<p>Worldwide amphibians and reptiles are declining with habitat fragmentation and destruction as the primary cause. Riparian areas are important for the herpetofauna, but as land is converted to agriculture or harvested for timber the areas are diminishing. The aim of this study was to examine amphibian and reptile abundance in relation to distance from water and in relation to habitat characteristics, foremost per cent deciduous trees. The survey was conducted during spring at six different locations, with continuous forest along streams or rivers, outside of Karlstad, Sweden. Animals were searched along four lines parallel to the water and each study area was visited five times. Statistical analyses were made for grass snake (<em>Natrix natrix</em>), common lizard (<em>Lacerta vivipara</em>) and frogs with joined data of common frog (<em>Rana temporaria</em>) and moor frog (<em>R. arvalis</em>). As expected both reptiles were positively correlated with per cent deciduous trees, with the strongest significance for the common lizard. For grass snake there was also a difference between survey periods, which might reflect the importance of weather. Frogs revealed no trends to trees, but there was a significant difference for habitat characteristics like amount woody debris and per cent bare ground. None of the species were correlated with distance from water which was surprising, especially for the frogs which is more dependent on water than the reptiles. Grass snakes hunt in the water, but the common lizard has no such associations to the water, yet the latter did reveal a slight trend towards being more numerous closer to the water. The causes behind lacking correlation to distance from water may be many, but water characteristics seem very important. Many amphibians prefer warm and calm ponds over running water that in general are colder and likely to inhabit more predators. It was assumed that the amphibians breed in the streams or rivers, but it is possible that other water bodies may have served as breeding sites, which mean the starting point was incorrect.</p>

Worldwide amphibians and reptiles are declining with habitat fragmentation and destruction as the primary cause. Riparian areas are important for the herpetofauna, but as land is converted to agriculture or harvested for timber the areas are diminishing. The aim of this study was to examine amphibian and reptile abundance in relation to distance from water and in relation to habitat characteristics, foremost per cent deciduous trees. The survey was conducted during spring at six different locations, with continuous forest along streams or rivers, outside of Karlstad, Sweden. Animals were searched along four lines parallel to the water and each study area was visited five times. Statistical analyses were made for grass snake (Natrix natrix), common lizard (Lacerta vivipara) and frogs with joined data of common frog (Rana temporaria) and moor frog (R. arvalis). As expected both reptiles were positively correlated with per cent deciduous trees, with the strongest significance for the common lizard. For grass snake there was also a difference between survey periods, which might reflect the importance of weather. Frogs revealed no trends to trees, but there was a significant difference for habitat characteristics like amount woody debris and per cent bare ground. None of the species were correlated with distance from water which was surprising, especially for the frogs which is more dependent on water than the reptiles. Grass snakes hunt in the water, but the common lizard has no such associations to the water, yet the latter did reveal a slight trend towards being more numerous closer to the water. The causes behind lacking correlation to distance from water may be many, but water characteristics seem very important. Many amphibians prefer warm and calm ponds over running water that in general are colder and likely to inhabit more predators. It was assumed that the amphibians breed in the streams or rivers, but it is possible that other water bodies may have served as breeding sites, which mean the starting point was incorrect.

Growth rate is an important life history trait, which impacts fitness indirectly through its effect on the age and size at maturity, as well as directly through costs associated with accelerated growth such as increased predation risk. Genetic variation and plasticity in growth are widespread in nature, and local adaptation of growth rate may evolve due to divergent selection in different environments, for example related to predation risk, temperature or time constraints. I studied local adaptation of larval life history in the moor frog Rana arvalis, in a local network of ponds close to Uppsala. Local adaptation of growth rate and survival was studied in a reciprocal transplant experiment between ponds with different habitat characteristics. Meanwhile, differences among the populations in intrinsic growth, activity and response to predation were studied in a common garden experiment in the laboratory, where tadpoles were raised in the presence or absence of a predator and tested in direct predation trials. In the field, differences in growth among populations were found, independent of which pond the tadpoles were raised in, indicating that the ponds were similar growth environments. Survival differences among the populations depended on the pond, but local populations did not do better than foreign ones. In the laboratory, similar patterns in growth rate were found. All populations were highly plastic in their response to predation, having lower growth and activity in the predator-induced treatment and decreased mortality in the predation trials. Tadpole size was an important factor in escaping predation. One population clearly grew faster than the others in the field and in the lab, which could be explained in terms of its habitat of origin but was most likely related to the relatively late hatching of this population. Future studies are necessary concerning the possible costs of this accelerated growth and the importance of breeding phenology. Apart from the one differential population, I did not find evidence of local adaptation in the field or in the laboratory. The influence of habitat characteristics on tadpole life history was difficult to study, due to the limited number of ponds and many environmental differences among them. However, this thesis was a valuable pilot study concerning the design of experiments to study factors promoting and constraining local adaptation in landscape mosaics. An understanding of local adaptation at the scale at which gene flow occurs is important for the conservation of populations in fragmented landscapes as well as for the study of ecological speciation.

<p>During the last decades many amphibian species and populations have experienced declines and extinctions in different parts of the world. Anthropogenic activities are believed to account for these declines, and one of the hypothesized causes has been the increased level of ultraviolet-B (UV-B) radiation due to depletion of the stratospheric ozone layer. </p><p>Although negative effects of UV-B radiation on development of many amphibian species have been demonstrated, a number of potentially critical issues around assessment of amphibian UV-B radiation tolerance have remained unexplored. For instance, next to nothing is known about geographic variation in UV-B tolerance and about possible carry-over effects of early UV-B exposure to later life-stages. Likewise, synergistic effects with other stressors, as well as sublethal effects on growth have received little attention. </p><p>The results from field and laboratory experiments show that <i>R. temporaria</i> and <i>R. arvalis</i> are relatively tolerant to even high levels of UV-B in terms of embryonic survival. However, it was found that even normal levels of UV-B can reduce early embryonic growth. In addition, the effects of early exposure to UV-B became manifested mostly or only after a considerable time-lag (i.e. at metamorphosis). Furthermore, it was found that the sublethal effects of UV-B may become manifested only in combination with other stressors, such as low pH, and this synergism may differ among different populations. No evidence for genetic differentiation in UV-B tolerance was found.</p><p>These findings suggest that even a relatively tolerant species, such as <i>R. temporaria</i>, may be sensitive to increased levels of UV-B radiation, but that this sensitivity may be highly population, environment and trait dependent. The observed carry-over effects over life-stages emphasise the importance of the early life environment on later life fitness.</p>

During the last decades many amphibian species and populations have experienced declines and extinctions in different parts of the world. Anthropogenic activities are believed to account for these declines, and one of the hypothesized causes has been the increased level of ultraviolet-B (UV-B) radiation due to depletion of the stratospheric ozone layer. Although negative effects of UV-B radiation on development of many amphibian species have been demonstrated, a number of potentially critical issues around assessment of amphibian UV-B radiation tolerance have remained unexplored. For instance, next to nothing is known about geographic variation in UV-B tolerance and about possible carry-over effects of early UV-B exposure to later life-stages. Likewise, synergistic effects with other stressors, as well as sublethal effects on growth have received little attention. The results from field and laboratory experiments show that R. temporaria and R. arvalis are relatively tolerant to even high levels of UV-B in terms of embryonic survival. However, it was found that even normal levels of UV-B can reduce early embryonic growth. In addition, the effects of early exposure to UV-B became manifested mostly or only after a considerable time-lag (i.e. at metamorphosis). Furthermore, it was found that the sublethal effects of UV-B may become manifested only in combination with other stressors, such as low pH, and this synergism may differ among different populations. No evidence for genetic differentiation in UV-B tolerance was found. These findings suggest that even a relatively tolerant species, such as R. temporaria, may be sensitive to increased levels of UV-B radiation, but that this sensitivity may be highly population, environment and trait dependent. The observed carry-over effects over life-stages emphasise the importance of the early life environment on later life fitness.