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Aim The objective of this work was to determine if the existence of ancient forests on cliffs was specific to the Niagara Escarpment, Canada, or part of a globally widespread pattern. Location Sixty‐five cliff sites were visited in five countries in the temperate climatic zone, and trees were sampled for age and growth rate on forty‐six of these. Methods Two hundred and twenty‐four core samples or cross‐sections were taken from trees on cliffs that varied in height, aspect, rock‐type, and exposure. General observations were also made of regeneration of the tree species forming the mature canopy, and other habitat conditions. Results The evidence shows that ancient slow‐growing forest occurs on most cliffs. Age and growth rate distributions were similar at all treed sites. Small‐statured Thuja, Juniperus, or Taxus stems with age estimates in excess of 1000 years were found in the United States, the United Kingdom and France, and small Pinus and Quercus stems nearly 400 years in Germany. There was a high rate of recurrence of plants in the genera Polypodium, Asplenium, Cystopteris, Campanula, Rosa, Prunus, Hedera, and Sorbus. Most of the sites appear to be habitats of completely natural origin. Conclusions We conclude that ancient natural forest is a normal feature of cliffs, at least in the temperate zone.

diameter) per treatment. The tubes were then placed in a water bath with a temperature gradient from top to bottom of 20 to 10 °C. We used a spectrophometric assay procedure 10 to establish the TMA concentration in 10 litres of the medium that had previously contained four fish (ides, Leuciscus idus, 10 cm long), and recorded the resulting vertical migration behaviour of daphnids exposed to this medium. TMA concentration in this 'fish' water was between 10 and 25 ȖM.We found that even low concentrations of TMA induce Daphnia to migrate to deeper waters during the day in our test system. At night, they migrate back to the surface when exposed to small amounts of TMA, and stay near the bottom when TMA levels are high (more than 100 ȖM). When the lowest TMA concentration that induces vertical migration is compared with the activity in the fish water, it is clear that the reaction of Daphnia to fish water is stronger than just to TMA alone. This indicates that, although TMA is an active component of the 'fish factor', it is likely to be part of a cocktail of substances that deter Daphnia. The other substances probably help to reduce the chemical threshold that induces migration. It is not clear whether the TMA concentrations used in this study represent realistic values for aquatic systems, as we could find no published details of TMA concentrations in aquatic systems.It has been shown 9 that the fish kairomone is broken down by bacteria. We therefore compared the average day depth of daphnids exposed to 75 ȖM TMA in autoclaved water, and with the antibiotic ampicillin added and the TMA dissolved in non-autoclaved lake water. The migration activity of the Daphnia in non-sterile water slowly decreased over time (Fig. 2). After 72 hours, the average day depth of the animals in non-sterile conditions was no longer significantly different from the average day depth of animals in sterile control medium.To investigate whether simply adding any substance to the water induces vertical migration, we added the same amount of TMAO and triethylamine to sterile water (both at 75 ȖM). As with the control Daphnia, there was no significant increase in day depth. We therefore conclude that the reaction to TMA is a specific one, and not simply a response to a change in conductivity or ionic strength of the medium.

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Cyprt.pedi.urn reginae is a terrestrial orchid with a boreal-temperate main range and a glacial-disjunct southern range primarily in the southern Appalachian Mountains. During the summer of 2001, tissue for allozyme and RAPD analysis was collected from four populations of C. reg/nae in its glaciated range of Ohio, and from five populations in its unglaciated range. Allozyme analysis of 10 putative loci revealed a single polymorphic PGM locus in seven of nine populations. Excess heterozygosity at this locus was observed in the same seven populations. Two of thirty-one RAPD primers exhibited repeatable variation at five loci. RAPD data indicated slightly higher estimations of genetic diversity than allozymes at the species and population level, although much of this variation was distributed among populations. AIlozyme data indicated low species and population-level diversity when compared to average values for lv plants, other orchids and other CMprl.pedi.urn species. Allozyme data also indicated a level of among-population differentiation similar to average values for plants and orchids. Among-population differentiation was high when compared to other Cypn.pedi.tim species. Species and population-level allozyme diversity estimates were low when compared to estimates from plants with life-history characters similar to C. rag/nae. Among-population differentiation was not different from other plants with similar life-history characters. Higher levels of allozyme diversity were identified in populations at glaciated sites compared to populations at unglaciated sites. Low levels of genetic variation in this species may be attributed to severe range contraction during the Wisconsin glaciation and subsequent reductions of genetic diversity due to genetic drift. Genetic drift may have been particularly intense in populations at unglaciated sites due to infrequent appropriate habitat, isolation, and small population size. Relatively high levels of allozyme diversify in populations at glaciated sites may be explained by the existence of C. regi.nae populations close to the glacial margin of the Laurentide ice sheet during the Wisconsin glaciation. These populations may have served as genetic reservoirs that initially colonized wetland habitats after glacial recession. RAPD data followed patterns of habitat quality. Higher levels of RAPD variation were observed in populations at sites with higher quality habitat that supporfed relatively large populations.V ACKNOWLEDGMENTS Many people have made contributions to my education and to this thesis.Without these contributions I would not have had the opportunity, inspiration or guidance to be a graduate student and complete this work. Primarily, my appreciation is for my mother and father who have never hesitated to support anything that I have wanted to do. This support has manifested itself in many ways. Most importantly they have been incredible friends. I also owe my appreciation to Travis Knowles, my advisor as an undergraduate student at Francis Marion University. Travis he...