La dispersion est définie comme le mouvement d'un individu entre le site de naissance et le premier site de reproduction ou entre deux sites de reproduction. La dispersion se traduit par des échanges d'individus et des flux de gènes entre les populations et est donc reconnue comme un trait d'histoire de vie clé de part son rôle déterminant sur de nombreux processus écologiques et évolutifs comme la dynamique ou la génétique des population, la répartition spatiale des espèces ou encore la capacité des espèces à faire face aux changements brutaux induits par les activités humaines. Pourtant les conséquences de la dispersion en terme de valeur sélective individuelle restent mal connues malgré leur importance dans l'évolution de la dispersion. Le but de cette thèse est d'identifier plus précisément les conséquences de la dispersion en terme de valeur sélective individuelle en utilisant à la fois des approches corrélative et expérimentale dans une population sauvage de passereaux migrateurs, le gobe mouche à collier (Ficedula albicollis). Grâce à des données à long terme comprenant plus de 20 ans de suivi, des différences entre les individus dispersants et philopatriques ont pu être mises en évidence à la fois à l'échelle de la vie des individus et à l'échelle annuelle, celle de l'événement de reproduction. Les résultats mettent en évidence des effets de la dispersion dépendant à la fois des conditions et du phénotype des individus et soulignent donc le fait que la balance entre les coûts et les bénéfices est le résultat d'interactions subtiles entre l'environnement et les caractéristiques de l'individu. D'autre part, l'expérience de dispersion forcée a permis de démontrer clairement l'existence de coûts liés à l'établissement dans un environnement non familier que seuls certains individus sont capables de surmonter. Enfin, l'absence de différence dans les décisions majeures de reproduction une fois les individus établis, suggère que la dispersion doit majoritairement être adaptative, une fois les coûts de l'installation surmontés / Dispersal is commonly defined as the movement of an individual from its natal or previous breeding site to a new breeding site. Because dispersal involves movements of individuals and genes among populations, it is widely recognized as a key life history trait with strong effects on many ecological and evolutionary processes, such as population dynamics and genetics but also species spatial distribution or response to brutal environmental variations induced by human activities. Yet, the consequences of dispersal in terms of individual fitness remain poorly understood despite their crucial importance in the understanding of the evolution of dispersal. The aim of this PhD is to get better insights in the fitness consequences of dispersal using both correlative and experimental approaches at different scales, i.e. annual and lifetime scales, in a wild patchy population of migratory passerine bird, the collared flycatcher (Ficedula albicollis). Using a long term data set encompasses more than 20 years of data, differences between dispersing and philopatric individuals were showed both at a lifetime and annual scale. The results highlighted strong phenotypic- and condition-dependent effects of dispersal and underline that the balance between the costs and benefits of dispersal is likely to be the result of subtle interactions between environmental factors and individuals’ phenotype. Moreover, the experiment of forced dispersal demonstrated that dispersal might entail costs linked with settlement in a new habitat, which only some individuals may overcome. Nevertheless, the absence of difference in major fitness related decisions after settlement suggests that dispersal is mostly adaptive for individuals overcome such costs

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The principle of competitive exclusion holds that the strongest competitor for a single resource can exclude other species. Yet in many systems, more similar species appear to stably coexist than the small number of limiting resources. Understanding how and when similar species can stably coexist has taken on new urgency in managing biological invasions and their ecological impacts. Recent theoretical advances emphasize the importance of predators in determining coexistence. The effects of predators, however, can be mediated by behavioral changes induced in their prey as well as by their lethality. In this dissertation, I ask how considering multiple trophic levels changes our understanding of how a grass invasion (Pennisetum ciliare) affects species diversity and dynamics in southeastern Arizona. In considering interactions with plant consumers, and with the predators of those consumers, this research reveals more general ecological processes that determine species diversity across biological communities. I first present evidence from a grass removal experiment in the field that shows increased emergence and short-term survival of native perennial plants without grass. This is consistent with Pennisetum ciliare causing the observed concurrent decline in native plant abundance following invasion. I then present results from greenhouse and field studies consistent with that suppression of native plants being driven primarily through resource competition rather than increased rodent granivory. Granivorous rodents do not solely function as consumers, however, because they cache their harvested seeds in shallow scatter-hoards, from which seeds can germinate. Rodents thus act also as seed dispersers in a context-dependent mutualism. The primary granivores in areas invaded by Pennisetum ciliare are pocket mice (genus Chaetodipus), which have a well-studied tendency to concentrate their activity under plant cover to avoid predation by owls. Because the dense canopy of the grass may provide safer refuge, I hypothesized the pocket mice may be directly dispersing native seeds closer to the base of the invasive grass. Such a behavior could increase the competitive effect of the grass on native plant species, further driving the impacts of the invasion. By offering experimental seeds dusted in fluorescent powder and tracking where the seeds were cached, I show that rodents do preferentially cache experimental seeds under the grass. This dispersal interaction may be more general to plant interactions with seed-caching rodents across semi-arid regions that are experiencing plant invasions. Finally, I ask how the predator avoidance behavior exhibited by these rodents affects their ability to coexist with one another. Not only could their diversity affect that of the plant community, but the effects of plant invasions can cascade through other trophic levels. Theoretical understanding of how similar predator avoidance strategy alters coexistence had not yet been developed, however. Instead of a field study, therefore, I modified a general consumer-resource model with three trophic levels to ask whether avoidance behavior by the middle trophic level alters the ability of those species to coexist. I found that more effective avoidance behavior, or greater safety for less cost, increased the importance of resource partitioning in determining overall niche overlap. Lowering niche overlap between two species promotes their coexistence in the sense that their average fitness can be more different and still permit coexistence. These results provide novel understanding of behavioral modifications to population dynamics in multi-trophic coexistence theory applicable to this invasion and more broadly.

<p>In chimpanzees, most females disperse from the community in which they were born to reproduce in a new community, thereby eliminating the risk of inbreeding with close kin. However, across sites, some females breed in their natal community, raising questions about the flexibility of dispersal, the costs and benefits of different strategies and the mitigation of costs associated with dispersal and integration. In this dissertation I address these questions by combining long-term behavioral data and recent field observations on maturing and young adult females in Gombe National Park with an experimental manipulation of relationship formation in captive apes in the Congo.</p><p>To assess the risk of inbreeding for females who do and do not disperse, 129 chimpanzees were genotyped and relatedness between each dyad was calculated. Natal females were more closely related to adult community males than were immigrant females. By examining the parentage of 58 surviving offspring, I found that natal females were not more related to the sires of their offspring than were immigrant females, despite three instances of close inbreeding. The sires of all offspring were less related to the mothers than non-sires regardless of the mother’s residence status. These results suggest that chimpanzees are capable of detecting relatedness and that, even when remaining natal, females can largely avoid, though not eliminate, inbreeding.</p><p>Next, I examined whether dispersal was associated with energetic, social, physiological and/or reproductive costs by comparing immigrant (n=10) and natal (n=9) females of similar age using 2358 hours of observational data. Natal and immigrant females did not differ in any energetic metric. Immigrant females received aggression from resident females more frequently than natal females. Immigrants spent less time in social grooming and more time self-grooming than natal females. Immigrant females primarily associated with resident males, had more social partners and lacked close social allies. There was no difference in levels of fecal glucocorticoid metabolites in immigrant and natal females. Immigrant females gave birth 2.5 years later than natal females, though the survival of their first offspring did not differ. These results indicate that immigrant females in Gombe National Park do not face energetic deficits upon transfer, but they do enter a hostile social environment and have a delayed first birth. </p><p>Next, I examined whether chimpanzees use condition- and phenotype-dependent cues in making dispersal decisions. I examined the effect of social and environmental conditions present at the time females of known age matured (n=25) on the females’ dispersal decisions. Females were more likely to disperse if they had more male maternal relatives and thus, a high risk of inbreeding. Females with a high ranking mother and multiple maternal female kin tended to disperse less frequently, suggesting that a strong female kin network provides benefits to the maturing daughter. Females were also somewhat less likely to disperse when fewer unrelated males were present in the group. Habitat quality and intrasexual competition did not affect dispersal decisions. Using a larger sample of 62 females observed as adults in Gombe, I also detected an effect of phenotypic differences in personality on the female’s dispersal decisions; extraverted, agreeable and open females were less likely to disperse. </p><p>Natural observations show that apes use grooming and play as social currency, but no experimental manipulations have been carried out to measure the effects of these behaviors on relationship formation, an essential component of integration. Thirty chimpanzees and 25 bonobos were given a choice between an unfamiliar human who had recently groomed or played with them over one who did not. Both species showed a preference for the human that had interacted with them, though the effect was driven by males. These results support the idea that grooming and play act as social currency in great apes that can rapidly shape social relationships between unfamiliar individuals. Further investigation is needed to elucidate the use of social currency in female apes.</p><p>I conclude that dispersal in female chimpanzees is flexible and the balance of costs and benefits varies for each individual. Females likely take into account social cues present at maturity and their own phenotype in choosing a settlement path and are especially sensitive to the presence of maternal male kin. The primary cost associated with philopatry is inbreeding risk and the primary cost associated with dispersal is delay in the age at first birth, presumably resulting from intense social competition. Finally, apes may strategically make use of affiliative behavior in pursuing particular relationships, something that should be useful in the integration process.</p> / Dissertation

Increasing habitat fragmentation and rapid global warming is changing the conditions for species populations and ecological communities around the world. This presents challenges for the maintenance of biodiversity and a dominant paradigm for conservation in fragmented habitats is given by island biogeography and metapopulation (or metacommunity) ecology. In this thesis I approach key concepts (area, connectivity and community assembly) in island biogeography and metacommunity ecology within the context of a dynamic land uplift archipelago. The presented work consists of two interwoven themes: (i) A methodological theme in which statistical approaches are developed to deal with the complexities of multispecies dynamic systems, and (ii) an applied theme dealing with community assembly and island biogeography of bryophytes on young land uplift islands. To describe island connectivity for entire species assemblages, an approach using functional principal component analysis (fPCA) on patch connectivity functions (the connectivity of an island as a continuous function of a variable representing the spatial scale of species dispersal capacities) was developed. In addition, a new statistical method, functional co-inertia analysis (fCoIA), for analyzing co-variation between multivariate species data and continuous functions was developed and applied to the relation between bryophyte species incidences and the island age/area-dynamics. Primarily asexual bryophyte species are dispersal limited and presence probabilities are related to island connectivity. No such patterns were found for species, at least occasionally, producing spores. Our results suggest that bryophyte dispersal is regulated by the contribution of spores to a regional spore rain and that bryophyte species with low spore output at the landscape level may be extra vulnerable under habitat fragmentation and loss. Having specialized asexual propagules increases the presence probabilities on islands, partly compensating for the dispersal limitation in asexual species. This suggests a trade-off between dispersal and establishment capacity, but also points to the importance of local dispersal for maintaining populations under the succession driven spatial turnover of microsites on the islands. Bryophyte colonization is strongly limited by habitat availability when a given habitats is rare, but there seems to exist a threshold over which other processes (e.g. dispersal limitation) become more important. Species with more vagile life history strategies appear to be stronger affected by the area of available habitats than many perennial species

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: It is known that many hyphomycetous fungi are dispersed by wind, water and insects. However, very little is known about how these fungi may differ from each other regarding their ability to be disseminated by different environmental vectors. Consequently, to obtain an indication of the primary means of spore dispersal employed by representatives of the genera Acremonium, Aspergillus and Penicillium, isolated from soil and indoor environments, we monitored spore liberation of cultures representing these genera in an airflow cell. The experimental data obtained, of plate counts conducted of the air at the outlet of the airflow cell, were subjected to an appropriate analysis of variance (ANOVA), using SAS statistical software. Intraspecific differences occurred regarding aerial spore release. Under humid conditions, however, Penicillium species were more successful in releasing their spores than Aspergillus and the Acremonium strain. Under desiccated conditions the Aspergillus took longer to release their spores than representatives of Acremonium and Penicillium. The taxa that were investigated did not differ from each other regarding the release of spores in physiological salt solution (PSS). Although not proven, indications are that water may act as an important dispersion agent for these fungi, because washing of cultures with PSS resulted in all cases in an immediate massive release of colony forming units. Subsequently, using standard plate count techniques, conidial adhesion of the fungi mentioned above to synthetic membranes, leaf cuttings and insect exoskeletons differing in hydrophobicity and electrostatic charge were investigated. We found that the different genera showed different adhesion profiles for the series of test surfaces, indicating differences in physico-chemical characteristics of the fungal spore surfaces. In general, the Penicillium strains showed a greater ability to adhere to the test surfaces, than the aspergilli, while the representative of Acremonium showed the least adherence. No significant difference in the percentage spore adhesion was found between hydrophobic and hydrophilic materials. Furthermore, evidence was uncovered supporting the contention that, under dry conditions, electrostatic surface charges play a role in the adherence of fungal spores to surfaces, because adherence was positively correlated (Correlation coefficient = 0.70898, p = 0.001) to positive electrostatic charges on the lamellar surfaces. In the next part of the study, standard plate count methods were used to determine the relative adhesion of the above mentioned hyphomycetous fungi, as well as a polyphyletic group of yeasts, to the test surfaces submerged in 10 mM sodium phosphate buffer (pH 7.0). As was found with the experiments with the dry surfaces, both intraspecific and intergenus differences were uncovered. Overall, the fungi adhered better to hydrophilic surfaces than to hydrophobic surfaces. This indicated that the fungal surfaces were covered with relatively hydrophilic compounds such as carbohydrates. Subsequently, it was demonstrated that all the fungi adhered to plasma membrane glycoprotein coated polystyrene and the presence of fungal carbohydrates on the surfaces of the fungal propagules was confirmed using epi-fluorescence microscopy. Differences in the strategy of the fungal genera to release their airborne spores, as well as differences in their adhesion profiles for the series of test materials, may be indicative of a unique environmental niche for each genus. In future, this phenomenon should be investigated further. / AFRIKAANSE OPSOMMING: Hifomisete fungi is daarvoor bekend om te versprei deur middel van wind, water, en insek vektore. Maar nietemin, daar is bykans geen kennis m.b.t. hoe hierdie fungi van mekaar verskil t.o.v. hul vermoë om versprei te word deur omgewings vektore nie. Gevolglik was spoorvrystelling van kulture, verteenwoordigend van die genera Acremonium, Aspergillus en Penicillium gemoniteer om ‘n aanduiding te kry van primêre wyse van spoorverspreiding waardeur verteenwoordigers van die onderskeie genera ingespan word. Eksperimentele data ingewin, vanaf plaat tellings wat uitgevoer was op lug afkomstig vanuit die uitlaat-klep van die lugvloei kapsule, was onderwerp aan ‘n toepaslike analise van afwyking (ANOVA), deur gebruik te maak van ‘n SAS statistiese pakket. Intraspesie verskille is waargeneem t.o.v. lug spoorvrystelling. Desnieteenstaande was Penicillium meer suksesvol onder vogtige kondisies t.o.v. spoorvrystelling in vergelyking met Aspergillus en die Acremonium stam. Onder droë kondisies het verteenwoordigers van Aspergillus langer geneem om hul spore vry te stel as verteenwoordigers van onderskeidelik, Penicillium en Acremonium. Geen verskille was waargeneem m.b.t. spoorvrystelling in fisiologiese soutoplossing (FSO) tussen die verskillende filogenetiese stamme nie. Alhoewel dit nie bewys is nie, wil dit voorkom asof water as belangrike verspreidingsagent van die betrokke fungi dien, aangesien die spoel van kulture met FSO tot ‘n oombliklike enorme vrystelling van kolonie-vormende eenhede gelei het. Gevolglik, deur gebruik te maak van standaard plaattellings tegnieke, was spoor aanhegting van bogenoemde fungi aan sintetiese membrane, blaar snitte en insek eksoskelette wat verskil in terme van hidrofobisiteit en elektriese lading, ondersoek. Daar was gevind dat die aanhegtingsprofiele m.b.t. hierdie reeks toetsoppervlaktes van die verskillende genera verskil, wat op sigself ‘n aanduiding was van verskille in fisieschemiese eienskappe van die swamspoor oppervlaktes. Penicillium stamme het ‘n hoër aanhegtings vermoë aan die toetsoppervlaktes getoon as die aspergilli, terwyl die verteenwoordiger van Acremonium die laagste aanhegting getoon het. Geen betekenisvolle verskille i.t.v. persentasie spoor aanhegting was gevind tussen hidrofobiese en hidrofiliese oppervlakte nie. Daarbenewens was die argument dat spoorvrystelling onder droë kondisies beïnvloed word deur elektrostatiese oppervlak ladings, bevestig deur ons bevindinge, want aanhegting het positief gekoreleer (Korrelasie koëffisient = 0.70898, p = 0.001) met positiewe ladings op die oppervlaktes. ‘n Standaard plaattellingstegniek was aangewend in die volgende fasset van die studie om die relatiewe aanhegting van bogenoemde hifomisete fungi, sowel as ‘n polifilitiese groep giste aan die toetsoppervlaktes, gedompel in 10 mM natrium fosfaat buffer (pH 7.0) vas te stel. Intraspesie en intragenus verskille was weereens waargeneem, net soos in die geval van die eksperimente met die droë oppervlakte. In die algemeen het die swamme baie beter geheg aan hidrofiliese oppervlaktes in vergelyking met hidrofobiese oppervlakte. Dit was ‘n aanduiding dat die swamspoor oppervlaktes bedek was met relatiewe hidrofiliese verbindings bv. koolhidrate. Verder was daar bewys dat alle swamme ingesluit in hierdie studie die vermoë het om plasmamembraan glikoproteïn bedekte polistireen te bind, en gevolglik was die teenwoordigheid van van koolhidrate op die swamspore bevestig m.b.v epi-fluoresensie mikroskopie. Verskille in die strategie van swamme om spore in die lug vry te stel, sowel as verskille in die aanhegtingsprofiele vir ‘n reeks toetsmateriale, mag net ‘n aanduiding wees van ‘n unieke omgewings nis vir elke genus wat in hierdie studie ondersoek is. Hierdie verskynsel moet dus in die nabye toekoms nagevors word.

Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / Dispersal plays an essential role in determining the distribution of populations of species, especially species expanding their ranges. Two disciplines are concerned with gaining understanding of spread of species, namely restoration ecology and invasion biology. Con- ceptual understanding of dispersal, its mechanisms and its management is essential to both disciplines. Nevertheless, the disciplines have quite opposite objectives: in restoration ecol- ogy, spread of indigenous species into transformed landscapes is promoted, while invasion biology aims to prevent the (further) spread of alien species into pristine or restored habi- tats. Despite these two opposite objectives of facilitating spread and preventing spread of their respective target species, these disciplines have essentially the same requirements in terms of information needed for restoration. In this thesis, I will present two modelling studies—one looking at the impact of two different seed-feeding alien control agents on the spread of Hakea sericea, the other investigating the recolonisation by Dicerothamnus rhinocerotis of an old field dominated by Cynodon dactylon. Based on these studies, I will draw conclusions for the management in each case. In a second step, I will compare these two seemingly-different studies and draw conclusions on how these two disciplines can learn from each other, and how conclusions drawn and management recommendations developed for the one discipline can be translated for the other. The invasion biology study concluded that seed-feeding biocontrol agents do have a considerable impact on the velocity of the spread of the target species. In addition, management recommendations included the possibility of substituting seed-feeding biocontrol agents with an increased fire frequency where the negative impact on natural vegetation, on the site invaded by the target species, is acceptable. The restoration study concluded that the main impact on the velocity of spread, and the speed of the return of the shrub species onto the old fields, is the availability of micro-sites. A sensitivity analysis showed the even a slight change from 1% to 2% increases the velocity and pattern of spread dramatically. The other parameters playing an important role are the mean rate of establishment and the time span between

The thesis deals with the ecology of lichens in two contrasting types of forest, epiphytic lichens in old Picea abies forest of the fi re-refugia type and epigeic as well as epixylic lichens in a successional sequence of fire- susceptible Pinus sylvestris forests. Results in five separate papers form the basis for a discussion of general patterns of dispersal, succession and life strategies in lichens. The study sites were located in Medelpad and Väs­terbotten, in the central and northern part of Sweden, respectively. Special attention has been paid to the rare, pendulous, spruce-1ichen Usnea longissima and the coexisting lichen species. U. longissima is largely restricted to north-facing hill slopes covered with old, mesic spruce forest that is characterized by a very long continuity not disturbed by fire. A mar­ked decline in the number of sites with U. longissima was found. The decline was mainly due to the effect of different forestry practices as the species is very sensitive to environmental disturbances. The epiphytic lichen vegetation of six tree species occurring in the spruce forest is described. Clear successional trends with increasing tree size were • obtained for Alectoria sarmentosa, Bryoria fuscescens coll., B. nadvornikiana, Usnea filipendula' and U. subflorida'na, to a lesser extent for Bryoria capii-“" laris while U. longissima had no relationship to tree size or age. TTstudy of the litterfall of macrofragments of epiphytic lichens showed that thallus fragments were dispersed throughout the year with late autumn, winter and early spring as the most critical periods. It is suggested that dispersal through thallus fragmentation is more important in fruticose than in foliose species and that U. longissima has a shorter range of propagule transport than the other species of Alectoria, Bryoria and Usnea studied. The latter proposition was supported through a study of the horizontal patterns of lichen occurrence in the spruce forest. It is shown that the diversity in ground vegetation, after an initial in­crease, declines with succession in the pine forests. A mechanism of succes­sion in ground vegetation is presented which suggest that variations in habi­tat heterogeneity, i.e. the diversity of substrates caused by the initial dis­turbance and the stand development, largely determines diversity changes dur­ing succession. Trends of increasing thallus size, increasing size of asexual reproductive propagules and increased competitive ability with succession formed the basis for recognizing three types of strategies in Cladonia» It is concluded that lichens have features that are compatible with the r-K continuum and that they are variously adapted to both the stability of the substrates and that of the forest as a whole. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1983, härtill 5 uppsatser</p> / digitalisering@umu

published_or_final_version / abstract / Ecology and Biodiversity / Doctoral / Doctor of Philosophy