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Seed dispersal in aquatic habitats is often considered to be a complex multistage process, where initial seed shadows are redistributed by water (hydrochory). The roles of hydrochory in seed dispersal and influencing population genetic structure were examined in Helmholtzia glaberrima using both ecological and genetic techniques. Ecological experiments showed that water can redistribute seeds and seedlings over local scales and that hydrochory can provide the potential for very long distance seed and seedling dispersal. Patterns of seedling genetic structure were affected by micro-drainages that direct water flow within populations and influence water-borne seed dispersal on a local scale. Strong non-equilibrium dynamics and persistent founder effects were responsible for the patterns of genetic structure observed among established populations of H. glaberrima. Classical metapopulation models best described dispersal patterns, while water-borne seed dispersal could potentially explain patterns of genetic differentiation within a stream system, it could not explain the distribution of genetic variation among stream systems. The current study found that although hydrochory influenced seed dispersal and seedling genetic structure within a population, it had little effect on the spatial pattern of genetic variation among established populations of H. glaberrima. Moreover, even though prolonged buoyancy and viability in water provide the potential for long-distance hydrochory, results presented here do not support the hypothesis that flowing water is an effective long distance seed dispersal vector for H. glaberrima. Taken together, these results suggest that the relative importance of gene flow via water-born seed dispersal in H. glaberrima may be low compared with that of some other riparian species.

abstract: As an industrial society, humans have increasingly separated agricultural processes from natural ecosystems. Many areas of the Southwestern US, however, maintain traditional practices that link agricultural systems to the natural environment. One such practice, diverting river water into fields via earthen irrigation canals, allows ditch water to recharge groundwater and riparian vegetation to prosper along canal banks. As there is growing interest in managing landscapes for multiple ecosystem services, this study was undertaken to determine if irrigation canals function as an extension of the riparian corridor. I was specifically interested in determining if the processes within semi-arid streams that drive riparian plant community structure are manifested in earthen irrigation ditches. I examined herbaceous and woody vegetation along the middle Verde River, AZ, USA and three adjacent irrigation ditches across six months. I also collected sieved hydrochores--seeds dispersing through water--within ditches and the river twelve times. Results indicate that ditch vegetation was similar to streamside river vegetation in abundance (cover and basal area) due to surface water availability but more diverse than river streamside vegetation due to high heterogeneity. Compositionally, herbaceous vegetation along the ditch was most similar to the river banks, while low disturbance fostered woody vegetation along the ditches similar to high floodplain and river terrace vegetation. Hydrochore richness and abundance within the river was dependent on seasonality and stream discharge, but these relationships were dampened in the ditches. Species-specific strategies of hydrochory, however, did emerge in both systems. Strategies include pulse species, which disperse via hydrochory in strict accordance with their restricted dispersal windows, constant species, which are year round hydrochores, and combination species, which show characteristics of both. There was high overlap in the composition of hydrochores in the two systems, with obligate wetland species abundant in both. Upland species were more seasonally constant and abundant in the ditch water than the river. The consistency of river processes and similarity of vegetation suggest that earthen irrigation ditches do function as an extension of the riparian corridor. Thus, these man-made irrigation ditches should be considered by stakeholders for their multiple ecosystem services. / Dissertation/Thesis / M.S. Biology 2010

Riparian ecosystems are of great importance in the landscape, connecting landscape elements longitudinally and laterally and often encompassing sharp environmental gradients in ecological processes and communities. They are influenced by fluvial disturbances such as flooding, erosion and sediment deposition, which create dynamic and spatially heterogeneous habitats that support a high diversity of species. Riverine ecosystems belong among the world’s most threatened systems. In rivers throughout the world, human alterations to fluvial disturbance regimes have resulted in degraded ecosystems and species loss. For example, in Sweden, watercourses of all sizes have been channelized to facilitate timber floating, but in the last 10–20 years the impacts in some of the affected rivers have been reduced by restoration actions. The objectives of this thesis are to evaluate how riverine ecosystems in general, with specific focus on riparian communities, are affected by (1) restoration of channelized reaches by boulder replacement, (2) ice formation, and (3) restoration of in-stream wood abundance in the stream channel. Objective (1) was assessed by quantifying the retention of plant propagules in channelized and restored stream reaches and by evaluating effects on riparian plant and bryophyte communities in disconnected and re-opened side channels. Retention of plant propagule mimics was highest at low flows and in sites where boulders and large wood had been replaced into the channel. Propagules are however unlikely to establish unless they can be further dispersed during subsequent spring high flows to higher riparian elevations suitable for establishment. Thus, immigration to new suitable sites may occur stepwise. Our study demonstrates that restoration of channel complexity through replacement of boulders and wood can enhance retention of plant propagules, but also highlights the importance of understanding how restoration effects vary with flow. We detected no differences in riparian diversity between re-opened and disconnected side channels, but we did observe significant differences in species composition of both vascular plant and bryophyte communities. Disconnected sites had more floodplain species, whereas restored sites had more species characteristic of upland forest. This suggests that the reopening of side channels resulted in increased water levels, resulting in new riparian zones developing in former upland areas, but that the characteristic floodplain communities have not had time to develop in response to the restored fluvial regime. Objective (2) was approached by evaluating the effect of both natural anchor ice formation and experimentally created ice in the riparian zone. Riparian plant species richness and evenness proved to be higher in plots affected by anchor ice. Plants with their over-wintering organs above the ice sheet suffered from the treatment but the overall species richness increased in ice-treated plots. Objective (3) was evaluated by studying wood recruitment and movement, channel hydraulics, propagule retention and fish abundance in streams restored with large wood. Only one stream experienced reduced velocities after large wood addition. The large size and reduced velocity were probably also the reasons why this stream proved to be the best one in trapping natural, drifting wood. Increased retention and decreased mechanical fragmentation in large wood sites will lead to decreased loss of detritus from the site and therefore higher availability of coarse particulate organic matter which can result in more species rich shredder communities. Our study did not show that the occurrence of large wood had an important role in controlling density or biomass of brown trout.

Process domains are formed by geomorphological process, these geological formation act as water pathways for river systems and affects hydrochory potential for seeds. Hydrochory acts differently depending on fluvial settings and is an important factor for diversity in the riparian zone along streams and lakes. The aim of this study was to (1) determine if process domains influence plant species abundance and diversity, and (2) if certain environmental factors associated with different process domains affects species abundance and diversity. The sample sites are parts of a dendritic water system located in tributaries for Hjuksån summer 2017 in northern Sweden. Seed samples were collected from three process domains (lake, rapids and slow-flowing) and later identified in lab. A greater species abundances and seed amount were found at lakes compared to rapids and slow-flowing reaches but there were no significant different between the process domains. None of the environmental factors showed to be important but there were indications that number of boulders might influence seed dispersal. Shannon Diversity index showed to be highest along slow-flowing reaches, but again no significant difference. Understanding process domains and their unique compositions in species abundance and diversity is for example an important factor for restoration techniques of anthropogenic modified streams.

I have studied the genetic variation of single species using morphological variation and enzyme electrophoresis. I have striven to understand the interaction between the breeding structure and the ecology of the species in relation to the community, in which it lives. The work was done in the county of Västerbotten, northern Sweden. In the Skeppsvik archipelago I have studied the population structure of Silene dioica: ecotypic variation in other populations. I have also studied the genetic diversity of Angelica archangelica, Bistorta vivipara, Viscaria alpina and the earthworm Eiseniella tetraedra along the free-flowing Vindel and Sävar Rivers and the regulated Urne River. The island populations of S. dioica are subdivided into several breeding units and levels of differentiation among subpopulations within islands were about twice as high as among islands. Restricted seed and pollen dispersal creates patches made up of related individuals that may diverge as a result of drift. Frequent seed and pollen dispersal occurs among islands and they will receive the same alleles. This may explain the pattern of differentiation observed. In contrast, the patches within islands may be founded by only a few individuals. * S. dioica exhibits morphological differentiation in vegetative and floral characters between serpentine, cold spring, rich forest and coastal habitats. There was no association between  genetic and geographical distance or between genetic distance and habitat. Serpentine and cold spring, which represented the most extreme habitats were also most differentiated. Populations of S. dioica are subject to herbivory; predation may exert a selective pressure on vegetative characters. A number of selective forces such as pollinators and fungal parasites act on reproductive characters. Assuming that water dispersal is important I tested several hypotheses to explain patterns of genetic diversity expected to be exhibited by riparian organisms along free-flowing and regulated rivers. I show that dispersal, distribution and breeding structure are important determinants of the evolution of the riparian flora. Patterns of genetic diversity may be exhibited at many spatial scales, e.g. among entire rivers, and between types of riverbanks within a river reach. Populations must be sampled at a spatial scale relevant to the hypothesis to be tested. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 2002, härtill 5 uppsatser.</p> / digitalisering@umu

In this study three aspects of sexual reproduction in Everglades plants were examined to more clearly understand seed dispersal and the allocation of resources to sexual reproduction— spatial dispersal process, temporal dispersal of seeds (seedbank), and germination patterns in the dominant species, sawgrass (Cladium jamaicense). Community assembly rules for fruit dispersal were deduced by analysis of functional traits associated with this process. Seedbank ecology was investigated by monitoring emergence of germinants from sawgrass soil samples held under varying water depths to determine the fate of dispersed seeds. Fine-scale study of sawgrass fruits yielded information on contributions to variation in sexually produced propagules in this species, which primarily reproduces vegetatively. It was hypothesized that Everglades plants possess a set of functional traits that enhance diaspore dispersal. To test this, 14 traits were evaluated among 51 species by factor analysis. The factorial plot of this analysis generated groups of related traits, with four suites of traits forming dispersal syndromes. Hydrochory traits were categorized by buoyancy and appendages enhancing buoyancy. Anemochory traits were categorized by diaspore size and appendages enhancing air movement. Epizoochory traits were categorized by diaspore size, buoyancy, and appendages allowing for attachment. Endozoochory traits were categorized by diaspore size, buoyancy, and appendages aiding diaspore presentation. These patterns/trends of functional trait organization also represent dispersal community assembly rules. Seeds dispersed by hydrochory were hypothesized to be caught most often in the edge of the north side of sawgrass patches. Patterns of germination and dispersal mode of all hydrochorous macrophytes with propagules in the seedbank were elucidated by germination analysis from 90 soil samples collected from 10 sawgrass patches. Mean site seed density was 486 seeds/m2 from 13 species. Most seeds collected at the north side of patches and significantly in the outer one meter of the patch edge (p = 0.013). Sawgrass seed germination was hypothesized to vary by site, among individual plants, and within different locations of a plant’s infructescence. An analysis of sawgrass fruits with nested ANOVAs found that collection site and interaction of site x individual plant significantly affect germination ability, seed viability, and fruit size (p < 0.050). Fruit location within a plant’s infructescence did not significantly affect germination. As for allocation of resources to sexual reproduction, only 17.9% of sawgrass seeds germinated and only 4.8% of ungerminated seeds with fleshy endosperm were presumed viable, but dormant. Collectively, only 22% of all sawgrass seeds produced were viable.

La mise en place de réseaux écologiques est considérée comme l'un des moyens de pallier aux effets néfastes de la fragmentation sur la biodiversité. Dans les paysages agricoles, les éléments linéaires non cultivés peuvent constituer de larges réseaux, et jouer un rôle d'habitat-refuge et/ou de corridor de dispersion pour les espèces végétales. L'objectif de cette thèse est de comprendre quel rôle un réseau dense de fossés de drainage peut jouer dans le maintien et la dispersion d'espèces végétales dans un paysage agricole intensif du nord de la France. Nous avons également cherché à savoir dans quelle mesure les caractéristiques du paysage, la connectivité du réseau et les traits d'histoire de vie des espèces végétales impactent la dispersion des propagules au sein du réseau de fossés. Nos résultats montrent que les fossés jouent bien un rôle de corridor écologique pour les espèces végétales. En ciblant plus précisément les espèces hydrochores, nous avons démontré qu'elles dépendaient essentiellement de la composition et de la connectivité du réseau de fossés et des éléments immédiatement adjacents aux berges. Le réseau détermine également la structuration des flux de gènes chez deux espèces végétales de berges de fossés. Enfin, nos résultats montrent que la réponse des espèces à un gradient de connectivité du réseau dépend d'une combinaison de traits de dispersion, et qu'une diminution de cette connectivité entraîne une convergence fonctionnelle de ces traits à l'échelle de la métacommunauté. L'ensemble de ces résultats permet de mieux comprendre le rôle de corridor des fossés pour les espèces végétales, afin de permettre leur intégration au sein des projets de continuités écologiques dans les paysages agricoles. / The establishment of ecological networks is considered as one of the solutions to mitigate the negative effects of fragmentation on biodiversity. In agricultural landscapes, non-crop linear elements may form large networks, and constitute refuge habitats and/or dispersal corridors for plant species. The objective of this study is to understand which role may a dense drainage ditch network play for the maintenance and dispersal of plant species in an intensive agricultural landscape located in northern France. In addition, we also investigated the impact of landscape characteristics, network connectivity and plant species life-history traits on propagule dispersal within the ditch network. Our results indicate that ditches are indeed ecological corridors for plant species. By focusing more specifically on hydrochorous species, we demonstrated that they essentially depend on ditch network composition and connectivity and on elements immediately adjacent to the banks. The network also drives patterns of gene flow for two ditch bank plant species. Finally, our results also indicate that species’ response to ditch network connectivity depends on a combination of dispersal traits, and that connectivity reduction leads to functional convergence of those traits at the metacommunity scale. Together, these results provide a better understanding of the corridor role of ditches for plant species, in order to include these features into ecological network planning in agricultural landscapes.

Long-distance dispersal of Rumex alpinus was studied in the Giant Mountain in the National Park. The invasion of R. alpinus is there kind of problem. The work builds on a thesis from year 2007 (20007 Červenková), in which was made the model of the invasion of R. alpinus in the area of the Giant Mountain. The measurements of the seeds spread take place at four localities, three of them were for measuring of water dispersal and one was for measuring of winter dispersal. Anemochory was measured using traps in the meadow up to a distance of 50 m. The seeds were dispersed by wind to a distance of 20 meters. Hydrochory was measured using a network's traps in the streams up to 100 m. The largest measured water dispersal was 100 m. Hydrochory therefore proved to be an important factor, which influenced the invasion of R. alpinus. The storms and flood had the great influence on the hydrochory and anemochory. The prediction exponential curves were compiled from the data about the wind dispersal. The curves express the spread to more than a measured distance. The field dispersion curves were compared with theoretical curves, which were used in the model of the invasion from 2007. It turned out that the theoretical curves overestimate the spread of R. alpinus by wind. The dispersion of seeds was underestimated in the...

Coleanthus subtilis ist eine durch die FFH-Richtlinie geschützte, weltweit sehr seltene Art, welche periodisch trockenfallende Standorte in Flussauen (Primärhabitate) bzw. durch den Menschen geschaffene Staugewässer (Sekundärhabitate) besiedelt. Die Erarbeitung der aktuellen Verbreitungsbilder der Art in Sachsen und ihrer Besiedlungshistorie waren Ausgangspunkt für die Analysen zur Ökologie dieser Art. Anhand von Analysen zu den Ausbreitungsmechanismen, Standortansprüchen und Reaktionsmöglichkeiten von C. subtilis wurden grundlegende Beiträge zum besseren Verständnis der Strategien dieser Art erbracht. Die Arbeit gibt Hinweise für eine artenschutzgerechte Bewirtschaftung der Staugewässer insbesondere für die Regulierung von Zeitpunkt, Dauer, Intensität und Häufigkeit von Wasserstandsabsenkungen sowie hinsichtlich einzelner Praktiken im Zusammenhang mit einer fischereilichen Nutzung. Weiterhin zeigt die Arbeit auf, wie C. subtilis auf bestimmte, von den durchschnittlichen Wasserstandsschwankungen abweichende, Bedingungen reagieren kann. Damit sind nun wichtige Grundlagen zum nachhaltigen Schutz und zur Förderung von C. subtilis, insbesondere in Sekundärhabitaten, vorhanden. / Coleanthus subtilis is a globally rare species protected by the European Union Habitats Directive. This grass establishes on periodically drying sites in river floodplains (primary habitats) but also in man made ponds and reservoirs (secondary habitats). The identification of the present distribution patterns as well as the reconstruction of the colonisation history of C. subtilis in Saxony were the basis for analyses about the ecology of this species. By analysing dispersal mechanisms, habitat demands and response traits of C. subtilis fundamental contributions to a better understanding of the strategies of this species are given. The thesis provides information about optimum time, duration, intensity and frequency of water level reductions and about the consequences of different management practices particularly with respect to fishery in ponds and reservoirs inhabiting C. subtilis. Further the thesis shows how C. subtilis can cope with deviations from mean water level fluctuations. In summary important fundamental knowledge for the sustainable conservation and promotion of C. subtilis, particularly in secondary habitats, has been established.