocial stress relatively late in individuals' lives and/or were restricted to women. Thus, the first aim of the present thesis was to examine these findings in both genders using a measure of early psychosocial stress comprised of 24 categories of retrospectively assessed stressors (e.g., sexual abuse, physical abuse, parental divorce, rated quality of family life) during the first 7 years of life. It was hypothesised that individuals with high, as opposed to low, levels of early psychosocial stress would pass through life history stages earlier. The second aim was to examine how early psychosocial stress affects characteristics associated with life history traits, such as individuals? length, number and type of heterosexual relationships, number of sex partners, adult attachment styles, number of pregnancy terminations, and attitudes and behaviours towards contraceptive use. High levels of early psychosocial stress were predicted to be associated with characteristics reflecting a quantitative, as opposed to a qualitative, reproductive approach (e.g., more sex partners, more short-term relationships, insecure attachment styles). The third aim was to examine how early psychosocial stress is related to mate choice because numerous studies have identified what traits individuals' desire in a mate but not whether early psychosocial stress affects these choices. ... Early psychosocial stress generally had no effects on age at first sex, age at first birth, the number of pregnancy terminations, and mate choices. On the other hand, individuals with high, as opposed to low, levels of early psychosocial stress were more likely to be insecurely attached, had more short-term sexual relationships (men only), had more extra-pair copulations, were more likely to be divorced/separated, had a greater lifetime number of sex partners (men only), and had lower self-rated frequencies of contraception use. Overall, some of these findings are consistent with life history theory, which suggests that individuals with high levels of early psychosocial stress (i.e., those living in environments of high risk and uncertainty) should reach biological maturation earlier, engage in behaviours that facilitate earlier and more frequent reproduction to minimise the chances of lineage extinction. Implications for public health, limitations of the present study and future directions are also discussed.

Rising archipelagos provide unique settings for the study of the temporal and spatial dynamics of their biota. This offers the possibility to study the ecology and genetics of early successional processes; both between islands that differ in age and within islands when already established organisms have to keep pace with the changing environment. I have worked in the Skeppsvik Archipelago housing about 100 islands that due to land uplift vary in age, thus representing various stages of primary succession. I have utilized a naturally created metapopulation of Silene dioica, which in this archipelago is a dominant plant of the deciduous border, offering the possibility to study subpopulations on islands of different ages and in different phases of primary succession. Many plant species exist as metapopulations, which consists of many local populations which may differ in size and degree of connectivity. Metapopulations are further characterized by recurrent colorizations and extinctions of local populations, meaning that a species continually must disperse and relocate to allow for persistence in this system. For a dioecious plant species, gene flow is in the shape of seeds and pollen and to allow for the persistence of populations, it is necessary that levels of seed dispersal and pollen gene flow are enough to ensure both colonisation, establishment and subsequent population growth. Levels of seed dispersal and pollen gene flow is in turn influenced by how the two sexes partition resources between reproduction, growth and survival. In paper I, I combined a field survey, a common garden experiment and a nine-year demographic study to assess the demographic consequences of sex-specific resource allocation and to investigate if differential costs of reproduction may be a driver in the evolution of sexual dimorphism in dioecious Silene dioica. Significant somatic intersexual dimorphism was found with females being the larger sex, both in terms of above – and belowground biomass. Furthermore, the reproductive effort of females exceeds that of males across a growing season which largely confirms what has been observed earlier in dioecious, herbaceous plant species. According to the cost of reproduction hypothesis, high reproductive investment should result in trade-offs with somatic and/or life-history traits. Somatic trade-offs were not observed, and instead I found strong, positive associations between reproductive investment and vegetative growth in both males and females. Compensation mechanisms were found in both sexes although females are generally more efficient at compensating their reproductive costs. At the end of a flowering season, after having paid the current costs of reproduction, females are better than males at provisioning perennial roots and rosettes potentially influencing the ability to set future flower buds and winter survival. Trade-offs were found between current and future reproduction and survival, but this is condition dependent and compensation through frequency of flowering plays an important role. The cost of reproduction hypothesis appears to play some role in driving the somatic and demographic sexual dimorphisms observed in this system but sexual selection acting on males will be a fruitful avenue for future research. In paper II, I investigated the population genetic consequences of metapopulation dynamics in Silene dioica. The occurrence of islands in different phases of primary succession together with successional gradients across islands, makes it possible to investigate the genetic dynamics occurring in an age-structured metapopulation across several hierarchical levels. Genetic diversity and differentiation were estimated in eight young, recently colonised populations and in ten populations of an intermediate successional stage. Young populations were less genetically diverse compared to older populations, indicating that bottlenecks, created by small founding groups derived from a limited number of source populations, reduce the genetic diversity within newly founded populations. The observation of strong genetic structure both between islands and between patches with islands, indicates that gene flow is restricted across several spatial levels in this system. However, the lack of statistically significant differences in genetic differentiation between young and intermediate populations, indicates that levels of gene flow may not be high enough to reduce the genetic differentiation that arise from the initial founder event. The patterns of sexual dimorphism and the roles of males and females in Silene dioica have evolved to allow persistence in an ecological and population context of this species. The nature of this habitat, where islands rise up from the sea creating new environments for colonisation while at the same time, autogenic primary succession processes eventually leads to extinction, means that S. dioica continuously must relocate within successional phases for its persistence. The obvious success of this dioecious plant is apparent as it is one of the few dominant species in the deciduous border. This suggests that levels of seed dispersal and gene flow are sufficient enough to allow for establishment and persistence of island populations and that the sexual dimorphisms that have evolved in this metapopulation system act to increase levels of gene flow. The "live hard – die young" strategy, with extensive flowering bouts, which we find in the males may have evolved as a way of maintaining sufficient levels of genetic diversity in the metapopulation but will only be a possible strategy if there are continuous opportunities for re-establishments. Thus, the continuous land uplift that is occurring in the northern part of the Gulf of Bothnia may very well be a prerequisite for the long-term persistence of this dioecious, perennial plant species. / Landhöjningsprocesser i skärgårdsmiljöer skapar nya habitat som gör det möjligt att studera naturliga populationer i ett rumsligt och tidsmässigt sammanhang. Detta möjliggör studier av ekologi och genetik i tidiga successionsprocesser, både mellan öar som skiljer sig åt åldersmässigt och inom öar, där redan etablerade organismer måste anpassa sig till en föränderlig miljö. Jag har utfört studier i Skeppsviks skärgård som rymmer cirka 100 öar. På grund av landhöjningen så varierar dessa öar i ålder och de representerar således olika stadier i primärsuccession. Jag har använt mig av en naturlig Silene dioica metapopulation lokaliserad i Skeppsviks skärgård. Många växtarter existerar i metapopulationer, vilket består av ett antal lokala populationer som kan skilja sig åt i storlek och grad av anknytning. Metapopulationer kännetecknas även av återkommande koloniseringar och utrotningar av lokala populationer, vilket innebär att en art kontinuerligt måste sprida sig för att garantera sin fortlevnad i detta system. Genflöde inom dioika växtarter är i form av pollen och frön, och för att populationer skall kunna överleva så är det nödvändigt att nivåerna av fröspridning och pollen-genflöde är tillräckliga för att säkerhetsställa både kolonisering, etablering och efterföljande populationstillväxt. Nivåer av fröspridning och pollen-genflöde påverkas i sin tur av hur de två könen partitionerar resurser mellan reproduktion, tillväxt och överlevnad. I den första studien har jag kombinerat en fältundersökning, ett frilandsexperiment och en nioårig demografisk studie för att undersöka de demografiska konsekvenserna av könsspecifik resursallokering och för att utreda om könsspecifika skillnader i reproduktiv kostnad kan vara en drivkraft för evolutionen av sexuell dimorfism hos den dioika växten Silene dioica. Jag upptäckte signifikant somatisk intersexuell dimorfism där honor hade betydligt mer ovanjordisk och underjordisk biomassa jämfört med hanar. Över en växtsäsong så investerar honorna mer resurser i reproduktion, vilket i stor utsträckning bekräftar vad som tidigare har observerats i örtartade, dioika växter. Enligt hypotesen för reproduktiv kostnad så bör en hög investering i reproduktion leda till trade-offs med somatiska egenskaper, t.ex. tillväxt. Jag observerade inga somatiska trade-offs och istället fann jag positiva associationer mellan reproduktion och tillväxt hos både honor och hanar. Båda könen verkar ha utvecklat kompensationsmekanismer, även om honorna generellt är mer effektiva i hur de kompenserar för sina reproduktiva kostnader. Vid slutet av en växtsäsong, efter att ha betalat för de nuvarande reproduktiva investeringarna, så är honor bättre än hanar på att allokera resurser till fleråriga strukturer, såsom bladrosetter och rötter. Detta kan potentiellt påverka hur de anlägger sina knoppanlag för nästkommande år och hur väl de överlever vintern. Trade-offs hittades mellan nuvarande reproduktion och framtida reproduktionsmöjligheter och överlevnad men detta var habitat-specifikt och kompensation med hjälp av hur ofta en växt blommar under sin livstid spelar en viktig roll. Hypotesen för reproduktiv kostnad verkar vara en del av förklaringen till den somatiska och demografiska könsdimorfism som observerats i detta system men sexuell selektion, som verkar på hanar, kan vara ett möjligt område för framtida studier. I den andra studien undersökte jag populationsgenetiska konsekvenser av metapopulationsdynamik i Silene dioica. Förekomsten av öar i olika faser av primär succession tillsammans med olika grader av succession inom öar gör det möjligt att undersöka den genetiska dynamiken som uppträder i en åldersstrukturerad metapopulation över flera hierarkiska nivåer. Genetisk mångfald och differentiering uppskattades i åtta unga, nyligen koloniserade populationer och i tio populationer av ett intermediärt successionsstadium. Unga populationer hade lägre genetisk diversitet jämfört med äldre populationer, vilket indikerar att genetiska flaskhalsar, skapade av fåtal antal koloniserande individer, s.k. founders, som härrör från ett begränsat antal källpopulationer, minskar den genetiska diversiteten inom nybildade populationer. Observationen av stark genetisk strukturering, mellan och inom öar, indikerar att genflödet är begränsat över flera rumsliga nivåer i detta system. Bristen på statistiskt signifikanta skillnader i genetisk differentiering mellan unga och intermediära populationer indikerar emellertid att nivåer av genflöde kanske inte är tillräckligt höga för att minska den genetiska differentieringen som uppstår från den ursprungliga founder-händelsen. Mönstren av sexuell dimorfism och hanarnas och honornas roll har utvecklats för att möjliggöra fortlevnad i ett ekologisk och populationsmässigt sammanhang hos Silene dioica. I denna livsmiljö, där öar stiger upp ur havet och skapar nya miljöer för kolonisering samtidigt som autogena primära successionsprocesser leder till utrotning, måste S. dioica kontinuerligt sprida sig mellan olika successionsfaser för att överleva. Den uppenbara framgången för den här dioika växten är uppenbar eftersom den är en av de få dominerande arterna i lövkanten. Detta tyder på att nivåer av fröspridning och genflöde är tillräckliga för att möjliggöra etablering och beständighet av ö-populationer och att de sexuella dimorfismer som har utvecklats i detta metapopulationssystem verkar för att öka nivåerna av genflöde. "Lev hårt – dö ung" -strategin med omfattande blomningar som vi finner hos hanarna kan ha utvecklats som ett sätt att upprätthålla tillräckliga nivåer av genetisk diversitet i metapopulationen men den kommer endast att vara en möjlig strategi om det finns kontinuerliga möjligheter för re-etableringar. Således kan den kontinuerliga landupphöjningen som förekommer i norra delen av Bottniska viken mycket väl vara en förutsättning för den långsiktiga beständigheten av denna dioika, fleråriga växtart. / <p>Felaktigt angivet "Dissertation for PhD" i kolofon.</p>

Les coûts de la reproduction sont un compromis biologique (trade-off ) fondamental en théorie des histoires de vie. Par ce compromis, le succès, pour un organisme, d’un évènement de reproduction réduit sa survie et sa fertilité futures. Pour les écologues, ce trade-off correspond principalement à un compromis physiologique résultant d’un processus d’allocation ayant lieu à chaque instant et au niveau de chaque individu. Au contraire, en démographie évolutive, il est envisagé comme un trade-off génétique découlant du polymorphisme génotypique d’un gène pléiotropique agissant de manière antagoniste sur la reproduction aux jeunes âges et la fitness aux âges élevés. L’étude des mécanismes des coûts de la reproduction, physiologiques et génétiques, de leur possible cohabitation et de leur effets relatifs, croisés et conjoints est le sujet de cette thèse. Un examen attentif de la définition originelle des coûts de la reproduction par Williams (1966), nous permet de construire un modèle théorique des coûts physiologiques intégrant leurs aspects mécaniques et évolutifs. Cette construction nous permet d’induire l’intensité des coûts de la reproduction selon la position d’un organisme sur trois continuums d’histoire de vie: "slow-fast", "income-capital breeders" et "quantity-quality".A partir de la décomposition, par Stearns (1989b), de l’architecture des contraintes d’histoire de vie en trois parties – le niveau génotypique, la structure intermédiaire et le niveau phénotypique – nous étendons notre modèle conceptuel pour y intégrer à la fois des trade-offs physiologiques et génétiques. Cela nous permet d’inférer les effets de l’environnement, de sa variance et de la stochasticité individuelle sur la détectabilité de chaque famille de coûts. La différence entre coûts physiologiques et génétiques se retrouve également dans leur modélisation mathématique. Il est donc nécessaire de développer de nouveaux modèles permettant d’incorporer coûts physiologiques et génétiques. Nous proposons ensuite une méthode vectorielle de construction d’un tel type de modèle, que nous appelons Matrice de Projection de Population Multitrait (MPPM). Ce dernier peut implémenter chaque type de coût en l’intégrant dans la matrice en tant que trait. Nous étendons ensuite aux MPPMs les techniques d’analyse de sensibilité, standards en démographie évolutive, des modèles à un trait aux MPPMs. Surtout, nous décrivons un nouvel outil d’analyse, pertinent en théorie des histoires de vie et en démographie évolutive: la Trait Level Analysis. Elle consiste à comparer des modèles qui partagent les mêmes propriétés asymptotiques. Ceci est rendu possible par le repliement d’une MPPM selon certains traits, une opération qui réduit le nombre de traits du modèle en moyennant ses transitions selon les abondances ergodiques relatives. Ainsi, la Trait Level Analysis permet de mesurer l’importance évolutive des coûts de la reproduction en comparant des modèles implémentant ces coûts, avec des versions ergodiquement équivalentes de ces modèles mais repliées selon les traits supportant les compromis. Nous utilisons des méthodes, classiques et nouvelles, de calculs des moments de la fitness – gradient de sélection, variance du succès reproducteur, variance environnementale – que nous appliquons aux modèles avec coûts et sans coûts afin de mesurer leurs effets démographiques et évolutifs. Nous présentons les effets conjoints des coûts physiologiques et génétiques sur la distribution par âge des taux vitaux d’une population. Nous montrons également comment les coûts physiologiques influencent les deux composants de la sélection efficace, en aplatissant le gradient de sélection d’un côté et en accroissant la taille efficace de la population de l’autre. Enfin, nous démontrons comment l’effet tampon des coûts sur les variances environnementales et démographiques améliore la résilience d’une population soumise aux coûts physiologiques de la reproduction / Costs of reproduction are pervasive in life history theory. Through this constraint, the reproductive effort of an organism at a given time negatively affects its later survival and fertility. For life historians, they correspond mostly to a physiological trade-off that stems from an allocative process, occurring at each time-step, at the level of the individual. For evolutionary demographers, they are essentially about genetic trade-offs, arising from a genetic variance in a pleiotropic gene acting antagonistically on early-age and late-age fitness components. The study, from an evolutionary demographic standpoint, of these mechanisms and of the relative, cross and joint effects of physiological and genetic costs, is the aim of this thesis. The close examination of Williams (1966)’s original definition of the physiological costs of reproduction led us to produce a theoretical design of their apparatus that accounts for both their mechanistic and evolutionary mechanisms. This design allowed us to make predictions with regards to the strength of costs of reproduction for various positions of organisms on three life-history spectra: slow-fast, income-capital breeders and quality-quantity. From Stearns (1989b)’s tryptic architecture of life history trade-offs –that divides their structure into the genotypic level, the intermediate structure and the phenotypic level – we devised a general framework, which models the possible cohabitation of both physiological and genetic costs. From this, we inferred differing detectability patterns of both types of costs according to the environmental conditions, their variance and individual stochasticity. We could also establish that both costs buffer environmental variations, but with varying time windows of effect. Their dissimilarity emerges also from the differences between mathematical projection models specific to each cost. A new family of evolutionary models is therefore required to implement both physiological and genetic trade-offs. We then describe the vector-based construction method for such a model which we call Multitrait Population Projection Matrix (MPPM) and which allows incorporating both types of costs by embedding them as traits into the matrix. We extend the classical sensitivity analysis techniques of evolutionary demography to MPPMs. Most importantly, we present a new analysis tool for both life history and evolutionary demography: the Trait Level Analysis. It consists in comparing pairs of models that share the same asymptotic properties. Such ergodic equivalent matrices are produced by folding, an operation that consists in reducing the number of traits of a multi-trait model, by averaging transitions for the traits folded upon, whilst still preserving the asymptotic flows. The Trait Level Analysis therefore allows, for example, to measure the evolutionary importance of costs of reproduction by comparing models incorporating them with folded versions of these models from which the costs are absent. Using classical and new methods to compute fitness moments – selection gradient, variance in reproductive success, environmental variance - in models with and without the costs, we can show their effects on various demographic and evolutionary measures. We reveal, in this way, the combined effects of genetic and physiological costs on the vital rates of an age-structured population. We also demonstrate how physiological costs affect both components of effective selection, as they flatten the slope of selection gradients and increase the effective size of a population. Finally, we show how their buffering of environmental and demographic variance confer greater resilience to populations experiencing physiological costs of reproduction