Erhaltung und Wiederansiedlung des Kleinen Rohrkolbens ( Typha minima ) - Vegetationsaufnahmen, Monitoring und genetische Herkunftsanalysen

Abstract.: Galeuchet D. J. and Holderegger R. 2005. Conservation and re-introduction of Dwarf Bulrush (Typha minima) - vegetation surveys, monitoring and genetic analysis of origin. Bot. Helv. 115: 15-32. Typha minima was formerly widespread along fast flowing alpine rivers but is now red-listed as critically endangered. To assess its conservation perspectives, we surveyed the few remaining natural populations along the alpine part of the River Rhine from 1997 to 2002 and determined their genetic diversity using isozyme electrophoresis. Six of the populations became extinct or extremely small, probably due to shading by taller plants and trampling, while six other populations remained stable or increased, partly due to habitat restoration measures. The largest populations, with areas of more than 10'000 m2, are found in secondary habitats which are regularly disturbed due to water regime management. Of the 19 investigated isozyme loci, only six were polymorphic. Allelic diversity (1.4-1.8) was low in all populations, and the number of multilocus genotpyes (1-18) was low for 11 of 13 investigated populations. Genetic diversity was also studied for ex-situ cultivations of T. minima in Swiss botanical gardens and reintroduced stands.These artificial populations (each with 1-3 multilocus genotypes) were genetically similar to natural populations (average genetic distance 0.094). For two ex-situ cultivations with unknown origin, the likely origin could genetically be defined. Hybridisation between two ex-situ cultivations of different origin (i.e. a potential risk of genetic introgression) was detected in one botanical garden. It is concluded that the long-term conservation of T. minima requires both the restoration of regularly disturbed, sparsely vegetated river margins and the re-introduction of plants from ex-situ cultivations with appropriate origi

Performance of Lychnis flos-cuculi from fragmented populations under experimental biotic interactions

To study genetic effects of habitat fragmentation on plant performance and plant response to biotic interactions, we performed a greenhouse study with plants from 27 populations of the common plant Lychnis flos-cuculi differing in size, isolation, and microsatellite heterozygosity. We germinated seeds of 449 plants and grew up to nine offspring per maternal plant in single pots assigned to a factorial competition-by-pathogen infection treatment. We applied competition by sowing seeds of the grass Anthoxanthum odoratum into half of the pots. Moreover, half of the plants were inoculated with infective sporidia of the anther smut Microbotryum violaceum. Significant variation among populations in most size measures indicated genetic differentiation between populations. Plants from smaller populations developed fewer flowers than plants from larger populations indicating a genetic Allee effect. A decrease in flower number was also observed for populations with decreased microsatellite heterozygosity, suggesting higher inbreeding depression. Competition and pathogen infection reduced plant size independently from one another and independent from the fragmentation of the habitats of plant origin. While pathogen infection increased the total number of flowers per plant, it decreased the number of uninfected flowers per plant. This study demonstrates that even common species are negatively affected by habitat fragmentation. At the same time, it suggests little effect of habitat fragmentation on plant response to experimental competition and pathogen infection

Between-Population Outbreeding Affects Plant Defence

Between-population crosses may replenish genetic variation of populations, but may also result in outbreeding depression. Apart from direct effects on plant fitness, these outbreeding effects can also alter plant-herbivore interactions by influencing plant tolerance and resistance to herbivory. We investigated effects of experimental within- and between-population outbreeding on herbivore resistance, tolerance and plant fitness using plants from 13 to 19 Lychnis flos-cuculi populations. We found no evidence for outbreeding depression in resistance reflected by the amount of leaf area consumed. However, herbivore performance was greater when fed on plants from between-population compared to within-population crosses. This can reflect outbreeding depression in resistance and/or outbreeding effects on plant quality for the herbivores. The effects of type of cross on the relationship between herbivore damage and plant fitness varied among populations. This demonstrates how between-population outbreeding effects on tolerance range from outbreeding depression to outbreeding benefits among plant populations. Finally, herbivore damage strengthened the observed outbreeding effects on plant fitness in several populations. These results raise novel considerations on the impact of outbreeding on the joint evolution of resistance and tolerance, and on the evolution of multiple defence strategies

Erhaltung und Wiederansiedlung des Kleinen Rohrkolbens (Typha minima) – Vegetationsaufnahmen, Monitoring und genetische Herkunftsanalysen

Galeuchet D. J. and Holderegger R. 2005. Conservation and re-introduction of Dwarf Bulrush (Typha minima) - vegetation surveys, monitoring and genetic analysis of origin. Bot. Helv. 115: 15-32. Typha minima was formerly widespread along fast flowing alpine rivers but is now red-listed as critically endangered. To assess its conservation perspectives, we surveyed the few remaining natural populations along the alpine part of the River Rhine from 1997 to 2002 and determined their genetic diversity using isozyme electrophoresis. Six of the populations became extinct or extremely small, probably due to shading by taller plants and trampling, while six other populations remained stable or increased, partly due to habitat restoration measures. The largest populations, with areas of more than 10'000 m2, are found in secondary habitats which are regularly disturbed due to water regime management. Of the 19 investigated isozyme loci, only six were polymorphic. Allelic diversity (1.4-1.8) was low in all populations, and the number of multilocus genotpyes (1-18) was low for 11 of 13 investigated populations. Genetic diversity was also studied for ex-situ cultivations of T. minima in Swiss botanical gardens and reintroduced stands.These artificial populations (each with 1-3 multilocus genotypes) were genetically similar to natural populations (average genetic distance 0.094). For two ex-situ cultivations with unknown origin, the likely origin could genetically be defined. Hybridisation between two ex-situ cultivations of different origin (i.e. a potential risk of genetic introgression) was detected in one botanical garden. It is concluded that the long-term conservation of T. minima requires both the restoration of regularly disturbed, sparsely vegetated river margins and the re-introduction of plants from ex-situ cultivations with appropriate origi

SEM observations of zinc diffusion induced disordering in GaAs/AlGaAs multiquantum well structures

Characterization of impurety diffusion induced disordering in GaAs/AlGaAs multiquantum well structures, grown by molecular beam epitaxy, has been carried out by scanning electron microscopy

Habitat fragmentation and adaptation: a reciprocal replant-transplant experiment among 15 populations of Lychnis flos-cuculi

1. Habitat fragmentation and variation in habitat quality can both affect plant performance, but their effects have rarely been studied in combination. We thus examined plant performance in response to differences in habitat quality for a species subject to habitat fragmentation, the common but declining perennial herb Lychnis flos-cuculi. 2. We reciprocally transplanted plants between 15 fen grasslands in north-east Switzerland and recorded plant performance for 4 years. 3. Variation between the 15 target sites was the most important factor and affected all measures of plant performance in all years. This demonstrates the importance of plastic responses to habitat quality for plant performance. 4. Plants from smaller populations produced fewer rosettes than plants from larger populations in the first year of the replant-transplant experiment. 5. Plant performance decreased with increasing ecological difference between grassland of origin and target grassland, indicating adaptation to ecological conditions. In contrast, plant performance was not influenced by microsatellite distance and hardly by geographic distance between grassland of origin and target grassland. 6. Plants originating from larger populations were better able to cope with larger ecological differences between transplantation site and site of origin. 7. Synthesis: In addition to the direct effects of target grasslands, both habitat fragmentation, through reduced population size, and adaptation to habitats of different quality, contributed to the performance of L. flos-cuculi. This underlines that habitat fragmentation also affects species that are still common. Moreover, it suggests that restoration projects involving L. flos-cuculi should use plant material from large populations living in habitats similar to the restoration site. Finally, our results bring into question whether plants in small habitat remnants will be able to cope with future environmental change